DEGRADATION OF PHENOL BY A CATALYTIC OZONATION YOGESWARY A/P PALANIAPPAN

Transcription

1 DEGRADATION OF PHENOL BY A CATALYTIC OZONATION YOGESWARY A/P PALANIAPPAN A thesis submitted in fulfilment of the requirements for the award of the degree of Master of Engineering (Chemical) Faculty of Chemical and Natural Resources Engineering Universiti Teknologi Malaysia JANUARY 2006

2 BORANG PENGESAHAN STATUS TESIS PSZ 19:16 JUDUL: DEGRADATION OF PHENOL BY CATALYTIC OZONATION SESI PENGAJIAN : 2005/2006 Saya YOGESWARY A/P PALANIAPPAN (HURUF BESAR) mengaku membenarkan tesis (PSM/Sarjana/Doktor Falsafah)* disimpan di Perpustakaan Universiti Teknologi Malaysia dengan syarat-syarat kegunaan seperti berikut : 1. Tesis adalah hakmilik Universiti Teknologi Malaysia. 2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran di antara institusi pengajian tinggi. 4. ** Sila tandakan ( ) SULIT TERHAD (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972) (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan) TIDAK TERHAD Disahkan oleh (TANDATANGAN PENULIS) (TANDATANGAN PENYELIA) Alamat Tetap : 504 Desa Permai, P.M. DR. MOHD RASHID Pedas, (Nama Penyelia) Negeri Sembilan Tarikh : Tarikh : CATATAN : * Potong yang tidak berkenaan ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD. Tesis dimaksudkan sebagai tesis bagi ljazah Doktor Falsafah dan Sarjana secara penyelidikan, atau disertai bagi pengajian secara kerja kursus dan penyelidikan atau Laporan Projek Sarjana Muda (PSM).

3 I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in terms of scope and quality for the award of the degree of Master of Engineering (Chemical) Signature : Supervisor : Date :

4 ii I declare that this thesis entitled Degradation of phenol by catalytic ozonation is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree. Signature Name of candidate Date :.. :.. :...

5 To my beloved mother and father iii

6 iv ACKNOWLEDGEMENTS First and foremost I would like to offer my unreserved gratitude and praises to Almighty God for His generous blessing and the undying bestowed upon me during the course of this study. This study has been carried out under the supervision of Dr.Mohd Rashid, a lecturer of the Department of Chemical Engineering, Universiti Teknologi Malaysia. His continuous guidance, assistance and support throughout the course of the study are deeply acknowledged. I express my special thanks to all the staffs of the Faculty of Chemical and Natural Resources Engineering, and colleagues for their kind assistance and cooperation. I thank the staff from the Faculty of Science and Faculty of Mechanical for their cooperation. The support of Petronas Research and Scientific Services on the Nitrogen Adsorption analysis of catalyst is acknowledged. Finally, special gratitude is also extended to my family and my friends for their encouragement and moral supports. May God reward all of you in the hereafter.

7 v ABSTRACT Screening on the catalytic ozonation of phenol over zeolite-based catalyst i.e Beta and ZSM-5 was investigated under room temperature condition using a semi continuous system. The degree of degradation of 100ppm of phenol was measured on the treated samples. The results showed that the performance of Beta was better than ZSM-5 with the degradation of phenol of 67.4 and 49.0%, respectively after 90 minutes of reaction time. In addition, the degradation of phenol was higher in the presence of both catalysts compared to without any catalyst. Further screening of beta catalyst impregnated with ferum and titanium showed that the degradation of phenol was slightly increased with the presence of Fe-beta compared to Ti-beta catalyst. Thus, Fe-beta was furthered subjected to different experimental variables such as ozone gas flow rate, temperature and ph of phenol solution, mass and metal weight percent impregnated in the catalyst, concentration and the volume of phenol to be treated. It was observed that a smaller percentage of metal loading catalyst resulted a higher degradation compared to those with higher metal loading catalyst. As expected, the degradation of phenol increases with ozone flow rates and mass of catalyst. Interestingly, the degradation of phenol was significantly high under basic condition where the degradation was almost complete i.e 98.1% at initial ph 11. On the contrary, the degradation of phenol decreases with increasing temperature, concentration and volume of phenol solution.

8 vi ABSTRAK Proses pengozonan telah dilakukan ke atas air sisa fenol dengan menggunakan mangkin zeolite i.e Beta dan ZSM-5 pada keadaan suhu bilik dan semi-continuous reactor. Kadar degradasi fenol yang berkepakatan 100ppm telah dikaji ke atas sampel yang telah dirawat. Mangkin Beta menunjukkan keputusan yang terbaik berbanding ZSM-5 dengan mencapai degradasi fenol sebanyak masing-masing 67.4 dan 49.0% selepas tindak balas selama 90 minit. Tambahan pula, degradasi fenol adalah tinggi dengan kehadiran kedua-dua mangkin tersebut berbanding dengan pengozonan tanpa mangkin. Seterusnya, pengubahsuaian mangkin Beta dengan logam ferum dan titanium menunjukkan degradasi fenol meningkat dengan kehadiran mangkin Fe-Beta berbanding dengan mangkin Ti-Beta. Oleh yang demikian, mangkin Fe-Beta telah dipilih untuk eksperimen seterusnya yang menguji kecekapannya dari segi beberapa parameter seperti kadaralir ozon, suhu dan ph air fenol, jisim mangkin dan kandungan ferum dalam mangkin, kepekatan dan isipadu fenol yang diuji. Keputusan, mendapati hanya sedikit amaun ferum sahaja yang diperlukan bagi meningkatkan degradasi fenol berbanding dengan peratus kandungan ferum yang lebih tinggi. Seperti yang dijangkakan, degradasi fenol meningkat dengan kadaralir ozon dan jisim mangkin yang digunakan dalam process pengozonan. Degradasi fenol meningkat secara mendadak dalam keadaan bes dimana degradasi fenol mencapai sebanyak 98.1% pada ph 11. Sebaliknya, degradasi fenol menurun dengan meninggikan suhu, kepekatan dan isipadu air fenol.

9 vii TABLE OF CONTENTS CHAPTER TITLE PAGE TITLE DECLARATION DEDICATION ACKNOWLEDGMENT ABSTRACT ABSTRAK TABLE OF CONTENTS LIST OF TABLE LIST OF FIGURE LIST OF APPENDICES i ii iii iv v vi vii xi xiii xvi 1 INTRODUCTION AND OVERVIEW 1.1 Introduction 1.2 Objectives of the Study 1.3 Scopes of Work 1.4 The Importance of the Study 1.5 Overview of the Thesis

10 viii 2 LITERATURE REVIEW 2.1 Ozone and Its Background Information Ozone and Its Function Ozone and Its advantages and disadvantages Decomposition of Ozone Toxicity of Ozone and Human Beings Catalysts Type of Catalytic Reaction Heterogeneous Catalyst Study of catalytic ozonation process 2.4 Zeolite-Based Catalyst The Structure of Zeolites Framework Structure of Zeolites Zeolite Beta Catalyst ZSM-5 Catalyst Transition Metal and Their Application in Wastewater treatment 2.5 Modification of Zeolite-Based Catalyst Impregnation Method 2.6 Phenol Ozonation of Phenol 2.7 Process flow Scheme METHODOLOGY 3.1 Screening of Zeolite Based Catalyst 3.2 Screening of Zeolite with Metal-Based Catalyst 45 49

11 ix 3.3 The Effects of Operating Variables on the Degradation of Phenol 3.4 Analysis of Phenol High Performance Liquid Chromatography Chemical Oxygen Demand Total Organic Carbon Characterization of Catalyst X-ray Diffraction Nitrogen Adsorption (NA) RESULTS AND DISCUSSION 4.1 Performance of Zeolite Beta and ZSM-5 Catalyst in Degradation of Phenol Effect of Ozone Flow Rates Effect of Ozone Flow Rates Without Catalyst Effect of Ozone Flow Rates With Catalyst Effect of Concentration of Phenol Effect of Concentration of Phenol without Catalyst Effect of Concentration of Phenol with Catalyst Effect of Reaction Time Effect of Modified Beta Catalyst with Metals on Degradation of Phenol 4.3 Determination of Best Operating Conditions of Fe-Beta Catalyst in Catalytic Ozonation of Phenol 75 81

12 x Effect of Metal Weight Percent Effect of Ozone Gas Flow Rates Effect of Phenol Concentration Effect of Initial ph Effect of Mass of Catalyst Effect of Temperature Effect of Volume of Phenol to be Treated 4.4. Characterization of Metal-Based Fe-Beta Catalyst X-ray Diffraction of Beta and Fe- Beta catalyst Nitrogen Adsorption of Beta and Fe-Beta catalyst CONCLUSION AND RECOMENDATIONS 5.1 Conclusion 5.2 Recommendations REFERENCES 115 APPENDICES 123

13 xi LIST OF TABLES TABLES TITLE PAGE 2.1 Oxidizing potential of various reagents Comparison of the degradation of three model compounds under various conditions List of catalytic ozonation studies of phenol and phenolic compounds List of catalytic ozonation studies of non-phenolic compounds Experimental conditions for the degradation of phenol by metal-based zeolite catalyst The effect of ozone flow rates with and without catalyst The effect of phenol concentration with and without catalyst The effect of reaction time in ozonation with and without catalyst TOC removal without and with catalysts Specific surface area and average pore diameter of zeolitebased catalyst The degradation of phenol versus reaction time with and without modified Beta catalyst COD removal of 100ppm of phenol using Beta and Beta metal-based catalyst 79

14 xii 4.8 Degradation and COD removal of phenol in the presence of Fe-Beta under different metal wt% TOC removal with different metal weight % The effect of ozone flow rates against reaction time with Fe- Beta catalyst TOC removal with different ozone gas flow rates The effect of different concentration of phenol against reaction time The effect of initial ph of the solution against reaction time The rate of ozone decomposition at different ph values Effect of mass of 1wt% Fe-Beta catalyst in the ozonation process TOC removal with different mass of catalyst Degradation of phenol and COD removal for different temperature using Fe-Beta The effect of volume of phenol against reaction time XRD data of Beta and Fe-Beta catalyst Nitrogen adsorption data of Beta and Fe-Beta catalyst 110

15 xiii LIST OF FIGURES FIGURES TITLE PAGE 1.1 Reported pollution incidents investigation by the Environment and heritage service Two types of aqueous ozone reaction Concentration/time relationships between exposure o ozone and human response Primary building unit of SiO 4 and AlO 4. tetrahedral Primary and secondary building units in zeolites Zeolite structure Framework structure of zeolite The structure of Beta catalyst The structure of ZSM The formula structure of phenol Reaction of phenol with ozone Summary of the experimental procedures of the study Semi-continuous catalytic ozonation experimental set up Schematic diagram on the preparation of the metal-based zeolite 50

16 xiv 4.1 HPLC spectrum of the untreated and treated phenol sample COD removal with and without catalyst with different concentration of phenol Degradation of phenol with and without catalyst versus reaction time Degradation of 100ppm phenol with and without metal-based Beta catalyst versus reaction time Degradation of 1600ppm phenol with Beta and Beta metal-based catalyst versus reaction time Degradation of phenol with different metal weight percent against reaction time The effect of ozone flow rates against reaction time HPLC spectrum of phenol degradation under 2.1 L/min The effect of different concentration of phenol against reaction time HPLC spectrum at different initial ph of solution Phenol removal with time using ozone bubbling Effect of initial ph of phenol against reaction time The effect of the catalyst amount on the reaction efficiency; catalyst concentration Degradation of phenol with Fe-Beta catalyst against temperature Effect of volume of phenol against reaction time (a) XRD pattern of Beta catalyst, (b) XRD pattern of Fe-Beta catalyst XRD pattern of the reference Beta sample 109

17 xv LIST OF APPENDICES APPENDICES TITILE PAGE A B Detail and specification of the ozone generator 123 Preparation of one percent of the metal weight in catalyst 127 C Calculation of degradation of phenol 129 D Calculation of COD removal 136 E Calculation of TOC removal 143 F A) The original copy of HPLC chromatograph for phenol solution taken at various reactions time 146 B) The original copy of HPLC spectrum at different initial ph of solution 153 C) XRD pattern of Beta catalyst 157 D) XRD pattern of Fe-Beta catalyst 159

18 CHAPTER 1 INTRODUCTION AND OVERVIEW 1.1 Introduction Water is an essential ingredient to a healthy lifestyle. Doctors recommend we drink 6-8 glasses of water per day for optimum health, but this is often difficult when you don't like the taste or odor of your water, or are concerned about the quality of your drinking water. Next to air, water is the substance most necessary for human existence. Practically every living cell in the body depends on water to carry out essential functions. Sufficient amounts of water in the body can increase energy and endurance, help in body weight control, aid digestion and elimination, lubricate joints, and encourage a feeling of well being. It is not difficult to understand why drinking enough water is so extremely important when we realize that nearly 70% of the body's weight is made up of water. Water is so important that a minute reduction of body water (4-5%) will result in a decline of 20-30% in work performance. Breathing, digestion, elimination,

19 2 glandular activities and heat dissipation can be performed only in the presence of water. This combined with the role of water in dissolving the body's waste products and flushing out toxins explains why we cannot survive very long without adequate amounts of water. It makes common sense that with all the important functions that water has in the body, the quality of water you drink can radically affect your health and well being. That is why it is vitally important that you drink only pure water. Water pollution occurs when a body of water is adversely affected due to the addition of large amounts of material to the water. When it is unfit for its intended use, water is considered polluted. Two type water pollutants exists ie point source and non point source. Point source of pollution occurs when harmful substances are emitted directly into a body of water. A non point source delivers pollutants indirectly through environmental changes. An example of this type of water pollution is when fertilizer from a field is carried out into a stream by rain, in the form of run-off, which in turn affects aquatic life. Generally, there was compiled ten categories have been defined by EPA as major contributors of water pollution: 1 Industrial, including pulp and paper mills, chemical manufactures and food processing plants 2 Municipal, including publicly owned sewage treatment works that may receive indirect discharges from small factories or businesses 3 Combined sewers, including storm and sanitary sewers that, when combined, may discharged untreated wastes during storms 4 Storm sewers and runoff, including runoff from streets, paved area and lawns that enters a sewer, pipe or ditch 5 Agricultural, including crop production, pastures, rangeland or feedlots 6 Silvicultural, including forest management, harvesting and road contraction

20 3 7 Construction, including highway building and land development 8 Resource extraction, including mining, petroleum drilling and runoff from mine tailing sites 9 Land disposal, including leach ate or discharge from septic tanks, landfills, hazardous-waste disposal sites 10 Hydrologic, including channelization, dredging, dam construction and stream-bank modification. Figure 1.1: Reported pollution incidents investigation by the Environment and heritage service Figure 1.1 shows that the agriculture, industry and sewage are contributed a large amount of pollutants. Many causes of pollution including sewage, fertilizer, textile, oleo chemicals contain nutrients such as nitrates, phenol, phosphates. In excess levels, nutrients over stimulate the growth of aquatic plants and algae. Excessive growth of this type of organisms consequently clogs the waterways, use up dissolved oxygen as they decompose, and block light deeper waters. This, in turn, proves very harmful to aquatic organisms as it affects the respiration ability or fish

21 4 and other invertebrates that reside in water. The major sources of water pollution can be classified as municipal, industrial and agricultural (Figure 1). Municipal water pollution consists of waste from homes and commercial establishments. For many years, the main goal of treating municipal wastewater was simply to reduce its content of suspended solids, oxygen demanding materials, dissolved inorganic compounds, and harmful bacteria. The basic method of treating municipal wastewater fall into three stages and they are primary, secondary and tertiary treatment In primary treatment some process are carried out including grit removal, screening, grinding and sedimentation. Secondary treatment, which entails oxidation of dissolved organic matter by means of biologically active sludge, which is then filtered off and tertiary treatment, in which advanced biological methods such as granular filtration and activated carbon adsorption are employed. In recent year, the application of oxidizing chemicals in the treatment of drinking water and wastewater continues to be an active topic of scientific research and an interest to water utility practitioners. Thus, considerable attention has been paid to the study of chlorine dioxide, potassium permanganate, ozone, ozone/h 2 O 2 and UV/ H 2 O 2. Ozone, due to its high oxidation and disinfection potential, has recently received much attention in water treatment in water treatment technology. It is applied in order to improve taste and color as well as to remove the organic and inorganic compounds in water. Ozonation has been a treatment method widely used for tackling various industrial wastewaters. Many researches have been conducted to study the effects of ozone on different type of wastewater (Esplugas et al., 2002; He et al., unknown; Wu et al., 2000; Stockinger et al., 1996; Oquz et al., 2005). Recently catalytic ozonation has been attracting the interest of the scientific community dedicated to the study of ozone processes in water treatment. Catalytic ozonation was found to be effective for the removal of several organic compounds from drinking water and wastewater (Canton et al., 2003; Phu et al., 2001; Gimeno

22 5 et al., 2005; Einaga et al., 2004; Andreozzi et al., 1998; Ma and Graham., 2000 and Qu et al., 2004). Catalytic ozonation can be considered firstly as homogeneous catalytic ozonation, which is based on ozone activation by metal ions present in aqueous solution, and secondly as heterogeneous catalytic ozonation in the presence of metal oxides or metals/metal oxides on supports. The aim of the work is to study the effectiveness of degradation of phenol using catalytic ozonation with zeolite-based catalyst. Two different types of zeolite catalysts i.e zeolite beta and ZSM-5and ferum and titanium as transition metal were investigated in the study. As a comparison, ozonation of phenol solution without catalyst was also carried out in this study. In addition, the influences of various variables also were studied in this study. 1.2 Objectives of the Study In general, the study is to investigate the effectiveness of catalytic ozonation on the degradation of phenol under different operating variables, such as ozone flowrate, temperature and ph of phenol solution, mass and metal weight % in the catalyst, concentration and the volume of phenol treated. The main objectives of the study were: 1. To study the performance of zeolite beta and ZSM-5 in catalytic ozonation treatment of phenol. 2. To study the performance of modified zeolite catalyst impregnated with titanium and ferum in catalytic ozonation of phenol, and 3. To identify the best operating conditions of the selected metal-based zeolite catalyst in catalytic ozonation of phenol.

23 6 1.3 Scopes of Work The study is to investigate the performance of zeolite-based catalyst in catalytic ozonation of phenol. The catalytic ozonation of the zeolite-based catalysts was investigated under same operating conditions and the effectiveness of each of the catalyst was observed. The best performed zeolite-based catalysts either Beta or ZSM-5, was selected and modified with metals to check on its performance on the degradation of phenol in the following experiments. The selected zeolite-based catalyst was modified with metals i.e ferum and titanium, by impregnation method. The catalytic ozonation of the metal-based zeolite catalysts was tested on 100 and 1600ppm of phenol solution and their respective performance on degradation of phenol was observed for a total period of 90 minutes. The best-performed metal-based zeolite catalyst was chosen from the study for further experiments. The performance of the selected metal-based zeolite catalyst was further investigated under different experimental variables such as ozone flow rate, temperature and initial ph of phenol solution, mass and metal weight percent impregnated in the catalyst, concentration and the volume of phenol to be treated where finally, the best operating conditions on the degradation of phenol was identified. The degradation of phenol in the study was determined using HPLC method. In addition, the degree of degradation was also determined indirectly through Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) of the samples.

24 7 1.4 The Importance of the Study To date, research on the application of zeolite-based catalyst on treating of organic substances in wastewater is well known. ZSM-5 and Beta are two commonly used zeolite-based catalysts in wastewater treatment. However, a comparative performance study between in these two catalysts on the degradation of phenol solution is not available in literature. Thus, it is aptly that such study be carried out to investigate their relative performance in degradation of phenolic solution, particularly under the influence of ozonation. In addition, study on the performances of modified-metal-based zeolite catalyst using ferum and titanium on the degradation of phenolic compound under influence of ozonation is very limited. Therefore, the catalytic ozonation of titanium and ferum in zeolite catalyst was tested and their respective performance on degradation of phenol was investigated in the process of selecting the best-performed metal-based zeolite catalyst in this study. The selected metal-based zeolite catalyst was further subjected to various operating variables, in which the study hopes to find, if any, the best operating conditions that influence the degradation of phenol solution. 1.5 Overview of the Thesis The thesis has been organized in five chapters. Chapter 1 presents the introduction and overview of the thesis. It described the objectives and scopes of the study. The importance of the study is also given in this chapter. It presents the reader the general contents of the thesis.

25 8 Chapter 2 presents the pertinent literatures on the ozonation and catalytic ozonation technique performed by other researchers. It presents an overview of the recent developments in catalytic ozonation processes, which acts as a basis for this study. The chapter also describes the characteristics of zeolite and phenolic solution, which present the background of the study. Chapter 3 describes the methodology of the whole research activity involved in this study. The description of the experimental rig, the procedures of the experiments and method of analysis are presented in this chapter. The method of modifying zeolite catalyst impregnated with selected metals is also presents in this chapter. Others indirect methods for the determination of degradation using TOC and COD indicators, apart from using HPLC and the methods of characterization of the catalyst are also described in this chapter. Chapter 4 presents the results and discussion on the degradation of phenol in catalytic ozonation treatment using both zeolite and modified metal-based zeolite catalyst. The performance of these zeolite catalysts on the degradation of phenol and the optimum operating conditions of the best-selected metal-based zeolite catalyst found in the study is present in this chapter. In addition and as a comparison, results on the ozonation of phenol solution without application of catalyst were also given in this chapter. Finally, Chapter 5 gives the overall conclusion of the study. Suggestion for possible research work in future has been given in this chapter.

26 CHAPTER 2 LITERATURE REVIEW 2.1 Ozone and its Background Information Ozone is an allotrope of oxygen having three atoms to each molecule. Ozone is a colorless gas that has odor most often described as smell of air after a spring electrical thunderstorm. Ozone is a powerful oxidant and able to oxidize a great number of organic and inorganic materials. Ozone formed by passing dry air through a system of high voltage electrodes, the oxygen in the air is dissociated by the impact of electrons from the discharge electrode. The atomic oxygen then combines with atmosphere oxygen to form ozone in the following reaction: O + O 2 O 3 Pure ozone melts at a temperature of C ± C and boils at C ± C (Rice et al., 1986). At C, pure ozone condenses to a dark blue liquid that explodes easily.

27 Ozone and it function Ozone is not only a very powerful oxidizing agent but also a very powerful non-chemical disinfection. It has the best feature of decomposing to a harmless, nontoxic, environmentally state material and oxygen. In Europe, ozone is used in many purposes: color removal, taste and odor removal, turbidity reduction, organic removal, micro flocculation, and manganese oxidation. Most of the application based on ozone s high oxidizing power. Table 2.1 shows the oxidizing potential of various reagents. The table concluded de that ozone is strongest oxidant compared to the rest of oxidizing reagents stated in Table 2.1. Table 2.1: Oxidizing potential of various reagents Oxidizing reagents Oxidizing potential Ozone 2.07 Hydrogen peroxide 1.77 Permanganate 1.67 Chlorine dioxide 1.57 Hypo chlorous acid 1.49 Chlorine gas 1.36 Hypo bromous acid 1.33 Oxygen 1.23 Bromine 1.09 Hypoiodous acid 0.99 Hypochlorite 0.94 Chlorite 0.76 Iodine 0.54

28 Ozone and its Advantages and disadvantages In the field of wastewater treatment, ozone is used for various purposes: oxidation of organic or mineral compound, disinfection, pretreatment before coagulation or filtration. Using ozone to treat water has many advantages, including the following: 1) Possesses strong oxidizing power and requires short reaction time, which enables the germs, including virus, to be killed within a few second. 2) Produces no taste and odor 3) Provides oxygen to the water after disinfecting 4) Requires no chemicals 5) Oxidizes iron manganese 6) Destroy and remove algae 7) Reacts with and removes all organic matter 8) Decays rapidly in water, avoiding any undesirable residual effects 9) Removes color, taste and odor 10) Aids coagulation Ozone has certain advantages over chlorine for disinfection of wastewater: 1) Ozone increases dissolved oxygen in the effluent 2) Ozone has a briefer contact time 3) Ozone has no undesirable effects on marine organisms 4) Ozone decreases turbidity and color The use of ozone to treat water has some limitations 1) Toxic (toxicity is proportional to concentration and exposure time) 2) Cost of ozonation is high compared with chlorination 3) Installation can be complicated 4) Ozone-destroying device is needed at the exhaust of the ozone reactor to prevent toxicity and fire hazards 5) May produce undesirable aldehydes and ketones by reacting with certain organics

29 12 6) No residuals effect is present in the distribution system, thus post chlorination is required 7) Much less soluble in water than chlorine; thus special mixing devices is necessary and 8) It will not oxidize some refractory organics or will oxidize too slowly to be practical significance Decomposition of ozone Molecular ozone can oxidize water impurities via direct, selective reactions or can undergo decomposition via a chain reaction mechanism resulting in the production of free hydroxyl radicals. Ozone decomposition proceeds through the following five-step chain reaction (Kasprzyk et al., 2003): O 3 + H 2 O 2HO + O 2 (1) K 2 = 1.1 x 10-4 M -1 S -1 O 3 + HO - O 2 + H O 2 (2) K 2 = 70 M -1 S -1 O 3 + HO O 2 +H O 2 O 2 + H + (3) O 3 + HO 2 2O 2 + HO (4) K 2 = 1.6 x 10 9 M -1 S -1 2HO 2 O 2 + H 2 O 2 (5) Ozone reacts in aqueous solution on various organic and inorganic compounds, either by a direct reaction of molecular ozone or through a radical type reaction involving the hydroxyl radical induced by the ozone decomposition in

30 13 water. Figure 2.1 shows that, ozone decomposition proceeds with chain reactions including initiation step, propagation steps and chain breakdown. Figure 2.1: Two types of aqueous ozone reaction. M: Organic compounds, M oxid : oxidized compounds, OH - : Hydroxyl radical, R : Hydroxide ion, OH :Hydroxide radical, R : radical from organic (Hoigne and Bader, 1983) The ph value of the solution significantly influences ozone decomposition in water. Basic ph causes an increase of ozone decomposition. At ph<3 hydroxyl radicals do not influence the decomposition of ozone. For 7<pH<10, the typical halflife time of ozone is from 15 up to 25min. The step of reaction was discussed in chapter 4 section Toxicity of Ozone to Human Beings Figure 2.2 shows the various concentration/time relationships for human exposure and responses to ozone. Exposure to atmosphere ozone levels below 1ppm

31 14 for as long as 10 minutes is non-symptom. Exposure to levels of 100ppm for minutes or 10000ppm for 30 seconds can be fatal. Normally, human ole factory capabilities can detect ozone in the ambient air at levels of about 0.1ppm. Figure 2.2: Concentration/time relationships between exposure to ozone and human response (Rice et al., 1986) Because of its toxicity, the Occupational Health and Safety Administration (OSHA) have set the maximum human allowable exposure to ozone for an eighthour period at 0.10ppm and for a 15 minutes dose at 0.30ppm.

32 Catalyst Catalyst is a substance that can cause a change in the rate of a chemical reaction without itself being consumed in the reaction. The changing of the reaction rate by use of a catalyst is called catalysis. Substances that increase the rate of reaction are called positive catalysts or, simply, catalysts, while substances that decrease the rate of reaction are called negative catalyst or inhibitors. Catalyst work by changing the activation energy for a reaction i.e the minimum energy needed for the reaction to occur. This is accomplished by proving a new mechanism or reaction path through which the reaction can proceed. When the path has lower activation energy, the reaction rate is increased and the reaction is said to be catalyzed. If the activation energy for the new path is higher, the reaction rate is decrease reaction is said to be inhibited. For industrial application there are several characteristic needed for catalyst (Pirkanniemi and Sillanpaa.,2002): 1) High activity 2) Resistance for poisoning and stability in prolonged use at elevated temperature 3) Mechanical stability and resistance to attrition 4) Non-selectivity in most cases 5) Physical stability in various condition

33 Types of Catalytic Reactions Catalysts can be divided into two main types - heterogeneous and homogeneous. In a heterogeneous reaction, the catalyst is in a different phase from the reactants. In a homogeneous reaction, the catalyst is in the same phase as the reactants Heterogeneous catalysis A heterogeneous catalyst exists in a different phase from the reactant molecules. Typical examples involve a solid catalyst with the reactants as either liquids or gases. Many important industrial reactions are catalyzed by the surfaces of special solid materials. Heterogeneous catalysts are often composed of metals or metal oxides. The greater the surface area of a heterogeneous catalyst, the more reactions can take place. Thus, in manufacturing heterogeneous catalysts techniques are used to maximize the surface area (e.g. using highly porous structures). The initial step in heterogeneous catalysis is the adsorption of reactants onto the surface of a catalyst. The surfaces of metal catalysts are highly reactive in comparison to interior atoms. Interior atoms have fully satisfied bonding interactions with neighbor atoms. Atoms on the surface lack a complete set of bonding partners, and thus can bind and react with other molecules in the environment. Most examples of heterogeneous catalysis go through the same stages: One or more of the reactants are adsorbed on to the surface of the catalyst at active sites. Adsorption is where something sticks to a surface. An active site is a part of the surface, which is particularly good at adsorbing things and helping them to react.

34 17 There is some sort of interaction between the surface of the catalyst and the reactant molecules, which makes them more reactive. This might involve an actual reaction with the surface, or some weakening of the bonds in the attached molecules. The reaction happen at this stage, both of the reactant molecules might be attached to the surface, or one might be attached and hit by the other one moving freely in the gas or liquid. The product molecules are desorbed. Desorption simply means that the product molecules break away. This leaves the active site available for a new set of molecules to attach and react. A good catalyst needs to adsorb the reactant molecules strongly enough for them to react, but not so strongly that the product molecules stick more or less permanently to the surface. Silver, for example, isn't a good catalyst because it doesn't form strong enough attachments with reactant molecules. Tungsten, on the other hand, isn't a good catalyst because it adsorbs too strongly. Metals like platinum and nickel make good catalysts because they adsorb strongly enough to hold and activate the reactants, but not so strongly that the products can't break away. 2.3 Study of Catalytic Ozonation process Ozone is a powerful oxidant able to oxidize a great number of organic and inorganic materials. Ozone based technologies research is also being focused on the catalytic ozonation where the presence of catalyst significantly improved the oxidation rate of organic compounds compared to non-catalytic ozonation. However, the characteristics of the wastewater such as ph, temperature and concentration of organic pollutant play an important role in organic degradation (Adam et al.,1997). The pertinent literatures on the catalytic ozonation and catalytic ozonation technique studied by other researchers are presented in following section.

35 18 Stockinger et al., (1996) investigated the ozonation of synthetic wastewater containing 1000mg/L of N-methylmorpholine-N-oxide (NMMO) in batch experiments at different ph-values. The authors found that increasing ph caused higher initial elimination rates of NMMO as well as higher formation rates of nitrate. NMMO can be oxidized by ozone most efficiently at neutral ph values. The authors stated that an increase of the ph causes a higher ozone self-decomposition due to the oxidation of NMMO by OH-radicals that are formed particularly at high ph, thus increased the elimination rate of NMMO at higher ph-values. Stockinger and his coworkers concluded that the shortest elimination period NMMO was obtained at ph 7, whereas at ph 4 (low concentration of OH) and at ph 8.5 (high concentration of OH and high ozone self-decomposition), the degradation time was longer. The oxidation rate of total organic carbon (TOC) was lowest at ph 4 and had about the same value in experiment at ph 7 and 8.5. Ormad et al. (1997) presented the degradation of organochloride compounds by O 3 and O 3 /H 2 O 2 where their study was to identify the best system between O 3 and O 3 /H 2 O 2. The oxidation process were carried out using ozone (O 3 ) in basic medium (ph 9.4) at low dosage of ozone (0-1.5g/liter) and in the presence of hydrogen peroxide (H 2 O 2 ) with 0.5 H 2 O 2 /O 3 molar ratio. During the treatment many compounds were removed (dichlorobenzophenone, tetradifon, chlorobenzene and trichlorobenzene). The author found that, approximately 80% of chlorobenzene was degraded with 0.23g O 3 / liters in both O 3 and O 3 /H 2 O 2 treatments. A total disappearance was achieved using O 3 /H 2 O 2 after dosage of 1.51 g O 3 /liter. Using a dosage of 0.23g O 3 / liters, 50 and 62% percent degradation of 1,2,4- tricholorobenzene (1,2,4-TCB) was achieved in the treatment of O 3 and O 3 /H 2 O 2, respectively. The authors identified that O 3 /H 2 O 2 was more effective than O 3 alone to remove 1, 2, 4-TCB. Finally, only 7% of initial 1,2,4-TCB remained after the consumption of 1.51g O 3 /liter in O 3 /H 2 O 2 treatment. The authors was reported that, the pesticide tetradifon was totally removed (<98%) with a dosage of 0.23g O 3 /liter in both treatment. The degradation of dichlorobenzophenone was achieved 80 and 85% with a dosage of 0.35 go 3 /liter with O 3 and O 3 /H 2 O 2, respectively. The O 3 /H 2 O 2 system appears to be more efficient than the O 3 /high ph system alone to remove chlorobenzenic compounds under this experimental condition.

36 19 Cooper and Burch., (1999) investigated the potential of heterogeneous catalytic ozonation on the oxidation of aqueous halocarbon compounds. The experiment was carried out using alumina and modified alumina material for oxalic acid oxidation. The authors found that there are some differences between alumina and modified alumina, but no significant difference between the two modified alumina materials (Fe 2 O 3 / Al 2 O 3 and TiO 2 / Al 2 O 3 ) in the degradation 1000ppm of oxalic acid, chloroethanol and chlorophenol. Table 2.2 shows the observed degradation at the end of the experimental time or when complete degradation had occurred. Table 2.2: Comparison of the degradation of three model compounds under various conditions. Compound Observed % degraded with O 3 alone Experimental observed % degraded with ozone plus: Al 2 O 3 Fe 2 O 3 /Al 2 O 3 TiO 2 /Al 2 O 3 Oxalic acid Chloroethaonal Chlorophenol Degradation of 0.002moldm -3 2,4-Dichlorophenoxyacetic acid (2,4-D) by catalyzed ozonation using TiO 2 /UVA/O 3 and Fe(II)/UVA/O 3 systems was investigated by Piera et al., (2000). The lowest reduction rate appears with the use of the TiO 2 photocatalyzed reaction in absence of ozone (after 2h only 35% the initial 2,4-D has reacted). For the rest experimental situations (TiO 2 /UVA and Fe(II)/UVA), with the presence of ozone in solution, 2,4-D is almost fully degraded in no more than 45 minutes. The researchers found that the presence of TiO 2 and Fe(II) significantly enhanced the reaction rate. The best results were obtained using Fe(II), with a t 1/2 of 2,4-D degradation. The authors found that a similar behavior was observed on the concentration of TOC with reaction time. The reason that make the Fe(II)/UVA/O 3 system the faster for 2,4-D degradation among the different combinations studied in the present work seem to be : the ratio OH produced per O 3 consumed is 1:1, and the particularly fast steps for O 3 activation. In addition, the

37 20 Fe(II)/UVA/O 3 system a different reaction pathway can be envisaged. Fe(II) directly reacts with O 3 to generate the intermediates FeO 2+, species that evolves to OH and indicated by the following reaction mechanism (2.1) and (2.2): Fe 2+ + O 3 FeO 2+ + O 2 (2.1) FeO 2+ + H 2 O Fe 3+ + OH + OH - (2.2) Gracia et al., (2000) stated that the TiO 2 - catalyzed ozonation of raw EBRO river water. Degradation of organic matter and TOC removal were measured and comparing the presence of catalyst with ozone alone. The authors found that the TOC removal obtained was greater in the presence of TiO 2 catalyst in the ozonation system compared with ozonation alone, under the same operating conditions. The percentage of TOC reduction was 13.4% with the presence of catalyst in ozonation process while TOC reduction was 11.2% and 9.6% for ozonation alone and catalyst without ozone, respectively. The TOC removal was slightly increased to 16.4% with the presence of catalyst at a high dosage of ozonation. The study concluded that the removal of TOC increases in the presence of catalyst in ozonation process and increases with ozone dosage. Kasprzyk et al., (2003) found that O - or OH radicals are generated (the O 2 - transfer an electron to another ozone molecule to form an ozonide anion, O 3 -, which is the chain reaction promoter and produces OH radicals). Free radicals can initiate a radical chain reaction both on the surface of the catalyst and in the bulk of the aqueous phase. The authors also stated that the ozone decomposition depends on the ph of the solutions. At acidic ph to neutral ph, free radicals are not formed, which results in lower catalytic ozone decomposition. However, at basic ph, ozonide and atomic oxygen adsorbed on the surface and free hydroxyl radical are formed. The authors concluded that the reaction kinetics was strongly to depend on ph where ozone decomposition increases with increasing ph of the solution. At ph 6.0, the ozone decomposition rate in organic phase is and increases at higher ph, i.e at ph 10.3 and 11.4, the ozone decomposition constant is 1.8 and 2.4 min -1, respectively. The ozone decomposition constants in aqueous phase at ph 6 and 10

38 21 are and 2.1 min -1. The authors concluded that the values strongly depends on ph and increases with increasing ph of the solution. Canton et al., (2003) investigated the mineralization of 100mg/L of phenol in aqueous solution by ozonation using iron and copper salts and light with Fe(II) catalyst under room temperature. The authors found that the lowest reduction appears with ozonation alone (44%) while the combination of ozone with light or with iron slightly improves the TOC removal, at 56 and 52%, respectively. However, introduction of light and iron, leads to an important increase in mineralization, obtaining more than 90% in only one hour and almost complete mineralization (97%) in two hours. The performance of Fe(II) was observed with more concentrated pollutants i.e 250ppm of phenol where the ozonation combined with light and Fe(II) system is the most effective process to reduce TOC, allowing 90% reduction in two hours. An organic carbon removal rate of phenol was 0.97, 1.35 and 1.65gC -1 for 100, 250 and 500ppm, respectively. The study indicates that the phenol degradation rates increases with increase in phenol concentration. Tong et al., (2003) studied the characteristics of MnO 2 catalytic ozonation of sulfosalicylic acid (SSal) and propionic acid (PPA) in water. The experiments were focused on different type of MnO 2 on SSal and PPA and the ph of solutions at temperature 20 0 C. The TOC and COD contents of the aqueous solution were measured and concentration of SSal and PPA were analyzed by HPLC. The authors found that there was no difference using different type of MnO 2 (12.3mg Mn 2+ /O 3, 3g- MnO 2 /O 3, 3g -MnO 2 /O 3, 5.1g MnSO 4 /O 3 ) in catalytic ozonation of SSal at ph 1.0. Then, the similar experiments were carried out using same type of catalysts at ph 6.8. The authors reported that the catalytic ozonation using - MnO 2 /O 3 and 3g - MnO 2 /O 3 have no catalytic efficiency, which shows that the ph of solution was a dominant factor on MnO 2 catalytic ozonation process. Similar results was obtined in buffered solution ph=8.5. The study proved that degradation of SSal with MnO 2 /O 3 and3g -MnO 2 /O 3 decreases with increasing ph of SSal solution. Similar experiments were carried out on PPA solution which the authors found that the

39 22 removal of PPA by ozonation alone was negligible because both PPA and iron PPA were not reactive to ozone. In addition, no improvement was observed using different type of MnO 2 at ph 1.0 and 6.8. Graham et al., (2004) studied on the influence of ph on the degradation of phenol and chlorophenol i.e 4-chlorophenol (CP), 2, 4-Dichlorophenol (DCP) and 2, 4, 6-trichlorophenol (TCP) with potassium ferrate. The experiment was carried out over a wide range of ph (5.8-11) and at different ferrate and pollutant molar ratio. The authors found that the maximum phenol degradation ( 80% at ferrate: phenol=5:1) occurs at a ph approximately 9.2. At similar ph, a complete degradation of CP was observed at ferrate: CP molar ratios>6. In case of DCP, much greater degradation was observed under ph (70% degradation at 5:1 molar ratio). The authors also observed that the very high degree of TCP degradation at ph 5.8 and 7 when the rate of ferrate decomposition was high. They concluded that ph was an important factor that influence the nature of the reaction between the oxidant and relations species. Thus, the overall extent of compound degradation by ferrate was found to be highly ph dependent, and the optimal ph (maximum degradation) decreased in the order: phenol/cp (ph 9.2), DCP (ph 8), TCP (ph7) Qu et al., (2004) observed the performance of Cu/Al 2 O 3 catalyst in the ozonation of alachlor under constant temperature of 20 0 C. A Cu/Al 2 O 3 was used as a catalyst and experiment without catalyst was also carried out, and the results were compared to those of the catalytic process. The authors found that Cu/Al 2 O 3 was a very effective in the ozonation process where the removal rate of alachlor in total organic carbon (TOC) with ozonation in the absence of Cu/Al 2 O 3 was only above 20% in 180 min, while the reduction of TOC in the presence of Cu/Al 2 O 3 was more than 60%. Correspondingly, more organic ions created and fewer by-products produced in mineralization of alachlor in ozonation. The results clearly indicated that the use of Cu/Al 2 O 3 substantially enhanced the mineralization of alachlor in ozonation.

40 23 Beltran et al., (2004) reported the use of TiO 2 /Al 2 O 3 catalyst to improve the ozonation of oxalic acid in water under 20 0 C. Heterogeneous catalytic ozonation experiments were carried out under the conditions by varying the gas flow rate, agitation speed, catalyst particle size, and temperature, mass of catalyst, initial oxalic acid concentration and ozone concentration. The authors found that oxalic acid was sufficiently removed from water in the presence of ozone and a TiO 2 /Al 2 O 3 at ph 2.5 with the oxalic acid conversion of 80% in three hours. There effect of gas flow rate was not observed on the oxalic acid removal rate until the value of this variable was increased higher than 24L/h. Additionally, agitation speeds higher than 400min -1 did not lead to any improvement of the oxalic acid removal rate. The authors reported that the effect of oxalic acid concentration was not so clear and the removal rate was increased with mass of catalyst. The removal rate of oxalic acid was between 22 and 79% at temperature of 10 and 40 0 C, respectively after three hours of reaction. The removal rate was decreased with increasing the temperature (more than 40 0 C) as increase of temperature leads to decrease of ozone solubility in water, which possibly was the main factor that influences the process efficiency at higher temperature. Einaga and Futamura (2004) studied the catalytic oxidation of benzene with ozone over alumina-supported manganese oxides under room temperature (22 0 C) to observe the behavior of benzene oxidation and CO x formation. The author found that the rate of benzene oxidation is almost independent of Mn loading level of MnO 2 /Al 2 O 3 in the range 5-20 wt%. A strong correlation was observed between the decomposition rate of 100ppm benzene and ozone. Catalyst was significantly deactivated due to the buildup of the intermediates on the catalyst surface during the course of benzene oxidation. The weakly bound compound was removed by heat treatment at C in the O 3 flow. A higher temperature (430 0 C) is necessary for the complete oxidation of the latter species. Ozonation of the azo dye Cationic Red X-GRL was investigated by Zhoa et al., (2004) in bubble column reactor at varying operating parameters such as oxygen flow rates, temperature, initial Cationic Red X-GRL concentration and ph. The authors found that the increase in ph yield an increased conversion of dye although

41 24 the differences were almost negligible at ph 8.14 and The concentration of hydroxyl radical, which can enhance the indirect attack rate, to dye is also increased with ph. The evolution of the conversion of dye with different initial dye concentration was also investigated and the authors concluded that increased of initial dye concentration leads to a decreased in conversion of dye. Dye has completely disappeared if the starting concentration is 7.25 x 10-5 M, while 96 and 83% conversion was reached in the initial dye concentration is 1.32 x 10-4 M and 2.10 x 10-4 M, respectively after 6 min of reaction time. The authors also found that the conversion of dye increase when increase in oxygen flow rates where the conversion of dye are 93, 87 and 67% for oxygen flow rates of 100, 70 and 40L/hr, respectively. Oguz et al., (2005) investigated the ozonation of synthetic wastewater containing Bomaplex Red CR-L dye in a semi-batch reactor by ozonation, as a function of initial dye concentration (400, 600, 800 and 1000mg/L), temperature (18, 40 and 70 0 C), ozone-air flowrate (5, 10 and 15 L/min), ph (3, 6, 9.3 and 12) and ozone generation percentage (0.7, 1.1 and 1.4%). The authors found that the efficiency of dye removal was increased with ph, ozone generation rate and decreased with increasing temperature, but remained with increasing ozone- air flowrate and initial dye concentrations. The efficiency of COD removal from synthetic wastewater was increased with increasing ph, ozone generation percentage, but deeply changed with increasing initial dye concentration, ozone-air flowrate. However, the efficiency of COD removal decreased with increasing temperature. In this study, dye removal from synthetic wastewater in excess of 99% was obtained at an oxidation time of 15 min. The efficiency of COD removal was between 56 and 35% at an oxidation time of 30 minutes. The authors concluded that ozonization was an efficient process for dye removal from synthetic wastewater of Bomaplex Red CR-L. But ozonization alone was not an efficient method to remove all the compounds from the textile wastewater. Table 2.3 presents the list of catalytic ozonation of phenol and phenolic compounds and Table 2.4 presents the list of catalytic ozonation of non-phenolic compounds.

42 25 Table 2.3: List of catalytic ozonation studies of phenol and phenolic compounds Paper title Wastewater Type of catalyst Parameter Major findings Author Mineralization of phenol in aqueous solution by ozonation using iron or copper salts and light Comparison of different advanced oxidation processes for phenol degradation. System = O 3, O 3 /UV, O 3 /H 2 O 2 /, O 3 /UV/H 2 O 2 The important role of the hydroxyl ion in phenol removal using pulsed corona discharged Phenol and substituted phenol AOP remediation Characterization and activity of Fe-ZSM-5 catalyst for the total oxidation phenol in Phenol Ferum Laboratory installation Pollutant concentration = 100 and 250 ppm Flow rate= 5.5 g/hr, ozone concentration = 15.3g/dm 3 free evolution of ph, room temperature and catalyst concentration =1mM Fe(III) and 1mM Fe(II) Pilot plan installation Pollutant concentration = 100, 250 and 500 ppm, Flow rate= 7.5 g/hr, ozone concentration = 15.3g/dm 3 free evolution of ph, room temperature and catalyst concentration =1mM Fe(III) and 1mM Fe(II) Phenol - Concentration of phenol= ppm, ph = 3-9, batch operation, recirculation flow = 100L/hr, temperature = C Phenol - Temperature = 10 0 C, Volume reaction = 250mL, Ozone flow = 50g/hr, concentration of phenol= 50ppm Phenol, 4- nitrophenol and 4- cholorophenol Phenol TiO 2 Temperature= 20 0 C, Ozone concentration =10-4 M, Ozone flow rate= 50L/hr, TiO 2 concentration=1.5g/l, Phenol concentration=2.1 x 10-3 M, ph 6.3, concentration of nitrophenol = 1.4 x10-3 M, ph 4.7, p-cholorophenol concentration= 1.6 x 10-3, ph 5.1 Fe-ZSM-5 and Fe2O 3 /silicalite Reaction volume = 250mL, Temperature = 343K, atm pressure, catalyst weight = 0.2g, Si/Fe ratio = Catalytic ozonation is more effective than simple ozonation for all the cases studied Ozonation process gave a best result at basic ph condition The effect of solution ph on phenol oxidation using corona discharge mainly contributed to the effect of solution ph on the ozone oxidation In general, the presence of titania favours COD and TOC elimination even for those processes where the parent compound depletion rate is decelerated Framework Fe can catalyze more completely Canton et al., (2003) Esplugas et al., (2002) He et al., (unknown) Gimeno et al., (2005) Phu et al., (2001)

43 26 aqueous solution 43 to 203, concentration of phenol= 2500ppm phenol oxidation than the extra framework Fe does Oxidation of aqueous phenol by ozone and peroxidase Phenol - Phenol concentration = 0.3mM-10mM Ozone decomposition in aqueous solution increases significantly Catalytic oxidation of benzene with ozone over alumina-supported manganese oxides An investigation of catalytic ozonation for the oxidation of halocarbon in drinking water preparation. Degradation of phenolic wastewater over Ni-oxide 2,4-dichlorophenoxyacetic acid degradation by catalyzed ozonation : TiO 2 /UVA/O 3 and Fe(II)/UVA/O 3 systems The influence of ph on the degradation of phenol and chlorophenol by potassium ferrate Catalytic and photocatalytic ozonation of phenol on MnO 2 supported catalysts Benzene MnO 2 /Al 2 O 3 Chlorophenol, oxalic acid and chloroethanol Alumina and alumina with TiO 2 /O 3 and Fe 2 O 3 /O 3 Room temperature= 295K Volume reaction =400cm 3, 10% titanium catalyst Phenol Ni-oxide Concentration of phenol=200mg/dm 3, catalyst concentration= g/dm 3, particle size range= mm, ph solution= 6-10, Temperature= K, 2,4- dichlorophenox yacetic Phenol, chlorophenol TiO 2, Fe(II) Potassium ferrate Volume reaction=100cm 3, temperature=25, Concentration of solution=2 x 10-3 mol/dm 3, ph=2, TiO 2 =2g/dm 3 Fe(II) = 10-3 mol/dm 3, ozone flow rate= 1.4 g/hr Concentration: Phenol =0.064M, trichloroethylene=0.01m, 4- chlorophenol=0.047m, 2,4- dichlorophenol=0.037m, 2,4,6 trichlorophenol=0.031m, various ph, room temp Phenol MnO 2 Volume reaction= 100cm 3, Phenol conc= 100ppm catalyst weight=1.0g, stirring rate=450ppm, temperature=298k, ozone conc= 2.15mg/L, gas flow rate= 50cm 3 /min with the ph Benzene oxidation almost independent of Mn loading level of MnO 2 /Al 2 O 3 in the range 5-20wt% Some difference between alumina and modified alumina but no significant difference between the two modified alumina materials Increase in catalyst amount causes an increase in the oxidation efficiency Presence of TiO 2 and Fe(II) significantly enhance the reaction rate. The best result obtained using Fe(II) ph was an important factor that influence the nature of the reaction between the oxidant and relation species Mn/TiO 2 catalyst showed significantly higher degradation activity, the main product being Wu et al., (2000) Einaga et al., (2004) Cooper and Burch, (1999) Christosko va et al., (2001) Piera et al., (2000) Graham et al., (2004) Villasenor et al., (2002)

44 27 Oxidation of aromatic compounds with UV radiation/ozone/hydrogen peroxide Effects of ozonation on the biodegradability of substituted phenols Catalytic ozonation for persistent organic pollutants mineral from water Aromatic compound Phenolic compound o-nitrophenol, pentachlorophe nol, hexachlorohexa ne benzoquinone H 2 O 2 Ozone production= g/hr, gas floe rate=60 ph is an important L/hr, reaction volume=2.5l, initial conc of variable which have phenol= 1.06 x 10-3 mol/l, temperature= C major contribution of the free-radical - ph = 7.02 Ozonation may be an effective means of reducing the toxicity of phenol-containing wastewaters Fe, Cu, Mn, Al 2 O 3 Ozonation air flow= 20L/h, ozone concentration= mgo 3 /min, ph=5.7, temperature= 21, pollutant solution debit=10ml/min, catalyst volume=12.5cm 3 (7.5g), reaction time=20min Operational parameter influence distinguished that catalytic activity increase together with temperature, organic substrate concentration, spatial velocity and decreasing. Morkini et al Adam et al., (1997) Buleandra et al

45 28 Table 2.4: List of catalytic ozonation studies of non-phenolic compounds Paper title Wastewater Type of catalyst Parameter Major finding Author The ozonation of pyruvic acid in aqueous solutions catalyzed by suspended and dissolved manganese Pyruvic acid Manganese oxide Catalyst weight=0-200mg, Volume reaction=800ml, Ozone flow rate= 36L/hr, ph = 2-4, Degradation of atrazine by manganese catalyzed ozonation-influence of radical scavengers. Ozonation of alachlor catalyzed by Cu/Al 2 O 3 in water Mesoporous materials for water treatment processes Characteristics of MnO 2 catalytic ozonation of sulfosalicylic acid(ssa) and propionic acis (PPA) in water Ozonation of wastewater containing N-Methylmorpholine-oxide (NMMO) Ozonation of aqueous Bomaplex red CR-L dye in a semi-batch reactor. Atrazine Manganese ph=7.0, Mn concentration=1000mg/l, ozone flow rate=85l/hr, atrazine concentration=3µm, Alchlor Cu/Al 2 O 3 Ozone flow rate=0.488mg/min, temperature=20 0 C, reaction volume=75ml, concentration of alachlor=200mg/l, Cu loading=10wt.%, Wastewater Ni/Al 2 O 3 Ozone flow rate=60dm 3 /h, reaction SSa and PPA MnO 2, β-mno 2, γ- MnO 2 volume=400cm 3, Volume reaction=150ml of PPA or SSa, SSa concentration=2.5 x 10-3 M, PPA concentration=2.0 x 10-3 M, ph= 2.5, 6.8, 8.5 NMMO - Concentration of NMMO=100mg/l Ozone concentration =59-65mg/L, gas flow rate=40ml/min, temperature=25 0 C Bomaplex red CR-L dye - Dye concentration= mg/l, temperature= C, ozone flow rate= 5-15 L/min, ph=3-12. Advanced oxidation processes represent a powerful mean for the abatement of refractory and/or toxic pollutants in wastewaters Small amount of Mn greatly increased the degradation rate of atrazine. Cu/Al 2 O 3 substantially enhanced the mineralization of alachlor in ozonation No difference was observed using different type of MnO 2 Increasing ph caused higher initial elimination of NMMO as well as higher formation rates of nitrate Efficiency of COD was increased with ph, ozone generation rate, dye concentration and ozone flow rate but decreased with increasing temperature Andreozzi et al., (1998) Ma and Graham., (2000) Qu et al., (2004) Cooper and Burch., (1996) Tong et al., (2003) Stockinger et al., (1996) Oquz et al., (2005) Catalytic ozonation of refractory organic model compounds in aqueous Oxalic acid, acetic acid, Aluminum oxide Ozone gas flow rate=100l/hr, ozone concentration=50g/nm 3, catalyst

46 29 solution by aluminum oxide A TiO 2 /Al 2 O 3 catalyst to improve the ozonation of oxalic acid in water. salicylic acid, succinic acid weight=2g, initial concentration of TOC=60mg/L Oxalic acid TiO 2 /Al 2 O 3 Gas flow rate= 12-36L/h, agitation speed= min -1, temperature= C, ozone gas concentration=15-45mg/l, catalyst concentration= g/l, oxalic acid concentration= 1.6 x 10-2 catalyst particle size= mm, mm The removal rate decreased with increasing the temperature. Agitation speed did not lead any improvement of the oxalic acid removal. Beltran et al., (2004)

47 Zeolite-Based Catalysts Zeolites are a family of crystalline aluminosilicate minerals. The first zeolite was described in 1756 by Cronstedt, a Swedish mineralogist who coined the name from two Greek words meaning boiling stones, referring to the evolution of steam when the rock is heated. About fifty natural zeolites are now known and more than one hundred and fifty have been synthesized for specific applications such as industrial catalysis or as detergent builders. Zeolites have a cage-like structure consisting of SiO 4 and AlO 4 tetrahedral joined by shared oxygen atoms (Figure 2.3). The negative charges of the AlO 4 units are balanced by the presence of exchangeable cations notably calcium, magnesium, sodium, potassium and iron. These ions can be readily displaced by other substances, for example heavy metals and ammonium ions. Figure 2.3: Primary building unit of SiO 4 and AlO 4. tetrahedral Zeolites were chosen as catalysts in this study, due to demonstrated enhancement of organic dye compound degradation, which was reported by many researchers (Fujita et al, 2004; Phu et al, 2001). Zeolites also has been reported that highly oxidative media promotes oxidation reaction molecules adsorbed on the

48 32 surface of solid particles. Zeolites may also act as ion exchanges because the loosely bound nature of the extra framework metal ions allows for exchange of other types of metal when in aqueous solution The Structure of Zeolites. Zeolite structure contains two types of building units namely, primary and secondary. A primary building unit (PBU) is the simpler and is illustrated in Figure 2.4, a tetrahedron of (TO 4 ) of 4 oxygen ions surrounding a central ion of either Si 4+ or Al 3+. These PBU are linked together to form a three- dimensional framework and nearly all oxygen ions are shared by two tetrahedral. Figure 2.4: Primary and secondary building units in zeolites.

49 33 Zeolite structure also contains secondary building units (SBUs), which are formed by the linking of primary building tetrahedral (PBU). They consist of single and double rings of tetrahedral, forming the three dimensional structure of the zeolite material. Secondary building units may be assembled in different ways to produce different types of framework. Zeolite structures consist of silicon cations (Si 4+ ) and aluminium cations (Al 3+ ) that are surrounded by four oxygen anion (O -2 ). Each oxygen anion connects two cations and this yields a macromolecular three- dimensional framework, with net neutral SiO 2 and negatively charged AlO - 2 tetrahedral building blocks. The negative charge rises from the difference in formal valency between the silicon and aluminium cation, and will be located on one of the oxygen anion connected to an aluminium cation. Commonly, the negative charged is compensated by additional non-framework cations like sodium (Na + ), which is generally present after the synthesis of the zeolite. However for catalysis applications, sodium ions are mostly replaced by proton (H + ) that form a bond with the negatively charged oxygen anions of the zeolites and the structure of zeolite is presented in Figure 2.5 (Masschelein, 1982). Figure 2.5: Zeolite structure

50 Framework Structure of Zeolites A defining feature of zeolites is that their frameworks are made up of 4- connected networks of atoms. One way of thinking about this is in terms of tetrahedra, with a silicon atom in the middle and oxygen atoms at the corners. These tetrahedra can then link together by their corners to from a rich variety of beautiful structures (Figure 2.6). The framework structure may contain linked cages, cavities or channels, which are of the right size to allow small molecules to enter - i.e. the limiting pore sizes are roughly between 3 and 10 Å in diameter. Figure 2.6: Framework structure of zeolite The zeolite structure consists of a pore system with channels in one, two or three dimensions and additionally inner cavities may be present. The diameters of the pores and cavities range from 3Å to 12 Å, which coincides with the dimensions of many hydrocarbon molecules for which they are applied as adsorbents and catalysts. The exact diameter of the pore depends on the coordination and the amount of cations and anions present in the structure that are interconnected by 12 membered ring (MR) channels, which means that there are 12 cations ( Si 4+ and Al 3+ ) and 12 O 2- anions present in the ring. Ferrierite (FER) is a two-dimensional zeolite with 10 MR

51 35 main channels, which are interconnected via smaller 8 MR side channels. Another zeolite containing 10 MR channel in ZSM-5 (MFI). For this zeolite the straight 10MR channels are interconnected by 10MR zigzag channels, which make zeolite three-dimensional Mordinite (MOR) is a 12 MR zeolite with the channels running in only one dimension. The 12 MR channels contain small 8MR side pockets. The framework structure of zeolite beta possesses three-dimensional 12-membered ring pores with interconnected channels larger than most micro porous zeolites Zeolite Beta Catalyst Zeolite beta is high silica, large pores crystalline aluminosilicate and has been used as an acid catalyst in organic chemical conversion. The framework structure of zeolite beta possesses three-dimensional 12-membered ring pores with interconnected channels larger than most microporous zeolites and exhibits catalytic performances competitive with those widely used as catalyst on an industrial scale such as Y-type and ZSM-5 zeolites. Zeolite beta is one of the most commonly used catalysts in several aromatic alkylation processes. This type of catalyst has been widely studied, and its stability verified in industrial application. Zeolite beta, a highly performed, environmentfriendly catalyst, acts as a substitute for the solid H 3 PO 4 and AlCl 3 for benzene propylation. Under the reaction conditions, zeolite beta shows high activity, selectivity and stability, where benzene, the reagent act as a solvent and shows that it is able to extract carbonaceous deposit from the pores of the catalyst, to alleviate the deactivation to some degree. Figure 2.7 presents Beta catalyst formed by 12- memebered oxygen rings, which means the window is formed by 12 tetrahedral which are connected via shared oxygen atoms.

52 36 Figure 2.7: The structure of Beta catalyst ZSM-5 Catalyst The substitution of an aluminum ion (charge 3+) for a silicon ion (charge 4+) requires the additional presence of a proton. This additional proton gives the zeolite a high level of acidity, which causes its activity. ZSM-5 is a highly porous material and throughout its structure it has an intersecting two-dimensional pore structure. ZSM-5 has two types of pores, both formed by 10-membered oxygen rings. The first of these pores is straight and elliptical in cross section; the second pores intersect the straight pores at right angles, in a zigzag pattern and are circular in cross section. This unique two-dimensional pore structure allows a molecule to move from one point in the catalyst to anywhere else in the particle. The large openings are the elliptical, straight pores in ZSM-5. An 8-oxygen ring zeolite will not produce molecules with 6 or more carbons, molecules of this size will not fit into the small pores of these zeolites. Figure 2.8 presents the structure of ZSM-5 catalyst.

53 37 Figure 2.8: The structure of ZSM Transition Metal and Their Application in Wastewater treatment Transition metals are the 38 elements in groups 3 through 12 of the periodic table. As with all metals, the transition elements are both ductile and malleable, and conduct electricity and heat. The interesting thing about transition metals is that their valence electrons, or the electrons they use to combine with other elements, are present in more than one shell. This is the reason why they often exhibit several common oxidation states. There are three noteworthy elements in the transition metals family. These elements are iron, cobalt, and nickel, and they are the only elements known to produce a magnetic field. Compared to Group II elements such as calcium, transition elements form ions with a wide variety of oxidation states. The transition metals show such a range of oxidation states because their partially filled d orbitals can accept or donate electrons in chemical reactions. Calcium ions typically do not lose more than two electrons, whereas transition metals can lose up to nine. The reason for this can be obtained by studying the ionisation enthalpies of both groups. The energies required

54 38 to remove electrons from calcium are low until you try to remove electrons from below its outer two s orbitals. In fact Ca 3+ has an ionisation enthalpy so high that it rarely occurs naturally. However a transition element like vanadium has roughly linear increasing ionisation enthalpies throughout its s and d orbitals, due to the close energy difference between the 3d and 4s orbitals. Transition metal ions are therefore commonly found in very high states. Transition elements tend to have high tensile strength, density and melting and boiling points. There are several common characteristic properties of transition elements: 1) They found colored compounds 2) They can have variety of different oxidation status 3) They are good catalyst 4) They are solid at room temperature 5) They found complexes The main parameter, which determines the catalytic properties of metal oxides, is acidity and basicity. The amount and the properties of the hydroxyl depend on the metal oxide. The hydroxyl groups formed at metal oxide surface behave as Bronsted acid site. Lewis bases are site located on the metal cation and coordinately unsaturated oxygen, respectively. Both Bronsted and Lewis acid sites are through to be the catalysts centres of metal oxide. Most of the commonly used metal oxides catalysts (Ti, V, Cr, Mn, Zn and Al) have state high oxidation state oxides. Fe, Co, Ni and Pb belong to group with intermediate stability of high oxidation state oxides. According to Kochetkova et al., (1992), catalytic activity of metal oxide catalysts during oxidation of phenol shows the following order. CuO > CoO > Cr 2 O 3 > NiO > MnO 2 > Fe 2 O 3 > VO 2 > Cd 2 O 3 > ZnO > TiO 2 > Bi 2 O 3

55 Modification of Zeolite-Based Catalyst Zeolite modification implies an irreversible change, unlike ion exchange or adsorption. There are a number of different ways that zeolites can be modified. The framework of the zeolite can be modified by synthesizing zeolites with metal cations other than aluminium and silicon in the framework. The framework of the zeolites can be modified by dealumination to increase the silica and increase the hydrophobic nature of the zeolite. There are many proprietary methods to modify zeolites that impart unique characteristics to them. The modification of zeolite catalyst is essential in order to control the acidity and shape selectivity. The modification will improve activity and selectivity of zeolite. The substitution of Al and Si into zeolite framework with some transition metal or non-transition metal has been performed by many researches (Anggoro., 1998). This step is known as a framework modification. Acidity structure properties of zeolite may be modified by incorporation of elements of different size and different chemical features. The elements can be loaded onto the zeolites by two different procedures; direct synthesis and post synthesis. Direct synthesis is carried out by introduction of the elements during the synthesis or crystallization stage. In the post synthesis, the elements are introduced after crystallization by ion exchanged. The combination of metal and acid sites will enhance the activity of reactants and the selectivity of desired products. Both metal oxide and acid site take part in the oxidation, dehydrogenation, and oligomerization of hydrocarbon in the methane oxidation process. So this catalyst is known as a bifunctional oxidative-acid catalyst. The degree of substitution of metals in zeolite framework can be determined by the Si/Al ratio (Anggoro., 1998).

56 40 The degree of zeolite acidity is also dependent on the Si/Al ratio. If the Si/Al increases, the acidity of zeolite decreases. This is because Al is bonded to four oxygen atoms in the tetrahedral directions and has a negative charged. Hydrogen ions will associate with negative charged framework oxygen to create Bronsted sites. Removing aluminium from the zeolite will reduce the acidity of zeolite. Zeolite containing catalysts can be loaded with metals in several ways. These include ion exchange of the zeolite from solution, impregnation from solution, adsorption from the gas phase and direct synthesis during catalyst formation of the solid metal component or its solution Impregnation Method The metal compounds are dissolved in a suitable solvent, commonly water, aqueous ammonia, dilute phosphoric acid and others. The solution is then slurries with the zeolite powder or shaken with the extrudates. This method differs from the exchange method in that the metal compound is associated with the catalyst rather than a replacement of cation by cation in the exchange procedure. Thus, the metals ions those are present as anions in the impregnation solution can be incorporated. Impregnation is the easiest method of making a catalyst. A carrier, usually porous, is contacted with a solution, usually aqueous, of one more suitable case of precipitated catalysts. The size and shape of the catalyst particles are that of the carrier. The impregnation technique requires less equipment since the filtering and forming steps are eliminated and washing may not be needed.

57 41 The disadvantages of impregnation are: It allowed only limited of material, which can be incorporated in the framework of catalyst. Interaction between impregnation solution and support are common place, and indeed useful in impregnation process. Several physical and chemical properties of metal oxides have to be considered when choosing the catalyst. The main physical variables are : surface area, density, pore volume, porosity, pore size distribution as well as mechanical strength and purity. The most important chemical properties are: chemical stability and especially the presence of active surface site such as Lewis acid sites, which are responsible for catalytic reactions. 2.6 Phenol Phenol, C 6 H 5 OH, a colorless, crystalline solid that melts at about 41 C, boils at 182 C, and is soluble in ethanol and ether and somewhat soluble in water. An aromatic alcohol, it exhibits weak acidic properties and is corrosive and poisonous. Phenol is sometimes called carbolic acid, especially when in water solution. It reacts with strong bases to form salts called phenolates. Phenol is important in industry in the production of certain artificial resins and in the synthesis of many drugs, dyes, weed killers, insecticides, and explosives. It is the simplest member of a class of hydroxy benzene derivatives, all of which contain a hydroxyl group attached to a benzene ring; these compounds may be thought of as derivatives of phenol and generically are called phenols. Figure 2.9 shows the formula structure of phenol.

58 42 Figure 2.9: The formula structure of phenol Ingestion of even small amounts may cause vomiting, circulatory collapse, paralysis, convulsions, and coma. Light sensitivity and sinus congestion are common with exposure to fluids or vapors. Fatal poising can occur through skin absorption. Phenol and related compounds rapidly denature all proteins they come in contact with, including skin. Severe burns may occur upon contact. A concentration of 1% phenol, used to prevent itching from insect bites and sunburn, applied over several hours, was reported to cause gangrene in one individual. Skin ulcerations, skin rashes, swelling, pimples, and hives have been widely reported. The anesthetic properties of phenols can allow extensive damage to skin tissue before pain is perceived. Phenol is a major pollutant present in the wastewater from several industries activities: coal mining, petrol refining, pharmaceutical production, steel and iron manufacture (U.S.EPA, 1980). Some researchers (Canton et al, 2003; Esplugas et al, 2002; Gimeno et al, 2005; Phu et al, 2001) were also comment that phenolic compound are prevalent in many industrial wastewater, including those from the manufacture of insect ides, herbicides, dye, pulp and paper and other synthetic chemicals. Depending on the number and nature of ring substituents, many phenolic compounds can be toxic.

59 43 Phenol, one of the most abundant pollutants in industrial wastewater, was chose as a model compound in this study due to extensive literature on phenol degradation by different type of advanced oxidation technologies. Although there have been many poisonings from phenolic solutions, phenol continues to be used in consumer products. The Environmental Quality ACT, 1974 has set a water quality standard for phenol of 1.0 mg/l, which discharge limit of phenol is 1.0 mg/l and the importance of developing treatment that achieve thus limit must be emphasized Ozonation of Phenol The reaction between ozone and organic matter can proceed in two different ways depending on the ozonation condition: through direct reaction of molecular ozone and the pollutants or indirectly through radical reaction (mainly through reaction with OH radicals) that can result from the decomposition of ozone. The direct reaction with molecular ozone is selective, while indirect reaction with hydroxyl radical is rather non-selective and faster. The combination of these two different pathways depends on the pollutants, the solution ph and the ozone dose fed. In general, phenol and substituted phenols have been found to be readily oxidisable (by molecular ozone) owing to the presence of the OH electron donor group, leading to electrophilic attack at reactive carbon (in the ortho and para position) on the aromatic ring. The reaction of phenol with ozone is controlled by the phenolate species in the ph range of drinking water. The mechanism of this reaction was found ozone is transformed into OH radicals in a first step, which subsequently led to the formation of hydroquinone and catechol. Figure 2.10 was shown the reaction between ozone and phenol solution.

60 44 Figure 2.10: Reaction of phenol with ozone 2.7 Process flow Scheme Ernst et al., (2004), were conducted the ozonation experiments in a semicontinues system (continuous for ozone gas supply, fixed volume of water sample). In their experiment, the reactor was 5.2L temperature-controlled glass column. The ozone was dispersed into solution by means of a porous glass membrane at the bottom of the column. Ozone gas flow was 100L/h and ozone concentration 50g/(Nm 3 ). The samples were taken every 5 minutes (each 100mL) during 60 minutes of the experiments and were filtered (0.45µm) subsequently. Beltran et al., (2002), were treated oxalic acid with TiO 2 powder catalyst. The experiments were carried out in glass cylindrical tank. Agitation was provided by a four blade turbine. The aqueous slurry (0.81) was prepared with a given amount

61 45 of powder catalyst (between 1 and 5 gram) and oxalic acid in concentration 8 x 10 3 M. The reactor was submerged in a thermostatic bath to keep the temperature constant. Once the slurry was achieved the experimental condition, an ozone-oxygen mixture with an ozone concentration between 7 and 55mg/L was feed to the reactor through a diffuser which situated at the reactor bottom. Then, samples were steadily withdrawn for analysis. In this study, the effectiveness of the treatment was evaluated in a semicontinuous system, which was built based on an example given in the above literature. Synthetic raw stock phenol solution was prepared by dissolving 0.12mL phenol into 1000mL distillation water to afford a solution of 100mg/L (100ppm). This concentration is convenient for study and most of the researchers was used 100ppm of wastewater for treatment (Canton et al., 2003; Esplugas et al., 2000; Gimeno et al., 2005; Villasenor et al., 2002; Stockinger et al., 1996; Oguz et al., 2005).

62 CHAPTER 3 METHODOLOGY As stated in the previous chapter the scope of work of the study comprised of firstly, screening of the zeolite-based catalysts, i.e Beta and ZSM-5, secondly modifying the selected zeolite based catalyst with ferum and titanium metals and finally the best-performed metal-based zeolite catalyst was subjected to various experimental operating conditions. Figure 3.1 presents the schematic experimental procedures or flow chart carried out in the study and is discussed in following section. 3.1 Screening of Zeolite-Based Catalyst The performance of the zeolite Beta (Si/Al: 25) and ZSM-5 (Si/Al: 30) (supplied by Zeolyst International) on the degradation of phenolic solution was first carried out in the experiments. The study was to screen the zeolite-based catalyst before it is modified with metals. Before being used as a catalyst, the zeolite-based

63 46 METHODOLOGY Catalytic ozonation Screening of zeolitebased catalyst Sec.3.1 Effects of operating variables Sec 3.3 Beta ZSM-5 Temperature 40, 55, 70 0 C Phenol conc. 200, 400, 800 ppm Ozone flow rate 0.6, 1.5,2.1 L/min Mass of catalyst 0.5, 3, 5 gm %wt of metal 2, 4, 6 wt% ph 3, 7, 11 Volume of phenol- 300ml, 500ml Best catalyst Modified with metals Screening of zeolite metal-based catalyst Sec 3.2 Ferum Titanium Analysis HPLC COD TOC Sec 3.4 (Analysis of phenol) Best Metal-based zeolite Catalyst Effect of operating variables Discussion and conclusion Figure 3.1: Summary of the experimental procedures of the study

64 47 catalyst was calcined to remove the organic species and impurities. Beta was calcined to C for period of 6 hours (Kunkeler et al., 1998) and ZSM-5 was calcined to C for period of 8 hours (Mohamed et al., 2005). Figure 3.2 presents the experimental set-up of the experiment. One gram of the powdered calcinated zeolite was added into a 100ppm (Villasenor et al., 2002) of 250mL phenol solutions (purchased from BDH chemical Ltd Poole England). The experiment was carried out at room temperature (Einaga et al., 2004) with a constant stirring rate of 300rpm (Hot plate stirrer Heidolph Model MR 3003). The solution was ozonated (Ozonia Model LAB2B) at the constant flow rate of 0.6L/min (Flow meter: OMEGA8 FL-1700 and FL-1800) for period of 60 minutes. Then, the experiment was stopped and the treated phenol solution was analyzed for its degradation. The concentration of ozone was controlled by variable output control knob setting of the ozone generator. A detail technical specification of the ozone generator is presented in Appendix A. The experiment was repeated with different concentration of phenol solution, reaction time and ozone flow rate. The best zeolite-based catalyst (i.e with the highest degradation of phenol) was selected and modified with metals for further investigation.

65 Cylinder Gas Excess ozonated air to KI solution Syringe CO 2, O 3 KI Solution NaOH Solution Flow meter Solution + catalyst Ozone generator Figure 3.2: Semi-continuous catalytic ozonation experimental set up.

66 Screening of Zeolite with Metal-Based Catalyst The selected zeolite-based catalyst was modified separately with metals ferum and titanium, by impregnation method using aqueous iron nitrate (reagent grade from Merck) and titanium (IV) ethoxide (Acros) solutions, respectively, followed by drying at C for 12 hours and subsequent calcinations at C for period of 6 hours. Figure 3.3 presents the flow chart of preparing metal-zeolite-based catalyst (Amin, N.A.S and Anggoro., 1999; Al-Jarallah et al., 1997). One percent of metal zeolite-based catalysts were prepared in the experiment. A small amount g of Fe (NO 3 ) 3 was mixed with approximately 10ml of distilled water until complete dissolved. Then 10g of selected zeolite-based catalyst was added to the solution and thoroughly mixed for at least 5 minutes. The mixture was kept to dry in an oven (Memmert) at C for a period of 12 hours and finally, the dried metal-based zeolite catalyst was calcinated (Carbolite type ELF 11/6B) at C for period of 6 hours in order to remove the organic templates and any possible impurities (He et al., 2002). The impregnated zeolite was characterized to confirm the presence of metal in the catalyst. The zeolite catalyst was ready to use in catalytic ozonation of phenol solution. The experimental procedures were repeated using g titanium (IV) ethoxide. A sample calculation on the preparation one percent of the metal in catalyst is presented in Appendix B. Catalytic ozonation of the metal-based zeolite catalysts was tested on 100 and 1600ppm of phenol solution and their respective performance on degradation of phenol was observed for a total period of 90 minutes reaction time similarly as in the previous experiment, one gram of the metal-based zeolite catalyst was utilized. The best-performed metal-based zeolite catalyst was selected and subjected for further experiments. The performance of metal-based zeolite on the degradation of phenol was tested under different experimental operating variables as discussed in the following section.

67 50 Distilled water Fe (NO 3 ) 3 (Metal salt) (0.4365g) 10 g zeolite catalyst Mixing Mixing Fe (NO 3 ) 3 solution Drying C, 12hrs Calcining Zeolite beta= C for 6hrs ZSM-5 = C for 8 hours Cooling Metal zeolite catalyst Figure 3.3: Schematic diagram on the preparation of the metal-based zeolite

68 The Effects of Operating Variables on the Degradation of Phenol The influence of different variables such as ozone flow rate, temperature and ph of phenol solution, mass and metal weight percent impregnated in the catalyst, concentration and the volume of phenol to be treated were investigated on the selected metal-based zeolite catalyst. The purpose of the experiment was to determine the best operating conditions of the degradation of phenol by the selected metal-based catalyst. In this study, the catalytic ozonation was carried out following the same experimental procedures as in the previous Section 3.1 but with a fixed reaction time of up to two hours. Table 3.1 presents the summary of the experimental variables (in column 1) and conditions (in column 2-8) carried out in the experiment. As presented in Table 3.1, each of the variables in column 1 was prepared and subjected to experimental conditions (in column 2-8). For an example, one gram of 2wt% of metal-based zeolite catalyst was used to treat 100pm of 250ml phenol solution with ozonation rate of 1L/min. The experiments was repeated with 4 and 6wt% of metal-based zeolite catalyst and subjected to the similar conditions. Similarly, the effect of other variables i.e ozone flow rate, temperature, ph, amount of catalyst, concentration and volume of phenol on the degradation of phenol was studied following the experimental conditions as presented Table 3.1. The values of the above parameters were chosen based on the conditions that have been used in the study of phenol treatment via ozonation and with catalysts. A typical concentration of phenol studied is 100ppm (Canton et al, 2003; Esplugas et al., 2002; Villasenor et al., 2002). The highest concentration of phenol studied so far was 2500ppm (Phu et al., 2001). However, in this study the maximum phenol concentration was controlled up to 1600ppm because concern about safety. High concentration of phenol needed large amount of oxidant to achieve a reasonable level

69 52 of phenol in the final solution. The evaluation of the treatment cost is at moment one of the aspect, which needs more attention. The aqueous phenol solution used in this study was prepared by diluting 0.12, 0.24, 0.48, 0.96, 2mL of the concentrated liquefied phenol into 1L of distillated water. These corresponded to 100, 200, 400, 800 and 1600ppm of phenol respectively. The temperature was controlled to room temperature to achieve best degradation of phenol and the ozonation process was carried out by some researchers under room temperature (Canton et al., 2003; Einaga et al., 2004; Piera et al., 2004; Adam et al., 1997). The maximum temperature studied for this study is 70 0 C (Phu et al., 2001) The ozonated gas flow rate has been used for ozonation of phenol in this study 1.0 L/min which follow the Cooper and Burch, 1999 and Morkini, The flow rate has been controlled up to 15 L/min by oguz et al., 2005 in ozonation of aqueous Bomaplex red CR-L dye in a semi-batch reactor.

70 Table 3.1: Experimental conditions for the degradation of phenol by metal-based zeolite catalyst variables Experimental condition Temperature ph Ozone flow rate L/min Metal weight %, wt% Amount of catalyst used, Volume of phenol Concentration of phenol, ppm gram treated, ml Metal weight %, Room Not (2, 4 and 6 wt %) temperature adjusted Ozone flow rates, Room Not (0.6, 1.5, 2.1L/min) temperature adjusted Temperature, (40, 55, - Not C) adjusted ph, (3, 7, 11) Room temperature Amount of catalyst Room Not used,(0.5, 3, 5 gram) temperature adjusted Concentration of Room Not phenol (200, 400, 800ppm) temperature adjusted Volume of phenol treated,(300, 500ml) Room temperature Not adjusted *The catalytic ozonation of phenol solution using metal-based zeolite catalyst was carried out up to 2 hours

71 Analysis of Phenol In this study, the determinations on the degree of degradation of phenol were performed using High Pressure Liquid Chromatography (HPLC), based on the Chemical Oxygen Demand (COD) and to some extend using total organic carbon (TOC) High Performance Liquid Chromatography Each of the treated samples of phenol was filtered using 0.45µm pore size nylon syringe filter prior to its determination using the high performance liquid chromatography (HPLC) with wavelength of 254nm UV adsorbance. The HPLC was equipped with an auto sampler (Waters 717 plus Auto sampler) and UV detector (Water 486 Tunable Absorbance Detector) and a reverse phase column (300 mm length, 3.9 mm inner diameter and 5µm particle size). A mixture of 40% acetonitrile (Fisher) and 60% of distilled water was used as the optimal mobile phase for phenol. The mixture was injected with a flow rate of 1 ml/min and 5µl volume of phenol. The percentage of degradation of phenol in the samples was calculated based on the peak area of the initial and the treated phenol solution as the following (Phu et al., 2001). Percentage of Degradation, %P = Where, P i P t = Peak area of initial phenol solution = Peak area of treated phenol solution P i P t x 100 P i (Eq 3.1)

72 Chemical Oxygen Demand The degradation of phenol in the experiment was also measured indirectly by determining the Chemical oxygen demand (COD) of the initial and the treated phenol solution. A 2mL of the sample was pipette in to the COD vial and placed on heated C COD reactor for two hours. Then, the sample was allowed to cool to C or less for approximately 20 minutes before it was determined calometrically at 420nm (HACH, 1992). The percentage COD removal in the sample was determined using the following equation, %COD removal = COD i COD t x 100 COD i Where, COD i is the initial chemical oxygen demand of phenol solution COD t is the final chemical oxygen demand of treated phenol solution (Eq 3.2) Total Organic Carbon The degradation of phenol in the experiment was also measured indirectly by determining the Total organic carbon (TOC) of the initial and the treated phenol solution. However, the determination of TOC was performed only on the selected set of experiment in this study.

73 56 Total organic carbon (TOC) of initial and ozonated samples were determined with TOC analyzer (Ve shimadzu) with 150 ml/min of gas flow rate and 300kPa of gas pressure. TOC analysis was performed by the Department of Physic, Faculty of Science, UTM skudai The percent degradation of phenol or reduction of the TOC in the sample was calculated by Equation 3.3 below. %TOC reduction = TOC i TOC t x 100 TOC i Where, TOC i = is the initial total organic carbon of phenol solution TOC t =is the final total organic carbon of treated phenol solution (Eq 3.3) 3.5 Characterization of Catalyst The characteristics of the based and modified zeolite-based catalysts were determined by x-ray diffraction and nitrogen adsorption technique. In this case, the crystallinity, pore size, the specific pore volume, specific surface area and average pore diameter of based and modified zeolite-based catalysts were determined by the techniques.

74 X-ray Diffraction The purpose of X-ray diffraction (XRD) patterns is to be able to determine the crystallinity and to confirm the structure of the catalyst. In addition, the technique is used to confirm if an element has been introduced into the lattice framework position within the structure of the catalyst with respect to the reference spectra. The crystallinity was determined by comparing on the intensity or area of one particular peak (or a number of peaks) to the intensity of the same peak of a standard sample which was designated to be 100% crystalline (Amin, N.A.S and Anggoro., 1999). The XRD crystallinity was calculated by Equation 3.4 below. X-ray crystallinity = Intensity of peak of sample x 100 Intensity of peak of standard (Eq 3.4) The XRD analysis was performed using Philips diffractometer (Model 1830) found at the Faculty of Mechanical, UTM. The XRD measurements on the catalyst was analyzed with CuKα radiation with λ = Å at 40 kv and 30 ma in the range of 2θ= 5 0 to 60 0 at a scanning speed of 4 0 per minute, with vertical goniometer at room temperature.

75 Nitrogen Adsorption The Nitrogen adsorption (NA) provides valuable information about the BET i.e surface area, micro pore area, micro pore volume and average pore diameter of a given samples. The sample was analyzed for nitrogen adsorption using a porosimeter (Micrometric Instrument Model ASAP 2000) with nitrogen gas as the adsorbate at 77K and with saturation pressure maintained at 760 mmhg. The analysis was performed at the Petronas Research & Scientific Sdn. Bhd., Kajang, Selangor.

76 CHAPTER 4 RESULTS AND DISCUSSION This Chapter presents the results and discussion of the studies. As presented in the previous chapter, the aim of the study was to investigate the performance of zeolite-based and modified zeolite-based catalysts subjected to different operating variables on the degradation of phenol solutions. The findings of the studies are presented and discussed in following section. A detail calculation of degradation of phenol is presented in Appendix C. Many studies have shown that the ozonation process is effective in removing a wide variety of organic contaminants (Langlais et al., 1991; Benitez et al., 1999). Thus, chemical oxidation using ozone is a way to reduce polyphenol content, and in addition, improve the biodegradability of these types of wastewaters, and hence the efficiency of the biological step (Benitez et al., 1999). From various researches carried out, the catalytic ozonation process is potentially a promising treatment technique to remove persistent organic pollutants in wastewater. Treatment occurs by adsorption, oxidation or both the adsorption and oxidation of organic compounds to CO 2, water and biodegradable organics.

77 Performance of Zeolite Beta and ZSM-5 Catalyst in Degradation of Phenol. The performance of the zeolite Beta and ZSM-5 catalyst on the degradation of phenolic solution was initially carried out in the experiments. In addition, as a comparison, a study on the degradation of phenol without application of catalyst was also performed. The aim was to screen the best performed zeolite-based catalyst before it is modified with metals in the following study. The preliminary experiment was carried out with three different experimental variables i.e ozone flow rate, concentration of phenol solution and reaction time. Other parameter such as temperature, mass of the catalyst used, ph solution and volume of phenol solution to be treated were made constant. The effects of the variables on the degradation of phenol are discussed in following section Effect of Ozone Flow Rates Table 4.1 presents the results of the effect of ozone flow rate on the degradation of phenol solution with and without catalyst, which shows that the degradation of phenol was higher with the presence of catalyst under both different flow rates of ozone after 60 minutes of reaction time. Similarly, the removal of COD and TOC was higher with the presence of catalyst. Thus, as expected, the degradation of phenol and removal of COD was higher with increase in the ozone flow rates.

78 Effect of Ozone Flow Rates Without Catalyst As in Table 4.1, in the case of without catalyst the degradation of phenol was increased from 44.9% to 69.3% with increased ozone flow rate of 0.6 to 2.1L/min, which indicates a significant degradation of phenol under ozonation influenced by increased ozone flow rate. Shiyun et al., (2003), found that a number of organic pollutants in water could be decomposed by ozonation such as phenols, amides, carboxylic acids, aromatics and halogenated derivatives. Ozonation of organic compounds in water with high ozone dosages usually produces oxygenated organic products that are more biodegradable. Table 4.1: Effect of ozone flow rates with and without catalyst Ozone flowrate L/min Catalyst Non catalyst ZSM-5 Beta Non catalyst ZSM-5 Beta Phenol degradation, % COD TOC Initial, mg/l Final, mg/l COD removal Initial, ppm Final, ppm TOC removal % % % % % % % % % Note: Concentration of phenol = 100ppm, reaction time=60 minutes, ph 6.5, concentration of ozone=2.142ppm.

79 62 However, Qu et al., (2004), described ozone is a powerful oxidant of various organic and inorganic compounds dissolved in water. Sometimes, it can completely decompose the organic pollutants and remove them from water. However, in most cases, the ozonation can only degrade the organic compounds in water to low molecular weight substances to present a very low removal rate of total organic carbon (TOC) and chemical oxygen demand (COD). An increase in flow is expected to cause a rise in the diffusion and mixing in the solution, which most probably will lead to improve the mass transfer for a successful reaction to occur. Under increase ozone flow rate, the free OH radicals are formed when ozone decomposed in water having a great oxidizing potential that increased the degradation rate of organic matter. There was a marked increase in the degradation of phenol of 24.4% when the ozone flow rate was increased from 0.6 to 2.1L/min, with an increment of degradation of 16.2% per one L/min ozone flow rate. During ozonation, the compounds produced are mainly intermediates. It is well known that ozonation is not only oxidation by ozone molecules but also by hydroxyl radicals generating system. A possible product is hydroxyl radical, which may react with the initial compound and all its intermediates. Carbon dioxide and water are also possible final products, as shown in Equations (4.1) to (4.3) (Shiyun et al., 2003): Compound i + O 3 Intermediates (1) O 3 Compounds + Intermediates + ( OH) intermediates (1)i + CO 2 + H 2 O 2 (+ OH), (Eq 4.1) intermediates (2)i + CO 2 + H 2 O 2 (+ OH), (Eq 4.2) Intermediates ( OH)i + CO 2 + H 2 O (Eq 4.3) The concentration of compound i and all the intermediates produced in the above reactions can be represented by CODi (COD of Compound i). Following is the discussion of COD analysis.

80 63 Similarly, results on the removal of COD of the solution (another indicator of organic degradation) were 44% and 49% for the ozone flow rate of 0.6 and 2.1 L/min, respectively. Only a slight improvement on the removal of the COD was observed even under increase ozone flow rate in this case compared to the degradation of phenol solution. The low percentage of COD removal observed probably due to the fact that the degradation of phenol resulted in the formation of other chemical species (non phenolic species) that contribute to the COD requirement of treated solution. Amat et al., (2003) found that, in the first stages of the ozonation process cleavage of the exocyclic double bond was the most likely process, to give benzaldehyde, in nearly quantitative yields. Then, opening of the aromatic ring occurs to give intermediates, which were in turn oxidized to small acids such as oxalic, formic and maleic acid, the final reaction products, together with CO 2 emission. A similar observation can clearly be seen from the HPLC spectrums of the treated phenol solution where the presence of other peaks were observed compared to the spectrum of the before treated phenol solution. Identifying of intermediates compounds was never carried out in this study. This finding was observed in all of the HPLC analysis of the sample and an example of the spectrum is presented in Figure 4.1.

81 64 Untreated Phenol Phenol Treated Figure 4.1: HPLC spectrum of the untreated and treated phenol sample Effect of Ozone Flow Rates With Catalyst Table 4.1 also presents the results of the degradation of phenol and COD removal using ZSM-5 and Beta catalyst under different ozone flow rate which showed that a similar trend whereby a higher degradation of phenol and removal of COD were observed with increase in ozonation. The application of both ZSM-5 and Beta catalyst in ozonation treatment improved the degradation of phenol under different ozone flow rate especially on the higher ozone flow rate of 2.1L/min compared to those without catalyst.

82 65 Bhat and Gurol, (1995) studied the ozonation of chlorobenzene in the presence of goethite and found the catalytic ozonation was more effective than ozonation alone. Similarly as observed in this study, the degradation of phenol was more effective with presence of zeolite-based catalyst than ozonation without presence of any catalyst. In addition, Naydenov and Mehandjiev, (1992) and Thompson et al., (1995) observed a mineralization of benzene and 1,4-dioxane in the aqueous solution obtained by ozonation in the presence of MnO 2. As presented in Table 4.1, the degradation of phenol was increased from 44.9% to 54.3% for 0.6L/min and from 69.3 to 74.1 for 2.1L/min without and with ZSM-5 catalyst. Similarly the degradation of phenol was also increased from 44.9% to 63.5% for 0.6L/min and 69.3 to 76.1% for 2.1L/min without and with Beta catalyst. However, the degradation of phenol was strongly enhanced using Beta compared to ZSM-5 catalyst under both different ozone flow rates. Degradation of phenol was increased from 54.3% (with ZSM-5) to 63.5% (with Beta) for 0.6L/min and 74.1% (with ZSM-5) to 76.1% (with Beta) for 2.1L/min. However, in a latter a lower percentage of degradation of phenol was observed which probably due to the permanent blockage of the catalysts active surface sites resulting in the decrease of catalytic activity. The COD removal of the solution was increased from 44% to 54% under 0.6L/min of ozone flow rate without and with the presence of ZSM-5 catalyst. A similar observation and a slightly higher COD removal were obtained i.e from 49% to 61%, with the presence of ZSM-5 catalyst at a higher ozone flow rate of 2.1L/min. Interestingly, the COD removal was much better with the presence of Beta catalyst compared to without catalyst where the percentage of COD removal increase from 44% to 66% and 49% to 70% under ozone flow rates of 0.6 and 2.1L/min,

83 66 respectively. Thus, based on the finding it seemed that Beta catalyst performed better than ZSM-5 catalyst in the removal of COD with the difference of 12% (i.e 66%-54%) and 9% (i.e 70%-61%) under ozone flow rate of 0.6 and 2.1L/min, respectively. The activity or performance of the catalyst was further investigated by analyzing the percentage of TOC removal after the ozonation process. However, the determination of the TOC removal was only performed on the samples under ozone flow rate of 2.1L/min. As presented in Table 4.1 the percentage of TOC removal obtained was significantly with the presence of catalysts compared to without catalyst added in the ozonation process under the same operating conditions. Without catalyst, the percentage of TOC removal was only 8.1% within 60 minutes of reaction time whereas with ZSM-5 and Beta catalyst the percentage of removal was drastically increased to 24% and 25.2%, respectively. Gracia et al.,(2000) reported that the TOC removal was greater in the presence of a catalyst in the ozonation system than without catalyst, performed under the same experimental conditions. In addition, Hayek et al., (1989) have shown that ozonation of phenol in the presence of catalyst Fe(III)/Al 2 O 3 leads to a significant increase of the TOC removals as compared to ozonation alone. Similarly, Hewes and Davinson, (1972) concluded that the presence of Fe(II), Mn(II), Ni(II) or Co(II) sulfate during ozonation of wastewaters induces an increase of TOC removal as compared to ozonation alone. A similar finding was also observed in this study where the enhancement of phenol degradation using either ZSM-5 or Beta was better when compared with ozonation without any catalyst. In addition and as observed in this study, the Beta was found to be the most effective zeolite-based catalyst compared to ZSM-5

84 67 catalyst with respect to phenol degradation and removal of COD especially under a lower ozone flowrate Effect of Concentration of Phenol The effect of concentration of phenol solution on the degradation of phenol with the presence of zeolite-based catalyst was also investigated in this study. A two extreme concentration of phenol solution i.e 200 and 800ppm was tested with and without catalyst under a fixed ozone flow rate of 1.0L/min. The results of the study are presented in following section Effect of Concentration of Phenol without Catalyst Table 4.2 presents the results of the degradation of phenol with and without catalyst under two extreme concentrations of phenol solution of 200 and 800ppm, which generally shows that the degradation and COD removal decreased with increasing concentration of phenol after 60 minutes of reaction time. The degradation of phenol without catalyst on 200 and 800ppm was 47.8% and 21.1%, respectively, which indicates that the degradation was lower for the higher concentration of phenol solution. Similarly, the COD removal on 200ppm phenol without the presence of any catalyst was 33% and removal of COD was decreased to 16% for the 800ppm concentration. The study demonstrates that the degradation and the removal of COD is influenced by the concentration of phenol in solution with other parameters remain unchanged. As expected, the increase in the concentration of phenol means that more of the generated ozone will have to react with undesirable organic intermediate

85 68 formed by the degradation of phenol apart from the phenol itself, thus, decreasing the effectiveness of degradation. However, varying in other operating parameter such as increase in ozone flow rate and reaction time could increase the degradation and COD removal of phenol. Canton et al., (2003), observed a similar result where the TOC removal decreases with phenol concentration. The authors found that the percentage of TOC removal was 90%, 50% and 21% for 100, 250 and 500ppm, respectively in their study of two hours reaction time. Their study indicates a lower degradation phenol with the increased in pollutants concentration, as observed in this study. The presence of organic matter in phenol solution can increase the percentage of ozone consumption. Therefore, it is anticipated that as the phenol becomes more concentrated, the consumption of ozone in the solution increases. Table 4.2: The effect of phenol concentration with and without catalyst Concentration of phenol 200ppm 800ppm Catalyst Non catalyst ZSM-5 Beta Non catalyst ZSM-5 Beta phenol degradation, % COD Initial, mg/l Final, mg/l COD removal, % Note: reaction time=60 minutes, ph 6.5, concentration of ozone=2.142ppm, Ozone flow rate=1l/min

86 Effect of Concentration of Phenol with Catalyst As presented in Table 4.2, the results on the degradation of phenol with the presence of ZSM-5 and Beta catalyst under different concentration of phenol presents a similar observation whereby a lower degradation of phenol and COD removal was obtained with increase concentration of phenol in the ozonation process. However, the degradation of phenol by catalytic ozonation was found to be more effective than ozonation without presence of any catalyst. The difference of degradation with and without ZSM-5 catalyst was 6.5% and Beta was 8.2% for 200ppm of phenol solution. While for 800ppm this was 14.0% and 16.4%, respectively. In both case the degradation of phenol increased with presence of catalyst as discussed in previous section. The degradation of phenol using ZSM-5 was 54.2% and 35.1% for 200 and 800ppm, respectively. In the case of Beta catalyst, this was 55.5% and 37.5% for 200 and 800ppm, respectively. The finding illustrated that Beta catalyst performed slightly better than the ZSM-5 catalyst. Figure 4.2 shows the percentage removal of COD under different concentration of phenol, which again illustrated that, the COD removal increased with the presence of zeolite-based catalyst and decreased with increasing the concentration of organic pollutants. It is noteworthy to observe that the COD removal was higher with the presence of Beta i.e 58% compared to ZSM-5 i.e 41% catalyst particularly in a lower concentration of phenol solution.

87 70 % COD remova Non catalyst ZSM-5 Beta Type of catalyst Phenol: 200 ppm Phenol: 800 ppm Figure 4.2: COD removal with and without catalyst with different concentration of phenol Effect of Reaction Time Contact time or reaction time is the time ozone has to oxidize and disinfect or the time the water is allowed to hold the disinfectant. The contact time needed varies with the matter to be oxidized. Time required for oxidation ranges from almost instantly to 10 minutes or more and more reaction time is better. There are several reasons more reaction is better: 1) Contaminants floc or precipitate at varying rates and with varying degrees of density, giving more time will often make a treatment system a success by providing time for material to fully precipitate which in turn enhances filterability.

88 71 2) Ozone must contact the contaminant to oxidize or disinfect, more contact time increases the odds that all water will be subjected to oxidation. The effect of reaction time on the degradation of phenol solution was also studied with and without zeolite-based catalyst. The concentration of phenol solution of 100ppm was treated with selected interval of ozonation time (i.e 15, 30, 45, 60, 75 and 90 minutes) under a fixed ozone flow rate of 1.0L/min and at room temperature. The percentage of degradation of phenol was measured at the end of the reaction time. In addition, the TOC removal was also measured but this was taken for only 90 minutes of reaction time and the results of the study is presented in following section. Table 4.3 presents the degradation of phenol under various reaction times, which shows the degradation of phenol increases with increase of reaction time. In addition, the degradation was higher with the presence of catalyst particularly with Beta catalyst. Similarly, the removal of TOC was higher in case of Beta catalyst compared to ZSM-5 and without any catalyst (Table 4.4). Table 4.3: The effect of reaction time in ozonation with and without catalyst Reaction time Concentration of phenol= 100ppm Time, min Non catalyst ZSM-5 Beta Degradation of phenol, % Note: Ozone flow rate=1l/min, concentration of phenol=100ppm, ph 6.5, concentration of ozone=2.142ppm, Ozone flow rate=1l/min

89 72 As presented in Table 4.3, the ozonation of phenol without catalyst causes the degradation of 35.3% merely after 90 minutes of reaction time. Approximately the same amount of phenol was degraded (37.7%) in the solution with ZSM-5 catalyst, which took 45 minutes of reaction time. In comparison, catalytic ozonation in the presence of Beta catalyst required only 15 minutes of reaction time to achieve a similar level of degradation. This indicates that the degradation was faster in the presence of Beta catalyst compared to others. Evidently, a marked difference of 18.4% of degradation was found between Beta and ZSM-5 catalyst after 90 minutes of reaction time. Figure 4.3 presents the percentage of phenol degradation against the reaction time, which clearly shows that the degradation rate (slope) increases with the presence of ZSM-5 and particularly Beta catalyst. The degradation rate of the latter was higher i.e 0.64% per minute compared to ZSM-5 catalyst, which was 0.46% per minute. This illustrates the performance of Beta is better than ZSM-5 catalyst in the degradation of phenolic solution under the study conditions. The degradation rate without catalyst was merely 0.36% per minute and as found in this study the presence of catalyst helps to increase the degradation of phenol. Phenol degradation, % Slope=0.64 Slope=0.46 Slope= Time, min Non catalyst ZSM-5 Beta Figure 4.3: Degradation of phenol with and without catalyst versus reaction time

90 73 Kasprzyk et al., (2004) stated that the degradation efficiency organic contaminants depend on the reaction time. The authors found that the degradation of Methyl tert-butyl ether (MTBE) was merely 53% after 3 hours of ozonation time. However, the same amount of MTBE was degraded within 1.5 hours with the presence of Perfluorooctylalumina (PFOA B ) catalyst. Similarly, the authors also found that the catalytic ozonation in presence of PFOA B required only 2 hours to achieve the same percentage of degradation of Ethyl tert-butyl ether (ETBE) and Tert-amyl methyl ether (TAME) when compared with the results of ozonation alone which took 3 hours of reaction time. A similar observation was observed in this study, where the degradation was increased in the presence of catalyst compared to ozonation without catalyst. The removal of TOC (Table 4.4) was higher with presence of catalyst than without catalyst after 90 minutes of ozonation time. TOC removal on ozonation of phenol without presence of any catalyst was 12.2% while with ZSM-5 and Beta catalyst increase to 21.6% and 23.5%, respectively. Similarly, Qu et al.,(2004) showed the removal rate of alachlor as a function of ozonation time with uncatalyzed (20%) and catalyzed system (60%) after 180 minutes of reaction time. The percentage removal of TOC in the study seems lower than the percentage of degradation of phenol as TOC represents the total degradation of intermediate products (due to degradation of phenol) as well as the phenolic solution itself. Table 4.4: TOC removal without and with catalysts Type of catalyst Concentration, ppm TOC removal, % Initial TOC Non Catalyst ZSM Beta

91 74 An all of the experiments carried out in this study showed that the performance of Beta catalyst was slightly better compared to ZSM-5 catalyst. In order to reason the difference, the specific surface area and average pore diameter of Beta, ZSM-5 was investigated, and the results are presented in Table 4.5. The specific surface area for Beta and ZSM-5 catalysts were 555 and 379m 2 /g, which indicates that Beta catalyst, has higher surface area than ZSM-5 catalyst and could be possibly due to its larger surface area that allows greater adsorption of phenol than ZSM-5. This means that Beta catalyst has higher active sides to react with the contaminants compared to ZSM-5 catalyst. Roostaei and Tezel., (2004), explained that the zeolites that posses large surface area, big pore size and a hydrophobic surface area good adsorbent for the removal of organic contaminants compared to those with hydrophobic surfaces but with a small surface areas. Tong et al., (2003) reported that the performance of MnO 2 catalyst in ozonation of sulfosalicylic acid was slightly higher than that of β- MnO 2 and γ-mno 2, which due to the fact that MnO 2 had a largest surface area compared to the others. Similarly, Beltran et al., (2004) observed that the TiO 2 /Al 2 O 3 catalyst works better than powdered TiO 2 at similar conditions, although conversion of oxalic acid after 3 hour of reaction time was similar. The different results are likely due to the distinct specific surface area of TiO 2 /Al 2 O 3 higher than powdered TiO 2 catalyst, which shows the specific surface area for TiO 2 /Al 2 O 3, and TiO 2 was 139 and 42m 2 /g, respectively. This parameter causes differences in the mechanism and kinetics of the process.

92 75 Table 4.5: Specific surface area and average pore diameter of zeolite-based catalyst TEST UNIT Beta ZSM-5 Specific surface area m 2 /g Average pore diameter A As indicated in Table 4.5, the average pore diameter of Beta was 2.3 orders of magnitudes than ZSM-5 catalyst, which could be another contributable factor that made Beta a better catalyst than ZSM-5. The catalyst, which has relatively small pore size, will be active towards small molecules only. Thus, Beta catalyst was selected for further investigation on the degradation of phenol. 4.2 Effect of Modified Beta Catalyst with Metals on Degradation of Phenol The mechanism of catalytic ozonation with the usage of transition metal ions as catalysts is based on ozone decomposition reaction followed by the generation of hydroxyl radicals. The ions present in the solution initiate the ozone decomposition reaction by the generation of the radical O The transfer of an electron from O 2 molecule to O 3 causes the formation of O - 2, and subsequently. In this section, the performance of Beta catalyst modified with metals i.e ferum and titanium on the degradation of phenol was studied under different reaction time and concentration of phenol. The catalytic ozonation of the metal-based zeolite catalysts was tested against reaction time and their respective performance on the degradation of phenol and COD removal was observed for a total period of 90 minutes reaction time. The aim was to screen the best performed metal-based zeolite catalyst (either Ferum or Titanium) before it is subjected to further experiments. The

93 76 results of the metal-based zeolite catalyst on the degradation of phenol are discussed in following section. Table 4.6 depicts the degradation of phenol versus reaction time with Fe- Beta and Ti-Beta catalyst subjected to two different concentrations of phenol (100 and 1600ppm) which shows the degradation of phenol increased with increase with reaction time. In addition, the degradation of phenol was slightly increased with the presence of metal-based Beta compared to parent Beta catalyst. Similarly, Legube and Leitner, (1999) stated that the presence of numerous metals (Fe, Mn, Ni, Co, Zn, Ag, Cr) in ozonation process able to enhance the efficiency of ozone for the removal (or the conversion) of different organic compounds in aqueous solution. Table 4.6: The degradation of phenol versus reaction time with and without modified Beta catalyst Concentration of Phenol =100ppm Concentration of Phenol =1600ppm Time, min Beta Ti-Beta Fe-Beta Beta Ti-Beta Fe-Beta Degradation of phenol, % Degradation of phenol, % Note: Ozone flow rate=1l/min, concentration of phenol=100ppm, ph 6.5, concentration of ozone=2.142ppm, Ozone flow rate=1l/min As presented in Table 4.6, the ozonation of 100ppm phenol with Beta catalyst (without metal-based) causes the degradation of 43.2% after 30 minutes of reaction time while the degradation of phenol was 55.1% and 57.8% with Ti-Beta

94 77 and Fe-Beta catalysts, respectively for a similar ozonation time. A 67.4% of phenol was degraded with Beta catalyst after 90 minutes of reaction time. Approximately the same amount of phenol was degraded (i.e 66.5%) in the solution with Ti-Beta catalyst, which merely took 60 minutes of reaction time. However, catalytic ozonation in the presence of Fe-Beta catalyst also required 60 minutes of reaction time to achieve 67.4% of degradation. The degradation was marginal in the presence of Fe-Beta catalyst compared to others. Kasprzyk., (2004) reported that metal-based catalyst of Al 2 O 3, TiO 2 γ- Al 2 O 3 and Fe 2 O 3 γ- Al 2 O 3 significantly influenced the degradation of oxalic acid, chloroethanol and chlorophenol from water. The modification of the alumina surface with both TiO 2 and Fe 2 O 3 resulted in a significant increase of the activity of the catalyst. Ferum species act as catalyst, while generating additional OH and ferryl radical, which could also oxidize the organic pollutants. In general, the reactions of ferrate with dissolved species have been found to be specific in nature, despite its high oxidation potential. In addition, the chemical reduction of ferrate can lead to the formation of insoluble Fe(III) species, which may have the capability of absorbing the organic compound and thereby removing it from solution (Graham et al., 2004). Graham et al., 2004 discussed that for ph<6 the ferrate is highly unstable and is reduced rapidly. In contrast, at high ph (>9) the ferrate is more chemically stable and persists much longer in solution. It would seem that the catalyst probably performs a dual function. First, it is clear that the presence of a heterogeneous surface increases the dissolution of the ozone. Secondly the catalyst will act as an initiator in the ozone decomposition reaction (cooper and Burch, 1999)

95 78 Figure 4.4 presents the degradation of 1600ppm phenol with and without the presence of metal-based Beta catalyst under the same operating conditions, which shows that a lower percentage of degradation of phenol was observed compared to 100ppm of phenol solution. A similar reason whereby the increase in the concentration of phenol means that more of the generated ozone will have to react with undesirable organic intermediate formed by the degradation of phenol apart from the phenol itself. Thus, the effectiveness of degradation was decreased. However, a similar trend was observed whereby the percentage degradation of phenol increases with increase in the reaction time. Phenol degradation,% Time, min Beta Ti-Beta Fe-Beta Slope=0.13 Slope=0.096 Slope=0.084 Figure 4.4: Degradation of 1600ppm phenol with Beta and Beta metal-based catalyst versus reaction time Evidently, as shown in Figure 4.4 that there was a marked difference on the degradation of phenol at high concentration with the presence of Fe-Beta catalyst compared to Beta and Ti-Beta catalyst. Ferum is known to be an excellent oxidation agent compared to titanium and this has been proven by many other studies (Phu et al., (2001); Canton et al., (2003); Piera et al., (2000); Graham et al., (2004)). This could be the reason for the finding. However and generally as stated before a lower

96 79 percentage of degradation of phenol was observed for the higher concentration compared to phenol with lower concentration. Several authors have mentioned that iron salts enhance the activity of ozone by an increase in the concentration of OH radicals. The role of iron has been related to the formation of FeO 2+ species which can produce OH radicals from water. The catalytic ozonation using Ferum system involves the direct reaction of Ferum with ozone resulting in the production of HO as shown in Equation (4.4) and (4.5) (Piera et al., 2000). Fe 2+ + O 3 FeO 2+ + O 2 (Eq 4.4) FeO 2+ + H 2 O Fe 3+ + HO + OH - (Eq 4.5) Table 4.7 presented the COD removal of 100ppm of phenol at the end of the 90 minutes reaction time with Beta and Beta metal-based catalyst, which again shows that Fe-Beta is a better catalyst compared to Beta, and Ti-Beta catalyst. The percentage of COD removal was 66, 58 and 42% for Fe-Beta, Ti-Beta and Beta catalyst, respectively. In all of the experiments, the performance of Fe-Beta catalyst was evident compared to Ti-Beta and thus the former was selected and subjected to further experiments to identify the optimum operating conditions on the catalytic ozonation of phenol. Table 4.7: COD removal of 100ppm of phenol using Beta and Beta metal-based catalyst Type of catalyst Initial COD, mg/l Final COD, mg/l % COD Beta Ti-Beta Fe-Beta Note: Ozone flow rate=1l/min, ph 6.5, concentration of ozone=2.142ppm

97 80 In drinking water treatment heterogeneous catalytic ozonation was reported remarkably more efficient in TOC removal than plain ozonation. In the presence of heterogeneous catalyst (CuO/Al 2 O 3 ), TOC removal (humic substances) was approximately 50% within 10min at 20 0 C, without catalyst only about 15% (Pirkanniemi and Sillianpaa, 2002). Cooper and Burch (1999) studied heterogeneous catalytic ozonation of halogenated hydrocarbons from groundwater. Conversion of chlorinated phenols was within 30min of contacts time complete in the presence of alumina or transition metal-alumina catalyst. Work carried out by Dhandapani and Oyama (1997), heiseig et al., (1997) and Lin et al., (2002) reported that metal oxides are active catalysts to decompose gaseous an aqueous ozone. However, their activity depends greatly on the type of metal oxide. According to Heisig et al., (1997), decomposition of gaseous ozone with MnO 2 supported on Al 2 O 3 was the highest followed by the Fe 2 O 3 and CuO. In the decomposition of aqueous ozone, the MnO 2 supported on Al 2 O 3 was also reported to posses the highest activity followed by the Fe 2 O 3 and CuO, while the TiO 2 did not contribute to any decomposition of aqueous ozone (Lin et al., 2002). Therefore, it is strongly anticipated that the activity of the metal oxides to decompose ozone subsequently determines their effectiveness to treat phenol in an ozonated system. The percentage of phenol removal obtained at 1600ppm phenol was low. From Figure 4.4, it can be justify that the degradation of phenol decreases when increase the concentration of phenol. Increment in the reaction time would lead to a continuous removal but a large amount of oxidant is needed to achieve a reasonable level of phenol in the final solution. The evaluation of the treatment costs is at moment one of the aspect, which needs more attention. Since generation of ozone is

98 81 costly, ozonation treatment for highly polluted water is not economically feasible. Thereby, further studies at high phenol concentration are neglected. In this study, ozonation of phenol was carried out using Ferum and Titanium metal catalyst. Ferum found to be best catalyst due to the higher degradation of phenol compared to Titanium. Following section is the determination of best operating condition using Fe-Beta in catalytic ozonation of phenol. 4.3 Determination of Best Operating Conditions of Fe-Beta Catalyst in Catalytic Ozonation of Phenol. The Fe-Beta catalyst was observed be a better-performed catalyst for a degradation of phenol. The influence of selected variables such as ozone gas flow rate, temperature and ph of phenol solution, mass and metal weight percent impregnated in the catalyst, concentration and the volume of phenol to be treated was studied to find the best operating conditions on the degradation of phenol. However, in order to confirm that ferum exist in the zeolite-based framework, a detailed characterization of the Beta and Fe-Beta catalysts was preliminary studied and the results are discussed in Section 4.4 of this thesis. While the influence of the selected operating variables on degradation of phenol using Fe-Beta catalyst is given in following section.

99 Effect of Metal Weight Percent In this experiment, the performance of Fe-Beta catalyst on the degradation of phenol was studied with one gram of the catalyst impregnated with different Fe weight percent of 2, 4 and 6wt%. The experiment was subjected to 1.0 L/min of ozone flow rate to treat 250mL of 100ppm phenol at room temperature with the total reaction time of 120 minutes. The catalytic ozonation of phenol using different metal weight percent of Fe-Beta catalyst was measured against reaction time and their respective performance on the degradation of phenol, COD and TOC (taken only at the end of the experiment) removal was observed. Table 4.8 presents the degradation and COD removal of phenol with different Fe weight percent, which shows that there was no significant degradation and removal of COD with increase in metal weight percent. As expected, the degradation of phenol (similarly COD removal) was increased with increase in the reaction time as observed from the previous experiments. As illustrated in Table 4.8, the degradation of phenol was 58.1% with 2 percent of metal weight and remained or slightly improved to 58.1 and 60.4% for 4wt% and 6wt%, respectively for 60 minutes of reaction time. The degradation of phenol was further increased to 67.9, 71.9 and 74.2% for 2, 4, 6 wt% of metal after 120 minutes of ozonation time. However, there was no marked difference having at a higher ferum loading in Beta catalyst on the degradation of phenol. The degradation rate of phenol with different metal weight percent was and 0.43 per minute for 2, 4 and 6 wt% of ferum weight percent respectively (Figure 4.5).

100 83 Table 4.8: Degradation and COD removal of phenol in the presence of Fe-Beta under different metal wt% Time, min Metal weight % = 2 Metal weight % = 4 Metal weight % = 6 %P COD, %COD %P COD, %COD %P COD, %COD mg/l mg/l mg/l Note: %P: Degradation of phenol; Initial COD= 295 mg/l; amount of catalyst used=1.0gram Einaga et al., (2004) observed that there was no significant difference on the degradation rate of benzene with increases the Mn loading from 5 to 20wt% on MnO 2 /Al 2 O 3 catalyst. The authors found that the benzene degradation rate was the same i.e 1.38 x 10-5, 1.40 x 10-5 and 1.13 x 10-5 for 5, 10 and 20 wt% of Mn loading, respectively. Increasing metal loading seems do not influence on the degradation rate of pollutant, which was also observed in this study. As discussed in Section 4.2, the degradation of phenol with 1 wt% of Fe-Beta catalyst was 75% within 90 minutes of reaction time, which clearly indicates that a smaller amount of ferum loading enhanced the degradation of phenol. Ma and Graham, (2000) reported that the highest removal of atrazine appeared to occur at the lowest Mn concentration in catalyst where in their study, further increase on Mn concentration did not cause any increase in the degradation of atrazine, rather cause it a slightly negative effect.

101 84 Phenol degradation,% Slope=0.47 slope=0.46 Slope= Time, min Metal:2 wt% Metal:4 wt% Metal:6 wt% Figure 4.5: Degradation of phenol with different metal weight percent against reaction time. An increased in metal loading catalyst should cause an increased in catalytic ozonation. On the contrary, it was observed that a smaller percentage of metal loading catalyst showed a higher degradation compared to those with higher metal loading catalyst. It seemed that only a very small percentage of metal is required to obtain a substantial degradation whereby a small amount of metal loading catalyst is warrant to initiate any radical chain reaction (Kasprzyk et al., 2003). However, it is anticipated that the increased in percentage of metal on the based catalyst would require a greater consumption of ozone to show any significant effect. The Beta is a microporous material with a large surface area. Metals impregnated on it are deposited on the surface, thus reducing the surface area. N 2 adsorption analysis was conducted on 1wt% of Fe-Beta and found that the BET surface area was reduced from 555m 2 /g fro Beta to 484m 2 /g. It is assumed that the BET surface area for 2, 4 and 6 wt% of Fe-Beta is low compared to the parent catalyst. Reduction in the surface area will subsequently decrease the support s active sites for adsorption. Ferum is a great oxidation potential, however, it can be

102 85 applied in small percentage to initiate the reaction or show its function. It can be concluded that the treatment occurs by adsorption and oxidation of organic compound to form CO 2, water and other intermediate organics. A similar trend on the degradation of phenol was observed based on the COD (Table 4.8) and TOC (Table 4.9) removal where the percentage of COD removal was slightly increased with time i.e 44, 46 and 53% for 2, 4 and 6wt%, respectively after 120 minutes of reaction time. As for the TOC, this was 17.7, 20.8 and 22.5% for 2, 4 and 6 wt%, respectively. Table 4.9: TOC removal with different metal weight % Metal weight % Initial TOC, ppm Final TOC, ppm TOC removal, % Note: reaction time=120 minutes Effect of Ozone Gas Flow Rates The effect of ozone flow rates i.e 0.6, 1.5 and 2.1 L/min on degradation of phenol against reaction time in the presence of Fe-Beta catalyst was studied in the following experiment. In general, it would be expected that increased in ozone flow rates would lead to increase in the degradation of pollutant in the solution which would increase with increase of reaction time. Table 4.10 presents the degradation and COD removal of the phenol where the degradation of phenol was 54.12% after 120 minutes of reaction time for

103 86 0.6L/min, while the same amount of phenol was degraded (51.9%) in 60 minutes for 1.5 L/min of ozone flow rate. Approximately a similar percentage of phenol was degraded (56.4%) in less than 30 minutes for 2.1L/min of ozone flowrate. The degradation of phenol increased from 73.6% to 84.8% as ozone flow rate was increased from 1.5 to 2.1L/min after 120 minutes of reaction time. This indicates that, a higher percentage of phenol degradation was observed at a higher ozone flowrate. A similar reason whereby the increases in the ozone flow rate causes the free OH radicals to form when ozone decomposed in the solution having a great oxidizing potential that increased the degradation rate of organic matter. Table 4.10: The effect of ozone flow rates against reaction time with Fe-Beta catalyst Time, min Ozone flowrate = 0.6 L/min Ozone flowrate = 1.5 L/min Ozone flowrate = 2.1 L/min %P COD, %COD %P COD, %COD %P COD, %COD mg/l removal mg/l removal mg/l removal Note: %P: Degradation of phenol; Initial COD=295 mg/l; amount of catalyst used=1 gram Figure 4.6 is the graphical presentation of the degradation rate of phenol against ozone flow rate, which clearly shows that the degradation rate of phenol increases with ozone flow rates. The degradation rate was 0.36, 0.53 and 0.57 per minute for ozone flow rate of 0.6, 1.5 and 2.1, respectively.

104 87 Phenol degradation,% Slope=0.57 Slope=0.53 Slope= Time, min OF:0.6 L/min OF:1.5 L/min OF:2.1 L/min Note: OF=Ozone flow rate Figure 4.6: The effect of ozone flow rates against reaction time Figure 4.7 is a series of HPLC chromatographs for phenol solution taken at various reaction times with the ozone flow rate of 2.1L/min, which clearly shows the gradual disappearance of phenol peak with reaction time. The HPLC spectrum also shows the presence of other unidentified peaks, which indicates the formation of byproducts resulting from the degradation of phenol. The degradation of these byproducts was also increasing (decrease in the peak area) with time, which concur that the reaction time is of the most important parameter in ozonation process. A similar pattern of observation was obtained with 0.6 and 1.5L/min of ozone flowrate. The original copy of HPLC chromatograph for phenol solution taken at various reactions time was attached in appendix F A similar trend on the degradation of phenol was observed based on COD removal (Table 4.10) where the percentage of COD removal was increased with time i.e 42, 49 and 56% for 0.6, 1.5 and 2.1L/min, respectively after 120 minutes of reaction time

105 a) 15 min b) 30 min c) 45 min Phenol Phenol Phenol d) 60 min e) 90 min f) 120 min Phenol Phenol Phenol Figure 4.7: HPLC spectrum of phenol degradation under 2.1 L/min

106 89 Table 4.11 presents the effects of ozone flow rates on the TOC removal of pollutant at the end of the experiment, which shows the TOC removal was slightly increases with ozone flow rate. The percentage of TOC removal was 11.7, 13.0 and 18.5% for 0.6, 1.5 and 2.1L/min, respectively. As discussed in previous section, the percentage removal of TOC in the study seems lower than the percentage of degradation of phenol as TOC represents the total degradation of intermediate products (due to degradation of phenol) as well as the phenolic solution itself. Table 4.11: TOC removal with different ozone gas flow rates Ozone flow rate Initial TOC, ppm Final TOC, ppm TOC removal, % Note: reaction time=120 minutes Effect of Phenol Concentration In this study, an experiment on was carried out to investigate the effect different concentration of phenol (i.e 200, 400 and 800ppm) against reaction time with constant ozone flow rate. As expected, a similar trend was observed in the degradation and COD removal of solution where the degradation and COD removal was increased with reaction time and decreased with the concentration of phenol. Table 4.12 presents that the effect degradation of phenol with different phenol concentration, which shows approximately 35.0% phenol degraded with the first 15 minutes and gradually increases to 62.8% after 120 minutes of reaction time for 200ppm of phenol. The degradation of phenol was 24.5% within 15 minutes of ozonation time and for a longer reaction time of 120 minutes, at least 46.1% of

107 90 phenol is degraded for 400ppm phenol. Finally, for 800ppm of phenol, the degradation was only 14.9% in the first 15 minutes and gradually increases to 30.7% after 120 minutes of reaction time. The percentage of COD removal was 75%, 64% and 53% for 200, 400 and 800ppm of phenol, respectively. It is theorized that the most of the ozone generated was used for destroying phenol and it intermediates causing insufficient ozone to degrade the remaining phenol quickly. Nevertheless, varying other operating parameters such as increase in ozone flow rate and reaction time could increase the degradation and COD removal of phenol as can be observed in previous experiments. Table 4.12: The effect of different concentration of phenol against reaction time Time, Phenol concentration = Phenol concentration = Phenol concentration = min 200 ppm 400 ppm 800 ppm %P COD, %COD %P COD, %COD %P COD, %COD mg/l mg/l mg/l Note: %P: Degradation of phenol; initial COD of 200ppm phenol=450mg/l, 400ppm phenol= 725mg/L and 800ppm phenol= 2125mg/L Figure 4.8 shows the degradation rate of phenol at different concentration where the degradation rate was decreased with concentration of phenol. The degradation rate was 0.43 per minute for 200ppm phenol. When the concentration of phenol increased from 200 to 400ppm, the degradation rate of phenol was 0.32 per minute and finally the degradation rate was decreased to 0.21 per minute for 800ppm

108 91 of phenol. The results clearly indicate that the degradation rate was decreased with increase in phenol concentration. Wu et al., (2000) observed a similar effect whereby the ozonation rate phenol decreased with increase in concentration of phenol without presence of any catalyst. Phenol degradation,% Slope =0.43 Slope =0.32 slope= Time, min [P]: 200 ppm [P]: 400 ppm [P]: 800 ppm Figure 4.8: The effect of different concentration of phenol against the reaction time Alnaizy and Akgerman (2000) observed similar results where approximately 90% oxidation of phenol was achieved in 20 min and complete oxidation was achieved in less than 30 minutes for 40ppm of phenol. The oxidation decreased significantly when the initial phenol concentration was increased to approximately 500ppm, only 14% was oxidized over a 30 minutes of reaction time. In addition they also observed that the reduction rate of COD was much slower than phenol oxidation rate.

109 Effect of Initial ph The major secondary oxidant formed from ozone decomposition in water is the OH radical. The stability of ozone largely depends on the water matrix, especially its ph, the type and content of natural organic matter (NOM) and its alkalinity. Ozone reacts with aqueous compounds in two ways: direct reactions of the molecular ozone with the compounds, and indirect reactions of the radicals resulting from the decomposition of ozone with the compound. The direct reactions are often highly solute selective and slow whereas the indirect radical reactions are nonselective and fast. Furthermore, the decomposition of ozone is catalyzed by OH - ions, and proceeds more rapidly with increasing ph. Therefore, ph of the aqueous solution is one of the most important environmental parameters significantly influences in the degradation of pollutant. The ph plays an important role in the formation of OH and, thus expected to enhance the pollutant oxidation rate. The oxidation by ozonation process involving hydroxyl radical has shown their potential to destroy organic compounds in wastewater. The main interesting characteristic of hydroxyl radicals is its oxidation potential that leads to an indirect attack on organic compounds, which is faster than a direct attack by molecular ozone. The ph of the water is important because hydroxide ions initiate ozone decomposition, which involves the following Equation (4.6) to (4.12): O 3 + OH - - HO 2 + O 2, k 1 = 70M -1 S -1 (Eq 4.6) - O 3 + OH 2 - O 3 + O 2 O 3 - HO O O 2, k 1 = 2.8 x 10 6 M -1 S -1 (Eq 4.7) + O 2, k 1 = 1.6 x 10 9 M -1 S -1 (Eq 4.8)

110 93 ph < 8 : O H + HO 3 K + = 5 x M -1 S -1 K - = 3.3 x 10 2 M -1 S -1 (Eq 4.9a) HO 3 OH + O 2, k -1 = 1.4 x 10 5 S -1 (Eq 4.9b) ph > 8 : O O - O 2, k = 10 8 M -1 S -1 K + = 5 x M -1 S -1 K - = 3.3 x 10 2 M -1 S -1 (Eq 4.10) O - OH + OH - (Eq 4.11) OH + O 3 HO 2 + O 2, k -1 = 1.0 x 10 8 M -1 S -1-2 x 10 9 M -1 S -1 (Eq 4.12) According to reactions (4.6) and (4.12) the initiation of ozone decomposition can be artificially accelerated by increasing the ph (Gunten., 2003). Since ph is a key condition for ozone stability in aqueous solution, it is important to examine the influence of ph in catalytic ozonation of phenol solution. Therefore, it is necessary to adjust the initial ph of the solution in order to determining its role in the degradation of organic pollutants. The effect of initial ph (selected ph 3, 7 and 11) of 100ppm phenol solution on the degradation of phenol was tested over a period of 120 minutes reaction time. The initial ph of the solution was adjusted using either sodium hydroxide or acid sulfuric and the solution was subjected to 1.0 L/min of ozone flow rate.

111 94 Table 4.13 presents the degradation and CODs removal of phenol against reaction time with different initial ph, which shows the degradation of phenol, was higher in a basic condition by two orders of magnitudes compared to the neutral and acidic conditions. The degradation of phenol increased significantly from 54.8 (at ph 7.0) to 98.1% (at ph 11) after 120 minutes of reaction time. In addition, approximately 88.2% of phenol was degraded within the first 15 minutes of the reaction time where almost complete degradation of phenol was observed in the basic condition. The rate of decomposition of ozone increases at high ph thus producing a higher concentration of hydroxyl radical and this leads to have a highest degradation of phenol (Freshour et al., 1996). The degree of degradation of phenol was similar in the case of acidic and neutral conditions. Table 4.13: The effect of initial ph of the solution against reaction time TIME, MIN PH 3 PH 7 PH 11 %P COD, %COD %P COD, %COD %P COD, %COD mg/l mg/l mg/l Note: %P: Degradation of phenol; Initial COD= 295 mg/l; amount of catalyst used= 1gram Esplugas et al., (2002) reported that the ozonation process of phenol (93-105ppm) gives a better efficiency at basic ph rather than neutral and acidic conditions. The authors stated the increased in the formation of the hydroxyl radical during ozonation at a higher ph contribute to this effect. Morkini et al., (1997) found that the degradation of 99.6ppm benzonic was 54.2%, 84.8% and 98.7% for acidic, neutral and basic condition, respectively, increasing from acid to base. The

112 95 author applied H 2 O 2 as a catalyst in their treatment and UV source to treat the organic compound. In this study, the catalytic ozonation carried out using Fe-Beta at high ph and the degradation can achieved 98.1%. It is more economical compared to Morkini et al., (1997) because no additional process (UV application) and the process are simple. The authors conclude that the presence of the hydroxyl radical during ozonation increase the efficiency of the degradation and a similar explanation can be given in this study. In addition, Zhang et al., (2004) reported that the concentration of OH radicals increases with ph of the solution, which have a high oxidation potential of 2.80V compared with ozone alone, which has an oxidation potential 2.07V. Thus, it is expected that the decomposition reaction is faster in basic conditions where these OH radicals are readily available. Figure 4.9 shows that the HPLC spectrum for the phenol samples taken at the end of ozonation time (120 minutes) with different ph. It can be seen that, the peak corresponding to phenol almost fully disappears with ph 11, and the intermediate compounds are further oxidized, as indicated by reduction in the peak areas compared to ph 3 and 7. The original copy of HPLC chromatograph for phenol solution taken at various ph was attached in appendix F. A similar pattern on the removal of COD was observed where 26% and 52% of COD was removed in 30 and 120 minutes with ph 3, respectively (Table 4.13). The removal was slightly increased to 34% and 53% after 30 and 120 minutes of reaction time, respectively when the ph increases to 7. Similarly, a higher removal was achieved i.e 55% and 79% after 30 and120 minutes, respectively when the ph was further increased to ph 11. A high percentage of COD removal was observed due to the decomposition of ozone at a faster rate, which produces more OH radical at basic ph compared to other ph condition. The OH radical causes an increase in the rate of the oxidation process. (Morkini et al., 1997, Wu et al., 2000, Kasprzyk et al., 2003).

113 96 ph 3 Phenol ph 7 Phenol ph 11 Phenol Figure 4.9: HPLC spectrum at different initial ph of solution Wu et al., (2000), was investigated the rate constants of ozone decomposition at different ph level and the result was listed in Table It is observed that the rate of ozone decomposition in aqueous solution increase significantly with ph.

114 97 Table 4.14: The rate of ozone decomposition at different ph values ph Rate constant of ozone decomposition, k 1 (s -1 ) x x He et al.,(unknown) found that the effects of ozone bubbling on phenol removal under different solution condition. The curves shows that the phenol removal proceed more rapidly with increasing ph and time. The phenol removal was greater at basic ph compared with acid and ph 6.8. A similar indication was observed in this thesis because the finding are have same trend with other researchers. Figure 4.10 shows the trend of phenol removal for different solution condition. 10mmol/L NaOH added No NaOH or H 2 SO 4 added 5mmol/L H 2 SO 4 added Figure 4.10: Phenol removal with time using ozone bubbling: Vol=200mL, C 0 (phenol)=50ppm, ozone flow rate was 0.65g/h. Figure 4.11 illustrates the degradation rate of phenol under different initial ph values where the degradation rate of phenol at ph 11 was 1.2 times (i.e 0.52/0.43) higher that those at ph 3 and 7. The finding indicates that higher ph value provides a higher concentration of hydroxyl ion to react with holes to form

115 98 hydroxyl radicals, subsequently enhancing the efficiency of the ozonation process (Doong et al., 2001). Freshour et al., (1996) observed that the degradation of 100mg/L oxalic acid at initial ph of 11.5 and 2.8, which shows that 67% oxalic acid, was degraded within 70 min at the higher ph and 45% at the lower ph as observed in this study. The authors reported that the ozone does not decompose rapidly in the acidic environment, and a direct attack of merely ozone on the compound predominates. However, at basic ph, the decomposition of ozone enhanced the forming of OH radicals in water, causing on indirect attack mechanism on organic pollutant. This enhances the degradation of organic pollutant in the solution. Phenol degradation, % Slope=0.52 Slope=0.43 Slope= Time, min ph 3 ph 7 ph 11 Figure 4.11: Effect of initial ph of phenol against reaction time.

116 Effect of Mass of Catalyst In order to investigate whether the mass of catalyst would influence on the degradation of phenol, an experiment of varying mass i.e 0.5, 3 and 5 gram of 1wt% Fe-Beta to treat 100ppm of 250mL phenol solution under 1.0L/min of ozone flow rate was performed over a period of 120 minutes reaction time. The degree of phenol degradation, COD and TOC (at end of experiment) were determined in the study. Table 4.15 presents the results on the effect of mass of Fe-Beta against reaction time, which generally shows the value of phenol degradation, was increased with increase ozonation time and mass of catalyst. The degradation of phenol with 0.5g of Fe-Beta catalyst was 48.0% in 90 minutes of reaction time. Approximately the same amount of phenol was degraded (47.2%) in the solution with 3g of Fe-Beta catalyst, which took 60 minutes of reaction time. In comparison, catalytic ozonation in the presence of 5 gram of Fe-Beta catalyst required only 45 minutes of reaction time to achieve a similar level of degradation. This indicates that the degradation was slightly faster in the presence of 5 gram of Fe-Beta catalyst compared to others. Similarly, Beltran et al., (2004) also observed the same effect in the process oxalic acid oxidation in the TiO 2 /O 3 system. The author reported that an increase in catalyst mass in the process oxalic acid ozonation on TiO 2 causes increase in efficiency of the process. In addition, Christoskava and Stoyanova (2001) in their study on degradation of phenolic wastewaters over Ni-Oxide found that the oxidation efficiency increases with the amount of catalyst.

117 100 Table 4.15: Effect of mass of 1wt% Fe-Beta catalyst in the ozonation process Time, min Mass of catalyst = 0.5 gram Mass of catalyst = 3 gram Mass of catalyst = 5 gram %P COD, %COD %P COD, %COD %P COD, %COD mg/l mg/l mg/l Note: %P: Degradation of phenol; Initial COD=295 mg/l, ozone flow rate=1.0l/min Table 4.15 indicates that, phenol was fast degraded at beginning of the process under different mass of catalyst. But, at end of the ozonation time the percentage of degradation of phenol was becoming almost close to each other with 60.0, 61.2 and 65.2% degradation for 0.5, 3 and 5 gram of Fe-Beta catalyst, respectively at 120 minutes of reaction time. A similarity in the percentage of degradation at the end of the experiment probably due to the permanent blockage of the catalysts active surface sites resulting in the decrease of catalytic activity. A similar trend of COD removal of the solution was observed where the percentage of COD removal was achieved 36, 61 and 63% within 30 minutes and was increased to 88%, 71% and 49% after 120 minutes for 0.5, 3 and 5g of Fe-Beta catalyst, respectively (Table 4.15). The effect of amount of catalyst used on the TOC removal during ozonation process is shown in Table 4.16 where 8.1, 31.7 and 39.6% of TOC removal with 0.5, 3 and 5 gram of Fe-Beta catalyst, respectively. The observation suggested that the

118 101 degradation of phenol increases with mass of catalyst, particularly during the very early stage of the reaction time. Table 4.16: TOC removal with different mass of catalyst Mass of catalyst, g Initial TOC, ppm Final TOC, ppm TOC removal, % Note: reaction time=120 minutes Christoskova and Stoyanova., 2001, found that the increase in the catalyst amount causes an increases in the oxidation efficiency. This is a reason to suppose that the reaction only proceeds on the catalyst surface and not homogeneously. An additional evidence for this conclusion is the fact that, after removing the catalyst from the reaction mixture, the oxidation process is ceased. Figure 4.12 shows that the effect of the catalyst amount on the reaction. Figure 4.12: The effect of the catalyst amount on the reaction efficiency; catalyst concentration: a) 2 g/dm 3 ; and b) 6 g/dm 3.