INTEGRATED OZONATION PROCESS FOR TREATMENT OF REFRACTORY ORGANIC POLLUTANT- RB5

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1 International Journal of Advanced Research in Engineering and Technology (IJARET) Volume 7, Issue 6, November-December 2016, pp. 5 52, Article ID: IJARET_07_06_006 Available online at ISSN Print: and ISSN Online: IAEME Publication INTEGRATED OZONATION PROCESS FOR TREATMENT OF REFRACTORY ORGANIC POLLUTANT- RB5 S. P. Sharma and J. P. Ruparelia Department of Chemical Engineering, Institute of Technology Nirma University, Ahmedabad, India ABSTRACT Textile and dyeing industries are one of the leading industrial sectors for producing colored wastewater. The effluents produced from these industries are problematic to treat because of their recalcitrant nature. Conventional treatment techniques are not suitable to treat this effluent due to presence of high amount of non-biodegradable compounds. Advanced Oxidation Process is gaining importance as an alternative to treat recalcitrant organic compounds as they are highly effective and environmental friendly. The foremost aim of present study is to analyze the performance efficiency of integrated ozonation process, i.e. ozonation combined with UV and Persulfate process to mineralize synthetic wastewater containing Reactive Black5 (RB5)as refractory pollutant. The effectiveness of process was analyzed on the basis of Total Organic Carbon and also effects of various operating parameters were also analyzed. Key words: Total Organic Carbon, Ozone Flowrate, Persulfate Dosage, Reactive dyes Cite this article: S. P. Sharma and J. P. Ruparelia, Integrated Ozonation Process For Treatment of Refractory organic Pollutant- RB5. International Journal of Advanced Research in Engineering and Technology, 7(6), 2016, pp INTRODUCTION Dyes and its intermediates have a wide range of applications ranging from paints, textile, paper & printing, plastics etc. Textile and dyeing sectors are considered to be highly water exhaustive sector among the various other sectors. Dye and textile industry is using approximately 8000 chemicals as dyes and producing more than products [1]. Effluents from textile, dyes & intermediate industries have high variation in its composition and are with highly toxic and bio-resistant in nature due to complex structure of dye [1,2]. Basically various physical, chemical or biological methods have been tested and are reported inefficient by the researchers for treating colored effluents. However, various technologies have been reported for color removal such as adsorption, coagulation, flocculation and reverse osmosis but these are ineffective treatment for COD reduction and leads to generation of secondary pollutants which are highly dangerous and need proper treatment before disposal [3-5]. Recently AOPs have drawn tremendous attention as effective alternative for treatment of effluent from textile and dye industries. It is well reported in literature that AOPs such as Ozonation, UV/O 3, 5 editor@iaeme.com

2 S. P. Sharma and J. P. Ruparelia UV/H 2 O 2 etc are efficient and prominent way to degrade organic pollutants to environmentally acceptable end products []. Ozonation is one of the mostpromising techniques to mineralize organic pollutants. Ozone molecule is very selective in nature and it selectively attack unsaturated bonds of chromophores which results in complete color removal [6, 7]. However, ozonation alone is not sufficient to degrade or mineralize organic pollutants to environmentally acceptable end products i.e, CO 2 and H 2 O. Ozonation leads to partial oxidation of organic pollutants to organic acids, aldehydes, ketones, etc. Nevertheless it is worthy to note that combining ozonation with UV and Persulfate will enhance its efficiency and leads to complete mineralization of organic pollutants intoco 2 and H 2 O [6-9]. Present paper focuses on the application of O 3 /UV/PS process as an advanced alternative treatment of colored effluents providing energy proficiency and environmental compatibility. In present work main focus is to analyze the performance efficiency in terms of Total Organic Carbon (TOC) removal. 2. MATERIALS & EXPERIMENTAL PROCEDURES 2.1. Materials All the experiments were carried out at lab scale using synthetic wastewater containing Reactive Black 5 dye. Reactive Black 5 is a reactive dye with molecular weight g mol -1 and it was purchased from local vendor and used without any further purification. Reagents and chemicals essential for this study such as Sulphuric Acid (H 2 ), Sodium Hydroxide (NaOH), Sodium persulphate (Na 2 S 2 O 8 ), Potassium Iodide (KI), (Sigma Aldrich) were of analytical grade and purchased from Sigma-Aldrich. Phillips (TUV G5 T5 11W) UV Light was used as UV light source. A positive displacement pump was utilize for recirculation of synthetic wastewater. Figure 1.Structure of dye 2.2. Methods As Shown in figure 2, all experiments were performed in a continuous recirculation mode. 3.0 Lit. of 500 mgl 1 dye solutionwas taken into the glass reactor. The inner diameter and height of the reactor were 70 mm and 870 mm respectively. Ozone was generated by supplying oxygen to Ozonator (Aquazone Solutions, Ahmedabad. India). Ozone flowrate was kept in the range of 30 to 60 LPH with an interval of 10 LPH. For intimate contact of pollutant and ozone, ventury (MK 287, Ozone Solutions, USA) was utilized. Initial ph of solution was adjusted using 1 N NaOH and 1 NH 2 solution. TOC to persulfate (PS) ratio was in the range of 1:10 to 1:60. The flow of synthetic wastewater was maintained at 0.5 LPM in all experiments. For the trapping of excess ozone, 2% KI solution was used and its concentration was measured by idometric method [10]. The performance of the O 3 /UV/PS method was determined by analyzing by Total Organic Carbon (TOC) (mg L 1 ) at different process operating conditions. TOC Analyzer (TOC-VCPH/CPN, Shimadzu Corporation, Japan) was utilized for measurement of TOC. 6 editor@iaeme.com

3 Integrated Ozonation Process For Treatment of Refractory organic Pollutant- RB5 Figure 2.Experimental set-up 2.3. Mechanism Ozonation process is efficient in degradation of organic pollutant but it has one major drawback that it lead to partial degradation of pollutants into secondary pollutants such as aldehydes, organic acids, ketones, etc [6-9]. To overcome this limitation UV and Persulfate can be used in combination with Ozonation process to provide complete mineralization of organic pollutants. Transformation of Persulfate into sulfate radicals can be achieved using heat, transition metal (Me n+ ), (Fe 2+ ), UV irradiation. Sulfate radical (, E 0 =2.6V) is more powerful oxidizing agent and it further react with water to generate hydroxyl radical ( OH ). However series of complex reactions are involved to recalcitrant organic compounds [11-13] H 2O H + + OH (1) S S2O 2 2 heat / UV O8 + M 2 + M (2) (3) + H 2O HO + H () + M M + products (5) HO + M M + products (6) 2 M + S O products (7) + HO chain termination (i.e., terminating free radicals) (8) 7 editor@iaeme.com

4 S. P. Sharma and J. P. Ruparelia + M chain termination (i.e., terminating free radicals) (9) 2 chain termination (10) HO + M chain termination (11) 2HO chain termination (12) 2M chain termination (13) Organic compounds are degraded by and OH mainly through three mechanisms: hydrogen abstraction, hydrogen addition, and electrontransfer[1]. 3. RESULTS AND DISCUSSION 3.1. Effect of Ozone Flowrate Ozonation and combined ozonation process is also influenced by change of ozone flowrate. Literature provide comprehensible glance mentioning that increasing flowrate will have positive impact on mineralization of recalcitrant organic pollutants [15,16]. Increasing the ozone concentration will positively affect the TOC as well as color remova[16]. 55 % TOC Removal Ozone Flow, LPH Figure 3 Effect of ozone flow on %TOC removal; (Initial ph:6; UV Intensity: 11 W; TOC:PS Ratio: 1:10) It is quite evident from the results shown in above graph that on increasing ozone flow rate mineralization of organic pollutant also increases in terms of %TOC removal. On doubling the ozone flow rate from 30LPH to 60LPH %TOC removal was also increased from 35% to 52% respectively Effect of ph Literature reveals that ph is one of crucial parameter in AOPs. Initial ph of solution plays a vital role in dictating treatment efficiency of process. Ozonation process is favored at high ph, this is endorsed by ability of ozone to commence formation of hydroxyl radical at higher ph. However, Persulfate radicals are also found to be more active at higher ph range.at ph above 8.5 sulfate radical will oxidize either O or OH to generate hydroxyl radical ( OH )[17]. At ph < 7 sulfate radicals will dominates whereas at ph 12 or ph >7 hydroxyl radicals dominates as active species for mineralization of organic matter [18]. H editor@iaeme.com

5 Integrated Ozonation Process For Treatment of Refractory organic Pollutant- RB5 Figure Effect of ph on %TOC removal; (O 3 Flow: 60 LPH; UV Intensity: 11 W; TOC:PS Ratio: 1:10) It is praise worthy to note that results obtained during present study support the findings of various researchers. As shown in results quoted in above figure there is increasing trend in mineralization rate as initial ph was increased from to 12. Around 60% increase in mineralization rate was observed on increasing ph from to Effect of UV Intensity UV act as catalyst for generationn of sulfate radicals and it eventually improves the Persulfate oxidation potential. Literature reveals that on increasing UV intensity the performance of process were enhanced due to generation of more and more hydroxyl radicals [19, 20]. 80 % TOC Removal UV Light Intensity, Watts Figure 5 Effect of UV Intensity on TOC Removal; (O 3 Flow: 60 LPH; ph:12; TOC:PS Ratio: 1:10) Above results obtained during present study agree completely to the findings of literature and shows that as intensity of UV light is increased from 11W to 66W there is commendable increase in degradation efficiency of organic pollutants 9 editor@iaeme.com

6 S. P. Sharma and J. P. Ruparelia 3.. Effect of Persulfate Dosage O 3 /UV/Persulfate process is also affected by amount of Persulfate dosage. Increasing Persulfate dosage will directly enhance mineralization rate of recalcitrant organic compounds. This phenomenon was attributed to fact that increasing Persulfate dosage will directly boost the reaction rate by providing additional sulfate radicals and thus augment performance efficiency of process [21]. However it is desired to obtain optimum Persulfate dosage because if Persulfate dosage is increased beyond optimum dosage then there will be negative effect on efficiency of the process as excessive will behave as scavenger for Persulfate as well as Persulfate radicals [22] S 2O8 + S 2O8 2 + S 2O8 (1) (15) 85 %TOC Removal :10 1:20 1:30 1:0 1:50 1:60 TOC:PS Ratio Figure 6 Effect of Persuphate Dosage on TOC Removal; (O 3 Flow: 60 LPH; ph: 12; UV Intensity: 66 W) As shown in above results, Persulfate dosage has to be optimized for better mineralization efficiency. In present study, 1:0 is optimum condition which gives maximum TOC reduction. However, it is worthy to note that as Persulfate dosage is increased beyond the ratio of 1:0 the mineralization rate decreased drastically.. CONCLUSION Present study explores reliable way for treatment of wastewater containing refractory pollutants. Integarted ozonation process (O 3 /UV/Persulfate) process proves to be a better alternative for complete mineralization of recalcitrant organic compounds such as RB5. Additionally it is worthy to note that at ph12 overall efficiency was maximum. Also, doubling the ozone flowrate from 30LPH to 60LPH will increase the mineralization rate by almost 20%. It is also identified from present study that as UV intensity is increased the efficiency of process is also increased simultaneously. However, it is worth noticing that optimum persulfate dosage has to be identified to get maximum efficiency of process editor@iaeme.com

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