Production of Activated Carbon from Acacia Arabica Sawdust

Transcription

1 Production of Activated Carbon from Acacia Arabica Sawdust by admin - Thursday, January 24, 2013 /?p=224 Production of Activated Carbon from Acacia Arabica Sawdust Moinuddin Ghauri a*, Muhammad Tahir a, Tauqeer Abbas a a Department of Chemical Engineering, COMSATS Institute of Information Technology, Lahore, Pakistan * Corresponding Author drghauri@ciitlahore.edu.pk Tel: Abstract In this article a technique to produce activated carbon from acacia arabica sawdust is described. The sawdust was first pyrolysed in a tube furnace under nitrogen gas atmosphere at a temperature range of 350 to 450? C. The pyrolysed samples were further treated with zinc chloride (ZnCl 2 ) to activate the carbon produced in the pyrolysis step. The samples of the formed activated carbon were used to carry out the adsorption study using Congo red as a model adsorbate dye. It was found that the most active carbon was produced when the pyrolysis temperature was 700? C for 30 minutes and ZnCl 2 to carbon mass ratio was 2.5: 1(ZnCl 2 : Carbon). The iodine value of this sample was found to be 905 mg/g sample. It was also found that the activated carbon produced using this technique can remove Congo red dye very efficiently from aqueous solution by adsorbing it. The adsorption data obtained in this study were also used to fit different adsorption kinetics and equilibrium models published in the literature. Keywords: Adsorption, Activated Carbon, Kinetics, Isotherm, Saw dust, Equilibrium. page 1 / 8

2 1. Introduction Wastewater from industries such as textile, paper, leather tanning, rubber, plastic and cosmetic is often polluted by dyes [1-4]. Discharging of wastewater containing dyes into the environment even in small amount has a deleterious effect on aquatic life, food web and can lead to allergic dermatitis, skin irritation, cancer and mutation. This is due to the presence of a large number of contaminants like toxic organic residues, acids, bases and inorganic contaminants [5-7]. The removal of the spent dyes from wastewater is a major problem due to their chemical stability. Dyes are difficult to remove by conventional effluent treatment methods such as coagulation, ozonation, chemical oxidation, membrane filtration, solvent extraction, precipitation, and microbiological techniques etc. [8-11]. The separation by adsorption using low cost adsorbent is considered to be a better option due to its low cost, easy availability of adsorbents, simplicity of design, high efficiency, ease of operation and biodegradability of many adsorbents [12-15].Activated carbon as an adsorbent is widely used because of its high adsorption abilities for a large number of chemicals [16-18]. The activated carbon is quite expensive material, and its cost prevents it to be used in a large number of separation applications. There are a number of studies going on to find economical process to prepare activated carbon. Many low cost materials such as coir pith carbon, fly ash, coir dust, sawdust, palm shells, biomass fiber waste, rice husk, coffee grounds and rubber wood saw dust etc. [19-28]; have been applied over the period of time with varying degree of successes for the removal of dyes from aqueous solutions. The present study is another effort to produce economically viable activated carbon. Activated carbon can be produced either by physical activation or chemical activation technique [29]. The physical activation technique consists of carbonization of the precursor material followed by gasification of the resulting char in steam or carbon dioxide. The chemical activation technique is performed by carbonizing the raw material that has been impregnated with chemical reagent (e.g., ZnCl 2, H 3 PO 4 and/or KOH). The chemical activation technique has been the subject of many studies in the past years as it presents several advantages over the physical activation technique. The chemical reagents promote the formation of cross-links, reduce volatile loss, and enhance the yield and increase the surface area of the resulted product [30, 31]. ZnCl 2 is one of the most widely used chemical activating agents for the preparation of activated carbon [32]. The purpose of present work was to test the possibility of activated carbon formation from acacia arabica (kikar) wood sawdust which is abundantly available as waste material in the furniture industry of Pakistan. For the preparation of activated carbon, experimentation schedule involved the variation of zinc chloride concentration, carbonization temperature and times in order to determine its influence on the characteristics of the activated carbon material formed. 2. Experimental 2.1 Material and Chemical Reagents Acacia arabica (kikar) wood sawdust, waste of the furniture industry was used for the production of activated carbon and it was collected from a local workshop. Zinc chloride, iodine, Congo red dye and all other chemicals used in this study were reagent grade and were obtained from Merck (Germany). page 2 / 8

3 2.2 Preparation of Activated Carbon page 3 / 8

4 Acacia arabica (kikar) wood sawdust was collected from the local furniture industry. Moisture, volatile matter, and ash contents of the raw material were determined according to the standard test methods ASTM D , ASTM D , and ASTM D , respectively. The proximate analysis of the raw material is shown in Table 1. The saw dust was divided into a number of small samples of approximately 50 grams. The samples were pyrolysed in a tube furnace at a temperature range between 350 to 400 o C in a nitrogen atmosphere for 3 to 4 hours. The carbonized samples were then ground to a particle size range between to mm. The post grinding chemical activation of was carried out with zinc chloride. In one experiment, 10g of the ground sample was taken in an Erlenmeyer flask and was stirrer at 100 rpm with a solution containing 25g of ZnCl 2 in 200 ml of distilled water held at 80 o C in a constant temperature water bath. For all the experiments, the chemical ratio (ZnCl 2 to precursor ratio) was varied from 1.25 to 5.0 in this study. The slurries containing ZnCl 2 and precursor were dried in an oven at 110 o C for 24 hours. The dried samples were placed in a stainless-steel tubular reactor (L= cm, i.d= 3.81cm) and heated (10 o C/min) to the final carbonization temperature under a nitrogen flow rate of 100 ml/min. Figure 1 shows the schematic diagram of the tubular reactor. The samples were kept at the final temperature for different carbonization times ranging between 30 to 120 minutes after which they were allowed to cool under the flow of nitrogen gas. The carbonized products were washed with 250ml of 0.2N HCl solutions by stirring at 80 o C for 30 minute followed by filtration. The filtered products were further washed with distilled water several times by stirring and filtration cycles until the ph of the washed water and the carbon mixture was higher than 6. The final washed products were then dried at 110 o C for 24 hours in an oven to give the activated carbon. In all the experiments pre carbonizing history, heating and nitrogen flow rates (100ml/min) were kept constant. The carbon activation experiments were carried out at different carbonization temperatures ranging from 450 to 800 o C. Figure 1: Schematic structure of tubular reactor used for activation process Table 1: Proximate analysis of acacia arabica (kikar) wood sawdust Component % age Moisture 3% Volatile matter 15% Ash 1% Fixed carbon 81% 2.3 Characterization of Activated Carbon page 4 / 8

5 The adsorption capacities of an activated carbon sample depend on the number of pores, their size and size distribution. These properties are measured by adsorbing some standards adsorbents on the activated carbon. The commonly used adsorbates are iodine, methylene blue, phenol and carbon tetra chloride. The results of these adsorption indices give a technical estimate of the adsorption capability of the activated carbon; however these adsorbents do not provide detailed information of the nature of the pore size and its distribution. To establish the pore size and its distribution BET method is used. Iodine adsorption is another common method to measure the surface area of the activated carbon [33]. In the present work, later technique was employed for the surface characterization of the formed activated carbon. The iodine number (mg of iodine adsorbed per g of active carbon) was determined according to ASTM D test method. 3. Results and Discussion 3.1 Characterization of Activated Carbon The effects of ZnCl 2 to precursor ratios, activation temperatures and the activation durations on the iodine number were studied. The following sections describe the details of these variables on the iodine number Effect of Chemical Ratio on Iodine Number The effect of different chemical ratios (ZnCl 2 mass to precursor mass ratio) on the experimentally found value of the iodine number is shown in Figure 2. It indicates that initially the iodine number increases as the chemical ratio is increased and shows a maximum iodine number (670) at a chemical ratio of 2.5. Thereafter the iodine number decreases as the chemical ratio is increased. This trend of the iodine number as a function of the chemical ratio indicates, that the activation carried out by varying the ZnCl 2 concentration strongly influence the development of the porous texture. The decrease in the iodine number at higher chemical ratios may be due to the formation of multi-layers of activating agent at higher chemical ratio. Similar results were reported for the preparation and characterization of activated carbon from impregnation pitch by ZnCl 2 [32]. Figure 2: Effect of ZnCl2 to carbon ratio on iodine number (Slurry mixing time 3 hr, temperature 450 o C, carbonization time 60 min). Figure 3: Effect of carbonization temperature on iodine number, (carbonization time 60 min, chemical ratio 2.5) Effect of Activation Temperature on Iodine Number page 5 / 8

6 The effect of carbonization temperature on the iodine member is shown in Figure 3. It shows that initially the iodine number increases as a function of carbonization temperature. The maximum iodine number 905 was observed at a carbonization temperature of 700 o C. A further increase in the carbonization temperature lowers the iodine number. This trend is due to the fact that at temperature around 450 o C pyrolysis reaction just commences and starts forming active sites on the carbon being formed. As the temperature is increased, the pyrolysis reaction becomes faster and more active sites on the carbon are formed. As the temperature is further increased beyond 700 o C, the active surface area decreases, this might be due to the sintering effect at higher temperatures causing shrinkage of char, and realignment of the carbon structure which results in reducing the iodine number. Similar trends were observed when activated carbon was produced from Terminalia Arjuna nuts for the removal of chromium (VI) from dilute aqueous solution [31]. Figure 4: Effect of carbonization time on iodine number (carbonization temperature 700 o C, chemical ratio 2.5) Effect of Activation Time on Iodine Number The variation of the iodine number with varying carbonization time from 30 to 120 minutes at a temperature of 700 o C and chemical ratio of 2.5 is shown in Figure 4. The iodine number first increases with the carbonization time and reached at its maximum value of 905 for 60 minute duration and thereafter it starts decreasing. At first the iodine number increases because the pyrolysis reaction has started and completes in about 60 minutes. The decrease in the iodine number after 60 minute may be due to the reasons that some of the pores being sealed off as a result of sintering at excessive time duration. It means that activation time is a critical factor in order to get the optimum surface area of the activated carbon formed by this route. When ZnCl 2 was used activating agent to prepare activated carbon from bituminous coal, a similar trend was observed [29]. 4. Conclusions The activated carbon prepared from acacia arabica (kikar) wood sawdust attained a maximum value of the iodine number of 905 mg per gram of the activated carbon. The sample which gave the maximum iodine number was carbonized at temperature of 700 o C, when the sample was held at this temperature for one hour. This sample had a ZnCl 2 to precursor mass ratio of 2.5. The present work has revealed that acacia arabica wood sawdust is a promising raw material for the preparation of activated carbon of high surface area. References 1. B.H. Hameed, Evaluation of papaya seeds as a novel non-conventional low cost adsorbent for the removal of methylene blue, J. Hazardous Material. Vol.162,2009.pp U.R. Lakshmi, V.C. Srivastava, I.D. Mall, D.H. Lataye, Rice husk ash as an effective adsorbent: Evaluation of adsorption characteristic for Indigo carmine dye, J. Environmental Management. Vol.90,2009.pp page 6 / 8

7 3. B.K. Nandi, A. Gosuami, M.K. Purkait, Adsorption characteristic of brilliant green dye on kaolin, J. Hazardous Material. Vol.161, 2009.pp D.D. Asouhidou, K.S. Triantatyllidis, N.K. Lazaridis, Sorption of reactive dyes from aqueous solution by ordered hexagonal and disordered mesoporous carbon, Micoporous and mesoporous Materials. Vol.117,2009. pp Y. Bulut, H. Aydin, A kinetic and thermodynamics study of methylene blue adsorption on wheat shells, Desalination. Vol.194,2006. pp M. Hajjiaji, A. Alami, A.E. Boouadili, Removal of methylene blue from aqueous solution by fiberous clay minerals, J. Hazardous Material. B135,2006.pp Ozcan, E.M. Oncu, A.S. Ozcan, Kinetics, isotherm and thermodynamics studies of adsorption of acid blue 193 from aqueous solution onto natural sepiolite, Colloid and Surfaces,vol. 277,2006. pp E. Lorenc-Grabowska, G. Gryglewicz, Adsorption characteristics of Congo red on coal-based mesoporous activated carbon, Dyes and Pigments. Vol.74,2007. pp K. Ravikumar, S. Ramlingam, S. Krishnan, K. Balu, Application of response surface methodology to optimize the process variable for Reactive Red and Acid Brown dye removal using a novel adsorbent, Dyes and Pigments. Vol.70,2006. pp D. Kavitha, C. Namasivayam, Experimental and Kinetic studies on methylene blue adsorption by coir pith carbon, Bioresource Technology. Vol.98,2007. pp G. Annadurai, R.S. Juang, D.J. Lee, Use of cellulose- based waste for adsorption of dyes from aqueous solutions, J. Hazardous Materials. B 92,2002.pp C.H. Weng, Y.F. Pan, Adsorption Characteristics of Methylene blue from aqueous solution by sludge ash, Colloid and Surfaces. Vol.274,2006.pp J.S. Macedo, N.B.C. Junior, L.E. Almeida, E.F.S. Vieira, Kinetic and calorimetric study of the adsorption of dyes on mesoporous activated carbon prepared from coconut coir dust, J. Colloid and Interface Science. Vol.298,2006.pp K. V. Kumar, K. Porkodi, Relation between some two- and three parameter isotherm models for the sorption of Methylene blue onto lemon peel, J. Hazardous Materials. Vol.138,2006.pp F.C Wu, R.L. Tseng, Preparation of highly porous carbon from fir wood by KOH etching and CO 2 gasification for adsorption of dyes and phenols from water, J. Colloid and Interface Science. Vol.294,2006.pp V.V.B. Rao, S.R.M. Rao, Adsorption studies on treatment of textile dyeing industrial effluent by fly ash, Chemical Engineering J.vol. 116,2006.pp S. Wang, H. Li, Dye adsorption on unburned carbon: Kinetic and Equilibrium, J. Hazardous Materials. B126,2005.pp B. Acemioglu, Adsorption of Congo Red from aqueous solution onto calcium-rich fly ash, J. Colloid and Interface Science, vol.274,2002.pp D. Park, S.R Lim, Y.S. Yun, J.M. Park, Development of new Cr(VI)-biosorbent from agricultural biowaste, Bioresource Technology. Vol.99,2008.pp R. Elangovan, L. Philip, K. Chandraraj, Biosorption of chromium species by aquatic weeds: Kinetic and mechanism studies, J. Hazardous Materials. Vol.152,2008.pp C. Bouchelta, M.S. Medjram, O. Bertrand, J.P Bellat, Preparation and Characterization of activated carbon from date stones by physical activation with steam, J. Analytical and Applied Pyrolysis. Vol.82,2008.pp S. Koutcheiko, C.M. Monreal, H.kodama, T. McCracken, Preparation and characterization of activated carbon derived from the thermo-chemical conversion of chicken manure, Bioresource page 7 / 8

8 Powered by TCPDF ( Production of Activated Carbon from Acacia Arabica Sawdust Technology vol.98,2007.pp T. Y, A. C. Lau, Characterization of activated carbon prepared from pistachio-nut shells by physical activation, Collide and Interface Science. Vol.267,2003.pp S.S. Baral, N. Das, T.S. Ramulu, S.K. Shaoo, S.N. Das, G.R. Chaudhury, Removal of Cr (VI) by thermally activated weed salvinia cucullata in fixed bed column, J. Hazardous Material. Vol.161,2009.pp V.S. Mane, I.D. Mall, V.C. Strivastava, Use of bagass fly ash as an adsorbent for the removal of brilliant green dye from aqueous solution, Dyes and Pigments pp X.S. Wang, Y. P. Tang, S.R. Tao, Kinetics, equilibrium and thermodynamics study on removal of Cr (VI) from aqueous solution using low-cost adsorbent alligator weed, J. Chemical Engineering. In Press. 27. J. Gue, W.S. Xu, Y.L. Chen, A.C. Lua, Adsorption of NH 3 onto activated carbon prepared from palm shells impregnated with H 2 SO 4, J. Colloid and Interface Science. Vol.281,2005.pp B.G.P. Kumar, L.R. Miranda, M. Velan, Adsorption of Bismark Brown dye on activated carbon prepared from rubberwood sawdust using different activation methods, J. Hazardous Materials. B126,2005.pp L.Y. Hsu, H. Teng, Influence of different chemical reagents on the preparation of activated carbons from bituminous coal, Fuel Processing Technology. Vol.64,2000.pp Namane, A. Mekarzia, K. Benrachedi, N. Belhaneche, A. Hellal, Determination of the adsorption capacity of activated carbon made from coffee grounds by chemical activation with ZnCl 2 and H 3 PO 4, J. Hazardous Materias. B119,2005.pp K. Mohanty, M. Jha, B.C. Meikap, M.N. Bisawas, Removal of chromium (VI) from dilute aqueous solution by activated carbon developed from Terminalia Arjuna nuts activated with zinc chloride, Chemical Engineering Science. Vol.60,2005.pp J.G. Gomez, A.M. Garcia, M.A.D. Diez, Preparation and characterization of activated carbons from impregnation pitch by ZnCl 2, Applied Surface Science. Vol.252,2005.pp D. O. Cooney, adsorption design for Wastewater Treatment, Lewis Publishers, New York USA, PDF generated by Hajvery University Lahore page 8 / 8