Optimization of production conditions for activated carbons from Tamarind wood by zinc chloride using response surface methodology J.N. Sahu a,b, * , Jyotikusum Acharya c , B.C. Meikap a,d a Department of Chemical Engineering, Indian Institute of Technology (IIT), Kharagpur, P.O. Kharagpur Technology, West Bengal 721302, India b Department of Chemical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia c School of Energy and Environment Management, Rajiv Gandhi Technical University (RGTU), Gandhinagar, Bhopal, Madhya Pradesh, India d School of Chemical Engineering, Faculty of Engineering, University of KwaZulu-Natal, Howard College Campus, King George V. Avenue, Durban 4041, South Africa article info Article history: Received 15 August 2009 Received in revised form 12 October 2009 Accepted 14 October 2009 Available online 12 November 2009 Keywords: Tamarind wood Activated carbon Chemical activation Optimization Adsorption abstract The low-cost activated carbon was prepared from Tamarind wood an agricultural waste material, by chemical activation with zinc chloride. Activated carbon adsorption is an effective means for reducing organic chemicals, chlorine, heavy metals and unpleasant tastes and odours in effluent or colored sub- stances from gas or liquid streams. Central composite design (CCD) was applied to study the influence of activation temperature, chemical ratio of zinc chloride to Tamarind wood and activation time on the chemical activation process of Tamarind wood. Two quadratic models were developed for yield of acti- vated carbon and adsorption of malachite green oxalate using Design-Expert software. The models were used to calculate the optimum operating conditions for production of activated carbon providing a com- promise between yield and adsorption of the process. The yield (45.26 wt.%) and adsorption (99.9%) of the activated carbon produced at these operating conditions showed an excellent agreement with the amounts predicted by the models. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Activated carbon is a black solid substance resembling granular or powder charcoal and are carbonaceous material that have highly developed porosity, internal surface area and relatively high mechanical strength. They are widely used as adsorbents in waste water and gas treatments as well as in catalysis (Grzybek, 1997; Lisovskii et al., 1997). Despite its prolific use in industries, acti- vated carbon remains an expensive material. In recent years, re- search interest in the production of low-cost alternatives to activated carbon has grown. Activated carbon has several impor- tant uses including solution purification (as in the clean-up of cane, beet and corn-sugar solutions), removal of tastes and odours from domestic and industrial water supplies, vegetable and animal fats and oils, alcoholic beverages, chemicals and pharmaceuticals and in the waste water treatment. It also finds use in purification of gases, liquid phase recovery, separation processes and as catalyst and catalyst supports. Many organic compounds such as chlori- nated and non-chlorinated solvents, gasoline, pesticides and triha- lomethanes can be adsorbed by activated carbon. It is also effective for removal of chlorine and moderately effective for removal of some heavy metals. It is used for liquid phase adsorption or de-col- orizations which are usually light, fluffy powders produced from low-density material such as sawdust or peat. However, for gas phase adsorption, there is a need for hard, dense granular materials produced from high-density raw materials such as bamboo, coco- nut shells, palm kernel shells, coal or coke. In practice, coal and agricultural byproducts of lignocelluloses materials are two main sources for the production of commercial activated carbons. Agricultural wastes have emerged as a better choice. Though raw agricultural wastes can be used as adsorbents without further treatment, activation could enhance their adsorp- tion capacity. The production of activated carbons from agricul- tural wastes convert unwanted, surplus agricultural waste, of which billions of kilograms are produced annually, to useful valu- able adsorbents, such as coconut shells (Dwivedi et al., 2008), fruit stones (Lussier et al., 1994), bagasse (Mohan and Singh, 2002), coir- pith (Kadrivelu et al., 2001; Namasivayam and Sangeetha, 2004), oil palm waste (Lua and Guo, 1998), and agricultural residues from sugarcane (Blanco et al., 2000), rice husk (Sahu et al., 2009), pea- nuts (Ricordel et al., 2001), sawdust (Mohanty et al., 2005b) and canes from some easy-growing wood species (Basso et al., 2002; Singh et al., 2008). Most of the activated carbons are produced by a two-stage process carbonization followed by activation. The first step is to enrich the carbon content and to create an initial porosity and the activation process helps in enhancing the pore structure. 0960-8524/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2009.10.031 * Corresponding author. Address: Department of Chemical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia. Tel.: +60 3 7967 5295 (O); fax: +60 3 7967 5319. E-mail addresses: jnsahu@um.edu.my, jay_sahu@yahoo.co.in (J.N. Sahu). Bioresource Technology 101 (2010) 1974–1982 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech