1 Removal of reactive dyes from aqueous solution by adsorption on coconut coir activated carbon Malay Chaudhuri * , Emad S. Elmolla, Rashidah Bt. Othman Department of Civil Engineering Universiti Teknologi PETRONAS Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia * Corresponding author. Tel: + 605-3687304, Fax: +605-3656716, E-mail: m_chaudhuri@petronas.com.my Abstract Activated carbon was prepared from coconut coir and adsorption of reactive dyes Remazol Red F-3B and Remazol Blue by the activated carbon was examined. Batch adsorption test showed that extent of dye adsorption was dependent on dye concentration, contact time, pH and carbon dose. Equilibrium adsorption was attained in 3 h and maximum adsorption occurred in the acidic pH range 1-3. Adsorption capacity of the activated carbon for the dyes was evaluated by batch equilibrium test and compared with that of a commercial activated carbon. According to Langmuir and Freundlich adsorption isotherms, the coconut coir activated carbon showed higher capacity for adsorption of Remazol Red F-3B than that of the commercial activated carbon. For Remazol Blue, both activated carbons showed comparable adsorption capacity. Coconut coir activated carbon is a suitable substitute for commercial activated carbon in the removal of reactive dyes from aqueous solution. Keywords: Reactive dyes, adsorption, coconut coir, activated carbon, Langmuir, Freundlich. Introduction Reactive dyes are used for dyeing cellulosic fibres. They consist of a chromophore and a functional group that binds the dyestuff to the fibre. The functional group, when applied to a fibre in an alkaline dye bath, forms a chemical bond with a hydroxyl group on the fibre which is much more resistant to unusual conditions of use than the physicochemical bond between other classes of dyes and cellulose. However, reactive dyes have a low degree of utilization, since the functional group also bonds to water, creating hydrolysis and hence 10-50% of the dye is unexhausted and remains in the dye bath waste. A considerable amount of research on wastewater treatment has focused on the removal of reactive dyes from dye bath waste, essentially for three reasons: reactive dyes represent 20-30% of the total dye market, large fraction of reactive dyes (10-50%) are wasted during the dyeing process and conventional wastewater treatment methods, which rely on adsorption and biodegradation, were found to be inefficient for complete elimination of many reactive dyes [1]. Adsorption is an effective treatment method that is widely used in the removal of contaminants from water and wastewater. This method has also been proven to be an important way to treat coloured effluents [2]. Adsorption of reactive dyes on coal- based commercial activated carbon has been studied [1, 3, 4]. The use of coal-based commercial activated carbon is limited because of its relatively high price and its feedstock is non-renewable [2]. Low-cost, renewable, and easily available plant-based materials are to be used as a source in the production of activated carbon. Adsorption of reactive dyes on activated carbon prepared from peach stones [2], coconut tree flower and jute fibre [5] and coir pith [6], and bagasse fly ash [7] have been studied. In this study, activated carbon was prepared from coconut coir and its capacity for adsorption of reactive dyes from aqueous solution was studied and compared with that of a commercial activated carbon so as to assess its suitability as a cost-effective substitute for commercial activated carbon. Materials and methods Activated carbon Coconut coir activated carbon was prepared according to a method used by Santhy and Selvapathy [6] for preparing coir pith activated carbon. Washed and dried coconut coir was treated with concentrated sulphuric acid and kept in a hot- 2nd International Conference on Engineering Technology 2009 (ICET 2009) 8-10 December 2009, Kuala Lumpur