Cashewnut sheath carbon: A new sorbent for defluoridation of water

Abstract

Cashewnut sheath, an agricultural waste discarded largely in India is identified for the preparation of an effective sorbent for fluoride removal. Experiments were conducted for the sorption of fluoride from aqueous solution using activated carbon from cashewnut sheath (CSC) in two phases, namely, batch studies and column studies. The influence of pH, adsorbent dose, particle size and contact time was investigated in batch studies. The adsorption process follows Freundlich adsorption isotherm. Continuous flow experiments in fixed bed columns packed with activated carbon were carried out in order to assess the feasibility of this for field applications. The carbon bed after exhaustion was regenerated with 0.1N hydrochloric acid. The influence of initial concentration of fluoride ion, flow rate, particle size and concentration of the regenerant on the performance of the column was studied. Comparative study was conducted with commercially available carbon impregnated with 2% aluminium sulphate solution. The results revealed that CSC is found to be active and efficient for fluoride removal.