KINETIC AND THERMODYNAMIC STUDY OF DEFLUORIDATION BY USING ACTIVATED VETIVERIA ZIZANIOIDESMegha Tharayil and P.S. HarikumarAbstract The present study describes the fluoride sorption from aqueous solution onto the activated Vetiveria zizanioides (AVZ) using phosphoric acid by batch sorption. The activation of Vetiveria zizanioides root powder was conducted using an impregnation ratio of 1:4 between Vetiveria zizanioides root powder and activating agent (H3PO4) for an activation time of 1h at 700 oC. The kinetic data were analysed using pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich model. Fitness of the sorption kinetic models of various initial fluoride concentrations at 303K were evaluated using correlation coefficient and sum of squares of the error (SSE). The sorption kinetics of fluoride on activated Vetiveria zizanioides was found to follow the pseudo-second order rate expression. Thermodynamic parameters revealed the spontaneous nature of fluoride adsorption with increase of entropy and an end othermic nature of sorption process. The environmental friendly and cost-effective material, activated Vetiveria zizanioides possess the potential to remove fluoride from water therefore it is suitable for the defluoridation application.
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