Defluoridation of waters using low-cost HNO<SUB align="right">3 activated carbon derived from stems of Senna Occidentalis plant

Abstract

A simple, accurate and reliable batch adsorption technique for the removal of fluoride has been developed using an active carbon derived from stems of Senna Occidentalis plant (NSOC). Various physicochemical parameters have been optimised. The maximum extraction of fluoride has been found to be at pH: 7 with an agitation time of 50 min at fluoride ion concentration of 5 mg/lit and at temperature of 30 ± 1°C. Adsorption isotherms have been modelled using Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms. The correlation coefficient (R2) and dimensionless separation factor (RL) values obtained for the present adsorption system confirm that the best fit is 'the Langmuir adsorption isotherm' model. Kinetics of adsorption processes have been studied and observed to be pseudo second-order kinetics. The active carbon has been characterised using FTIR and SEM-EDX techniques. The methodologies developed are applied to real ground water samples and found to be successful.