Fluoride removal studies from contaminated ground water by using bauxite

The present study explores the feasibility of utilizing bauxite for fluoride removal from synthetic and natural fluoride bearing groundwater samples of Orissa, India. Adsorption experiments with respect to variation in time, pH, adsorbate and concentrations of other anions namely NO3-, SO42-, CO32- and PO43- were carried out. Characterization of bauxite before and after fluoride adsorption was studied by XRD, FTIR and SEM-EDX to get a better insight into the mechanism of adsorption. The rate of adsorption was rapid and followed first order kinetics with intraparticle diffusion as the rate determining step. The system followed the Langmuir adsorption isotherm model with adsorption capacity of 5.16 mg g(-1). The competition of CO32- ions for surface sites is comparatively less as compared to NO3-, SO42- and PO43- in the concentration range of 5-20 mg g(-1) at solution pH of 6 during fluoride adsorption. The estimated thermodynamic parameters (Delta H degrees. Delta S degrees and Delta G degrees) indicated that the adsorption was spontaneous and exothermic in nature. (c) 2010 Elsevier B.V. All rights reserved.