Removal of fluoride from aqueous solution by using bael (Aegle marmelos) shell activated carbon: Kinetic, equilibrium and thermodynamic study

Fluoride is a toxic substance that is causing adverse effects on human health. Present study deals with the adsorption of fluoride from aqueous solutions by using activated carbon prepared from Bael Shell (ACBS). The batch adsorption experiments were carried out to find the fluoride adsorption capacity of ACBS from aqueous solution. The effect of various parameters viz. adsorbent dose (m), initial pH (pH(0)), contact time (t), initial concentration (C-0) and temperature (7) on the adsorption of fluoride have been studied. The study reveals that, the adsorption rate is found to be very fast. At the initial concentration of 4 mg/L, about 52% fluoride removal was found in 60 min contact time at the adsorbent dose of 2 g/L. The maximum uptake of 1.07 mg/g was found at lower concentration (4 mg/L) and 2.4 mg/g at higher concentration (8 mg/L) at the optimum dose and 30 degrees C temperature. The sorption kinetics could be well represented by pseudo-second-order kinetic model. The adsorption isotherm data fits Redlich-Peterson, Langmuir, Radke-Prausnitz, Toth, Temkin and Freundlich isotherm well. In thermodynamic study the Delta G degrees values are found to be in the range of-23.47 to-26.398 kJ/mol with increase in temperature from 293 K to 323 K. The positive Delta H degrees (5.103 kJ/mol) value confirms the endothermic nature of the overall sorption process. The Delta S degrees value is found to be 0.098 kJ/mol K. The adsorption of fluoride onto ACBS is an endothermic process. Fluoride from field water samples was successfully reduced to the permissible limit by ACBS. (C) 2016 Elsevier B.V. All rights reserved.