A comparative study on the batch performance of fluoride adsorption by activated silica gel and activated rice husk ash

A comparative study was done for removal of fluoride by activated silica gel (ASiG) and activated rice husk ash (ARHA) through batch techniques. The fluoride removal performance of both adsorbents such as ASiG and ARHA was evaluated as a function of the initial concentration, adsorbent dose, contact time and pH. The adsorbent dose characterized as having high selectivity for fluoride and larger adsorption capacity. Characterization of ASiG and ARHA before and after fluoride adsorption was studied by SEM and FTIR study was done to get a better insight into the mechanism of adsorption. The rate of adsorption was rapid and followed pseudo-second-order kinetics for both adsorbents. The system followed the Langmuir isotherm model for both ASiG and ARHA with adsorption capacity 0.244 mg g⁻¹ and 0.402 mg g^−l respectively.