Equilibrium and Kinetic Mechanisms of Fluoride Ions Adsorption onto Activated Alumina

Abstract

In this work, the fluoride adsorption by activated alumina (AAD) was evaluated in batch system. The point of zero charge of adsorbent was obtained. The effects of pH (2 to 12), temperature (30, 40 and 50 °C) and agitation (70, 100, 130 and 160 rpm) in the process were investigated. The adsorption kinetics and equilibrium were evaluated. The results show that the pHPZC of AAD is 7.04 and the highest adsorption capacities were obtained at pH 2 and 130 rpm. The temperature did not influence on the process. The equilibrium was achieved in 4 hours and the model that best described the kinetic data it was the pseudo-first order. The best fit to the experimental equilibrium data was obtained by Langmuir isotherm and the maximum adsorption capacity was 1.57 mg g-1, demonstrating the high efficiency of AAD on fluoride adsorption in batch system.