Removal of fluoride from aqueous solution using graphite: A kinetic and thermodynamic study

Abstract

Batch sorption system using various grades of graphite as adsorbents was investigated to remove fluoride ions from aqueous solutions. The system variables studied include initial concentration of the sorbate, agitation time, adsorbent dose, pH, co-ions and temperature. The experimental data fitted well to the Freundlich and Langmuir isotherms. Thermodynamic parameters such as ΔHº, ΔSº and ΔGº were calculated which indicated that the adsorption was endothermic and a physical process. Kinetic studies reveal that the adsorption follows reversible first order kinetics. XRD patterns of the adsorbent before and after adsorption were recorded to get a better in sight into the mechanism of the adsorption process.