Experimental Evaluation of Activated Termite Mound for Fluoride Adsorption

Abstract

The main objective of this study was to examine fluoride adsorption potential of thermally activated termite mound (TTM) under batch adsorption experimentalsetup. Thermal activation of the mound in between 100 to 5000C increased the adsorption efficiency (~ 50 to ~ 79%), whereas activation above 5000C decreased the efficiency. The removal of fluoride was optimal (~ 91%) in the pH ranging from 3 to 10. Adsorption kinetics data followed pseudo-second order equation (R2> 0.99). Freundlich and Dubinin-Radushkevich isotherms satisfactorily described the equilibrium isotherm data (R2> 0.98, χ2< 0.25). The obtained mean sorption energy, EDR, was 11.12 kJ/mol suggesting chemisorption as the predominant sorption mechanism. Fluoride adsorption was significantly decreased in the presence of CO3 2- and PO4 3- at a higher concentration range. TTM effectively reduced 7.56 mg/L fluoride in groundwater to below 1.5 mg/L. Fluoride loaded adsorbent was successfully regenerated with NaOH solution for effective reuse. The results of this study demonstrated that TTM could be a promising defluoridation material requiring further investigation for practical applicability.