Synthesis of Hydrous Aluminum (III) -Iron (III)- Manganese (IV) Ternary Mixed Oxide for Fluoride Removal

Abstract

A b s t r a c t — Hydrous Aluminum (III)-Iron (III)-Manganese (IV) ternary mixed oxide was synthesized by Co-precipitation method. It was found that the Al: Fe: Mn sample with 75:15:10 w/v ratio exhibited maximum adsorption capacity for fluoride. The use of mixed oxide for investigating fluoride removal efficiency at varied condition showed that the reaction was pH sensitive and the optimum pH was between 6.00 and 7.00. The characterization studies on the adsorbent by XRD, SEM-EDX and FT-IR analysis for fluoride adsorption were carried out to understand the adsorption mechanism. The particles were irregular in shape, highly porous. FT-IR studies revealed a little change after fluoride adsorption and showed formation of new fluoride– oxygen bond on the adsorbent surface. Applicability of different sorption kinetics model; was studied. The pseudo-second order equation described all kinetic data very well. The Langmuir isotherm equation described the equilibrium very well. The thermodynamic analysis of the equilibrium indicated that the adsorption reaction of fluoride with hydrous Al-Fe-Mn mixed oxide system for water was endothermic and spontaneous in nature. The presence of PO4 -3 showed significant effect on removal efficiency of Al-Fe-Mn oxide adsorbent.