Fluoride removal from water using magnetic iron oxide/aluminium hydroxide composite

Abstract

Magnetic iron oxide/aluminum hydroxide composite material was synthesized in three successive steps by chemical co-precipitation methods and characterized for its surface properties and mineralogy using potentiometric mass titration and X-ray diffraction spectroscopic method, respectively. The result of xrd peak indicated that the structure of iron oxide was crystalline regardless of the different mass ratio of iron oxide and aluminum hydroxide. The point of zero charge was 9.5 indicating that the surface of Fe₃O₄/Al(OH)₃ is positively charged which is favorable condition for the adsorption of fluoride ion. The adsorption of fluoride on iron oxide/aluminum hydroxide was investigated using batch adsorption techniques. Results showed that at optimal mass ratio 5:2 of Fe₃O₄/Al(OH)₃ and adsorbent dosage at 4 g/L, the fluoride removal efficiency was found to be 89% from the initial concentration 10 mg/L. The residual aluminum after adsorption of fluoride was found to be 0.01 mg/L. Adsorption isotherm models followed the order: Freundlich > Langumir > D-R. The maximum adsorption capacity of Fe₃O₄/Al(OH)₃ was found to be 6.67 mg/g in the concentration range used in this study. Kinetics studies showed that the adsorption of fluoride onto Fe₃O₄/Al(OH)₃ proceeds according to a pseudo-second-order reaction model with an average rate constant of1.93 x 10^-2min (mg/g). The magnetic Fe₃O₄/Al(OH)₃was found to be an effective adsorbent for fluoride removal from drinking water.