Removal of fluoride from aqueous solution with the superparamagnetic zirconia material

Nano-sized superparamagnetic zirconia material (ZrO(2)/SiO(2)/Fe(3)O(4), SPMZ) was applied for the sorption of fluoride from water and simulated industrial wastewater. The experiments showed that SPMZ possesses a satisfactory chemical stability at moderate acidic and basic conditions. Sorption and desorption develop very fast so that the equilibration is attained in few minutes. Fluoride sorption capacity increases with decreasing pH value. At pH = 4 the monolayer sorption capacity amounts to 14.7 mg/g (= 0.78 m mol g(-1)). Experiments with simulated wastewater of the semiconductor industry demonstrated the selective elimination of fluoride. Regeneration with NaOH of different concentrations showed that a 10(-3) N NaOH provides optimum conditions. Repeated sorption/regeneration cycles demonstrated the possibility of reusing the SPMZ material. The total amount of fluoride removed from solutions for all sorption runs after sorption/regeneration cycles in the service life primarily dominated the influence on the reduction of sorption efficiency rather than the solution pH value in the range of 4-5. The superparamagnetic material can be easily separated from the liquid phase by means of high gradient magnetic separator (HGMS). Thus, the SPMZ material opens a possibility for an efficient removal of fluoride from industrial wastewaters and raw water of the drinking water supply. (C) 2011 Elsevier B.V. All rights reserved.