Adsorption Properties of As(III) and Cr(VI) in Water Environment by Calcined Gibbsite

Abstract

The adsorption properties of As(III) and Cr(VI) by gibbsite (GB) calcined at 200 to 1150 °C was investigated on basis of their specific surface area, number of hydroxyl groups, surface pH and adsorption isotherms. The amount of As(III) and Cr(VI) adsorbed on the calcined GB at 300 or 400 °C was the highest. In the case of the calcination temperature was more than 700 °C, the amount adsorbed decreased with the increasing calcination temperature. In a single solution system, the amount of As(III) adsorbed on calcined GB was higher than that of Cr(VI). The amount of As(III) and Cr(VI) adsorbed on calcined GB was higher in a binary solution system than those in a single solution system. The pH in solution after As(III) and Cr(VI) adsorption was greater than that before adsorption. These results indicated that the adsorption mechanism of As(III) and Cr(VI) was as followed: the hydroxyl groups on calcined GB were exchanged to As(III) and Cr(VI) and they adsorbed n the calcined GB surface. In the case of coexistence of As(III) and Cr(VI), they could be removed better by calcined GB because the pH in binary solution was lower than that in single solution. Both As(III) and Cr(VI) in water environment could be removed by the calcined GB simultaneously.