Removal of chromium(III) from water samples by a low-cost sorbent: application to a mixture of chromium(III) and chromium(VI)

Adsorption of Cr(III) and Cr(VI) ions from aqueous solutions and water samples has been investigated using Powdered Marble Waste (PMW). The effect of solution pH, initial metal concentration, sorbent dose, shaking time, temperature, and foreign ions on the adsorption of Cr(III) was studied. It was found that the sorption capacity increased with the increase of Cr(III) concentration and temperature. ΔG0, ΔH0 and ΔS0 were also calculated. They indicated that the adsorption process was spontaneous and endothermic in nature. The removal of ~100% of Cr(III) and Cr(VI) ions in 1 : 1 molar ratio, after reduction of Cr(VI) to Cr(III), was attained. The procedure was successfully applied to remove chromium ions from aqueous and different natural water samples. Moreover, the adsorption mechanism is suggested.