Chromium adsorption on sodium sulfide treated sheep wool

Chromium adsorption from the aqueous phase was evaluated using Mongolian sheep wool as a biosorbent. The wool was chemically treated with sodium sulfide to enhance the adsorption capacity. The surface of the wool was analyzed by SEM. EDX and FTIR were also used for the analysis of differences in the wool after chromium adsorption. Chromium was detected in the wool after adsorption by EDX analysis. FTIR data indicated the intensity change in amide A and amide I, which shows chromium may be adsorbed to the amino and carboxyl groups of the wool. The sodium sulfide treated wool showed better adsorption capacity of chromium(III) than the untreated wool. In the case of chromium(III), the adsorption amount increased with the pH increased, while for chromium(VI), the adsorption value increased with the pH decreased. Kinetic analysis of the adsorption indicated that the removal of chromium followed pseudo-second order kinetic model for the whole contact time range. Langmuir isotherm model was used for the analysis of adsorption equilibrium and the adsorption followed well Langmuir isotherm. This study demonstrates the sodium sulfide treated wool is an effective and low-cost biosorbent for heavy metal adsorption.