Sorption and Reduction of Cr(VI) On Lignin, Cellulose, Hemicellulose and Chitin.

Biomaterials, such as crop residues and dead fungal biomass, have been demonstrated to be capable of reducing Cr (VI) to Cr (III). However, little is known about the mechanisms of Cr(VI) reduction by the biomaterials because of their complex compositions. Therefore, the aims of this work were to investigate the sorption and reduction of Cr(VI) on lignin, cellulose, hemicellulose and chitin, which are the main components of biomaterials. The materials before and after Cr(VI) reaction were analyzed using FTIR, ¹³C NMR and SIMS to identify the functional groups governing Cr (VI) reduction on these materials. Cr K-edge XAS was applied to determine the oxidation states and structures of Cr on the sorbents. The results showed that lignin possessed a high Cr(VI) reduction capacity due to its aromatic nature. Hemicellulose and chitin can also reduce Cr(VI) to Cr(III) while Cr(VI) reduction by cellulose was not observed. The differences in the Cr(VI) reduction capabilities of these aliphatic structures result from the differences in their functionalities. Therefore, the functional groups of these material play a key role in Cr(VI) reduction as well as the sorption of resultant Cr(III).