Chromium(VI) reactions of polysaccharide biopolymers

This study investigated the reaction mechanisms of toxic hexavalent chromium (Cr(VI)) with polysaccharide biopolymers, including cellulose, hemicellulose and chitin, to understand their roles in determining the Cr(VI) removal efficiencies of biomaterials containing these polymers. The Cr(VI) removal rates and capacities at pH 2 followed the order of hemicellulose > chitin ≫ cellulose. The Cr(VI) removals by these biopolymers were primarily due to the reduction of Cr(VI) to Cr(III). The hydroxyl groups of these biomaterials were the predominant reactive sites for Cr(VI) reduction, and the oxidation of the hydroxyl groups by Cr(VI) led to the formation of carboxyl groups. In addition to the reactivity of functional groups toward Cr(VI), the accessibility of functional groups in different biopolymers may also determine the reduction rates of Cr(VI) by the biopolymers.

► The mechanism of Cr(VI) reaction with polysaccharides involves Cr(VI) reduction.
► The hydroxyl groups in polysaccharides are responsible for the Cr(VI) reduction.
► The accessibility of functional groups also determine the Cr(VI) reduction rate.