Reduction mechanism of hexavalent chromium by functional groups of undissolved humic acid and humin fractions of typical black soil from Northeast China

Abstract

Soil organic which act as the main electron donors for Cr(VI) reduction; however, Cr(VI) reduction mechanism y different SOM fractions is still unclear, such as undissolved humic acid (HA) and humin (HM). In this study, HA and HM fractions extracted from typical lack soil from Northeast China were used to investigate the reaction mechanism etween humus functional groups and Cr(VI). According to the results, henol and hydroxyl were determined as the main electron donors for Cr(VI) reduction y HA and HM instead of carboxyl and carbonyl, which were more likely involved in Cr complexation. Furthermore, Cr(VI) reduction was more dependent on aromatic carbon, rather than aliphatic carbon, and functional groups on the article surfaces of HA and HM were much more active for Cr(VI) reduction than their interior art. Additionally, HM was found to have a relatively low Cr(VI) reduction capability compared with HA resulting from its high content of cellulose structures that are quite resistant to Cr(VI) oxidation. These results suggest that in the soil environment, undissolved HA tends to lay a much more important role than HM in Cr(VI) reduction and retention in the condition that their mass contents are comparable