AQDS-mediated dissimilatory reduction of iron (hydr)oxides induces the formation of large grain vivianite: A new insight for phosphorus pollution control in sediment

Abstract

Quinones plays a crucial role in iron (hydr)oxides dissimilatory reduction and the geochemical cycle of elements. However, the interfacial reactions and the subsequent effect of phosphorus (P) in sediments remain unclear. To clarify it, 9,10-anthraquinone-2,6-disulfonic acid (AQDS) was used to participate in reduction of hematite and goethite by Geobacter metallireducens GS-15, and the interfacial electron transfer between iron (hydr)oxides and AQDS were also explained. Results showed that AQDS had a higher promotion effect on the reduction of goethite than hematite, and more than 41% of goethite was reduced compared to the control check, with an 80.6 mg g−1 phosphorus immobilized. Vivianite was produced in this system, and the size of vivianite in hematite-AQDS and goethite-AQDS groups increased 7.59% and 57.78%, respectively, compared to the corresponding groups without AQDS. The highest weight of vivianite-P was in the Goe-AQDS group by X-ray absorption near edge structure (XANES). Electrochemical characteristics showed that the interfacial electron transfer rates of hematite and goethite with AQDS adding were 7.49 s−1 and 9.03 s−1, respectively. Therefore, high electron transfer efficiency led more microbial iron reductions, which generated high concentrations of Fe(Ⅱ) and facilitated the increasing of production and grain size of vivianite. These findings provide a new understanding of vivianite generation and phosphorus immobilization.