Surface interaction between metazeunerite and an indigenous microorganism Kocuria rosea: Implications for bioremediation of As-U tailings

Metazeunerite (Cu(UO2)2(AsO4)2·8H2O), a highly water-insoluble mineral, is shown to be an important solubility limiting phase controlling uranium and arsenic migration. This mineral has been identified in the shallow vadose zone of contaminated area at a closed uranium mine in the southwest of China. Consequently, modeling the evolution of U and As in vadose zone driven by indigenous microorganisms requires accurate knowledge of the mineral-microbe interaction process. In the present contribution, the surface interaction between metazeunerite and an indigenous bacteria Kocuria rosea was characterized by flow-cell ATR-FTIR spectroscopy, CLSM, SEM-EDS, XPS, and first-principle calculation. Results suggested that Kocuria rosea cells attached on the surface of metazeunerite and formed biofilm gradually through PO, CO, and COO– groups on the cells membrane in real time. Metazeunerite was eroded by the adhered Kocuria rosea cells layer by layer, whose surface functional groups could structurally couple to the metals on metazeunerite surface and eventually form multi-dentate complexes. Furthermore, As(V), located in the mineral lattice of metazeunerite, was transformed to As(III) by Kocuria rosea after 24 h while U(VI) was not reduced and did not result in lattice structure destruction and reductive dissolution. The results of the study will help to design long-term effectiveness of bioremediation strategies of As-U contamination.