The generation of biogenic manganese oxides and its application in the removal of As(III) in groundwater.

The generation of biogenic manganese oxides (BMnOx) by Microbacterium sp. CSA40, and As(III) removal efficiency and mechanism by BMnOx were investigated in this study. The propagation and growth of Microbacterium sp. CSA40 was conducted in half-strength Luria Broth with 10 mg/L Mn(II), then high concentration of Microbacterium sp. CSA40 was added to PYG medium making its OD600 = 0.9 ± 0.05 for BMnOx generation. The initial Mn(II) concentrations, excessively oligotrophic condition, and pH had great influence on generation of BMnOx by Microbacterium sp. CSA40. An appropriate Mn(II) concentration (50 mg/L) was obtained for generation of BMnOx, and higher or lower Mn(II) concentration would interfere Mn(II) oxidization performance. Mn(II) oxidation ability performed best in weak alkaline conditions and would be restricted in an excessively oligotrophic condition. As(III) oxidization and As(V) adsorption proceed simultaneously by BMnOx, what is more, more than 90% of total As was removed by 0.5 g/L BMnOx. During the application process, no Mn(II) was released in the solution, that is, BMnOx retained its ability for Mn(II) oxidization caused by activity of Microbacterium sp. CSA40. Therefore, BMnOx would be a pollution-free, cost-effective, and high-efficiency material for As(III) treatment in groundwater.