Arsenite removal from aqueous solution by a microbial fuel cell-zerovalent iron hybrid process

Conventional zerovalent iron (ZVI) technology has low arsenic removal efficiency because of the slow ZVI corrosion rate. In this study, microbial fuel cell (MFC)-zerovalent iron (MFC-ZVI) hybrid process has been constructed and used to remove arsenite (As(III)) from aqueous solutions. Our results indicate that the ZVI corrosion directly utilizes the low-voltage electricity generated by MFC in the hybrid process and both the ZVI corrosion rate and arsenic removal efficiency are therefore substantially increased. The resultant water qualities are compliant with the recommended standards of EPA and WHO. Compared to the ZVI process alone, the H2O2 generation rate and output are dramatically improved in MFC-ZVI hybrid process. Strong oxidants derived from H2O2 can rapidly oxidize As(III) into arsenate (As(V)), which helps to improve the As(III) removal efficiency. The distribution analysis of As and Fe indicates that the As/Fe molar ratio of the flocs in solution is much higher in the MFC-ZVI hybrid process. This phenomenon results from the different arsenic species and hydrous ferric oxides species in these two processes. In addition, the electrosorption effect in the MFC-ZVI hybrid process also contributed to the arsenic removal by concentrating As(V) in the vicinity of the iron electrode.