Fabrication of dynamic zero-valent iron/MnO2 nanowire membrane for efficient and recyclable selenium separation

Controllable selenium separation processes are essential from the viewpoint of human health, electronics industry and environmental protection due to the vital role of selenium in the human body and photovoltaic devices, and the adverse impacts emanating from selenium pollution in surface and groundwater by the highly toxic and high lethal at higher selenium concentrations. Herein, a dynamic zero-valent iron/MnO2 nanowire hybrid membranes (ZVINM) with high chemical activity and excellent recoverability have been developed based on in situ chemical deposition nanoscale zero-valent iron (NZVI) on the surface of ultralong MnO2 nanowires to self-assemble into to hybrid membrane, and the applicability of this hybrid membrane for selenium separation was evaluated. To investigate the retention efficiency, the selenium separation behavior on ZVINM was examined by various separation conditions such as operating pressures, selenium concentrations and NZVI content, solution pH, interfering ions and penetration times. The as-prepared ZVINM shows excellent separation performance with the maximum retention efficiency of 95%. The appropriate selenium separation on ZVINM was obtained at an acidic pH range of 2-6 with a high separation efficiency (over 85%), and the rejection rate was decreased by increasing solution pH, indicating that the selenium separation process was promoted under strong acid conditions and inhibited under strong alkali environment. In addition, it was found that the carbonate ions and higher selenium concentration have a strong inhibitory effect on selenium separation. More importantly, the ZVINM is demonstrated to have excellent selenium recoverability and regenerative because of its dynamic coating characteristics. Therefore, the high selenium retention efficiency and excellent recycling capabilities of ZVINM make the hybrid membrane as a potential candidate for practical application in selenium separation.