An integrated electrocatalytic membrane reactor and nanofiltration system for highly efficient removal of arsenic (III) from water

Arsenic (As) contamination in drinking water and groundwater has become as a major environmental concern due to extremely strong toxicity of As. Herein, a facile, efficient and energy-saving integrated membrane process via coupling the electrocatalytic membrane reactor (ECMR) and nanofiltration (NF) membrane is developed for the arsenic removal from As(III)-contained water. The ECMR, constructed with the one-dimensional (1D) MnO2 nanowires (NWs) loaded in the flat carbon membrane as anode, exhibits superior catalytic activity for the electro-oxidation of As(III). The maximum conversion rate of As(III) to As(V) achieves 96.0 % in the ECMR. The NF membrane is employed to filter the resultant permeate from ECMR. The concentration of As(V) after NF treatment is reduced to below 10 μg L−1 (99.5 % removal rate of As(V)) even if the As(III) concentration in the feed solution of ECMR is up to 2000 μg L−1, under a reaction temperature of 20 °C, a current density of 0.4 mA cm−2, a residence time of 10 min, an electrolyte Na2SO4 concentration of 15 g L−1 reaction conditions. The energy consumption of the whole integrated process was only 0.00211 kWh/μgAs. The superior catalytic performance of ECMR with 1D MnO2 NWs can be attributed to large electrochemical active surface area, 1D nanostructure with highly exposed (310) plane of 1D MnO2 NWs as well as strong interaction of oxide with the carbon membrane surface and the porous structure.