Effective removal of trace arsenic from groundwater by capacitive deionization

In this paper, functionalized CNTs and Fe3O4 were compounded by co-precipitation method and the binder-free capacitive deionization (CDI) electrodes were innovative prepared by electrophoretic deposition (EPD) technique. The effects of applied voltage, flow rate and solution pH on the adsorption capacity of arsenic were investigated. The results confirmed that introduction of different functional groups (–COOH, -SO3H and -PO3H2) and composite transition metal oxide (Fe3O4) led to the materials not only with enhanced hydrophilicity but also with higher capacitance. The CDI test showed that trace arsenic can be effective treated to less 2 μg/L, which satisfied the World Health Organization (WHO) drinking water standard (below 10 μg/L). The CNTs-X@Fe3O4 electrode was found to maintain specific adsorption of arsenic through selectivity experiments. In addition, the combined electro-sorption and chemisorption effectively produce higher adsorption capacity, faster adsorption rate and high selectivity. Therefore, the electrode prepared by EPD has a high prospect of application in arsenic removal by CDI.