Abstract
As(III) removal from groundwaters is challenging because of its neutral charge and low surface affinity under circumneutral pH conditions. In this work, we investigate the influence of Ca2+ and Mg2+ on the removal of As(III) by a redox active polyvinylferrocene (PVF) functionalized electrode in a modified double potential step chronoamperometry (DPSC) setup. In the absence of divalent cations, nearly 90% As(III) removal is achieved over ten continuous cycles by single-pass DPSC, even in the presence of competing anions, however the presence of divalent cations at concentrations ≥1.25mM significantly inhibits As(III) removal. The divalent cations enhance arsenic removal in the first (removal) step but suppress electrode regeneration in the 2nd step. Our results suggest that Ca2+/Mg2+ either acts as a bridge between the electrode surface and As anions or the sorption of Ca2+/Mg2+ increases the positive charge on the electrode surface thereby facilitating As(V) sorption. We show that effective electrode regeneration can be achieved using an NaOH wash however the overall complexity of the process increases. Overall, we conclude that the influence of divalent cations on As removal by electro-sorption processes needs to be taken into consideration for application of this technology for real groundwater treatment.
Published Version
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