Influence of cations on As(III) removal from simulated groundwaters by double potential step chronoamperometry (DPSC) employing polyvinylferrocene (PVF) functionalized electrodes.

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 ≥ 1.25 mM 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. [Display omitted] • Double Potential Step Chronoamperometry (DPSC) effectively removes As from solution. • Divalent cations Ca2+ and Mg2+ seriously inhibit As removal by DPSC. • Cations enhance As removal in 1st step but limit electrode regeneration in 2nd step. • Ca2+ and Mg2+ act as bridge between As and the polyvinylferrocene electrode. • Effective electrode regeneration can be achieved using an NaOH wash. [ABSTRACT FROM AUTHOR]