As(III) removal in KMnO4-Fe2+ process

A novel process, KMnO₄-Fe²⁺ process, was developed in this study for As(III) removal. In this process, As(III) was removed by permanganate oxidation and subsequent coagulation with the Fe(III) formed in-situ, which was generated by oxidizing Fe(II) with permanganate. As(III) removal in KMnO₄-Fe²⁺ process decreased with increasing pH at various permanganate dosages and ferrous dosages. Zeta potential analyses demonstrated that entrapment of arsenate in the precipitates shifted the PZC of the floes from pH ~5.8 to pH 5, indicating the specific interaction of arsenate with Fe(III) formed in-situ. The presence of calcium ions can increase As(III) removal significantly in KMnO₄-Fe²⁺ process at pH 7. At the optimum dosages of permanganate and ferrous, the KMnO₄-Fe²⁺ process was much more efficient than the KMnO₄-Fe²⁺ process for As(III) removal by 15-38% at pH 5-9. The great difference in As(III) removal in these two processes was not ascribed to the uptake of arsenic by the MnO₂ formed in-situ but to the different properties of conventional Fe(III) and the Fe(III) formed in-situ.