Could manganate be an alternative of permanganate for micropollutant abatement?

Permanganate (MnO4−), an oxidant that has been applied in water treatment, has highly varied reactivity toward pollutants. In this study, we found manganate (MnO42−) could destruct diverse functional groups, with oxidation rates being higher than that of permanganate under acidic and neutral conditions. Mechanistic study revealed manganate rapidly disproportionated to permanganate and colloidal MnO2 in solution. Under acidic conditions, the in-situ formed colloidal MnO2 possess higher reactivity than permanganate and primarily contributed to the degradation of pollutants. The reactivity of in-situ formed colloidal MnO2 is highly sensitive to pH and decreased dramatically with increasing pH. Consequently, the contribution of MnO2 to pollutant removal decreased with elevating pH, which also leads to the decreased degradation efficiency of micropollutants at high pH. Manganate is an intermediate produced during the manufacturing process of permanganate. This study indicates that manganate might be an alternative of permanganate for water purification under acidic and neutral conditions. [Display omitted] •MnO42− is superior than MnO4− in pollutant removal efficiency.•The freshly in situ formed colloidal MnO2 is the predominant oxidant after dosing MnO42−.•The freshly in situ formed colloidal MnO2 is more reactive than preformed MnO2.•The treatment efficiency of MnO42− is pH specific.•Cation suppressed the performance of MnO42− while DOM alleviated the suppression.