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 (MnO₄^2-) 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.