Ozone pre-oxidation to accelerate the ripening of manganese oxides filter for efficient manganese removal from drinking water

Manganese (Mn) is a common contaminant with a strict limit value in drinking water, which is traditionally removed by virtue of manganese oxides (MnOx) filter, in which the performance and stability depend on its ripening. Herein ozone (O3) is employed as a pre-oxidant to ripen MnOx filter for the removal of Mn from drinking water, with KMnO4 as a control. The O3 pre-oxidation (OPO) assisted filter presents more excellent performance in Mn removal during the whole start-up period and achieves a significant shortening of the start-up time from 74 days to 41 days as well as ripening time from 108 days to 80 days compared with the KMnO4 preoxidation (KPO) filter. The O3 facilitates the generation of active vernadite via the direct oxidation of manganese ions (Mn2+) and promotes the evolution of deposited MnOx by assembling Mn2+ from water during the 120-day reactions. The vernadite nanosheets with low crystallinity (16.23-30.35 %) and abundant Mn(III) species (44.19-48.48 %) in deposited MnOx formed by OPO act as the active components to promote the adsorption and subsequent oxidation of Mn2+, thus enhancing Mn removal from water. The OPO costs less than KPO in completing the start-up of MnOx filter and avoids the chemicals pollution. This work establishes a novel strategy to accelerate the start-up and ripening of MnOx filter for efficient removal of Mn from drinking water.