New Strategy for Enhanced Mn(II) aq Removal from Drinking Water by MnO x (s)-Coated/Natural Ore Media Activation of Peroxymonosulfate

Manganese (Mn) contamination of groundwater is widespread and poses a global challenge to ensuring access to safe drinking water. MnOx(s)-filter media is commonly employed in conventional household drinking water treatment systems for Mn(II)aq removal due to its cost-effectiveness. However, these treatment systems may struggle to consistently meet health-based standards under certain conditions, and water supply systems may also experience issues. Thus, we investigate whether conventional MnOx(s)-media can activate peroxymonosulfate (PMS) via advanced oxidation processes to enhance Mn(II)aq removal efficiency. Batch experiments demonstrated superior Mn(II)aq removal efficiency using the novel method compared to the conventional approach for a range of PMS concentrations, MnOx(s)-media types and dosages, and pH values. A PMS-activated MnOx(s)-coated sand system (MCS) exhibited greater Mn(II)aq removal potential than a PMS-activated natural Mn ore (NMO) system (PMS = 500 μM, 96.8% vs 30.0%). Results identified the involvement of adsorbed oxygen (Oads) and suggested the potential role of surface-reactive Mn species in the oxidation of Mn. Characterization of the reaction products revealed the formation of stable MnO2 precipitates. Both radical (i.e., •OH and SO4•–) and nonradical (i.e., 1O2 and electron transfer) pathways contributed to Mn(II)aq removal in the PMS-activated MnOx(s)-coated sand system, whereas removal in the PMS-activated NMO system is driven by a nonradical pathway. This study proposes a promising alternative for enhanced removal of Mn(II)aq from drinking water, especially in anoxic, reducing groundwater wells, and provides insight into the underlying mechanism of Mn(II)aq removal.