Polyphenol-mediated interfacial deposition strategy for supported manganese oxide catalysts with excellent pollutant degradation performance

In persulfate-based advanced oxidation process (PS-AOPs), fixing nanosized metal oxide on processable substrates is highly desirable to avoid the aggregation and loss of nanocatalysts during the practical application. However, it is still challenging to develop a versatile strategy for the deposition of metal oxide nanocatalysts on various substrates with different physicochemical properties. Herein, polyphenols are utilized as a “molecular glue” and reductant to mediate the interfacial deposition of MnO₂ nanocatalysts on different substrates. MnO₂ nanocatalysts were in-situ grown on macroscope mineral substrates (e.g., airstone) via an interfacial redox strategy between tannic acid (TA) and oxidized KMnO₄, and then employed as a fixed catalyst of peroxymonosulfate (PMS) activation for treating pharmaceutical and personal care products (PPCPs) in water. The fixed MnO₂ exhibited superior catalytic performance toward different PPCPS via a singlet oxygen (¹O₂)-dominated nonradical oxidation pathway. PPCPs in the secondary effluent of wastewater treatment plants could be effectively removed by a fixed-bed column of the fixed MnO₂ with long term stability. Redox cycle of Mn⁴⁺/Mn³⁺ and surface hydroxyl group of the fixed MnO₂ was proved to be responsible for the activation of PMS. This work provides a new avenue for developing fixed metal oxides for sustainable water treatment.