Commercial nanomaterials in wastewater treatment: A case study on manganese oxide-activated periodate systems

Heterogeneous periodate (IO4-, PI) activation systems have emerged as a promising technology alternative for organic wastewater decontamination, with activator choice being crucial. Although effective, conventional synthesis of transition metal materials can be restricted by complex preparation methods, low yields, and poor reproducibility. Herein, four commercially available manganese oxides (MnxOy) were directly selected to activate PI for contaminant removal. Manganese tetraoxide (Mn3O4) effectively activated PI, producing reactive species of singlet oxygen (1O2) and iodyl radicals (IO3•). The reaction rate of the Mn3O4 + PI system (0.22 min−1, near-neutral conditions) was 3.67, 1.29, and 2.00 times higher than those of the MnO + PI, MnO2 + PI, and Mn2O3 + PI systems, respectively. Moreover, the Mn3O4 + PI system demonstrated good resistance to co-existing environmental ions and natural organic matter, rapid removal of various refractory pollutants, and applicability confirmed by multiple reproducibility experiments and continuous flow operations. Differences in active species and intrinsic catalytic mechanisms were uncovered using capture experiments, electron spin resonance (ESR), electrochemical analyses, probes, and theoretical calculations. The distinct degradation product pathways of various oxidants and pollutants in different MnxOy systems were also thoroughly examined. This work provides a new perspective on selecting scalable production catalysts for oxidant-activated systems, while validating the versatile applications of commercial materials for further exploration.