Crystallinity and valence states of manganese oxides in Fenton-like polymerization of phenolic pollutants for carbon recycling against degradation

Abstract

Various MnOx phases and crystals were investigated in peroxymonosulfate (PMS) activation for oxidation of aqueous phenolic pollutants. MnOx with controlled crystal structure (α, β, γ, and amorphous-MnO2) and redox states (Mn2O3, and MnO) can induce different oxidative pathways toward organic polymerization against degradation in acidic conditions. Surface MnII (s) and MnIII (s) of MnOx tend to bond with PMS to generate confined Mn(II, III) (s) − (HO)OSO3 − complexes to initiate a nonradical electron-transfer pathway (ETP). Meanwhile, highvalence MnⅣ (s) in MnOx will directly attack micropollutants and spontaneously be reduced to low-valence states (MnII (s) and MnIII (s)) to initiate ETP. Mn2O3 can activate PMS to generate other radical species for mineralization. ETP will selectively initiate one-electron abstraction of phenol molecules into monomer phenoxy radicals and polyphenols on catalyst surface. Thus, manganese crystal structures will govern the surface redox species to induce multiple oxidation pathways toward different polymer products for water decontamination and carbon recycle.