Doping strategy-tuned non-radical pathway on manganese oxide for catalytic degradation of parabens

Abstract

Non-radical oxidation processes with singlet oxygen (1O2) and mediated electron transfer have emerged as efficient methods for the selective degradation of aqueous pollutants in peroxymonosulfate (PMS)-based catalytic systems. On this basis, in this study, transition- and lanthanide-metal co-doped manganese oxide octahedral molecular sieve (Cu-Nd-OMS-2) was synthesized, characterized, and tested in the degradation of aqueous parabens. Methylparaben (30 mg/L) was degraded at 100% and mineralized at 92% within 40 min in the presence of Cu-Nd-OMS-2 and PMS (200 mg/L) in pH scale ranging from 3 to 8. Compared with pristine and mono-doped catalysts, the Cu-Nd-OMS-2, produced by the doping strategy, exhibited a superior catalytic activity for the oxidative degradation of several parabens through turning the mechanism with radicals into non-radical pathway. Electron paramagnetic resonance, quenching experiments and mechanism study indicated that 1O2 and mediated electron transfer contributed to the removal of parabens. Besides, the redox cycle of Mn(III)/Mn(IV) might be responsible for PMS activation, and abundant surface hydroxyl groups as well as oxygen vacancies on the catalyst further promoted the adsorption of pollutants and the generation of 1O2. Overall, the present study provides a novel and facile doping strategy on manganese oxide catalysts for fine-tuning radical/non-radical processes towards PMS-based water remediation.