Carbothermal reduction mediated oxidation states regulation of MnOx composites as efficient peroxymonosulfate activator for enhanced removal of paracetamol with the generation of multiple reactive oxygen species

Abstract

Multifarious manganese oxide materials have been proved to be promising catalysts for efficient peroxymonosulfate (PMS) activation and degradation of recalcitrant pollutants. However, the control of oxidation state of manganese for better catalytic performance is still a formidable challenge. Herein, a novel carbothermal reduction strategy is proposed to fabricate MnO_x/nitrogen-doped carbon (Mn-N-C-x) composites with chitosan as carbon and nitrogen source. Specifically, the ratio of Mn(II)/Mn(III) to Mn(IV) and the lattice oxygen amount can be facilely modulated through the reaction between carbon and MnO_x, and the optimized Mn-N-C-2/PMS can completely remove 60 mg/L paracetamol in 20 min. Further investigations of reaction parameters such as inorganic anions, natural organic matter (NOM), and actual wastewater indicate the excellent practicality of Mn-N-C-2/PMS systems. Quenching experiments combined with electron paramagnetic resonance (EPR) further disclose the existence of multiple reactive oxygen species like ·OH, SO₄^·-, ¹O₂, and O₂^·-. The plausible degradation mechanism is proposed according to the detected reaction intermediates. This work provide a novel recipe to develop highly efficient MnO_x catalysts with controlled oxidation states towards PMS activation and pollutant eliminations for green sustainable technology.