Peroxymonosulfate activated with waste battery-based Mn-Fe oxides for pollutant removal: Electron transfer mechanism, selective oxidation and LFER analysis

Abstract

Mn2O3-Fe2O3 catalyst was fabricated from spent alkaline batteries and used for effective elimination of acetaminophen (APAP) by activating peroxymonosulfate (PMS). APAP removal at various initial pH, its degradation pathway and the stability of catalyst were investigated. The Mn(III) was inferred to be the primary active site and Fe(III) could improve the corrosion resistance through intermetallic interactions. Chemical quenching experiments, electron paramagnetic resonance (EPR) spectroscopy, solvent exchange, open circuit potential (OCP) and chronoamperometry tests imply that APAP is oxidized by electron transfer through highly reactive surface-adsorbed PMS. Fourier transform infrared (FTIR), in situ Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) spectra and ionic strength experiments further revealed the interaction between the catalyst and PMS. The Mn2O3-Fe2O3/PMS system exhibits selective oxidation for different contaminants, and linear free energy relationship (LFER) was employed to investigate the effect of structure and properties of pollutant on the reaction kinetics. Pollutant with peak potential (Eop) > 0.91 V, the steady-state OCP in the Mn2O3-Fe2O3/PMS system, is resistant to oxidation; while pollutant with Eop < 0.91 V is prone to be oxidized and there is a good correlation between apparent first-order rate constant (k1) and Eop. The research not only puts in-depth study into PMS activation through environment-friendly Mn-Fe oxides from spent alkaline batteries, but also provides some new insights for nonradical mechanism, selective oxidation and LFER study.