Biochar assisted synthesis of α-MnO2 nanowires with superior performance for non-radical activation of peroxymonosulfate

Abstract

Non-radical activation of peroxymonosulfate (PMS) is a promising water treatment technology for removing refractory organics, but its mechanism is still ambiguous and the development of highly efficient catalyst is still a challenge. Herein, α-MnO2 nanowires were synthesized by a hydrothermal method with the assistance of biochar and their performance for PMS activation was studied. The characterization results show that the addition of biochar had little effect on the crystal phase and valence state of MnO2 but significantly reduced the size of nanowires. These nanowires had mesoporous structure, high surface area and oxidation ability, resulting in their superior performance for removing organic pollutants with PMS activation. The degradation of phenol by α-MnO2-PMS followed first order kinetics with an activation energy of 14.82 kJ mol−1. Electron paramagnetic resonance and radical scavenging experiments demonstrated that this activation process followed the non-radical mechanism. The quenching effect of scavengers led to the misleading role of singlet oxygen. In fact, surface activated PMS (MnO2–PMS*) rather than singlet oxygen was the reactive species. Weak acidic condition was conducive for the formation of MnO2–PMS* complexes. This catalyst exhibited good reusability and high activity for removing various organic pollutants, and the common substances in real water had little effect on its performance, suggesting its potential application in wastewater treatment.