The Laccase-Like Mechanism in Peroxymonosulfate-Based Oxidation System for Water Decontamination: Dual-Substrate Activation

Abstract

This study demonstrates that direct electron transfer (DET)-dominated peroxymonosulfate (PMS)-based advanced oxidation processes (PMS-AOPs) share a similar oxidation mechanism with laccase, including dual-substrate activation, DET mechanism, polymerization of organic pollutants, and relatively high redox potential at active site. To verify this point, a detachable catalyst (MnPc/CNT) was used. Neither manganese phthalocyanine (MnPc) nor carbon nanotubes (CNT) could efficiently catalyze PMS to remove phenol (PE), whereas MnPc/CNT achieved complete PE elimination primarily through a DET mechanism. In this process, PE was mainly removed via polymerization. Importantly, galvanic cell experiments and density functional theory calculations showed that MnPc/CNT can simultaneously activate both PE and PMS, whereas MnPc or CNT alone cannot. This dual-substrate activation phenomenon was seldom reported in PMS-AOPs. Comparative studies showed that MnPc/CNT, FePc/CNT, and CoPc/CNT exhibited significantly higher PE removal efficiency than NiPc/CNT, CuPc/CNT, and ZnPc/CNT, which correlated with their higher open circuit potentials. Since current catalyst design strategies for PMS-AOPs remain largely empirical and enzyme is highly efficient catalyst, this laccase-like mechanism means that the laccase-mimetic approach will be a promising direction for developing high-performance catalysts.