Enhanced peroxymonosulfate activation by supported microporous carbon for degradation of tetracycline via non-radical mechanism

Abstract

Carbon-based peroxymonosulfate (PMS) activator as a promising candidate for substituting metal-based heterogeneous catalysts has drawn increasing concerns. In this study, we reported two supported microporous carbon based PMS activators after treatment by KOH and ZnCl2 (denoted as SMC-K and SMC-Z). Their catalytic activity was evaluated and compared by the degradation efficiency of a typical antibiotics of tetracycline (TC). The results indicated that SMC-K exhibited a higher PMS activation performance than SMC-Z. TC degradation data followed the pseudo-first-order kinetics with reaction rate constants of 0.0818 and 0.0392 min−1, respectively. Based on the characterization results, SMC-K had an extensive microporous structure with abundant vacancy defects and catalytic active sites, accompanied by more basic site distribution. The PMS activation mechanism was further explored via quenching tests, electron paramagnetic resonance (EPR) and electrochemical impedance spectroscopy (EIS). TC degradation occurred via a non-radical oxidation mechanism: (1) direct oxidation by activated PMS where SMC-K acted as the electron transfer shuttle, (2) oxidized by 1O2 instead of SO4− or OH generated from PMS self-decomposition. Furthermore, a reasonable degradation pathway of TC based on the non-radical oxidation has been proposed. This work benefits to develop new treatment technologies for organic pollutants removal in practical application.