Non-radical activation of peroxymonosulfate by modified activated carbon for efficient degradation of oxytetracycline: Mechanisms and applications

Abstract

The application of heterogeneous metal-free catalysis for non-radical peroxymonosulfate (PMS) oxidation is of great significance because of its low environmental effects and mild oxidant dosage. The purpose of this study was to investigate the activation mechanism of PMS using acid-modified activated carbon and oxytetracycline (OTC) as a representative pollutant. Modified activated carbon (MAC)/PMS system was capable of achieving 100 % degradation efficiency of OTC within 60 min, with an observed rate constant (kobs) of 0.0414 min−1. The degradation of OTC is dominated by non-radical oxidation pathways involved in mediated singlet oxygen (1O2) and electron-transfer process through electron paramagnetic resonance (EPR) and radicals quenching studies. The activation of PMS is attributed to the structural defects of MAC, persistent free radicals, and oxygen functional groups such as C-OOH. Moreover, the MAC/PMS system consistently demonstrates high and reliable contaminant removal in various water matrices. A continuous-flow device utilizing MAC shows excellent performance in purifying micro-polluted water. Additionally, the degradation pathways of pollutants and changes in toxicity during the degradation process were identified through density functional theory (DFT) calculations, liquid chromatography-mass spectrometry (LC-MS), and toxicological analysis. Finally, the cultivation of green beans, peas, and wheat was found to significantly decrease the toxicity of contaminated water through degradation. This study proposes a low-cost method to enhance the activation pathway of non-radical PMS by utilizing modified activated carbon materials for pollutant remediation.