Heterogeneous catalytic ozonation of atrazine with Mn-loaded and Fe-loaded biochar

After reaction with permanganate or ferrate, the resulted Mn-loaded and Fe-loaded biochar (MnOx/biochar and FeOx/biochar) exhibited excellent catalytic ozonation activity. O-3 (2.5 mg/L) eliminated 48% of atrazine (ATZ, 5 mu M) within 30 min at pH 7.0, while under identical conditions, ozonation efficiency of ATZ increased to 83% and 100% in MnOx/biochar and FeOx/biochar (20 mg/L) heterogeneous catalytic systems, respectively. Radical scavenger experiment and electron paramagnetic resonance (EPR) analysis confirmed that hydroxyl radical (center dot OH) was the dominant oxidant. Total Lewis acid sites on MnOx/biochar and FeOx/biochar were 3.5 and 4.1 times of that on the raw biochar, which induced enhanced adsorption of O-3 and its subsequent decomposition into center dot OH. Electron transfer via redox pairs on MnOx/biochar and FeOx/biochar was observed by cyclic voltammetry scans, which also functioned in the improved catalytic capacity. Degradation pathways of ATZ in MnOx/biochar and FeOx/biochar ozonation systems were proposed, with 34.6% and 44.8% of dechlorination effect accomplished within 30 min of reaction, which was improved by 4.1 and 5.3 times compared to pure ozonation. After 12-hour treatment, acute toxicity of ATZ oxidation products was reduced from 38.3% of pure ozonation system to 14.5% and 6.3% of activated ozonation systems with MnOx/biochar and FeOx/biochar, respectively. Mn-loaded biochar and Fe-loaded biochar have great potential for heterogeneous catalytic ozonation of polluted water. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Biochar loaded with manganese and iron showed excellent catalytic ozonation activity, effectively removing atrazine with hydroxyl radicals as the main oxidant. The enhanced adsorption and decomposition of O-3 on the loaded biochar led to improved degradation pathways of atrazine, reducing toxicity of oxidation products significantly. This research indicates the great potential of Mn-loaded and Fe-loaded biochar for heterogeneous catalytic ozonation in water pollution treatment.