Degradation of ofloxacin by high-efficiency almond shell-based biochar via peroxymonosulfate activation: A study of the effect of pore structure

Biochar was regarded as an effective catalyst for peroxymonosulfate (PMS) activation to eliminate the antibiotic contamination. However, the roles of pores in biochar for PMS activation has rarely been studied. In this study, catalysts with different pore structures were prepared using the almond shells as starting materials, and their structure–function relationships were investigated. The pore structures in the catalysts mainly consisted of microporous and mesoporous. It was found that the pore structure was the key factor for ofloxacin (OFL) degradation, and the pore volume was positively correlated with the activity of the catalysts (R2 = 0.928). The surface reaction on the microporous materials could trigger the generation of various radicals and nonradical pathways, while the OFL oxidation was dominated by singlet oxygen (1O2) with tunable electron transfer process. The materials with broad mesoporous pore sizes can utilize their high mass transfer rate to rapidly activate PMS for OFL oxidation. It was also found that the pores with a size of 2–6 nm in the catalyst could shield some external influences and intercept the degradation intermediates inside the pore to maintain the degradation process. As a result, the TOC removal ratio (94.96%) could be achieved by the catalyst, which provided an effective route to solve the low TOC removal in 1O2 dominated systems.