New Insights into the pH-Dependent Removal of Sulfamethoxazole in Peracetic Acid Activation Systems: from Mechanistic Exploration to Practical Application Potentials

Peracetic acid (PAA) as emerging oxidant in advanced oxidation processes (AOPs) has attracted widespread attention in purifying water pollution. In this research, the removal of target contaminant (sulfamethoxazole, SMX) was investigated through PAA activation by a facile catalyst (Co@C), and the active sites of catalyst were identified as sp3-C, Oads, and Co0 by correlation analysis. Especially, different pH adjustment strategies were designed, including System A (adjusting pH after adding PAA) and System B (adjusting pH before adding PAA), to investigate the impact of oxidant acidity and alkalinity on solution microenvironment as well as effect and mechanism of pollutant removal. The results showed that HO· and CH3C(O)OO· dominated in System A, while Co(IV)O2+ was also observed in System B. Both systems showed optimal SMX degradation (98%). However, System A exhibited excellent water quality tolerance (efficiency > 78%), superior sustained catalyst activation (efficiency > 80% in 40 h), less ion leaching (41 μg L-1), and lower products toxicity. Moreover, the pH of solution after reaction in System B was intensely acidic, requiring costly pH adjustments for discharge. This study unveils the strategy of adjusting pH after adding PAA is preferable for water purification, enriching the emerging research of PAA-based AOPs for the remediation of environments. As emerging contaminants, the consumption of antibiotics is increasing. Due to their difficult biodegradability, antibiotics have become hazardous substances of great concern as they trigger bacterial resistance and threaten the ecosystem. In this research, two pH adjustment strategies, including System A and System B (adjusting pH after and before adding PAA), were designed to investigate the effective removal of sulfamethoxazole through peracetic acid activation by a facile catalyst (Co@C). In comparison, System A was more suitable for remediation of water pollution owing to its excellent water quality tolerance, superior catalyst sustained activation, less ion leaching, and lower products toxicity.