Non-free radical regulation mechanism based on pH in the peroxymonosulfate activation process mediated by single-atom Co catalyst for the specific rapid degradation of emerging pollutants

Abstract

Persulfate-based advanced oxidation technologies (PS-AOPs) show great potential in treating emerging pollutants because of their multiple reaction pathways induced by a variety of reactive species. However, the modulation of the reactive species in PS-AOPs and the specificity of reactive species for contaminants have still not received adequate attention. In this work, the feasibility of pH on modulating reactive species in PS-AOPs mediated by single-atom Co catalyst (Co_SA) and the relationship between each species and contaminant were deeply discussed. In the Co_SA/PMS system, Co(IV) was the predominantly active species in acidic conditions, and ¹O₂ was the predominantly active species in neutral and alkaline conditions. Specific degradation relationships with various pollutants were explored based on different major active species regulated under different pH conditions. Density Functional Theory (DFT) and experimental results demonstrated that organic pollutants with high E_HOMO (Energy of the Highest Occupied Molecular Orbital), low VIP (Vertical Ionization Potential) and ΔE (Energy Gap) were susceptible to oxidative degradation. Sulfonamide compounds, phenol compounds and tetracycline compounds tended to be attacked by ¹O₂. And the carbamazepine compounds and quinolone compounds tended to be attacked by Co(IV). This study will provide new perspectives on reactive species regulation and specific degradation of pollutants, and offer innovative ideas for rapid remediation of emerging pollutants in aquatic environments.