Chlorophenol red sensitized SnO2/ZnO coupled MnCo2O4 photocatalyst for enhanced acetaminophen degradation activated by peroxymonosulfate: mechanism and toxicity assessments.

Pharmaceutical pollutants pose significant risks to human health and aquatic ecosystems, underscoring the urgent need for enhanced advanced oxidation technologies for pollutant removal. This study presents a novel chlorophenol red (CPR) sensitized SnO2/ZnO coupled with a MnCo2O4 (MCO) activated peroxymonosulfate system for the efficient degradation of acetaminophen (ACT). Structural analyses show that the CPR-SnO2/ZnO photocatalyst exhibits a tetrahedral star morphology and features covalent surface bonding of CPR molecules, which enhances light absorption and promotes charge separation. Under experimental conditions with a CPR loading concentration of 0.6 wt%, the ACT degradation rate reached 96.59% within 35 min, while the total organic carbon (TOC) removal rate was 85.4% after 50 min. Moreover, the ACT degradation rate constant k was 0.0971 min-1, which is 17.65 times and 44.14 times higher than those of the single photocatalytic and single PMS systems, respectively. Mechanistic analysis indicated that the enhanced ACT degradation rate resulted mainly from two factors: the CPR sensitizers facilitate the transfer and migration of photogenerated e--h+ pairs, and PMS activation is driven by the rapid redox cycling of multivalent metal ions Mnn+ and Com+. Trapping-agent experiments demonstrated that singlet oxygen (1O2) and superoxide (O2·-) play dominant roles in the reaction system. Low-toxicity intermediates were identified using LC-MS, corroborated by T.E.S.T. assays and wheat growth tests. This paper provides a theoretical foundation for improving the pollutant degradation efficiency of photocatalytic PMS-activated systems and presents a competitive technological solution for practical wastewater treatment.