Defect-Rich La2CuO4/LaCoO3/ZnO Ternary p–n Heterojunctions for Ultrafast Peroxymonosulfate Activation and Ranitidine Degradation

To overcome the persistent occurrence of pharmaceuticals and personal care products (PPCPs) in conventional wastewater treatment, a series of La2CuO4-based Ruddlesden–Popper(R-P) perovskite peroxymonosulfate (PMS) activators were fabricated via the sol–gel method. To circumvent the inherently sluggish Cu+/Cu2+ redox kinetics of La2CuO4, a synergistic structural strategy involving partial B-site Co substitution and ZnO anchoring was employed to construct the multiphase La2CuO4/LaCoO3/ZnO composite. The catalytic performance of the optimized composite Co0.2-LC0.8O/ZnO40%, possessing a Co-doping molar ratio of 0.2 and 40 wt % ZnO loading, was systematically evaluated for ranitidine (RAN) degradation along with a comprehensive evaluation of the mechanistic pathways, byproduct ecotoxicity, and operational durability. The proposed system demonstrated rapid kinetics, achieving 83.2% RAN elimination within just 5 min, with the degradation process governed predominantly by singlet oxygen (1O2) and sulfate radicals (SO4•–). Mechanistic insights revealed that Co substitution and ZnO loading introduced abundant oxygen vacancies (OVs), significantly lowering the PMS activation barrier. The interfacial contact between the perovskite phases and ZnO substantially accelerated interfacial electron transfer, while simultaneously facilitating the progressive transformation and detoxification of the intermediate byproducts. The anchored ZnO effectively restricted Cu and Co ion leaching by 37.1% and 68.2%, respectively. The composite maintained a robust 92.6% removal efficiency across five cycles and exhibited broad-spectrum applicability against various organic pollutants, establishing a highly sustainable and efficient paradigm for emerging contaminant remediation.