MnO2/Cu2O S-scheme heterojunction enabling photothermal-enhanced peracetic acid activation for efficient metronidazole degradation.

Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have emerged as promising strategies for antibiotic removal. However, the efficiency of PAA-based AOPs remains constrained due to rapid charge carrier recombination and the overlooked contribution of photothermal effects to PAA activation. Herein, MnO2/Cu2O S-scheme heterojunctions were constructed through a hydrothermal-precipitation method, enabling the synergistic use of photothermal and photocatalytic effects for enhanced PAA activation. Notably, the MOCO-0.6/PAA/Vis system achieved 96.17% MTZ removal within 30 min, exhibiting an apparent rate constant (koβs) that was 1.89 times higher than that of the temperature-controlled system and 11.75 times higher than that under dark conditions, respectively. Infrared thermography revealed that the photothermal response of MnO2 and Cu2O elevated the reaction temperature, thereby reducing the activation energy barrier and accelerating the oxidation process. Crucially, the S-scheme heterojunction structure inhibited charge recombination and simultaneously promoted the Mn(IV)/Mn(III) and Cu(I)/Cu(II) redox processes during the reaction. Furthermore, the MOCO-0.6/PAA/Vis system maintained high MTZ removal efficiencies (>80%) in tap water, lake water, simulated chemical wastewater, and simulated hospital wastewater, demonstrating its strong resistance to matrix interference and applicability in complex environmental waters. LC-MS analysis combined with mung bean seed germination tests was further conducted to evaluate the toxicity evolution of the degraded solution. These findings highlight the synergistic contribution of photothermal-enhanced PAA activation and S-scheme-mediated photocatalysis in accelerating antibiotic degradation, providing a promising strategy for the practical treatment of antibiotic-contaminated wastewater under environmentally relevant conditions.