Insight into the key role of dynamic Pb0 sites in the synergistic photocatalytic removal of BPA and Pb(II) over a Z-scheme CuCo2S4/BiOIO3 heterojunction.

This study reports a CuCo2S4/BiOIO3 composite photocatalyst for simultaneous bisphenol A (BPA) degradation and Pb2+ reduction. The optimal CuCo2S4/BiOIO3(CCB-10) composite achieved BPA degradation kinetics 1.7 and 23.0 times greater than those of pristine BiOIO3 and CuCo2S4, respectively, and enhanced Pb2+ reduction rates by factors of 2.9 and 3.4 over the single components in single-pollutant systems. Performance was enhanced via a dual strategy: nitric acid treatment modulated the thickness and band gap of BiOIO3 nanosheets, and coupling with CuCo2S4 formed a Z-scheme heterojunction. This configuration optimized the band structure, promoting the generation of superoxide radicals (·O2-) and photogenerated electrons. Under low-intensity simulated solar light (80 mW cm-2), the composite achieved removal rates of 96.2% for BPA and 89.8% for Pb2+ in a mixed system, with reaction rates 2.3 and 2.6 times higher than those in single-pollutant systems, respectively. Pb2+ was reduced to Pb0, which deposited on the catalyst surface, generating active sites that accelerated BPA degradation and mineralization. GC-MS and in situ DRIFTS analyses revealed that Pb2+ optimized the BPA degradation pathway, suppressing the formation of persistent toxic intermediates such as phenol. This work demonstrates that in situ-formed heavy metal reduction products can serve as dynamic active sites to promote organic pollutant degradation, providing insights for catalyst design and advancing the application of photocatalytic wastewater treatment.