Treating Bisphenol A in real thermal paper leachates by visible-light photocatalysis with an iodide-mediated Z-scheme heterojunction.

Bisphenol A (BPA) released from thermal paper leachate is an overlooked source of endocrine-disrupting pollution in real aquatic environments, yet most photocatalytic studies are limited to deionized water or single-pollutant solutions without real matrix validation. Here we prepared an iodide-mediated Z-scheme g-C3N4/BiOIO3 heterojunction and systematically evaluated its performance in realistic scenarios. The photocatalyst achieved BPA removal below the detection limit with catalytic activity surpassing other reported bismuth-based catalysts, while requiring a lower dosage. More importantly, the system maintained efficient BPA removal across a pH range of 3.0-11.0 and in four untreated real waters (river, lake, tap, and rainwater). In thermal paper leachates prepared with actual rainwater and lake water, BPA was removed below the detection limit within 20 min. Zebrafish embryo assays showed that the treated leachates increased hatching rates from 20% to over 60% and eliminated pericardial edema, confirming that chemical removal translated into reduced toxicity. A continuous-flow reactor maintained over 90% BPA removal for 48 h, demonstrating the potential for continuous-flow operation. Mechanistic studies confirmed photogenerated holes and singlet oxygen as the dominant active species, with iodide serving as an efficient electron mediator to suppress charge recombination and preserve robust redox capability. This work demonstrates that combining chemical degradation with biological safety evaluation in source-specific leachates is feasible, moving beyond idealized water systems toward realistic wastewater scenarios.