Oxygen bridge mediated S-scheme Bi2WO6/FeOCl heterojunction for visible-light self-Fenton and PMS synergistic activation toward PPCPs degradation

Oxygen-bridged S-scheme Bi 2 WO 6 /FeOCl achieves 93% DCF and 91% CBZ removal. • Self-Fenton/PMS synergy generates multiple ROS (SO 4 ·− , ·OH, 1 O 2 , ·O 2 − , h + ). • System sustains >85% removal in real waters and > 90% in 300-min flow test. The built-in electric field at oxygen-bridge-connected heterojunctions is a key driving force for regulating S-scheme charge separation and PMS activation. To address the challenge of removing persistent pharmaceutical and personal care products (PPCPs) from water, a Fe–O–W/Fe–O–Bi double‑oxygen-bridge interface was precisely engineered using an in-situ hydrothermal growth strategy, leading to the successful preparation of a direct S-scheme Bi 2 WO 6 /FeOCl heterojunction. The built-in electric field within the interface significantly promotes the directional separation of charges, enhancing light absorption and carrier utilization efficiency. The optimal Bi 2 WO 6 /FeOCl ratio (3:1) efficiently degrades DCF and CBZ in a visible light/PMS system, exhibiting good activity in the pH range of 5–7 with a moderate decrease at pH 9, along with strong resistance to water matrices. The system sustains >90% removal for 300 min in a continuous-flow reactor. Radical trapping and EPR confirm synergistic interactions among SO 4 ·− , ·OH, ·O 2 − , 1 O 2 , and h + , further enhanced by the self-Fenton effect. DFT and LC-MS analyses elucidate the transformation pathways of DCF and CBZ. TOC tests verify that only partial mineralization is achieved under current conditions, and toxicity assessments confirm significantly reduced ecological risks of residual intermediates. This study provides an efficient and stable photocatalytic-PMS synergistic system for PPCPs-contaminated water remediation.