Directional Separation of Highly Reductive Electrons to the Reactive Center in a Magnetic S-Scheme ZnFe2O4/A-MoS2 Heterojunction for Enhanced Peroxymonosulfate Activation toward Pharmaceuticals and Personal Care Product Removal

Abstract

<p>Pharmaceuticals and personal care products (PPCPs) are ubiquitous in sewage, adversely affecting ecosystems and human health. In this study, an S-scheme magnetic ZnFe₂O₄/ammoniated MoS₂ (ZnFe₂O₄/A-MoS₂) heterojunction as a visible-light-driven PMS activator for PPCP degradation was developed. ZnFe₂O₄/A-MoS₂ achieves improved photocatalytic activity because the construction of S-scheme heterojunction promotes the separation of the highly reductive photogenerated electrons. The optimized photocatalyst (10%-ZnFe₂O₄/A-MoS₂, 0.2 g/L) achieved 100% removal of 2 ppm carbamazepine (CBZ) within 2.5 min at a PMS dosage of 0.5 mM (initial pH 7.0). Mechanistic investigation revealed that the separated electrons to the ZnFe₂O₄ reactive center of the heterojunction facilitated PMS activation and generated SO₄^·– as the dominant reactive species for CBZ degradation. The system exhibited excellent practicability in various samples of actual sewage, where most sewage components negatively impacted CBZ degradation. Further, the chloride ions in high-salinity sewage could be activated to generate additional reactive chlorine species for PPCP degradation. The heterojunction possesses outstanding reusability and stability in treating various water conditions. This work provides mechanistic and practical perspectives in developing novel S-type heterojunctions for recalcitrant pollutant treatment.<br></p>