Synergistic integration of dual Z-scheme Gd2Sn2O7/Ag3PO4/SnS2 heterojunction for accelerated visible-light photodegradation of sulfasalazine: Insights into DFT, toxicity, and antibacterial study

The persistence of pharmaceutical contaminants sulfasalazine (SSZ) in aquatic environments poses significant ecological risks, necessitating efficient removal strategies. This study integrated novel double-Z-scheme photocatalysts (Gd₂Sn₂O₇/Ag₃PO₄/SnS₂) using a hydrothermal method and subsequently ultrasonicated. The prepared photocatalysts were systematically assessed for photocatalytic efficiency, degradation of sulfasalazine (SSZ), and actuation of persulfate (PS) under visible light. The impact of the initial antibiotic concentration, reaction pH, photocatalyst dosage, and PS concentration on the efficiency of photocatalysis was thoroughly examined. The synergistic action of reactive oxygen species (•OH, ¹O₂, SO₄•⁻) was confirmed through radical quenching and EPR analyses. GC–MS analysis and density functional theory (DFT) suggested potential degradation mechanisms and pathways. Additionally, based on projections from the Quantitative Structure-Activity Relationship (QSAR), the toxicity of the intermediates was evaluated. The photocatalyst achieved 86.47 % SSZ degradation within 70 min under visible light and persulfate (PS) activation, reducing byproduct toxicity as confirmed by QSAR analysis. The nanocomposite was tested under visible light to determine its bactericidal effectiveness toward the pathogenic bacteria Escherichia coli and Staphylococcus aureus. This study highlights a scalable solution for antibiotic removal in wastewater, advancing environmental pollution mitigation technologies.