Engineered SnO 2/BiOI fibers via electrospinning for robust visible-light/peroxymonosulfate -driven multipollutant mineralization

Abstract

Engineered photocatalysts capable of operating under visible light and realistic water matrices are needed to address emerging pharmaceutical contaminants. Here, we fabricate SnO₂/BiOI fibrous heterostructures by electrospinning SnO₂ nanofibers decorated with solvothermally synthesized BiOI followed by calcination. The electrospun fibers provide a mechanically robust, high-surface-area scaffold, while BiOI incorporation enhances visible-light absorption and creates SnO₂/BiOI heterointerfaces. Textural, optical, and spectroscopic analyses reveal progressive surface decoration, increased surface area, and defect-rich Bi environments as BiOI loading increases. Using tetracycline (TC) as a model contaminant at neutral pH, SnO₂/BiOI composites markedly outperform pristine SnO₂ under visible light and/or peroxymonosulfate (PMS), with an optimal BiOI content (SBO2) under single-stimulus conditions and near-complete TC mineralization for the highest loading (SBO3) in the PMS + visible-light system. Radical scavenging indicates that SO₄^•− and ^•OH are the dominant reactive species, with O₂^•−, h⁺ and e⁻ playing secondary roles. A multipollutant mixture (TC, sulfamethoxazole, levofloxacin, lansoprazole) is mineralized by >80% in both Milli-Q and tap water, and SBO3 retains high activity over nine cycles with Bi and I leaching below 0.05% after 48 h. Density functional theory calculations, combined with XPS, support an S-scheme SnO₂/BiOI heterojunction, enabling spatial separation of strongly reducing electrons in BiOI and oxidizing holes in SnO₂. Although high PMS loadings can partially mask intrinsic catalyst differences, these results outline a practical design platform for heterogeneous (slurry), visible-responsive, PMS-assisted photocatalysts for pharmaceutical-laden effluents.