Metalloporphyrin-based hybrid photocatalyst for bisphenol A degradation: kinetics, HRMS-based analysis of transformation products, and toxicity assessment

Abstract

Bisphenol A (BPA) is a persistent endocrine-disrupting compound frequently detected in aquatic environments and inadequately removed by conventional wastewater treatment processes. In this work, a visible-light-active TiO₂-metalloporphyrin hybrid photocatalyst was developed via surface sensitization of TiO₂ with zinc tetrakis(4-carboxyphenyl)porphyrin (ZnTCPP) and evaluated for BPA degradation in aqueous media. The hybrid material was characterized by UV-Vis spectroscopy (UV-Vis), Fourier Transform Infrared (FT-IR) Spectroscopy, powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM), confirming successful porphyrin immobilization without altering the anatase crystal structure. Photocatalytic experiments under visible-light irradiation demonstrated efficient BPA removal, reaching up to 70% degradation within 180 min, while maintaining stable performance over three successive cycles. Kinetic analysis revealed that BPA degradation followed a power law kinetic model, with enhanced reaction rates under acidic conditions and optimized catalyst loading. Radical scavenging experiments indicated that superoxide and hydroxyl radicals were the dominant reactive species governing the oxidation process. High-resolution Orbitrap mass spectrometry enabled the identification of major transformation products and the elucidation of degradation pathways, which were dominated by aromatic hydroxylation and C–C bond cleavage reactions. In silico ECOSAR toxicity assessment showed a substantial reduction in acute and chronic aquatic toxicity for the main intermediates compared with the parent BPA molecule. Overall, the TiO₂-metalloporphyrin hybrid effectively extends photocatalytic activity into the visible region and enables efficient pollutant removal with reduced environmental risk, highlighting its potential for sustainable solar-driven water treatment applications.