Sustainable photocatalytic removal of cosmetic preservative parabens over a dual S-scheme TiO 2 /ZnO/g-C 3 N 4 catalyst under natural sunlight irradiation

sorption analyses. The results confirmed the successful construction of a well-coupled heterojunction with optimized band alignment, facilitating efficient charge transfer and visible-light utilization. Under sunlight irradiation, the TZC composite exhibited markedly enhanced photocatalytic activity, achieving 97.6% and 98.3% degradation of MeP and EtP, respectively, within 90 min of sunlight exposure. Kinetic analysis revealed first-order degradation behaviour, while radical quenching experiments identified ˙OH as the predominant reactive oxygen species responsible for the photocatalytic oxidation of parabens. The superior performance was attributed to the synergistic effects of the dual S-scheme charge transfer, which promoted the spatial separation of photogenerated charge carriers and preserved a strong redox potential. The heterogeneity test showed the catalyst was purely active in the solid phase and recyclable up to six cycles with a marginal decrease in efficiency of ∼8%. Furthermore, LC-MS analysis enabled the identification of intermediate degraded species, and a plausible degradation pathway was proposed. This study not only demonstrates the efficacy of a dual S-scheme TZC heterojunction in the solar-driven removal of cosmetic parabens but also provides mechanistic insights into its potential for sustainable water purification applications.