Degradation of Azo Dye Orange II Using BiOI/HKUST-1 Activated Persulfate under Visible Light Irradiation

Type I semiconductor heterojunction BiOI/HKUST-1 composites were prepared through a solvothermal method, with optimisation of the molar ratio and solvothermal reaction temperature. Comprehensive characterisation was conducted to assess the physical and chemical properties of the prepared materials. These composites were then evaluated for their ability to activate persulfate (PMS) and degrade high concentrations of azo dye orange II (AO7) under visible light conditions. The influence of various parameters, including catalyst dosage, PMS dosage, and initial AO7 concentration, were investigated. The AO7 degradation followed a pseudo-second order kinetic, and under visible light irradiation for 60 min, a degradation efficiency of 94.9% was achieved using a BiOI/HKUST-1 dosage of 0.2 g/L, a PMS concentration of 0.5 mmol/L, and an AO7 concentration of 200 mg/L. The degradation process involved a synergistic action of various active species, with O2-, 1O2, and h+ playing a pivotal role. Both BiOI and HKUST-1 could be excited by visible light, leading to the generation of photogenerated electron-hole pairs (e--h+); BiOI can efficiently scavenge the generated e-, enhancing the separation rate of e--h+ and subsequently improving the degradation efficiency of AO7. These findings highlight the excellent photocatalytic properties of BiOI/HKUST-1, making it a promising candidate for catalysing PMS to enhance the degradation of azo dyes in environmental waters.