Visible light catalytic degradation of acid orange II via BiOI/UiO-66(Zr) activation of peroxymonosulfate

Spherical BiOI/UiO-66(Zr) composite materials were synthesized using a solvothermal method. The compositions, structures, and optical properties of the materials were characterized through X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller measurements, and UV-Vis spectroscopy. The experimental investigation involved the activation of persulfate (PMS) by BiOI/UiO-66(Zr) for the visible light degradation of Acid Orange II. The effects of the BiOI to UiO-66(Zr) mass ratio, BiOI/UiO-66(Zr) dosage, PMS concentration, Acid Orange II concentration, pH, and inorganic anion species on the degradation system were explored. BiOI/UiO-66(Zr) exhibited excellent visible light responsiveness. Under the optimal conditions (BiOI to UiO-66(Zr) mass ratio of 1 : 0.3, BiOI/UiO-66(Zr) dosage of 300 mg L-1, 0.3 mmol L-1 PMS, 100 mg L-1 Acid Orange II, 25 degrees C, and pH 7.0), the degradation efficiency reached 98.5%. While HCO3- and CO32- significantly influenced the reaction system, NO3-, Cl-, and SO42- had minimal impact. The reaction process followed a first-order kinetic model. Mechanistic analysis indicated that efficient transfer of holes and electrons between BiOI and UiO-66(Zr) occurred during the degradation, enhancing the separation efficiency of photo-generated electron-hole pairs. The O-center dot(2)- and O-1(2) generated in the reaction system played a crucial role in photocatalytic degradation of Acid Orange II, with (OH)-O-center dot, SO4-center dot, and h(+) acting as auxiliary agents. The degradation process was a result of the synergistic action of various reactive radicals. Repetitive photocatalysis experiments demonstrated that the BiOI/UiO-66(Zr) composite exhibited excellent stability, with minimal reduction in degradation efficiency after four cycles.