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

Abstract

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 °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 ˙O₂⁻ and ¹O₂ generated in the reaction system played a crucial role in photocatalytic degradation of Acid Orange II, with ˙OH, SO₄⁻˙, 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.