Heterogeneous activation of persulfate by Bi₂MoO₆–CuS composite for efficient degradation of orange II under visible light

Here in, a special catalytic system of potassium persulfate (K₂S₂O₈, PS) activated by Bi₂MoO₆–CuS composite was established for the orange II (OII) degradation under visible light. The Bi₂MoO₆–CuS composite was synthesized by a two-step hydrothermal and solvothermal methods. The structure, morphology, light absorption and photocatalytic properties of the composite were respectively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible diffuse reflectance spectroscopy (UV–vis DRS). The removal efficiency of OII degradation in the Bi₂MoO₆–CuS/PS/vis system reached to 98% within 80 min, which was much higher than that of either Bi₂MoO₆ or CuS alone. A feasible mechanism analysis of OII degradation was proposed and validated by simple classical quenching experiments and electron spin resonance (ESR) spectroscopy. The high removal efficiency by the nanocomposite could be attributed to highly active species of O₂^·-, ·OH and SO₄^•− radicals in the Bi₂MoO₆–CuS photocatalytic oxidation system. Moreover, the composite material retained its activation performance even after 5 degradation cycles, which suggested its high stability.