Boosting the oxygen vacancies in ZnO–Co3O4 composite by copper doping for bisphenol A abatement using persulfate†

Abstract

Through surface leaching and ion exchange, nest-like Cu–Co₃O₄ and Cu–ZnO–Co₃O₄ composites were obtained from solid ZIF-67 and hollow ZIF-8–ZIF-67, respectively. Their characterizations suggested that the ratio of oxygen vacancies/lattice oxygen in Cu–ZnO–Co₃O₄ was much higher (1.61) than that of Cu–Co₃O₄ (0.47). The Cu–ZnO–Co₃O₄ composite exhibited an ultra-high persulfate (PDS) activation ability and could degrade the target organic contaminant molecule bisphenol A (BPA) in six minutes under the reaction conditions of 20 mg L⁻¹ BPA, 0.1 g L⁻¹ PDS and 0.1 g L⁻¹ Cu–ZnO–Co₃O₄, demonstrating a degradation rate constant (k) of 0.84 min⁻¹, which was over 28-fold higher than that of the reference, Cu–Co₃O₄ (0.03 min⁻¹). Notably, the robust reusability of the sample was also established based on three successive runs. The mechanistic study suggested that the influence of the active species derived from PDS followed the below order: ¹O₂ > HO˙ > O₂˙⁻ > SO₄˙⁻. The robust catalytic activity of Cu–ZnO–Co₃O₄ could be ascribed to the rich oxygen vacancies, small size of active particles and the porous structure.