Enhancement of photocatalytic activity of zinc/cobalt spinel oxides by doping with ZrO2 for visible light photocatalytic degradation of 2-chlorophenol in wastewater

• ZrO2-doped ZnCo2O4 nanoparticles were synthesized by hydrothermal coprecipitation.
• ZrO2-doped ZnCo2O4 was used for visible light photodegradation of 2-chlorophenol.
• Doping with ZrO2 appeared to stabilize the ZnCo2O4 phase.
• Complete 2-CP degradation was achieved within 180 min under optimal conditions.

ZrO2-doped ZnCo2O4 nanoparticles were synthesized by hydrothermal coprecipitation of sulphate precursors with Zn/Co atomic ratio of 0.5 followed by addition of 0.05 mmol of ZrO2 precursor and calcination at 250–650 °C for 3 h. Several characterization tools such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV–visible diffuse reflectance spectroscopy (UV–vis-DRS) were used for the morphological structure, chemical composition and optical properties of the catalysts. Doping with ZrO2 appeared to stabilize the ZnCo2O4 phase and suppress ZnO phase formation as evidenced by XRD. The produced ZrO2-doped ZnCo2O4 nanoparticles were evaluated as catalyst for visible light photodegradation of 2-chlorophenol (2-CP) in synthetic wastewater solutions. Presence of ZrO2 in the ZnCo2O4 structure was responsible for a significant shift in the UV absorption spectrum toward visible region and resulted in enhancing the visible light photocatalytic activity. The photocatalytic experiments were performed in a batch reactor under 150 W visible light irradiation (λ > 400 nm). Parameters affecting the photocatalytic activity of the catalyst such as the catalyst dose, solution pH, and 2-CP concentration were investigated and evaluated. Results indicated efficient degradation of 2-CP, the highest removal % was achieved by catalyst calcined at 350 °C.