Synthesis and characterization of nanolayered ZnO / ZnCr2O4 metal oxide composites and its photocatalytic activity under visible light irradiation

BACKGROUND Recently removal of emerging contaminants from water and wastewater has attracted considerable attention. The advanced oxidation process based on semiconductor photocatalysts may be a viable option to treat such contaminants; nanolayered ZnO/ZnCr2O4 metal oxide composite catalyst was prepared, characterized and photocatalytic activity checked for degradation of a model pollutant Acid Orange 10 (AO) under visible light irradiation. RESULTS Nanolayered ZnO/ZnCr2O4 metal oxide composite was synthesized by a combustion technique and characterized by XRD, FT‐IR, UV‐DRS, FE‐SEM and TEM measurements. ZnO/ZnCr2O4 metal oxide composite catalyst particles formed a nanolayer arrangement and with homogeneous shape in the range 30–50 nm. The ZnO/ZnCr2O4 metal oxide composite catalyst maximum efficacy was at pH 6.86 with 99% degradation of 0.01 g L−1 AO dye under visible irradiation. The visible photocatalytic degradation of AO was found to exhibit pseudo‐first‐order kinetics. Nanolayered ZnO/ZnCr2O4 metal oxide composite retained catalytic activity for a series of cyclic batch experiments. The reactive intermediates of the degradation process were identified by ESI‐Mass. CONCLUSION The fastest degradation of AO occurred under the optimal conditions 4 g L‐1 of nanolayered ZnO/ZnCr2O4 metal oxide composite, pH 6.86, 0.01 g L‐1 of AO and 180 min visible light irradiation. The visible photodegradation of AO was found to exhibit pseudo‐first‐order‐kinetics. The nanolayered ZnO/ZnCr2O4 metal oxide composite retained its catalytic activity at >93% even after three cycles of use.