Preparation and application of green calcium-based catalyst for advanced treatment of salty wastewater with ozone

This paper reports an ozone oxidation catalyst for the advanced treatment of salty wastewater. The green Al2O3-polydopamine (PDA)-CaxOy catalyst was synthesized using Ca2+ as the main active site, Al2O3 as carrier, and PDA as a coating agent. The efficiency of Al2O3-PDA-CaxOy to treat petrochemical wastewater was investigated by studying the effects of preparation and reaction conditions, such as Ca2+ concentration, calcination temperature and time, catalyst dosage, and pH on the chemical oxygen demand (COD) removal. Al2O3-PDA-CaxOy displayed good degradation effects, with a COD removal of 62%, which is higher than that of commercial catalysts. Structure and morphology characterization analyses of Al2O3-PDA-CaxOy revealed that Ca2+ was uniformly dispersed through the traction and anchoring effect of PDA. Compared with traditional acidification treatment, the surface modification method used herein was not detrimental to the morphology of the carrier. A reaction mechanism based on the Al2O3-PDA-CaxOy catalyst was proposed using electronic spin resonance spectroscopy.