Efficient Treatment of Phenol Wastewater by Catalytic Ozonation over Micron-Sized Hollow MgO Rods

Phenol is a nocuous water pollutant that threatens human health and the ecological environment. CoO_x-doped micron-sized hollow MgO rods were prepared for the treatment of phenol wastewater by catalytic ozonation. Magnesium sources, precipitants, initial precursor concentration, Co/Mg molar ratio, and catalyst calcination temperature were optimized to obtain the best catalysts. Prepared catalysts were also well characterized by various methods to analyze their structure and physical and chemical properties. In this process, CoO_x/MgO with the largest large surface area (151.3 m³/g) showed the best catalytic performance (100 and 79.8% of phenol and chemical oxygen demand (COD) removal ratio, respectively). The hydrolysis of CoO_x/MgO plays a positive role in the degradation of phenol. The catalytic mechanism of the degradation of O₃ to free radicals over catalysts has been investigated by in situ electronic paramagnetic resonance (EPR). The catalyst can be reused at least five times without any activity decline. The prepared CoO_x/MgO catalyst also showed excellent catalytic performance for removal and degradation of ciprofloxacin, norfloxacin, and salicylic acid.