Nickle and Cobalt Spinel Catalyzing Wet Air Oxidation of Refractory Pollutants under Mild Condition

Abstract

Refractory organic pollutants are critical issues in water or wastewater treatemnt, and catalytic wet air oxidation (CWAO) is a common method. To improve the efficiency and decrease the reaction conditions, a type of NiCo2O4 (NCO) spinel with urchin-like hollow strucutres was synthesized and used in CWAO of organics at low temperature and atmosphere pressure. Both scanning electron microscopy and X-ray photoelectron spectra were used to characterize NCO. The 3-D hierarchical architectures, solid state redox couple M2+/M3+ (M represents Ni or Co), and plenty of surface oxygen species were proved. Furthermore, the reaction path of CWAO with NCO as the catalyst was concluded, i.e. consecutive adsorption, surface oxidation, and re-oxidation of reduced NCO by O2. NCO showed excellent catalytic performance in CWAO of refractory organics, such as alkaline lignin and bisphenol A. The removal rates of total organic carbon exceeded 80% within 3 h. These findings promise a convenient and economical way for the treatment of refractory organics in water or wastewater.