Catalytic ozonation performance of calcium-loaded catalyst (Ca-C/Al2O3) for effective treatment of high salt organic wastewater

A novel Calcium-loaded catalyst (Ca-C/Al2O3) was prepared with a facile impregnation method, using polyethyleneimine (PEI)-polydopamine (PDA) as a coating agent and Al2O3 as supporter. The prepared Ca-C/Al2O3 catalyst showed a higher treatment performance for high salt organic wastewater, and removal rate of chemical oxygen demand (COD) was enhanced from 32.5% to 64.4% comparing with single ozonation. Besides, it also showed a good catalytic performance comparing with other catalysts reported in different literature. Catechol groups and reactive amine groups in the PEI-PDA coating worked as anchoring points for metal ions, facilitating the formation of dispersed calcium sites (Ca-O and Ca-N). Calcium sites and different types of nitrogen (graphite nitrogen, pyrrolic nitrogen, and pyridinic nitrogen) were identified as the active sites for the catalytic reaction. The analysis of electron paramagnetic resonance (EPR) and radical quenching tests revealed that hydroxyl radical (•OH) and singlet oxygen (1O2) were the reactive oxygen species (ROS) for treatment of high salt organic wastewater. According to the above results, the prepared Ca-C/Al2O3 catalysts showed a good catalytic permanence and used for advanced treatment of high salt organic wastewater.