Treatment of saline organic wastewater by heterogeneous catalytic ozonation with Al2O3-PEC-CaxOy as catalysts

Abstract

Al2O3-Pectin-CaxOy (Al2O3-PEC-CaxOy) was prepared as catalysts to improve the treatment of saline organic wastewater with heterogeneous catalytic ozonation. Compared with ozonation alone (33%), the removal rate of COD (62%) was significantly increased for Al2O3-PEC-CaxOy catalysts prepared under the optimized conditions. The introduction of pectin made Ca2+ firmly loaded on the support, and avoided the loss of active sites in the process of catalytic oxidation. In addition, the formation of porous carbon layer on the surface of the Al2O3 support after pectin calcination was conducive to improving the catalytic activity of the catalyst. Electron paramagnetic resonance (EPR) and radical quenching experiments showed that hydroxyl radical (•OH), superoxide radical (•O2−) and singlet oxygen (1O2) were the reactive oxygen species (ROS) that attributed to the organic matter removal. Both free radical and non-free radical pathways were involved in the degradation of organic pollutants during the catalytic ozonation process. The removal rate of COD was only decreased slightly after twenty times of continuous operation for Al2O3-PEC-CaxOy catalysts, indicating that Al2O3-PEC-CaxOy catalysts with the good catalytic stability and reusability. It showed a great significance for long-term practical application with the economical and effective performances.