Efficient degradation of organic pollutants by catalytic ozonation and photocatalysis synergy system using double-functional MgO/g-C3N4 catalyst

The catalytic ozonation and photocatalysis system, which was constructed by introducing ozone and using MgO/g-C3N4 as the catalyst, exhibited great degradation performance for phenol solution. The degradation efficiency was nearly 100% within 2 min, which was 18 and 1.5 times higher than individual photocatalytic and catalytic ozonation activity, and has not been reported in previous literature. In the catalytic ozonation and photocatalysis synergy system, MgO played a dual role: MgO could greatly promote the separation of photoinduced charges in photocatalysis due to the formation of C-O and Mg-N coordination bonds between g-C3N4 and MgO, as seen from the photocurrent intensity results. Simultaneously, MgO actively improved the utilization efficiency of ozone and accelerated the conversion of ozone into hydroxyl radicals (OH), which enhanced the catalytic ozonation activity. Thus, MgO was used as a bridge to realize the (O3/MgO/g-C3N4/Vis) synergy between catalytic ozonation and photocatalysis. The EPR results further confirmed this synergy, since the intensity of OH produced by catalytic ozonation and photocatalysis was greatly higher than the photocatalysis and catalytic ozonation progress. Meanwhile, the effects of the amount of ozone and catalyst, initial pH and concentration of the phenol solution on the synergy degradation performance were investigated. Furthermore, the mineralization capabilities of the synergy system for bisphenol A and 2–4 dichlorophenol and the cyclic stable performance were examined. Finally, the degradation mechanism of the synergy system was proposed. This work provided a new idea to design double-acting catalytic materials and developed a coupled oxidation technology to degrade organic pollutants.