High-efficiency removal of phenol and coking wastewater via Photocatalysis-Fenton synergy over a Fe-g-C3N4 graphene hydrogel 3D structure

To achieve rapid separation of electron-hole pairs and improve photocatalytic degradation activity, the Fe-g-C3N4 reduced graphene hydrogel (rGH/Fe-g-C3N4) with a 3D network structure was fabricated via the hydrothermal method. Using visible light irradiation, H2O2 was added to form a photocatalysis-Fenton synergy system. The results showed that the synergistic degradation rate constant of 10% rGH/Fe-g-C3N4 was 52% higher than that of the multiphase Fenton reaction and 1.5 times higher than that of the Fe-g-C3N4. In the seventh cycle, the catalytic efficiency was still as high as 86.9%. Based on the optimized conditions from phenol degradation, the system was further applied to coking wastewater treatment, and the degradation efficiency of TOC and COD in 60min reached 66.3% and 68.1%, respectively. Such high and stable degradation performance was ascribed to the synergy effect of photocatalysis and Fenton. Because of the photogenerated electrons not only can promote the Fe3+/Fe2+ cycle, accelerate the decomposition of H2O2, but also can quickly transfer to graphene and directly decompose H2O2 to form ·OH. Thus, a large amount of ·OH were generated through the two different channels, which greatly improve the degradation efficiency. Furthermore, rGH/Fe-g-C3N4 can be regenerated using filters without the need for additional complicated processing. This work provides an effective strategy for the deep treatment of industrial wastewater.