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 photocatalysisFenton synergy system. The results showed that the synergistic degradation rate constant of 10% rGH/Feg-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 60 min 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 center dot OH. Thus, a large amount of center dot 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. (C) 2020 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.