Application of ferric-carbon inner electrolysis coupling Fenton process pretreatment of coal tar distillation wastewater with a focus on optimization by the response surface method

Coal resources are abundant in China. The coal deep processing industry produces a large amount of coal tar. In China, the coal tar distillation process is important for obtaining chemical products such as naphthalene, anthracene, and phenanthrene. However, the wastewater generated from the coal tar distillation process is a typical degradation-resistant effluent, and the conventional sewage treatment process is not sufficient to treat it well. Alternative technologies must be developed. In this study, coal tar distillation wastewater was degraded utilizing the ferric-carbon inner electrolysis (FCIE) process following the Fenton process. The single-factor method and response surface method (RSM) were used to obtain the optimal conditions of the FCIE and Fenton processes, respectively. Under the optimal conditions, the total organic carbon (TOC) removal rates of the real coal tar distillation wastewater can reach 24.3% for the FCIE process, 65.1% for the Fenton process, and 73.6% in total. An analysis of variance was implemented, and the Box-Behnken RSM cubic model was obtained. This model shows less than 5% error between the calculated results and the experimental results. The TOC removal rate by the Fenton process followed the pseudo-zero-order kinetic model. This study could provide technical support for coal tar distillation wastewater pretreatment.