Heterogeneous Catalytic Ozonation Process For Advanced Treatment Of Coal Chemical Wastewater

Nowadays, coal chemical industry develops rapidly, however, a mass of coal chemical industrial wastewater included a variety of toxic pollutants was generated. As the biodegradation of coal chemical industrial wastewater is difficult, the effluent of biological processes can hardly reach the discharge and reuse standards. Thus, The management and treatment of coal chemical industrial wastewater is essential. In this paper, heterogeneous phase catalytic ozonation process was established, and this advanced technology was further used for the treatment of coal chemical industry wastewater. Firstly, components of the secondary effluent of coal chemical industry were analysed and classified. The results showed that this wastewater was a high salt wastewater with large chrominance and turbidity, refractory organics were main compounds and the biodegradation was difficult. Gas chromatography–mass spectrometry (GC/MS) measurement indicated that the determined organics were classified into 6 classes, including hydrocarbons, phenols, nitrogen heterocyclic rings, etc. The relative quantitative analysis showed that nitrogen heterocyclic rings was the main.Secondly, the MnOx catalysts were synthesized by impregnation method, and then the heterogeneous phase catalytic ozonation system was establish. The prepared catalyst was characterized by BET, SEM, XRD and XPS, the result showed that MnO2 was the effective materials for catalysis. The degradation of p-chlorophenol, which is a typical pollutant, was used to investigate the potential of coal chemical industry wastewater treatment by heterogeneous phase catalytic ozonation. Results suggested that O3 is effective for degradation of p-chlorophenol, and the presence of catalyst during ozonation enhanced this effect, both of them were first order reactions. With ozone dose of 28.6 mg/min, the decomposition rates of p-chlorophenol for O3 and O3/MnOx were 0.48 and 0.60 min-1, corresponding to half-life of 86 and 69 s, respectively. Compared with ozonation alone, the mineralization of p-chlorophenol was improved by heterogeneous phase catalytic ozonation.After 10 min, approximately 24.4% and 49.3% TOC removal ratio were obtained, respectively, and·OH played a critical role. With increasing of ozone dose, the reaction rate was improved. High temperature and alkaline environment expedited the reaction.When initial pH value increased from 7 to 11, the degradation rate increased about 2.5 times at 20℃.At last, the treatment of coal chemical industry wastewater by different advanced oxidation processes were investigated. Treatment effect and economic cost are analyzed and discussed. The results implied O3/UV/catalyst system is best for the degradation of TOC and COD, and O3/catalyst and O3/UV processes were suitable for application and dissemination. With high treatment and economic efficiency, The heterogeneous phase catalytic ozonation process that established in this paper is a new advanced oxidation process system for coal chemical industry wastewater treatment. It has high efficiency for removal the target pollutants, and low cost. Thus, it can be used to solve the bottleneck problem of the coal chemical industry wastewater treatment, and has the theoretical significance as well as the bright application prospect.