Study On Removal Of COD In High Salt Wastewater From Coal Chemical Industry

China is rich in coal resoiirces,however the reverse distribution characteristic of water resources and the strict request of "zero discharge" of national environmental protection administration restricts the development of the coal chemical industry.The treatment of high-salt wastewater is the key to the zero discharge" of coal chemical wastewater.At present the evaporation-crystallization technology treatment of high-salt wastewater will produce crystalline hetero-salt,which cannot be effectively utilized.Therefore,it is urgent to extract the main salts according to the industrial salt standard in the evaporation-crystallization process.The COD in the wastewater is one of the important factors affecting the purity of crystalline salts.In this study,adsorlption-catalyzed ozone oxidation was used to remove COD in high-salt wastewater from coal chemical enterprises,the main contents and results were summarized as following:(1)The industrial grade multi-walled carbon nanotubes were purified and oxidized,and then ZIF-8/WMCNTs composite adsorption materials was prepared.It was found that the best adsorption condition of ZBF-8/WMCNTs for organic matter in wastewater was that the dosage was 2.4 g·L-1,pH=7,and the adsorption time was 150 min.(2)The LX-111 polar resin and HI03 non-polar resin with strong adsorption capacity were selected,and the static adsorption-desorption experiments were carried out on the two resins to obtain suitable static adsorption conditions and desorbent.The dynamic adsorption-desorption process of LX-111 and H103 resin series adsorption towers was studied based on static adsorption conditions.It was found that under the condition of dynamic adsorption flow rate of 10 mL·min-1 and wastewater volume of 5 L,the residual COD concentration was 410 mg·L-1 in wastewater,while the COD removal rate was 62.7%.When ethanol was used as the desorbent,the desorption flow rate was better at 5 mL·min-1.(3)The single metal oxide catalyst was prepared by impregnation method,and the MnO2/Al2O3 and CUO/Al2O3 catalysts with good catalytic ozonation performance were screened out.The MnO2-CuO/Al2O3 double metal oxide catalyst was prepared in the same manner.Then,by exploring the catalytic ozone oxidation at different ratios of manganese and copper,the effect of COD removal was found to be significant when Mn:Cu=4:1.(4)The high specific surface area of MnOi-CuO/Al2O3(Mn:Cu=4:l)catalyst was prepared by hydrothermal method.The effects of different ozone flow rate,catalyst dosage and pH on COD removal by catalytic ozonation were studied.The COD removal rate in wastewater was reduced to 82%under the condition that the ozone flow rate was 300 L lr1 and the catalyst dosage was 12 g·L-1,The stability of the catalyst was tested and it was found that the catalytic ozonation performance remained stable when used multiple times.After the resin-catalyzed ozone oxidation combined treatment,the COD concentration in the wastewater is 81 mg·L-1,which basically meets the requirements of subsequent separation and extraction of salt,and this method provides a Possible industrial application for the removal of COD from coal chemical high salt wastewater.