Studies On The Electrochemical Oxidation Of Chlorobenzene And Organic Wastewater Advanced Treatment

Electrochemical oxidation technology has drawn extensive attention of scholars at home and abroad, due to its good performance, no extra pollutions and easy operation. In the process of electrochemical oxidation, chlorinated organic compounds can be dechlorinated through the reduction reaction on the surface of cathode, and then the reduction products are degraded on the surface of anode. Therefore, electrochemical oxidation exhibits good effect for degradation of chlorinated organic compounds. In this study, the fundamental research of electrochemical oxidation technology applied to degradation of chlorobenzene was carried out to investigate the influencing factors and reaction mechanism and acute toxicity of effluent. Then electrochemical oxidation technology was used in advanced treatment of chemical industry park organic wastewater (CIPOW).The electrode of Ti/RuO2-IrO2, which has been used in chlor-alkali industry, is employed as anode, and graphite as cathode. Physical characterization and electrochemical performance test were conducted. The results showed that ruthenium oxide and iridium oxide were well loaded on the surface of titanium substrate. The anode of Ti/RuO2-IrO2had oxygen evolution over-potential of about1.3V and showed good catalytic oxidation performance in the chlorobenzene solution containing chloride ion.During research, we found that electrochemical system, consisting of anode of Ti/RuO2-IrO2and cathode of graphite, had good capacity of degradating chlobenzene. Electrochemical degradation was affected by many factors. Higher initial chlorobenzene resulted in the decrease of electrochemical degradation rate and the chlorobenzene electro-degradation followed pseudo-first-order kinetics. The anode materials had great effect on electrochemical degradation of organic and the major reason might be the difference in hydroxyl radicals produced on the anode surface. The acidic condition and the presence of chloride ion in solution were favourable for chlorobenzene removal. Increase in the current density and reaction time led to the decrease of acute toxicity and the chloride ion made a difference to acute toxicity. The removal of chloric substituent in chlorobenzene was dependent more on the attack of hydroxyl radicals than on the nascent and reduction state hydrogen on graphite cathode. It was found that after chloric substituent was removed, the products could be degraded into low molecular organic acids, such as oxalic acid, malonic acid, fumaric acid, malic acid and so on. Then these low molecular organic acids were mineralized into CO2, however the mineralization rate was lower than the degradation rate of chlobenzene obviously.Electrochemical oxidation could significantly decrease COD and colour of EfOM form CIPOW. However, long reaction time and large energy consumption would limite its wide practical application. In the study, the combination of resin adsorption and electrochemical oxidation with some improvements of the latter was proposed, which greatly decreaced the energy consumption per tonnage water and ensured that the effluent reached the discharge standard. During the combination process treatment, resin removed the most of fulvic acid and electrochemical treatment removed humic acid, aromatic protein and soluble microbial by-products. Resin adsorption reduced acute toxicity and chronic toxicity of effluent. In the electrochemical process, acute toxicity had much to do with residual chlorine in solution, whereas chronic toxicity was probably caused by organics.