| Phenolic wastewater has been classified as one of the hazardous contaminants of key control over the world due to its high concentration,variety,risk and difficulty in governing.Recently,advanced oxidation process(AOP)has attracted widespread attention for its high efficiency in hazardous contaminants treatment.The electrochemical oxidation is one of AOPs,which can degrade pollutants by electron transfer between the electrodes.It has great development prospect in dealing with phenolic wastewater because of its advantages such as additives free,high selectivity,less side reactions and no secondary pollution.However,there are still many practical problems to be solved for electrochemical oxidation technology.For example,the current efficiency would be decreased by side reactions(hydrogen or oxygen evolution reaction),the treatment efficiency and the lifetime of electrodes could be reduced due to the electrodes pollution by the adsorption layer and oxide film.In order to solve these problems,two novel electrode were prepared by new materials and preparation method in this work.The performance of the electrodes was evaluated for the treatment of the simulate wastewater and practical industrial wastewater alone and by combining with recycling resin.Finally,a reasonable combination process was designed to treat production wastewater of Hua Qi chemical industry co.,LTD.The main research contents and results are listed as below:(1)Ti/PbO2 andTi/PbO2-Sn were successfully prepared by cathodic deposition and anodic oxidation methods.The electrodes has high oxygen evolution potential according to the structure characterization.The solution pH has significant influence on the oxygen evolution potential of electrode,and the oxygen evolution potential is higher in acid solution than in alkaline solution.The electrode has favorable stability with a working length of 333 days under industry working conditions.(2)Phenol was chosen as the target pollutant to evaluate the removal performance of Ti/PbO2 andTi/PbO2-Sn electrodes.Both electrodes demonstrated more desirable performance compared to the Ti/PbO2 electrode prepared by normal methods,and the Ti/PbO2-Sn electrode has the highest removal efficiency.Furthermore,the electrodes also had excellent performance on the oxidation of intermediate product(benzoquinone)of phenol in a diaphragm electrolytic cell under the optimal experimental conditions.(3)The secondary condensation reaction of high concentration of N-octyl phenolic resin was studied to explore the optimal condensation reaction conditions,and validate the feasibility of recovery of resin from N-octyl phenolic resin wastewater,A combined process including the recovery of high quality resin with heating acid condensation and its wastewater treatment by electrochemical oxidation was developed.The removal rate of phenol and formaldehyde can reach to 96%and 76%by this comined process,respectively.(4)The electrodes were also used to treat wastewater of Hua Qi Chemical Co.,Ltd.The effects of current density,electrolysis time,pH,electrolyte concentration and other parameters were studied,and the ideal operation conditions were determined.(5)A combined process of wastewater condensation,electrochemical oxidation and coagulation sedimentation was proposed based on above results,and has been implemented to treat the wastewater of Hua Qi Chemical Co.,Ltd.in an industrial application scale.The results show that the combined process could recover 290195 kg resin per year.The removal rate of phenol,aldehyde and CODCr in wastewater all exceed 90%.The effluent water can reach the third grade national integrated wastewater discharge standard(GB8978-1996). |
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