Study On Electrochemical Oxidation And Ultrafiltration Combined Process For Removal Of Micro-organic Compounds In Water

With the continuous yearning and pursuit of human beings for a better life,environmental issues,especially water environmental issues,have increasingly become the focus of social attention.The contradiction between increasingly stringent drinking water and sewage discharge standards and t he ever-increasing pollutant load generated by human activities is becoming more and more significant.In the past ten years,PPCPs,as an emerging organic pollutant,have been continuously discovered and reported in all aspects of the social cycle of wate r.Their potential risks to environmental safety and human health have also aroused worries and concerns of governments and people in various countries.Due to the generally complex structure and difficulted to degrade,then have environmental persistence.Traditional treatment processes have extremely limited degradation efficiency.Compared with traditional water treatment methods,electrochemical oxidation has the advantages of convenient operation,cost-effectiveness,and no secondary pollution,then presents obvious advantages on the efficiency of removing toxic and persistant organic micro-pollutants.The most important factor affecting electrochemical oxidation is the property of the electrode materials.Therefore,the development of novel and efficie nt electrode materials were with a decisive role in promoting the application of electrochemical oxidation and improving the efficiency of electrochemical oxidation systems.Pb O₂electrode has the advantages of good catalytic activity,high oxygen evolutio n potential,good corrosion resistance and economical price s,so it has be widely used.This paper has conducted in-depth research on the preparation process of ENBTA/PTFE/Pb O₂electrode material and the oxidative degradation mechanism of the electrochemical oxidation.A“twice anodic oxidation+cathodic polarization+anodic deposition”method were used to prepare the a low-energy consumption modified ENBTA/PTFE/Pb O₂ electrode materials.The research results show that the ENBTA/PTFE/Pb O₂ electrode has higher crystallinity,lower grain size and larger contact angle than other electrodes,which is conducive to the generation of oxidation radicals in the anode electrode,at the same time it has a longer service life,under the current density of 20m A/cm² conditions,its calculated service life is 9062.5 hours.When the initial concentration of each pollutant is 10 mg/L,the p H maintains original value,the current density is 20 m A/cm²,and the electrolyte Na₂SO₄ concentration is50 m M,the EBNTA/PTFE/Pb O₂ electrode all showed well degradation effect,which can degrade more than 95%within 20min,5min,and 25min for ciprofloxacin,carbamazepine,and sulfadiazine respectively,and the unit power consumption is 1.25,0.48,and 1.77 k Wh/m³respectively.Through the analysis of LC-MS data,there are 5degradation products of CIP within the ENBTA/PTFE/Pb O₂ electrode electrochemical oxidation system,the degradation pathway can be concluded that hydroxylation,ring cracking,defluorination and dealkylation are the ma in processes of its degradation reaction.In this paper,a differential column batch reactor(DCBR)electrochemical reactor with high mass transfer efficiency was constructed,ciprofloxacin was selected as the target pollutant,and a new commercial BDD electrode was used to investigate the feasibility of its oxidative degradation of pollutants.electrochemical oxidation.And using CFD to simulate the flow state,the result showed that the fluid flow state in the DCBR reactor is in an uniform flow state,which is conducive to the generation of hydroxyl radicals on the surface of the BDD anode and the reaction with target pollutants.This provides the possibility of promoting the electrochemical oxidation and degradation of pollutants.The degradation of the d ifferential column batch reactor based on BDD anodization can be divided into two processes,hydroxylation process and mineralization process.When the initial concentration of ciprofloxacin is10 mg/L,the p H is 7,the current density is 30 m A/cm²,and the electrolyte concentration is 50 mmol/L,the energy efficiency of the differential column batch reactor based on BDD anodization is the highest,and the unit power consumption approached 1.47 k Wh/m³.Through hydroxyl radical detection and oxidation mechanism analysis,indicated that indirect oxidation is the mainly mechanism of the BDD-DCBR reactor.Through LC-MS data analysis,a total of 10 intermediate products were detected during the degradation of ciprofloxacin,and three degradation pathways were inferred,hydroxylation,piperazine ring cleavage,and substitution reaction.Organic pollutants in water are generally considered to be the main cause of ultrafiltration membrane pollution,on the other hand electrochemical oxidation shows well degradation effect on organic pollutants.For this reason,this paper proposes a split electrochemical oxidation-ultrafiltration combined process,and simulates the treatment mechanism of the combined process using an actual polluted water.The electrochemical oxidation time has a significant impact on alleviati ng the ultrafiltration membrane pollution.When the electrochemical pre-oxidation time is increased to 120min,the reversible and irreversible pollution on the surface of the ultrafiltration membrane after three filtration cycles are reduced by 91.1%and 91.7%respectively and the membrane flux increased by 24%.Electrochemical pretreatment mainly reduces the load of organic foulants and change the nature of foulants to alleviate the membrane fouling of the combined process.When the electrochemical pretreatment time is extended,the main mechanism of ultrafiltration membrane fouling changes from complete pore blocking and cake layer to standard blocking and intermediate pore blocking.In addition,with the increase of electrochemical oxidation time,the electrochemical oxidation-ultrafiltration combined process can effectively reduce the generation of disinfection by-product precursors in the effluent.