Study On The Modification And Properties Of Polyethylene Anion Exchange Membrane

For a long time,the high concentration of chlorine-containing heavy metal wastewater has the characteristics of heavy toxicity,long-term discharge,and large fluctuations in water quantity and water quality,which not only affects ecological security,but also affects human health.The traditional treatment method is electrolysis.Although this method can effectively recover metal elements,it will generate chlorine gas in the anode area,which seriously affects the environment and the health of workers.This process can not only solve the problem of generating chlorine gas,but also make The hydrochloric acid can be recycled and reused in the room,which improves the economic benefit.As the core component of’two-mode three-chamber’’anion exchange membrane,its performance greatly affects the efficiency of the process.Although commercially available anion exchange membranes meet the requirements in terms of ion exchange capacity,water content,membrane surface resistance,and selective permeability,the treatment of high-concentration heavy metal wastewater requires membranes with good stability and mechanical properties.In order to meet the requirements of long-term use and high service life of ion exchange membranes,this paper proposes to prepare polyvinylidene fluoride（poly（1,1-difluoroethylene）,PVDF for short）polyethylene anion membranes,and then use them separately on the basis of PVDF polyethylene anion membranes.Polydopamine（PDA）and ethylenimine（PEI）surface infiltration modified anion exchange membrane and different proportions of polydopamine and sodium polystyrene sulfonate co-deposited modified anion exchange membrane.The aim is to prepare an anion exchange membrane（AEM）with high chemical and mechanical stability by using blending modification and wetting modification.The methods used to evaluate membrane properties in the experiments include basic properties（ion exchange capacity,water content,selective permeability,bursting strength）,electrochemical properties（membrane surface resistance）,Fourier transform infrared spectroscopy（Fourier transform infrared spectroscopy）,referred to as FTIR),scanning electron microscope（Scanning electron microscope）.In the experiment,6%PVDF was blended into the polyethylene anion film,and then the modified PVDF polyethylene anion film was infiltrated with a ratio of DA and PEI in a ratio of 1:2 to prepare a DA/PEI/PVDF polyethylene anion film.It was applied to the double-membrane three-chamber process to treat high-concentration Co Cl₂solution.The cell voltage,current efficiency,cobalt recovery and acid recovery were used to evaluate the performance of DA/PEI/PVDF polyethylene anion membrane in engineering applications.The main research contents and conclusions are as follows:（1）The preparation mechanism of PVDF polyethylene anion film was determined,and the PVDF polyethylene anion film was prepared by the technical route of crushing→banburying→open mixing→hot pressing,and different PVDF mass fractions（2%,4%,6%,8%,10%）on membrane performance,the results show that when the content of PVDF is 6%,the performance of ion exchange membrane is the best,and the oxidation resistance and acid resistance of the membrane are improved by 50%and 44%.The bursting strength is increased by 10%,which indicates that the PVDF polyethylene anion film has better chemical stability and mechanical stability in application,but the addition of PVDF makes the water content,selective permeability,film surface resistance,ionic Swap capacity performance degrades.（2）In view of the problems of PVDF polyethylene anion film,PDA and PEI were used to infiltrate and modify PVDF polyethylene anion film respectively,and the results showed that the effect of co-deposition modification was better than that of PDA and PEI,respectively.Effect.The self-aggregation effect of DA can make PEI more attached to the surface of the membrane,and the electrostatic interaction between PEI and PDA prevents excessive aggregation between PDA and makes the modified layer on the membrane surface smoother.（3）In order to further optimize the process conditions of PDA and PEI co-deposition modification,different ratios（1:0,1:1,1:2,1:3,1:4）of PDA and PEI were used to modify PVDF polymer.Vinyl anion.The results show that when the ratio of PDA and PEI is 1:2,the performance of the ion exchange membrane is the best.Compared with the PVDF polyethylene anion membrane,its ion exchange capacity is increased from 2.25mmol/L to2.62mmol/L,and the water content is increased from 38%.At 41%,the selective permeability increased from 83.6%to 86.2%,the film resistance decreased from 12.2Ωto 5.1Ω,the oxidation percentage decreased from 41%to 37.3%,and the acidification percentage decreased from 52%to 48.1%.（4）DA/PEI/PVDF polyethylene,PVDF polyethylene anion membrane-6,and Hangzhou Green and commercial membranes were applied to high concentration Co Cl₂solution to recover cobalt,in the range of current density 100 A/m2-400A/m2 The inner DA/PEI/PVDF polyethylene anion film is not as good as the commercial film in terms of cell voltage,current efficiency,cobalt recovery and acid recovery,but the difference is not large.Compared with PVDF polyethylene anion film-6,it is greatly improved.Better than commercial membranes in terms of membrane weight loss,ie better mechanical and chemical stability.Considering the long-term use in harsh environments,DA/PEI/PVDF polyethylene anion films are more suitable for use in double-film three-chamber processes.