| Membrane separation technology is an efficient and economical material handling technology.It is the use of special membrane separation performance,in the external pressure difference,the concentration difference,potential difference as a driving force,so that certain specific substances(such as organic molecules,inorganic ions,heavy metals,etc.)from the system was separated.A separation membrane(e.g.,ion exchange membranes,ultrafiltration membranes,reverse osmosis membrane)of the membrane separation technology as the core,it has an irreplaceable role in membrane technology have different functions.The ion exchange membrane,due to its specific ionic groups on its surface,allows the membrane to allow only specific ions to pass through during the application(eg,the cation is only allowed to pass through the cation and the anion is blocked)The ability to be called the selective permeability of the membrane.It is also because of the special performance of ion exchange membrane,it makes it a wide range of applications.But the product at home and abroad ion exchange membrane permselectivity only about 88% to 96%,there are still some leakage of counter-charged ions in a separation process while the limited tolerance of the harsh environment of the membrane,whereby the membrane separation technology in many occasions is limited,it is difficult to achieve the desired results.In this paper,after analyzing the selection mechanism of the selective exchange mechanism of the ion exchange membrane,it is considered that the choice of the permeability mechanism of the ion exchange membrane,There is a clear flaw in the early theory of Dunne equilibrium theory-it merely characterizes the process of ion permeation through the ion exchange membrane in the electrostatic field(no external electric field effect).For the ion state in the electrodeposition process It does not apply.And the theory of membrane potential rejection proposed by Wang Sanfan et al.Can more accurately explain the mechanism of membrane permeability under the action of electric field,"Membrane potential rejection_pore closure" theory shows that increasing the membrane surface and the membrane pore potential,while controlling the membrane pore size,making the membrane potential range is greater than the membrane pore diameter,can significantly improve the membrane permeability,The overall performance of the membrane.First,the study on the use of plasma glow discharge technology to graft thebenzoic acid betaine(SBMA)monomer on the polystyrene-based cation exchange membrane.The effects of membrane modification were investigated under different grafting monomer concentration,plasma discharge time,discharge power and discharge gas atmosphere.And the modification effect of the membrane was characterized by SEM,FTIR,the chloride ion leakage rate,resistance test analysis of the membrane before and after modification,characterization of membrane permselectivity and surface structural changes.The results show that the effect of ion exchange membrane is the best when the concentration of SBMA is 60 g/L,the intensity of plasma irradiation is 0.7 W.cm-2,the irradiation time is 7 min,and the irradiation gas atmosphere is argon.In the best condition,the active membrane contained in the original membrane was obviously increased,and the surface was dense and homogeneous,and the performance of the membrane was greatly improved.The chloride ion interception efficiency of the membrane was increased from 86% to98 % Or more,the film resistance decreased from the original 13.695 Ω.cm2 to 6.547Ω.cm2.Analysis of graft modification that increase the surface potential during the ion exchange membrane action range,At the same time by means of the self-polymerization of SBMA,the larger pores on the membrane surface are properly blocked,and finally to achieve the anti-charge ion barrier to achieve the purpose of improving the choice of membrane permeability.Secondly,for the existing product membrane surface resistance is high,poor corrosion resistance and other defects,the use of poly-fluorine polymer good oxidation resistance and nano-oxide strong conductivity characteristics,They are uniformly coated on the surface of the film at a certain ratio and concentration,and the coating material is firmly bonded to the surface of the film by an appropriate plasma discharge reaction to finally improve the oxidation resistance of the film and to reduce the surface resistance.The effects of the coating material type,the ratio of the composite coating,the concentration of the composite coating and the intensity of the plasma irradiation on the modification effect were investigated.The results show that the composite coating material is PTFE-TiO2,the mass fraction of PTFE is 10%,the ratio of TiO2/PTFE is 0.2%,the discharge power is 1 W.cm-2,and the discharge time is 10 min.The most outstanding.Under the optimum conditions,the surface of the original film was modified by surface coating,and the surface properties of the film were improved.The anti-oxidation performance of the film was improved from0.41 Mpa to 1.56 Mpa,Times the ability of the ion exchange membrane to cope with the harsh production environment is greatly improved,the film resistance is reducedby nearly 50%,and the electrical conductivity is more excellent.Finally,in order to verify the modification effect of the membrane,the modified film and the original film were applied in the small-film cobalt electrodeposition process to carry out the parallel experiment,the determination of the modified film in the application process of choice of permeability,energy consumption and stability Sexual,characterization of modified film application effect.In the selection of the permeability test,the unmodified film was installed in the process when the chlorine gas production rate remained at about 14%,that is,the choice of product cation exchange membrane permeability of about 86%.After the modified grafted ion exchange membrane,the chlorine production rate of the electrodeposition process is2.5% up and down,indicating that the modified cation exchange membrane has a selectivity of 97.5%.Under the energy consumption test,The current efficiency of the cation exchange membrane is about 2% higher than that of the original film,reaching96.5%,and it is basically stable after 15 h.The unit energy consumption of the modified membrane system is reduced by 100 Kw.h compared to the original film system in the case where the experimental system voltage and system current are the same.In the stability test,the chloride ion leakage rate of the modified membrane was stable at about 10% for 288 h after continuous operation.After 288 h,the chloride ion leakage rate of the membrane decreased with the increase of running time,And when the run time was 384 h,the chloride ion leakage rate increased to the original film level before the unmodified.And the original film in the run 96 h after the sharp changes in the run to 168 h,the membrane of chlorine production rate of 20%breakthrough to 240 months after the accumulation of electricity,break through 30%,the membrane of chloride ion blocking effect becomes difference.Parallel experiments show that the modified film in the application process is still stable and reliable,can be considered to further promote the application.Although the modification of the ion exchange membrane in this experiment makes the performance of the membrane greatly improved,but also can be seen,there are many aspects of the experiment needs to be improved.For example,the ion exchange membrane of different materials is modified and modified using other amphoteric polymers,and the modification effect of graft modification and coating modification is analyzed.Therefore,the research questions in this area in the future need to be strengthened. |
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