Effect Of Plasma Modified Ion Eexchange Membrane On Permeability Of Organic Electrolyte

The problems of separation and utilization of inorganic salt-organic electrolyte-non-electrolytic organic mixed solution system exist widely in the fields of desalination of milk whey,preparation of food additives,sugar desalination,pharmaceutical production and other high-salt organic wastewater treatment.As one of the separation technologies,electrodialysis can separate electrolyte and non-electrolyte mixtures efficiently,but it has poor separation effect on inorganic salt-organic electrolyte mixtures.The difference in the performance of anion exchange membrane is the main reason for the change of desalination rate in electrodialysis,and the charge of most organic electrolytes in the above solutions is negative charge,which makes optimizing the performance of anion exchange membrane become the key to improve the separation efficiency of inorganic salt-organic electrolyte mixture system.Therefore,the anion exchange membrane was modified by plasma acrylamide grafting using low temperature plasma technology,and the effect of the modified ion exchange membrane on the permeability of organic electrolytes was investigated.The electrodialysis separation efficiency of inorganic salt-organic electrolyte mixture system was improved by modifying the membrane surface to enhance the charge and cross-linking degree.Firstly,the effects of citric acid concentration in raw water,operating current of Electrodialysis on desalination rate and citric acid loss rate were investigated by single factor experiments.The working conditions of electrodialysis before and after modification of anion exchange membrane were determined as follows:0.4A constant current mode,30 g/L Na₂SO₄and 3 g/L citric acid mixed solution in the intermediate chamber,0.2 mol/L sulfuric acid solution in the cathode chamber and 0.2 mol/L in the anode chamber.Sodium hydroxide solution,electrodialysis desalination time 2 hours.The anion exchange membrane was modified by low temperature plasma liquid phase grafting and simultaneous irradiation with acrylamide as grafting coating solution.Aiming at the problem of large amount of experiments in plasma modification,uniform experimental design was adopted to construct a uniform experimental scheme with four factors?ion exchange membrane grafting immersion time,glow discharge current,discharge current duration,acrylamide concentration?and eight levels.Citric acid-sodium sulfate mixed solution was used as the representative of inorganic salt-organic electrolyte mixed solution system to study lime in electrodialysis.Selective permeability of citric acid and inorganic salt.Taking the desalination rate and citric acid loss rate of electrodialysis for 2 hours as the index,the DPS data processing software was used for statistical analysis and the optimal combination was obtained.The results were as follows:liquid phase grafting method soaked in acrylamide solution for 119 minutes,discharge time for 2 minutes,grafting concentration for 5%,discharge current for 6A,the desalination rate increased by 15.3%;The citric acid loss rate decreased by 10.1%when the discharge time was 70 min,the discharge time was 2 min,the grafting concentration was 2%,and the discharge current was 4.1A.At the same time,the electrodialysis desalination rate increased by 17%when the discharge current was 4A and the discharge time was 147 min,the discharge time was 3 min,the grafting concentration was 5%,the discharge time was 8 min,the grafting concentration was 8 min,the grafting concentration was 5%,and the citric acid loss rate decreased by 16.9%when the discharge current was 4A.SEM characterization of the optimized modified ion exchange membrane and the original membrane showed that the pore of the membrane was blocked in varying degrees,which further indicated that acrylamide monomer was crosslinked and successfully grafted on the surface of the ion exchange membrane,while the liquid phase grafted modified membrane was denser and more uniform.