Preparation And Characterization Of Anti-organic Fouling Anion Exchange Membranes For Electrodialysis

Electrodialysis（ED）is an efficient desalination technology.As the core of ED,anion exchange membrane（AEM）is susceptible to fouling by organic pollutants,and the existing anti-fouling AEMs still have the problem of instability of anti-fouling layers,which restricts the application of ED technology.This thesis conducted to solve the problem of unstable connection between anti-fouling layer and membrane body of AEM,obtaining new AEM with stable anti-organic fouling capacity and high desalination performance.The effects of different gradient cross-linked in-situ interpenetrating structures of AEM on ED performance and anti-fouling capacity were studied.The fouling mechanisms of sodium dodecylbenzene sulfonate（SDBS）and duck egg albumin on the anti-fouling AEM were preliminarily investigated.The results provide valuable references for the application of anti-fouling AEM in chemical industry and food industry for cleaner production.The details are as follows:（1）Based on anti-organic fouling property of the Ca-Na alginate（CA）with inherent hydrophilicity and electronegative property,a series of anti-fouling AEMs were developed successfully by in-situ interpenetration of an ionomer of N-methylimidazole ionizing poly（2,6-dimethyl-1,4-phenylene oxide）（IM-QPPO）to lateralized gradient cross-linked CA hydrogel,utilizing thermal drive and miscibility between ionomer solvent and water.The anti-fouling AEMs have qualified basic properties,including thermal stability,water uptake,swelling ratio,area resistance and permselectivity for ED process.IM-QPPO-0.10CA with optimal interpenetrating structure among the group exhibits the highest current efficiency（η）of 88.88%and the lowest energy consumption（EC）of 2.53 k Wh kg^-1Na Cl,which are comparable to those of commercial AMX(η=89.38%,EC=2.20 k Wh kg^-1Na Cl).IM-QPPO-0.10CA shows the strongest anti-fouling ability with no irreversible structure damage,while using SDBS as characteristic pollutant.The results of ultraviolet spectrum test indicate that SDBS causes surface fouling of IM-QPPO-0.10CA and permeable fouling of AMX.Moreover,the fouled IM-QPPO-0.10CA recovers to 99.60%of the originηvalue and only adds 0.10 k Wh kg^-1Na Cl of original EC after immersion in Na Cl solution.（2）The ED performance of IM-QPPO-0.10CA and commercial membrane AMX for salted egg white desalination was evaluated,and the self-made salted egg white was used to simulate the salted egg white solution in food industry.In two-hour ED processes,the commercial AMX and IM-QPPO-0.10CA both maintain highη(η_AMX=88.42%,η_{IM-QPPO-0.10CA}=89.80%),low EC(EC_AMX=0.44 k Wh kg^-1 Na Cl,EC_{IM-QPPO-0.10CA}=0.41 k Wh kg^-1 Na Cl)and considerable Na Cl fluxes(J_AMX=53.61 mg m^-2s^-1,J_{IM-QPPO-0.10CA}=54.45 mg m^-2s^-1).The albumin cannot penetrate through the AEMs,and protein recovery rate is close to 100%.In six-hour ED processes,AMX and IM-QPPO-0.10CA both remain highηabout 80%and low EC of 0.45 k Wh kg^-1 Na Cl.These results prove practical value and prospects of salted egg white ED desalination.