Preparation,optimization And Characterization Of Cation Exchange Membranes By Blending Of Chemically Modified Chitosan And Sulfonated Polyethersulfone

Ion exchange membrane(IEMs),as a kind of polymer material selectively permeating ions,has been widely used in fields such as electrodialysis and fuel cell for its advantages of environmental friendliness,high efficiency and energy saving.Most of the traditional IEMs have more dense membrane structure,which limits the ion transport capacity to a certain extent.Developing IEMs with excellent properties and high cost-effectiveness have commercial and practical implications.In this paper,sulfonated polyethersulfone(SPES)was used as membrane matrix,N-phthaloylated chitosan(NPHCs)and N-maleated chitosan(NMCs)as membrane material for IEMs.Based on blend method,porous cation-exchange membranes are obtained by solvent evaporation.The structure and physicochemical properties of the composite membrane were analyzed by infrared spectroscopy,X-ray diffraction,scanning electron microscopy,and differential scanning calorimetry.The water affinity of the membrane under different synthesis conditions was analyzed by a contact angle meter.The water content and ion exchange capacity of the membrane were determined under the different synthetic conditions;the change of membrane pores was examined by measuring the change of the diffusion coefficient of the membrane under different conditions.Through the single factor method and the response surface method,select the excellent performance of IEMs to investigate the desalination performance.The main conclusions are listed as follows:(1)Using dichloromethane as solvent and chlorosulfonic acid as sulfonation agent,SPES was prepared by electrophilic substitution reaction,and the sulfonation reaction was confirmed by FT-IR.The effects of sulfonation time and the amount of sulfonating agent on the degree of sulfonation(DS)were investigated in order to prepare SPES with different DS.The DS value increased with the increase of reaction time.Likewise,the maximum DS reaches in the aImount of sulfonating agent.(2)The composite membrane was obtained by blending SPES with NPHCs and the composite membrane showed a single glass transition temperature with good compatibility.The DS of the composite membrane can be increased to form a sponge fold structure,which is beneficial to the improvement of the water content.The ion exchange capacity also increases with the DS.Increasing the NPHCs in the composite membrane increased the water content,ion exchange capacity and porosity of IEMs.When the content of NPHCs continues to increase,and its pore size is continuously enlarged,resulting in a decrease in the mechanical strength of IEMs.Based on the results,the optimized blending ratio of membrane and sulfonation degree of the SPES should be 85:15(SPES:NPHCs)and 30%,respectively.By single-factor selection method,select the excellent performance of the porous IEMs.Blend membranes improve desalination efficiency compared to simple SPES membranes.(3)When using NMCs instead of the above NPHCs,The porous and smooth morphology of fabricated membranes was confirmed by SEM,indicating that the IEMs has good compatibility.Increasing the DS in the composite membrane will increase the sulfonated groups,which is in favor of the hydrophilicity of the composite membrane.Increasing the proportion of NMCs in the composite membrane improve the porosity of the membrane.NMCs can also increase water content and IEC.By response surface method,it can be seen from the data that the effect of NMCs content is greater than the effect of DS on the composite membrane.By response surface method,select the excellent performance of the IEMs and use this membrane compares with those of commercial membrane.(4)Through analysis,SPES/NMCs composite membrane is superior to the SPES/NPHCs composite membrane in terms of water content and hydrophilicity,but SPES/NPHCs composite membrane performs better in terms of membrane porosity and desalination efficiency.