| Swelling and bacterial contamination of ion exchange membranes have always attracted the attention of scholars around the world.And the study of these issues has guiding significance for improving the comprehensive performance of membranes.Crosslinking is an effective method to improve the chemical stability and mechanical properties of materials.Forming crosslinked structure in ion exchange membranes can not only effectively reduce the excessive swelling and decline in mechanical properties caused by high ion exchange capacity,but also can even induce the formation of ionic clusters in the membrane,forming a hydrophilic-hydrophobic phase separation structure,thereby giving the ion membrane excellent ion transport performance.It is worth mentioning that,in addition to the type of cross-linking agent,the structure of the cross-linking agent and the cross-linking density formed by it greatly affect the properties of the material.However,most studies only regulate the crosslinking density and polymer structure by changing the amount of cross-linking agent or the length of the cross-linking molecules,and very little research has been done on the effect of the functionality of the cross-linking molecules on the performance of ion exchange membranes.Therefore,investigating the influence of the functionality of the cross-linking agent on the properties of the membranes,to help researchers better understand the relationship between the structure and performance of the ion exchange membrane,is of great significance to guide the development of high performance ion exchange membranes.In this research,a series of cross-linked cation exchange membranes were designed and successfully prepared based on the ultraviolet cross-linking method,and the in-situ reduction of nano-silver technology was used to further improve the antibacterial and other properties of the ion exchange membranes.（1）A series of cross-linked sulfonated polysulfone cation exchange membranes were prepared by ultraviolet（UV）cross-linking.Bisphenol A-type polysulfone was used because of the photochemical activity of methyl groups on the main chain with polyfunctional acrylate cross-linkers which also had photoresponse to prepare a series of cross-linked sulfonated polysulfone cation exchange membranes.The effects of cross-linking functionality on the dimensional stability,mechanical properties,electrochemical properties and electrodialysis performance of the modified membranes were explored.Due to the different functionalities of the cross-linking agents during the preparation process,the three-dimensional network structure formed led to different densities and hydrophilic and hydrophobic structures in the membrane,which caused different physical and electrochemical properties to the ion exchange membranes.As the functionality of the crosslinking agent increased,the surface of membranes became smoother,water absorption was suppressed,and dimensional stability was enhanced.Among them,the cross-linked cation membrane（60SPSF-C2#）showed the optimal microphase separation structure,which exhibited the highest Na Cl removal ratio（91.7%）,the highest current efficiency（95.7%）and lowest energy consumption(6.55 k Wh·kg–1)during the desalination experiments.These results indicated that the functionality of the cross-linking agent can affect the three-dimensional network structure in the membrane,and had guiding significance for the development of high-performance ion exchange membranes.（2）Based on the above studies,a series of silver nanoparticles loaded cross-linked cation exchange membranes were prepared through ion exchange and UV-induced reduction processes.Scanning electron microscopy（SEM）,X-ray diffraction（XRD）,and X-ray photoelectron spectroscopy（XPS）analysis methods confirmed that the silver nanoparticles in situ generated were uniformly dispersed in the polymer matrix.In addition,due to the proposed synthesis strategy,crosslinked structure was formed in the membranes.The advantages of inorganic nanomaterials and polymers were combined in the silver nanoparticles loaded membranes,and the proper particle size and dispersion of the silver nanoparticles improved the mechanical properties of the membranes.In addition,the prepared cation exchange membranes exhibited good bactericidal activity against Escherichia coli,and showed a significant improvement on the electrochemical performance.These effects were caused by the obtained distribution of Ag NPs near ion exchange groups that increased the aggregation of water molecules around them,improving the efficiency of ion transport in terms due to the array broad ion transport channels were formed.The optimized CEM（60SPSF-C3#-Ag-2）exhibited enhanced Na Cl removal ratio of 67.5%with high current efficiency（96.9%）and low energy consumption(5.84 k Wh·kg–1).The largest distance from the outer boundary of the suppression zone to the outer boundary of the SPSF-C3#-Ag-2 was 4.8 mm,and the total antibacterial diameter was 2.4 times the width of the sample itself.These results indicated that the proposed synthesis strategy had potential application prospects in the fields of antibacterial and electrodialysis desalination of ion exchange membranes. |
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