Study Of Antifouling Anion Exchange Membrane Based On Charged And Hydrophilic Surface Modification

The hydrophilicity/hydrophobicity and electropositivity/electronegativity of anion exchange membrane（AEM）were regulated by surface modification of commercial AEM to enhance the antifouling performance.Nevertheless,the modified AEM suffered from the increment of transport resistance and loss of ion transport ability owing to the addition of modified layer.In this study,transport channels were constructed in the modified layer to reduce the loss of ion transport ability and enhance the antifouling performance of AEM.The main contents were as follows:（1）The presence of hydroxyl functional groups on Ti₃C₂T_x improved the hydrophilicity and electronegativity,thus enhancing the antifouling performance of AEM.Meanwhile,Ti₃C₂T_x with two-dimensional lamellar structure fabricated the interlayer transport channels in the modified layer,which reduced the transport resistance and loss of ion transport ability.Ti₃C₂T_x modified AEM（T-0.1/AEM）was prepared by electrodepositing Ti₃C₂T_x on the surface of commercial AEM.The results showed that the increment of area resistance for T-0.1/AEM compared to unmodified AEM was 0.45Ωcm².In the presence of foulants,the desalination rate of T-0.1/AEM increased 57.7%compared to that of unmodified AEM.However,the stability of AEM was reduced in the long-term operation.And the reduction for loss of ion transport ability was limited.（2）Dopamine was beneficial to increase the interaction between modified layer and AEM,boosting the stability of AEM.Rigid,irregular,and small size Mo S₂ flakes were easy to form loose structure,which endowed the modified layer with fast transport channels and further reduced the loss of ion transport ability.Hydrophilic and electronegative layer could enhance the antifouling performance of AEM.Dopamine and Mo S₂ modified AEM（P@M/AEM）was prepared by electrodepositing Mo S₂flakes and coating dopamine on the surface of commercial AEM.The results displayed that the stability of P@M/AEM was favorable in the long-time operation.The increment of area resistance for P@M/AEM compared to unmodified AEM was 0.40Ωcm²,lower than that of T-0.1/AEM.In the presence of foulants,the desalination rate of P@M/AEM increased 88.2%compared to that of unmodified AEM.However,the reduction for loss of ion transport ability was not obvious.And the enhancement of antifouling performance was limited.（3）Hyperbranched polyethyleneimine with dendritic structure was able to synthesize the thin layer and provide additional transport channels,obviously reducing the loss of ion transport ability.Oxygen-containing functional groups were evenly distributed in the modified layer after the reaction between hyperbranched polyethyleneimine and dopamine,which gave improved hydrophilicity and electronegativity to AEM,thus enhancing the antifouling performance.Hyperbranched polyethyleneimine and dopamine modified AEM（PEI-1800&PDA/AEM）was prepared by co-depositing hyperbranched polyethyleneimine and dopamine on the surface of commercial AEM.The results exhibited that the increment of area resistance for PEI-1800&PDA/AEM compared to unmodified AEM was 0.25Ωcm²,lower than that of P@M/AEM.In the presence of foulants,the desalination rate of PEI-1800&PDA/AEM increased 93.3%compared to that of unmodified AEM,higher than that of P@M/AEM.However,the enhancement of antifouling performance was not obvious while the reduction for loss of ion transport ability was obvious.（4）Porous covalent organic framework could serve as transport channels in the modified layer,obviously reducing the loss of ion transport ability.Meanwhile,covalent organic framework with abundant and evenly distributed functional groups was beneficial to improve the hydrophilicity and electronegativity of AEM,which obviously enhanced the antifouling performance.Dopamine was able to boost the stability of AEM.Covalent organic framework and dopamine modified AEM（TMCPa/PDA/AEM）was prepared by coating dopamine and interfacial polymerization of covalent organic framework on the surface of commercial AEM.The results revealed that the increment of area resistance for TMCPa/PDA/AEM compared to unmodified AEM was 0.28Ωcm².In the presence of foulants,the desalination rate of TMCPa/PDA/AEM increased 103.0%compared to that of unmodified AEM,higher than that of PEI-1800&PDA/AEM.In the long-time operation,the stability of TMCPa/PDA/AEM was favorable.In conclusion,the modified AEM was prepared,which simultaneously realized the optimization of ion transport ability and antifouling performance,providing a new insight for the preparation of antifouling membrane.