Fabrication And Application Of SP-PDA Interfacial Adhesion Layer Based Bionic Lithium-ion Imprinted Membrane

Membrane separation technology has been widely used in the field of ion separation due to the advantages of high efficiency,energy saving and continuous operation.However,the selective separation of lithium from water resources(such as spent lithium-ion battery leaching and salt lake water)by membrane separation technology still presents great challenges.In this paper,a bionic lithium ion-imprinted membrane(SP-IIM)with high selective adsorption performance and high chemical stability was prepared based on membrane separation technology and ion-imprinted technology.A novel polydopamine interfacial adhesion layer(SP-PDA)was introduced through polydopamine biomimetic modification technology.The differences in structure and properties of SP-IIM and traditional biomimetic lithium-ion imprinted membrane(IIM)were compared.The influences of different interfacial adhesion layers on the properties of ion-imprinted membranes were explored.To improve the application potential of ion-imprinted membrane in natural salt lake water,a biomimetic lithium ion-imprinted membrane with anti-fouling property(Si O₂@SP-PDA-IIM)was prepared via the introduction of nano-Si O₂ interlayer structure,which can endow the surface of the ion-imprinted membrane anti-fouling property.The effect of nano-Si O₂interlayer on the adsorption performance,adsorption behavior and anti-fouling performance of SP-PDA-based biomimetic lithium-ion imprinted membrane was investigated.The anti-fouling mechanism on the surface of ion-imprinted membrane was explored.The main research contents are as follows:A novel biomimetic ion-imprinted membrane(SP-IIM)with high chemical stability and high adsorption capacity for Li⁺was prepared by graft polymerization.Based on the improved polydopamine biomimetic modification technology,the SP-PDA interfacial adhesion layer was introduced between the PVDF base membrane and the ion-imprinted polymer layer.Compared with the traditional PDA interfacial adhesion layer,SP-PDA had a snowflake structure with larger loading area and more active sites(such as?OH and?COOH),which can graft more ion-imprinted polymers.The adsorption performance,adsorption behavior,regeneration and selective adsorption mechanism of SP-IIM were explored.In the optimal condition,the adsorption capacity of SP-IIM for Li⁺can reach 42.58 mg·g^-1.The adsorption process and behavior of SP-IIM for Li⁺were investigated by Langmuir and Freundlich isotherm adsorption models,pseudo-first-order and pseudo-second-order kinetic models.The results showed that the adsorption mode of SP-IIM for Li⁺was monolayer chemisorption.In the simulated spent lithium-ion battery leaching solution,SP-IIM can realize the selective adsorption of Li⁺,and the selective separation coefficients of Mn²⁺,Co²⁺,Ni²⁺were 6.71,5.84 and 3.03,respectively.The mechanism of selective adsorption of SP-IIM was explored based on DFT calculations,and the results showed that the chelation between 12C4 and Li⁺and the better dehydration of Li⁺were the fundamental reasons for the preferential adsorption of Li⁺on SP-IIM.After 5adsorption-desorption cycles,the adsorption capacity of SP-IIM decreased to 95.4%of the initial value,while that of IIM decreased to 82.5%of the initial value.This indicated that the possibility of peeling off of the ion-imprinted polymer layer on the surface of SP-IIM was reduced due to the higher chemical stability of SP-PDA.The anti-fouling performance and mechanism of Si O₂@SP-PDA-IIM were explored.In order to solve the membrane fouling issue during the application of ion-imprinted membranes,the surface of ion-imprinted membrane was endowed anti-fouling properties via the introduction of nano-Si O₂ interlayer.The results showed that due to the more active sites on the nano-Si O₂ surface,the uniformity of the ion-imprinted polymer layer was enhanced and its adsorption performance was improved.In the optimal condition,the adsorption capacity of Li⁺on Si O₂@SP-PDA-IIM can reach 231.77 mg·g^-1.The changes in the anti-fouling ability of the ion-imprinted membrane surface before and after the introduction of nano-Si O₂ interlayer were investigated through the BSA adsorption experiments.Based on the XDLVO theory,the mechanism of the anti-fouling behavior of the ion-imprinted membrane was explored.The results showed that thanks to the unique?OH groups on the surface of nano-Si O₂,the nano-Si O₂ interlayer significantly enhanced the hydrophilicity of the surface of the ion-imprinted membrane and provided a large amount of electron-donor surface tension(?^-),which can improve the anti-fouling performance of the ion-imprinted membrane.