| It is reported that 10-15%of the world’s total energy consumption is used to separate chemicals,and the energy consumption is extremely alarming.Membrane separation technology has been successfully applied in seawater desalination and water purification due to low energy consumption,green and high efficiency.With the fast development of industrial society,the chemicals preparation and purification involve huge quantities of chemical separation.However,the current separation process basically relies on the energy-intensive distillation separation technology,which has huge energy consumption.In the face of the more severe chemical separation environment,the application of membrane separation technology in organic solvent separation systems has become the technical means of energy saving and environmental protection.As the core component of organic solvent separation technology,the high flux,high precision and long-term use of solvent-resistant separation membranes has become the inevitable trend.Although the organic solvent separation membrane has been proposed in the early 1970s,but so far there is almost no large-scale application,which is mainly caused by the difficulty of developing membrane materials with both stability and high selectivity.Poly（aryl ether ketone）is at the top of special engineering plastics because of its high temperature and corrosion resistance,which is the preferred material for the fabrication of organic solvent separation membranes.Facing the requirements of high stability and high precision of chemical separation in organic solvent separation system,the other challenge is the construction of high-efficiency separation interface in addition to the solvent stability of membrane-based polymer.Organic solvent separation membranes are required to combine high flux,high selectivity and high stability to meet the needs of large amounts of organic liquids separation in industrial environments.In this article,poly（ether ether ketone）（PEEK）was selected as the research substrate to construct high-efficiency organic solvent separation membranes.It is realized that the whole chain of membrane production from the synthesis of membrane-based resin to separation membranes and finally realized the construction of the interface through molecular design,investigating the solvent-resistant properties of membranes and the precise separation performance.With the aim of solving the lack of solvent-resistant membrane-based resins and realizing the construction of the intra-membrane dual-functional polymers,the first part of the work was to prepare poly（arylene ether amine）resins（PEEKt）from molecular design.The 80000 g mol-1 PEEKt membrane-based resins were realized by investigating the effect of molecular weight on the thermal,aggregation state structure and mechanical properties of the polymers.Subsequently,PANI/PEEK composite powder and film were successfully prepared by hydrolysis and oxidation coupling,which realized the conversion of the dual-functional polymers.The effect of temperature,oxidant concentration,acid concentration and PEEKt film thickness on the micro-nanostructure of the films under domain-confined conditions of hydrolysis polymerization was investigated,and the dispersion state of PANI in PEEK was also investigated.The in-situ growth of PANI in the gap between PEEK molecule chains promoted the more orderly arrangement of PEEK chains,and the method of domain-confined polymerization realized the efficient composite of the two phases at the molecular level to improve the loading of PANI,which provided support for the subsequent preparation of PANI/PEEK composite separation membranes.Based on PEEKt membrane-based resins and the preparation strategy of composites in the previous part of the work,the second part of the work was developed to investigate the process of solvent-resistant PEEK separation membranes and hydrolysis co-polymerization with aniline.Firstly,PEEKt porous membranes were prepared by the Nonsolvent Induce Phase Separation（NIPS）method,and then the investigation of hydrolysis co-polymerization was carried out and the porous PANI/PEEK separation membranes were prepared.This method solves the problems of easy agglomeration and low loading of physical mixing and post-modification methods,which realizes in-situ modulation of membrane interfacial morphology to adapt to the application of solvent-resistant separation membranes in different environments.By exploring the causes of the interfacial microstructures,the modulation of PANI microstructures on the porous membrane surface was realized and the changes of membrane wettability and separation performance were investigated.The pure water flux of PANI/PEEK membrane was 302 L m-2 h-1 bar-1,and the rejection of BSA reached more than 97%.Based on the solvent-resistant properties of PANI and PEEK dual-functional polymers,the membranes also have excellent antifouling and solvent resistance.The membrane had highly efficient separation performance and cycling stability in oil-in-water（O/W）emulsions with solvents such as trichloromethane,toluene and dimethylsilicone,etc.The membranes maintain the stable state in both acidic,alkaline,and organic solvent environments.Due to challenges in achieving molecular-scale solute-solvent separation using single separation membranes of PEEK and PANI/PEEK composite membranes prepared in the previous chapter,the third part of the work carries out the study on the construction of precise separation interfaces and the stabilization of multiple interfaces by introducing graphene oxide（GO）with regular pores.Due to the phenomenon of swelling and exfoliation of GO separation layer,solvent-resistant polyaniline@graphene oxide/poly（ether ether ether ketone）（PANI@GO/PEEK）separation membranes were fabricated by bottom-up in-situ growth of polyaniline（PANI）to anchor the multiple interfaces.With the help of anchoring multiple interfaces by aniline confined polymerization,the pore size regulation of separation layer,defect repair and anchoring between the polymer,the nano-separation layer and the nano-sheet layer were achieved to obtain highly stable and efficient organic solvent separation membranes.The growth mechanism and micro-nano structural changes of the membranes in confined space were explored on the basis of this approach.The membrane methanol flux reached 50.2 L m-2 h-1,and the rejection of acidic magenta(AF,585 g mol-1)reached 92%.In addition,the PANI@GO/PEEK membranes showed excellent stability under 2 mol L-1 HCl,Na OH and high temperature conditions,and excellent durability after 240 days of immersion and 100h of long-term operation,with the stability reaching 8 times of untreated GO membranes.Based on the excellent stability and durability of solvent-resistant PANI@GO/PEEK separation membranes prepared in the previous chapter,in order to prepare separation membranes with both high flux and high rejection,the fourth part of the work explores the preparation of high-flux solvent-resistant separation membranes and structural reorganization of the membrane interface through the introduction of metal-organic framework particles（MOF）with rich pore structure.Because MOF powders are extremely difficult to form homogeneous and stable separation layers under vacuum assistance,this chapter innovatively proposes the preparation method of two-dimensional lamellae constrained three-dimensional nanoparticles,which realizes the enrichment of MOF particles on the surface of flexible membranes.By constructing nano-flux channels on the surface of PEEK membranes,the interfacial structure with GO as the framework,MOF as the active material,and PANI as the binder was built,resulting in the fabrication of solvent-resistant polyaniline@graphene oxide/UiO-66-NH2/poly（ether ether ketone）（PANI@GO/UiO-66-NH2/PEEK）separation membranes.With the integrated reforming of aniline confined polymerization,the transformation of MOF particles on the membrane surface from disorder to order was achieved,while the pore defects were repaired and the instability of the organic-inorganic interface was eliminated.Through the combination of molecular dynamics simulations and experiments,PANI chemical bond anchoring and cohesive energy-driven promotion of structural changes were confirmed.In this work,MOF particles were introduced to increase the nano-flux channels on the membrane surface to enhance the membrane flux while the solvent resistance remained unchanged,and the balance of high flux and high rejection was achieved,with methanol flux of 270.7 L m-2 h-1 and rejection of 95%for acidic magenta(AF,585 g mol-1).At the same time,the membrane showed excellent stability under ultrasonic and pressure conditions and long durability for 138days.In summary,the above four parts of the work have realized the whole chain of membrane fabrication from raw material to membrane formation and finally the construction of highly efficient separation interface.In this work,PANI/PEEK membranes were constructed and functional nanoparticles were introduced to construct the interfacial structure to improve the efficiency of solvent-resistant separation membranes,which is of great significance for the research of solvent-resistant separation membranes. |
