Preparation And Properties Of Polyether Block Amide Magnetic Membrane For O₂/N₂ Separation

O₂ and N₂ have been widely used in medical treatment,chemical,food preservation and other fields.How to economically and efficiently separate O₂ and N₂ from air has become a hot research topic in the field of chemical separation.Compared with cryogenic distillation and pressure swing adsorption,membrane separation process has shown outstanding advantages in O₂/N₂ separation field due to the characteristics of low energy consumption,high efficiency and environmental friendliness.Magnetic membrane prepared by blending magnetic particles and polymer can simultaneously increase O₂ permeability and O₂/N₂ selectivity by virtue of the additional reverse magnetic force of O₂ and N₂ in the membrane,which is an effective way to solve the trade-off problems between permeability and selectivity.However,the poor interfacial compatibility leads to the serious deterioration of the mechanical properties of the magnetic membrane.In addition,magnetic shielding results in the degree of improvement of the O₂/N₂separation performance was limited.Therefore,from two perspectives of improving the interfacial compatibility and optimizing the membrane structure,this study selected PEBA as polymer,and Fe₃O₄ as magnetic particles,then three kinds of polyether block amide magnetic membrane were prepared by surfactant-modified,ionic liquid blend and magnetic field induction.The influences of surfactant type,IL content,membrane structure and external magnetic field on the interface structure,mechanical properties and O₂/N₂ separation performance of the magnetic membranes were investigated.The specific contents and main conclusions are as follows:（1）Surfactant modified PEBA/Fe₃O₄ magnetic membrane was prepared by establishing Fe₃O₄ functionalized with surfactant（SDS,CTAB,Triton X-100）in a PEBA membrane.The interfacial compatibility,physical and chemical properties and O₂/N₂ separation performance of the magnetic membrane were studied.The results show that the Triton X-100 played a role in enhancing interfacial compatibility,and the mechanical properties of the modified magnetic membrane were enhanced.Compared with the PEBA/Fe₃O₄@SDS and PEBA/Fe₃O₄@CTAB magnetic membranes,when the magnetic field intensity was 60 mT and the Fe₃O₄ content was10 wt%,the PEBA/Fe₃O₄@TX100_（10）magnetic membrane exhibited better gas separation performance with a O₂ permeability coefficient of 35.36 Barrer and a O₂/N₂ selectivity of 4.3.PEBA/Fe₃O₄@TX100 magnetic membrane with high Fe₃O₄ content has excellent mechanical properties and separation performance.At 60 mT,the PEBA/Fe₃O₄@TX100_（15）magnetic membrane doped with 15 wt%of modified Fe₃O₄exhibited the optimum performance with a O₂ permeability coefficient of 45.44 Barrer and a O₂/N₂ selectivity of 5.44,compared with pure PEBA membrane,which were increased by 116.69%and 89.55%,respectively.（2）PEBA/Fe₃O_4（10）/IL magnetic membrane was fabricated by blending 1-butyl-3-methyl imidazolium hexafluorophosphate and Fe₃O₄ in PEBA membrane.The effects of IL concent on physical and chemical structure,magnetic induction intensity and O₂/N₂ separation performance of PEBA/Fe₃O₄/IL magnetic membrane were studied.The IL improved the interfacial compatibility,and increased the magnetic induction intensity of PEBA/Fe₃O₄/IL magnetic membrane.With the increase of IL content,the saturation magnetization of PEBA/Fe₃O₄/IL magnetic membrane firstly increased and then decreased.When the Fe₃O₄content was 10 wt%and IL content was 5 wt%,the saturation magnetization of PEBA/Fe₃O_4（10）/IL_（5）magnetic membrane was 12%higher than that of PEBA/Fe₃O_4（10）magnetic membrane.At the same time,IL played an important role in enhancing O₂/N₂separation performance.When the magnetic field intensity was 60 mT,the O₂ permeability and O₂/N₂ selectivity of PEBA/Fe₃O_4（10）/IL_（5）magnetic membrane reached 47.82 Barrer and 4.67,respectively.Which were 52.10%and 23.54%higher than that of PEBA/Fe₃O_4（10）magnetic membrane.（3）PEBA/Fe₃O₄ magnetic membrane with an anisotropic structure were constructed through the process of solvent evaporation under an external magnetic field,and Fe₃O₄magnetic particles in the membrane concentrated near the membrane surface by the magnetic inducement.The effects of anisotropic structure and the amount of Fe₃O₄ on magnetic induction intensity and O₂/N₂ separation performance of Ani-PEBA/Fe₃O₄ magnetic membrane were investigated.The results showed that Ani-PEBA/Fe₃O₄ magnetic membrane was successfully prepared by magnetic induction.Fe₃O₄ particles were enriched on the surface of the polymer membrane,which weakened the magnetic shielding and increased the magnetic induction intensity the magnetic membrane.The saturation magnetization of the Ani-PEBA/Fe₃O_4（10）magnetic membrane filled with 10 wt%of Fe₃O₄was increased by 53%compared with that of the PEBA/Fe₃O_4（10）magnetic membrane.Furthermore,the anisotropic structure significantly improved the O₂/N₂ separation performance.With the increase of Fe₃O₄ content,the O₂/N₂separation performance of Ani-PEBA/Fe₃O₄ magnetic membrane increased gradually.At 60mT,the O₂ permeability coefficient and O₂/N₂ selectivity of the Ani-PEBA/Fe₃O_4（10）magnetic membrane were 36.84 Barrer and 4.55,which were 17.18%and 20.37%higher than that of PEBA/Fe₃O_4（10）magnetic membrane,and compared with pure PEBA membrane,which were increased by 75.68%and 58.54%,respectively.