Preparation And Property Research Of High-Performance Oil/Water Separation Membranes Based On Poly (Ether Ether Ketone) Fiber

As a kind of high-performance engineerning plastics,PEEK had been prepared in1978 by ICI(Imperial Chemical Industries Ltd,UK).As the advantages of corrosion resistance,solvent resistance,water absorption resistance,high strength,thermal stability,low density,flame retardance,radiation resistance,environmental friendliness,good biocompatibility and insulation,PEEK has irreplaceable value in the fields of aerospace,automobile industry,medical treatment,electronic appliances,national defense and military industry.Among all the advantages of PEEK,corrosion resistance,solvent resistance,water absorption resistance,high strength and thermal stability exactly meet the characteristics required in practical application of the current oil/water separation membranes.In this paper,PEEK fiber was used as a basic material to prepare PEEK textiles and PEEK felts via weaving and nonwoven technologies.After modification and functionalization,the textiles and felts exhibited special wettabilities,which could be used in oil/water separation and maintained the excellent performance of PEEK to the most extend.Furthermore,the wetting behaviors of droplets on membrane surface at metastable state were investigated by fabricating hierarchical micro-structures on the membrane surface,which extended the working mechanism of oil/water separation membrane at metastable state.Overall,the main contents of this paper are as follows:1.First of all,PEEK multifilament was woven into PEEK textile.Then,PEEKOH textile was obtained by surface hydroxylation of PEEK textile.PEEK-OH and PEEK textiles formed a couple of membranes with opposite wettability,that was PEEKOH textile showed under-water oleophobicity and PEEK textile showed under-water oleophilicity.PEEK-OH exhibited excellent separation performance after pre-wetted by ethanol and water successively,such as high flux,admirable selectivities and good oil rejection heights.Moreover,it was found that pre-wetting PEEK-OH textile by ethanol could increase the interaction force between the membrane surface,pore walls and water moleculars,helping the textile wetted by water more completely.Thus,the rejection height towards low polarity solvents was improved.PEEK-OH could not only be used for the separation of oil-water mixture,but also intercept low polar oil after wetted by high polar oil,thus the separation of insoluble highly polar oil and low polar oil mixture was achieved.Original PEEK textile was also used as ‘water-removing'separation membrane after pre-wetted by dichloromethane and n-hexane,which exhibited high flux,admirable selectivity and good rejection height as well.In addition,both of PEEK and PEEK-OH textiles remains high strength,corrosion resistance,solvent resistance and thermal stability of PEEK fibers to a great extent.They could still show high selectivities after treatment in certain severe conditions.2.Firstly,Ni-Co LDH polygonal nanosheets were deposited on PEEK felt in situ by hydrothermal method to fabricate hierarchical micro-structures on the membrane surface.Then,polypyrrole(PPY)was deposited on the membrane surface through vapor deposition to obtain the separation membrane PEEK-LDH-PPY.Due to the suitable hydrophilicity of PPY,PEEK-LDH-PPY can be completely wetted by water and non-polar oil with under-water oleophobicity and under-oil water hydrophobicity,respectively.In addition,the pore size distribution and surface hierarchical roughness of PEEK-LDH-PPY were regulated by the deposition of Ni-Co LDH polygonal nanosheets.As a result,PEEK-LDH-PPY achieved dual superlyophobicity,namely under-water superoleophobicity and under-oil superhydrophobicity.Moreover,it exhibited good switchable stability and could switch between under-water oleophobicity and under-oil hydrophobicity for more than 20 times.PEEK-LDH-PPY can be used as ‘oil-removing' membrane after pre-wetted by water and ‘water-removing'membrane after washed by ethanol and pre-wetted by organic solvents with low polarities and low surface tension,such as n-hexane.With the pre-wetting effect of ethanol,PEEK-LDH-PPY exhibited high selectivities and rejection heights when used as ‘oil-removing' membrane.Furthermore,the membrane could also separate immiscible organic liquids with difference PSE.Last but not least,PEEK-LDH-PPY remains the high strength,good corrosion resistance,solvent resistance and thermal stability of PEEK.3.PEEK felt was prepared using PEEK fibers.Then thermal pressing and surface sulfonation were utilized to adjust the pore size and surface wettability of the PEEK felt to develop oil/water separation membrane.Moreover,the effects of hot-pressing temperature,pressure and sulfonation time on the separation performance of the membranes were discussed.Furthermore,the membrane surface was treated by UV/ozone cleaner to create more crystallization sites.Then,flower-like ZnO nanoneedles were deposited on the membrane surface in order to construct hierarchical rough structures.The as-prepared membrane is under-water superoleophobic.After wetted by ethanol and water successively,water would trap into the micro-structures on the membrane surface and sandwich between the membrane and oil,which makes oil droplets more inclined to suspend at Cassie state on the membrane surface.In this way,the direct contact between oil droplets and membrane surface could be reduced and thus the anti-fouling performance and rejection height of the membrane improved significently.Moreover,ZnO modified surface sulfonated PEEK felt remained the excellent solvent resistance and good thermal stability.After immersion in organic liquids and thermal treatment at 100 ?,the as-prepared felt could maintain its high selectivities.Besides oil/water mixture,the felt could also separate immiscible organic liquids with large difference in polarity.