Study On Structre Control And Molecular Separation Performance Of Pe-based Polyamide Composite Membrane

Polyethylene lithium battery separator(PE)has ultra-thin thickness,strong mechanical properties(including tensile strength and puncture resistance,etc.),flatness and dimensional stability.PE is often used as packaging material.When used as a separation membrane,its thinner thickness can sufficiently reduce the internal concentration polarization of the membrane,so it is used in the fields of nanofiltration membrane(NF)and forward osmosis membrane(FO).However,ordinary PE membranes have a relatively hydrophobic surface structure and a large pore size,which makes it difficult to effectively separate brine and dye water.Therefore,it is necessary to improve the wettability of the membrane and reduce the surface pore size of the membrane.In this paper,a variety of qualified polyamide composite membranes were successfully prepared through a variety of hydrophilic modification membrane surface and interfacial polymerization methods.The effect of the hydrophilic layer material on the interfacial polymerization reaction on the membrane surface has been systematically studied,as well as the membrane performance test.The interfacial polymer film prepared in this paper is expected to be applied to functional packaging materials.The main tasks completed in this paper are as follows:By exploring the Michael addition reaction and Schiff base reaction between DA and PEI,the most suitable reaction time,concentration and other conditions for improving the hydrophilicity of the PE base membrane were found,and the two-sided hydrophilic PE membrane was successfully prepared.By exploring the influence of the reaction time of the water phase and the oil phase of the interfacial polymerization,and the post-treatment temperature on the performance of the membrane,a single-sided polyamide composite membrane with better performance was finally prepared.It is concluded that when dopamine hydrophilic treatment is performed on the PE base film for 3 hours,the MPD deposition time is 15 min,the oil phase reaction time is 3 min,and the post-treatment is 90℃ and 5 min.The performance of the polyamide composite film is the best.Each step of the film is characterized by infrared the response was successful.The nanofiltration performance of the membrane is verified by the interception and flux of salts of different molecular weights and vitamins of larger molecular weight,and the actual production and operability of the membrane is explored through long-term performance testing of the membrane.The flux of the final prepared polyamide composite membrane is about 2 L·m-2·h-1·bar-1,the rejection rate for salt is about 50%,and the rejection rate for vitamins is 80%-90%.The hydrophilic treatment of the membrane is carried out through the Michael addition reaction between TA and APTES and the Schiff base reaction,and then the interfacial polymerization is carried out on this basis.The performance test in the forward osmosis mode shows that the membrane is reacted in the hydrophilic layer for 2 hours.In the interfacial polymerization reaction,the aqueous phase is reacted with 3%MPD aqueous solution for 20 minutes,and the oil phase is 0.15%TMC in n-hexane.The obtained membrane has the best performance.The final TFC membrane has a water flux of 30L·m-2·h-1 in forward osmosis mode,and a JS/JW value of 0.38g/L,which is better than commercial FO membranes,with a dye retention rate of 99.9%.In the nanofiltration mode,the membrane has the ability to trap different dyes such as methyl violet,and has good resistance to organic solvents.After immersing the membrane in different organic solvents for 15 days,the membrane still has good performance.Through the Michael addition reaction between TA and PEI and the Schiff base reaction to improve the hydrophilicity of the PE-based membrane,the porous polyamide composite membrane was successfully prepared by the method of interfacial polymerization.And proposed a new method of membrane removal of dyes-a separation method that combines retention and adsorption.The membrane is mainly adsorbed in the first 3-6 hours.In the later stage,the pores of the membrane are gradually blocked by the adsorbed dOye on the surface,which causes the pore size to become smaller.The loose low-pressure nanofiltration membrane in this mode has a high flux,the water flux of the membrane reaches 62 L·m-2·h-1·bar-1,and the dye removal rate of the membrane reaches 96%.