Preparation And Properties Of Nanofiltration Membranes Based On Hydrophilized Nonwovens

As a method for preparing composite membranes,interfacial polymerization has attracted extensive attention from researchers due to its advantages such as simple equipment,rapid reaction,and easy control.It has become the main method for preparing nanofiltration membranes,but it is usually necessary to choose ultrafiltration membranes as the substrate of the interfacial polymerization composite membrane,such as polysulfone,polyethersulfone,polyacrylonitrile,etc.Therefore,the research and development of a method for preparing composite nanofiltration membranes by interfacial polymerization based on macroporous substrates has important theoretical and application value for reducing the manufacturing cost of nanofiltration membranes and expanding the application range of nanofiltration membranes.In this paper,a kind of polyamide composite nanofiltration membrane with the structure and characteristics of nanofiltration membrane was prepared by the method of interfacial polymerization based on the microporous hydrophilic polypropylene nonwoven substrates.The main conclusions of this paper are as follows:(1)A micro-channel hydrophilic modified polypropylene microporous with high flux and filtration efficiency under low pressure driving was prepared by co-depositing catechol/polyethyleneimine on polypropylene non-woven fabric.With the microfiltration membrane as membrane material,driven by low pressure gravity,the removal efficiency of solid suspended particles in surface water is 85%,the removal efficiency of TOC and TN in water body is 22.62%and 40.13%,respectively,and had certain removal effect on organic matter in water body.(2)With the micron-channel hydrophilic modified polypropylene nonwovens as the structure,adding the surfactant sodium dodecyl sulfate in the aqueous phase,using the method of interfacial polymerization,the polyamide composite nanofiltration membrane with typical structure and characteristics of nanofiltration membrane was prepared by adjusting the reaction conditions,the concentration of surfactant and the standing time.The results showed that the addition of surfactant be conducive to improve the integrity of the polyamide functional layer of composite membrane.By adding the surfactant sodium dodecyl sulfate,the coverage of the polyamide layer on the surface of the composite membrane prepared at low monomer concentration was increased,and the rejection rate of bovine serum albumin(BSA)could reach more than95%.With the increase of monomer concentration,the polyamide functional layer on the surface of the composite membrane become more complete,ultra-thin and compact,the flux of the composite membrane decreased,and the interception efficiency increased.When the concentration of piperazine is 1.5 w/v,%,and the concentration of1,3,5-benzoyl chloride is 2.5 w/v,%,the polyamide functional layer on the surface of the composite membrane can completely cover the surface of the hydrophilic modified nonwovens without obvious defects.Driven by a low pressure of 0.15MPa,the flux of the composite membrane is 23.12 L·m^-2h^-1,and the rejection rate of Na₂SO₄ is as high as 96.31%,while the rejection rate of Na Cl is only 18.44%.The composite membrane had good separation performance for divalent anions,but poor rejection effect for univalent anions,and has the typical structure and characteristics of nanofiltration membrane.