The Basic Study On Fabrication Of Hollow Fiber Composite Nanofiltration Membranes Through Interfacial Polymeriztion Technology

Up to date, membrane separation technology such as ultrafiltration andnanofiltration becomes the next generation technology for solving the worldwidecrisis of water shortages. Nanofiltration （NF） as the typical membrane seperationtechnology involves separation of monovalent and divalent salts, or organic soluteswith molecular weight in the range200-1000g mol1. Although the interfacialpolymerization （IP） as the prevailing technique has been widely used to fabricatethin-flm-composite （TFC） NF membranes for water treatment, IP technique ismainly applied to flat-sheet membranes which are packaged into spiral-woundmodules, and rarely utilized for the fabrication of hollow fiber modules with thehigher packing density. From the pratical point of view, the hollow fiber moduleshave the better performance and wider applications.In this study, TFC nanofiltration membranes were newly developed through IPtechnique on the lumen side of hollow fiber support membranes by exploring novelcombination of reacting monomers. Firstly, the effects of the conditions （such as theconcentration of MPDA, the impregnated time of MPDA, the concentration of TMC,reaction time, the concentration of surfactant and the concentration of protonacceptor） of interface polymerization on the performance of the fabricated NFhollow fiber membrane were explored. Secondly another monomer （piperazine: PIP）in water phase was added in the interfacial polymerization system. And we foundthat the molecular weight cut off （MWCO） of NF membranes can be adjusted to beless than300.0g mol^-1and the pure water permeability can reach as high as3.14Lm^-2h^-1bar^-1based on the different combinations of reacting monomers （MPDA andPIP）. The NF membranes demonstrated different rejections for different salts in theorder of R（Na₂SO₄）>R（MgSO₄）>R（NaCl）>R（MgCl₂） and well pressure resistance.The novel NF membranes were further utilized to remove typical contaminantsof dyes by varying the factors of operating pressures, feed concentrations and pHvalues. For both of safranin O and aniline blue dyes, the rejection can be higher than90%under testing conditions, and the much important finding was that the excellentperformance of NF membranes to remove dyes from waste water can be maintainedin a wide range of pH values. At the operating pressure of6bar, the feedconcentration of200ppm and pH value of11, the rejection of the fabricated hollowfiber composite membrane on the safranin O and anniline bule were as high as95.32%and98.71%respectively. Therefore, the novel NF membranes are promisingfor removing crucial dyes as the next-generation technique for industrial wastewatertreatment.