Study On The Preparation Of Polysulfone Hollow Fiber Substrate For Composite Membrane

In this paper, polyamide/ polysulfone(PSf) composite hollow fiber membrane was prepared by using PSf ultrafiltration hollow fiber membrane as support membrane, m-phenylene diamine(MPD) and piperazine(PIP) as the monomer in aqueous, trimesoylchloride(TMC) as the monomer in organic phase, fabricating an ultra thin polyamide functional layer on the substrate through interfacial polymerization. Spinning technics of hollow fiber, the effects of pre-treatment of substrate and the structure of monomers on the performance of composite membrane, and separate capability of composite membrane were studied.PSf hollow fiber membrane was prepared by dry-wet spinning technics, using kinds of additives, the effect of additives on the structure and performance of substrate membrane was researched. The components in composite additives make the induce-porous mechanism cooperate effectively, resulting in the spinning solution having proper dispersibility and stabilization, controlling the wetting capability of coagulating solution in spinning dope effectively, controlling the formation of membrane, preparing PSf hollow fiber membrane with steady performance, proper hole, and high flux. The membrane has a rejection of 85% for the solution of egg white albumin at the concentration of 4g/L, and water flux more than 250 L .m^-2.h^-1 under an operating pressure of 0.1MPa. Spinning technics of substrate membrane with composite additives was investigated in detail.Two monomers in aqueous were selected, reacting with TMC, PA/PSf composite membranes were prepared. The results showed as follows, when using PIP as monomer, the composite membrane prepared has a good rejection for salt with two charges, but a worse rejection for salt with one charge. It has a salt rejection of 96.4% for MgSO₄ at the concentration of 2g/L, and a high water flux of 94.4 L .m^-2.h^-1 under an operating pressure of 0.7MPa. But a low salt rejection for NaCl, lower than 30%. When using MPD as monomer, the composite membrane prepared has a good rejection both for salt with one charge and two charges, but a low permeating flux. Separate capability of Polypiperazine trimesoyl amid/PSf nanofiltration composite membrane was studied, it has a good rejection for multi-valent ions and substance with molecular weight higher than 300.Polypiperazine trimesoyl amid/PSf nanofiltration composite hollow fiber membrane was prepared using substrate pre-treated with ethanol. The permeating flux of composite membrane increased about one times for MgSO₄ at the concentration of 2g/L, under an operating pressure of 0.7MPa, while salt rejection changed little. Hydrogen bond was formed between porous substrate and ultra thin polyamide functional layer, it strengthened the action between composite membrane and water compound, according to the model of dissolve and diffuse from the mechanism of membrane separating.