Studies On The Preparation Of Polyamide/Polysulfone Nanofiltration Hollow Fiber Composite Membrane

The paper was aimed to prepare high performance nanofiltration hollow fiber composite membranes with ultra low pressure and ultra high permeating. Polysulfone was chosen as the material for making the porous substrate because of its excellent compress-to-denseness resistance, its cheap price and its great availability. By fabricating an ultra thin polyamide functional layer on the polysulfone substrate through interfacial polymerization taking piperazine as the monomer in aqueous phase and trimesoyl chloride as the monomer in organic phase, high performance nanofiltration composite membranes of ultra low pressure and ultra high permeating flux were prepared. Using 0.1% MgSO₄ as the feed liquid, the plate composite membrane (I) prepared has a salt rejection of 96.1% and a permeating flux of 85.2 L·m^-2·h^-1 under an operating pressure of 0.4MPa, while another one (â…¡) has a salt rejection of 23.7% but a high permeating flux of 397.8 L·m^-2·h^-1. A hollow fiber composite membrane (â…¢) has a salt rejection above 93% and a permeating flux above 40 L·m^-2·h^-1 under a pressure of 0.6MPa.The study conducted research on the following four fields:â…  . The characteristics of the interfacial polymerization system of piperazine aqueous solution/trimesoyl hexane solution were systematically investigated. The results show that at a certain molar ratio between the two monomers, piperazine and trimesoyl, at the two phase interface, a dense functional layer with ultra low pressure, high permeating flux and high salt rejection formed by controlling the time of interfacial polymerization, such as the composite membrane (â… ). High performance nanofiltration composite membranes with varied permeating flux and salt rejection were obtained by changing the monomer concentrations in both phases properly, in the case of composite membrane (â…¡). A heat treatment to composite membrane, preferred in a 70 ℃ hot air bath for 20 minutes can improve the salt resistance of the composite membrane.â…¡. The performance of the nascent polyamide/polysulfone composite membrane under varied operational conditions was examined. The permeating flux of the original composite membrane gradually reduced to a bottom, and the salt rejection of the original composite membrane gradually increased to a platen. It was found that the functional layer of the nascent composite membrane is loosen and the loosen layer became dense under acertain pressure, and thus obtain a higher and steady salt rejection.III. PSf hollow fiber substrates with different morphology were spun using a triple orifice spinneret /coextrusion-composite spinning technology by regulating the composition of the inner and outer dopes. Through composite coating, it indicates that the substrate with a thin and dense skin layer requires a short polymerization time and the composite membrane prepared is of a high salt rejection, a high flux and a low operating pressure. The permeating flux of a current excellent polysulfone hollow fiber substrate is about 200 L-m"2-h"', and its rejection to PEG20000 is about 99%.IV , The technology of the interfacial polymerization on a hollow fiber substrate was investigated, and a preferable sample as (III) was obtained. The prefered condition are the concentration of piperazine in water phase being 0.4%, the concentration of trimesoyl hexane in organic phase being 0.1%, the time of immerged in water phase being 4 minute, the polymerization time being 1 minute, and a proper annealing in a 70 °C hot air bath for 20 minutes.