The Reserch On Fabrication And Solvent Resistant Properties Of Ethylenediamine Modified Polyimide Nanofiltration Membrane

Considering environment issues and energy consumption, polyimidenanofiltration membrane was used as a novel material for separating mixtures inorganic solution. Solvent resistant nanofiltration applying into the high energycomsuption separation processes has been substituted for the conventional methodsuch as distillation. Due to the instability of polyimide in a solvent system,polyimide nanofiltration (NF) membrane applied to the solvent medium is quitedifficult. In other words, the membrane is easily dissolved or swollen in an organicsolvent, resulting in poor separation performance. In order to expand the range ofapplications of polyimide solvent nanofiltration membrane, improving the stabilityof polyimide membrane in organic solvents and obtaining an efficient solvent-stableperformance is an urgent problem to be solved.In this paper, polyetherimide (PEI) and Lenzing P84polyimide nanofiltrationmembranes were prepared via the phase-inversion process. The prepared membraneswere cross-linked by the vapor-phase EDA and5mass%methanolic solution ofethylene diamine. The optimum crosslinking time of the polyimide nanofiltrationmembranes was obtained according to the results of gel content test and filtrationexperiments. The optimum crosslinking time of PEI and Lenzing P84nanofiltrationmembranes cross-linked by EDA vapor were all about one hour. However, whenthe memebranes were modified in EDA solution and the ideal crosslinking time ofPEI and Lenzing P84were45min and15min, respectively, the crosslinking effectsof the two polyimide membrane were excellent, showing outstanding solventresistance property.In addition, the effects of the polyethylene glycol (PEG-amine, Mw600Da)additives on the performance of PEI and Lenzing P84polyimide solvent resistantnanofiltration membranes were investigated. The results on the filtrationexperiments of different solvents demonstrated that when the content of PEG was7mass%, both PEI and Lenzing P84polyimide membranes modified by EDA vaporand EDA methanolic solution showed the best comprehensive performance that thesolvent permeability was greatly improved, and the rejection rate of Rose Bengalwas exceeded99%. Frontier Transform Infrared Spectroscopy (FTIR) and DSCmeasurements results indicated that the amino group of PEG-amine and the imidegroup from the PEI and Lenzing P84polyimide occured a crosslinking reactionduring the blending process. The PEG-amine not only play a role of a pore-formingagents, but also play a part of a cross-linking agent to improve the permeability andenhance the solvent resistant performance of the polyimide membranes.