Polyimide thin film composite (TFC) membranes via interfacial polymerization on hydrolyzed polyacrylonitrile support for solvent resistant nanofiltration

Highly permeable, selective and solvent resistant nanofiltration (SRNF) membranes are desirable for the separation of substances on a molecular level in organic solvent. Polyimides have attracted significant attention for their chemical, structural and thermal stability. In this work, hydrolyzed polyacrylonitrilepolyamide acid (H-PAN/PAA) composite membranes were prepared via interfacial polymerization of m-phenylenediamine (MPD) and 1,2,4,5-benzenetetra acyl chloride (BTAC) on hydrolyzed polyacrylonitrile (H-PAN) supports. The formed H-PAN/PAA membranes were then transformed into H-PAN/PI thin film composite (TFC) membranes by a chemical imidization method. The effects of acetone as co-solvent in organic phase solution, the additives in the aqueous solution and the imidization time on the performance of the prepared PI TFC membranes were investigated. The chemical composition and the morphology of the prepared composite membranes were characterized by using FTIR, SEM and AFM. The hydrophilicity of the membrane surface was also measured. Using Rhodamine B (RB) with molecular weight (MW) of 479 dalton (Da) and Coomassie brilliant blue (CBB) G250 (MW = 854 Da) as model chemicals, the rejections of the prepared SRNF membranes for 100 mg L-1 of RB-ethanol solution and CBB G250-ethanol solution were about 92.8% and 99%, respectively. Their ethanol permeances were about 0.79 L m(-2) h(-1) bar(-1) and 0.69 L m(-2) h(-1) bar(-1), respectively. After being immersed respectively into CCl4, toluene, ethanol, acetone and methanol pure solvents for 30 days, the rejections of the prepared SRNF membranes remained quite stable.