Preparation, characterization, and application of thin film composite nanofiltration membranes

The active aromatic polyamide layers of thin film composite nanofiltration (NF-TFC) membranes were prepared via interfacial polymerization (IP) from three different types of polyamine: p-phenylenediamine (PPD), inphenylenediamine (MPD), or piperazine (PRP), and trimesoyl chloride (TMC) on polysulfone/sulfonated polysulfone (PSf/SPSf) alloy substrates. Chemical components, cross section structures, and thermal properties of the polyamide active layers and the bulk membranes, characterized by Fourier transfer IR spectroscopy and attenuated total reflection IR spectroscopy, scanning electron microscopy, and differential scanning calorimetry and thermogravimetry, respectively, revealed an interpenetrating layer between the polyamide active layer and the substrate. A ridge-valley structural active layer was formed on the PSf/SPSf substrate for the NF-TFC membrane with a thick polyacrylamide (PA) layer. Compared with the NF-TFC membranes on PSf substrates, those on PSf/SPSf alloy substrates had a higher permeability without losing the selectivity by introducing the hydrophilic SPSf into the hydrophobic PSf substrates. The binding between the modified substrate and the active PA layer was also improved. Good separation performances using these NF-TFC membranes were obtained in the polyvalent ion separation, the ground water softening, and the treatment of wastewater from adipic acid plants in a wide pH range. (C) 2005 Wiley Periodicals, Inc.