Preparation and properties of nanocomposite polysulfone/multi-walled carbon nanotubes membranes for desalination

Novel nanocomposite membranes for application in desalination were fabricated from polysulfone (PSf) and multi-walled carbon nanotubes (MWNTs) functionalized with dodecylamine (DDA) and anti-fouling properties of the membranes were studied during filtration of bovine serum albumin (BSA) solutions. Phase inversion process with dimethylacetamide as solvent and polyvinylpyrrolidone as a porogen was used to prepare flat sheet nanocomposite PSf/DDA-MWNTs membranes. Before embedding MWNTs in the polymer matrix, they were treated with HNO3 for the introduction of carboxylic groups on nanotube surface and then modified with DDA. The prepared DDA-MWNTs were characterized using scanning electron microscope, infrared spectroscopy and thermal gravimetric analysis. The long alkyl chains of DDA functionalized MWNTs seem to enhance the interfacial adhesion and compatibility between inorganic nanotubes and PSf matrix. The changes in surface hydrophilicity, morphology and roughness of fabricated nanocomposite membranes as a function of DDA-MWNTs loading were evaluated by using contact angle goniometry and atomic force microscopy. The prepared nanocomposite membranes possessed significantly higher permeability with improved protein fouling resistance than the pristine PSf membrane during filtration of BSA solutions. The membrane prepared with 0.5 wt.% loading of DDA-MWNTs displayed the highest flux recovery (83%) and lowest total flux loss (29%) with reduced irreversible fouling resistance (17%).