Multilayer composite surfaces prepared by electrostatic self-assembled technique for desalination

Electrostatic self-assembly (ESA) technique was applied to prepare self-assembled multilayer membranes and the metal-ion removal permeability of resultant membranes was studied. In order to prepare these membranes, electrolytes of cetyl trimethyl ammonium chloride (CTAC) and poly(acrylic acid) (PAA) were alternately deposited onto negatively and positively charged polyacrylonitrile copolymer membranes made of poly(acrylonitrile-co-acrylic acid) [P(AN-co-AA)] and poly(acrylonitrile-co-N,N-dimethylethyl ammonium bromide) [P(AN-co-EDAMA)], respectively. The polyacrylonitrile copolymer base membranes were prepared by phase-inversion method and then layers of CTAC and PAA were alternately deposited onto the surface. In the following work, the surface and metal-ion removal properties of the modified membranes were studied. The effect of the alternated positively or negatively charged layers on the removal properties for metal ions of Fe2+ and Fe3+ were observed for membranes with PAA or CTAC terminal layers. The resultant membranes with PAA and CTAC self-assembled layers showed metal-ion removal capability and the permeability varied for Fe3+ and Fe2+. Also, the experimental results revealed that the top deposited layer influenced the metal-ion removal permeability of resultant membrane due to the charge properties of the membrane surface. It was proposed that such membrane modified with ESA multilayer could be applied for desalination as a novel metal-ion removal technique.