Self-assembly of inner skin hollow fiber polyelectrolyte multilayer membranes by a dynamic negative pressure layer-by-layer technique

In the past studies, electrostatic layer-by-layer (LbL) adsorption of oppositely charged polyelectrolytes has proven to be a promising method for the preparation of polyelectrolyte multilayer membranes (PEMMs). Till now, this method was mainly used to assemble flat sheet and tubular membranes. Since hollow fiber membrane has some advantages such as high-packing density, self-contained mechanical support and hence the consequent economical superiority, this study therefore seeked to assemble inner skin hollow fiber PEMMs by using a dynamic LbL adsorption technique. The assembly process was successfully accomplished by alternatively dynamically filtrating polyacrylic acid (PAA) and polyethyleneimine (PEI) on a hydrolyzed hollow fiber polyacrylonitrile(PAN) membrane under a negative pressure condition. In the case of pervaporation separation of 95 wt.% ethanol-water mixture (50 C), the membrane obtained with only 4.5 and 6.5 bilayers had separation factor of 245 and 1338 while the permeate fluxes were 290 and 120 g/(m(2) h), respectively. The pervaporation separation behavior of various alcohol/water mixtures with the alcohols being t-butanol, 2-propanol and ethanol were also investigated. Finally, scanning electron microscopy and atomic force microscopy clearly confirms a uniform and defect-free layer formed on the inner surface of hollow fiber support. Since different polyelectrolyte pairs could be used to assemble PEMMs for different uses, it was expected that the dynamic negative pressure LbL adsorption technique could also potentially be used to prepare many types of PEMMs in other fields. (c) 2008 Elsevier B.V. All rights reserved.