The influence of filler concentration on the compaction and filtration properties of Zirfon (R)-composite ultrafiltration membranes

During ultrafiltration, a transmembrane pressure difference is applied acro ss a polymeric membrane. This pressure difference results in solute transpo rt through the membrane and mechanical compression of the membrane. The ult rasonic time-domain reflectometry (UTDR) technique is used to measure mecha nical compression of the membrane structure in real time while water permea bility is simultaneously measured during ultrafiltration in a specially des igned crossflow filtration cell. The membranes used in this study are Zirfo n(R) organo-mineral membranes fabricated using 0.9-mum zirconia particles a t three different loadings. Thickness changes and the permeability of compo site ultrafiltration membranes are obtained simultaneously and in real-time as a function of filler concentration and transmembrane pressure. Results indicate that the presence of ZrO2 particles in the polymeric matrix influe nces the membrane permeability as well as compression of the membrane struc ture. Increasing the filler concentration decreases the elastic strain comp onent but increases the lime-dependent strain component. Both the initial a nd the time-dependent strain increase with increasing pressure. The Aux dec line is more severe at higher pressures and appears to be due to localized deformation in the membrane skin layer. This study provides the first quant itative information regarding compaction of organo-mineral Zirfon(R) membra nes. (C) 2001 Elsevier Science B.V. All rights reserved.