Separation and Purification Technology 22-23 (2001) 663 – 669 The influence of filler concentration on the compaction and filtration properties of Zirfon ® -composite ultrafiltration membranes P. Aerts a,d, *, A.R. Greenberg b , R. Leysen a , W.B. Krantz c , V.E. Reinsch b , P.A. Jacobs d a Flemish Institute for Technological Research (VITO), Process Technology, Boeretang 200, B-2400 Mol, Belgium b Department of Mechanical Engineering, Membrane Applied Science and Technology Center, Uniersity of Colorado at Boulder, Boulder, CO 80309 -0427, USA c Department Chemical Engineering, Membrane Applied Science and Technology Center, Uniersity of Colorado at Boulder, Boulder, CO 80309 -0427, USA d Centre for Surface Chemistry and Catalysis, Faculty of Agricultural and Applied Biological Sciences, Katholieke Uniersiteit Leuen, Kardinaal Mercierlaan 92, B-3001 Leuen, Belgium Abstract During ultrafiltration, a transmembrane pressure difference is applied across a polymeric membrane. This pressure difference results in solute transport through the membrane and mechanical compression of the membrane. The ultrasonic time-domain reflectometry (UTDR) technique is used to measure mechanical compression of the membrane structure in real time while water permeability is simultaneously measured during ultrafiltration in a specially designed crossflow filtration cell. The membranes used in this study are Zirfon ® organo-mineral membranes fabricated using 0.9-m zirconia particles at three different loadings. Thickness changes and the permeability of composite ultrafiltra- tion membranes are obtained simultaneously and in real-time as a function of filler concentration and transmembrane pressure. Results indicate that the presence of ZrO 2 particles in the polymeric matrix influences the membrane permeability as well as compression of the membrane structure. Increasing the filler concentration decreases the elastic strain component but increases the time-dependent strain component. Both the initial and the time-dependent strain increase with increasing pressure. The flux decline is more severe at higher pressures and appears to be due to localized deformation in the membrane skin layer. This study provides the first quantitative information regarding compaction of organo-mineral Zirfon ® membranes. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Membrane compaction; Ultrasonic time-domain reflectometry; Real-time measurement; Ultrafiltration; Composite membrane www.elsevier.com/locate/seppur 1. Introduction Zirfon ® ultrafiltration composite membranes consist of an asymmetric polysulfone (PSF) mem- * Corresponding author. Tel.: +32-14-335638; fax: +32- 14-321186. E-mail address: peter.aerts@agr.kuleuven.ac.be (P. Aerts). 1383-5866/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S1383-5866(00)00165-9