Colloids and Surfaces A: Physicochem. Eng. Aspects 243 (2004) 43–47 Grafting of ZrO 2 powder and ZrO 2 membrane by fluoroalkylsilanes Sebastian R. Krajewski a , Wojciech Kujawski a,∗ , Fréderic Dijoux b , Céline Picard b , André Larbot b a Faculty of Chemistry, Nicolaus Copernicus University, ul. Gagarina 7, 87-100 Torun, Poland b Institut Européen des Membranes, UMR 5635, Campus CNRS, 1919 route de Mende, 34293 Montpellier Cédex 5, France Received 6 June 2003; accepted 6 May 2004 Available online 17 July 2004 Abstract The hydrophobic properties of zirconia membrane have been obtained by grafting fluoroalkylsilane on the surface of the ceramic material. Several different grafting experiments were conducted using zirconia powders to determine the optimal conditions of grafting. The determined optimal conditions were then applied for the preparation of the hydrophobic membranes. The following grafting parameters were studied: the ratio of the amount of fluoroalkylsilane compound to zirconia mass in the grafting solution, the time and the temperature of grafting. Thermogravimetric analysis (TGA) was used as a technique for the characterization of the grafted powders. The TGA scans allowed to determine the grafting efficiency. The liquid entry pressure (LEP) and the water flux through the grafted membranes were also measured. The determined LEP and water fluxes proved that grafting process was very efficient. Contact angle measurements were additionally done to prove the hydrophobic character of the membrane surface. The hydrophilic character of ZrO 2 membrane can be changed into a hydrophobic one by grafting 1H,1H,2H,2H—perfluorodecyltriethoxy- silane on the surface of the membrane. The performed experiments allowed to determine the optimal conditions of grafting process. Obtained membranes show good hydrophobic character. © 2004 Elsevier B.V. All rights reserved. Keywords: Grafting; Fluoroalkylsilane; Zirconia; Ceramic membrane; Hydrophobicity 1. Introduction Porous materials are applied in many industrial processes such as catalysis, chromatography, filtration or membrane separation [1–3]. Ceramic membranes are widely used nowadays in various applications, essentially in the separa- tion of liquid media [1]. Ceramic membranes are prepared from metal oxides, e.g. alumina, zirconia or titania [2,4]. These kind of membranes are of the great interest thanks to their chemical and ther- mal stability [2,4]. However, ceramic membranes show a hydrophilic behaviour due to the presence of the surface hy- droxyl (–OH) groups [3–7]. The chemical modification of ceramic membranes has been reported from different research groups. The change of ∗ Corresponding author. Tel.: +48 56 611 43 15; fax: +48 56 654 24 77. E-mail address: kujawski@chem.uni.torun.pl (W. Kujawski). hydrophilic character into the hydrophobic one is nowadays of a particular interest [3,6–12]. During the last decade group of Prof. Cohen and co-workers [13–20] reported several papers on the surface modification of different ceramic membranes. As reported by Font et al. [13], the strong chemisorption of different organic solvents (e.g. alcohols, toluene, cyclohexane) on silica membranes imparted a hydrophilic character to the alumina membranes, thus reducing the pore size and the hydraulic permeability of water. Rovira-Bru et al. [14] re- ported the modification of zirconia with terminally grafted poly(vinylpyrrolidone) (PVP). Zirconia surface was modi- fied by a graft polymerisation process consisting of silyla- tion step followed by a surface graft polymerisation of PVP. Such PVP layer can be effective in reducing the surface adsorption of water-soluble macromolecules [14]. Castro et al. [15–17] demonstrated that the permeability charac- teristics of different silica membranes could be altered by graft polymerisation of PVP on the silica membrane sur- face. Graft polymerisation of PVP and poly(vinylacetate) 0927-7757/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2004.05.001