Colloids and Surfaces A: Physicochemical and Engineering Aspects
Grafting of ZrO2 powder and ZrO2 membrane by fluoroalkylsilanes
Introduction
Porous materials are applied in many industrial processes such as catalysis, chromatography, filtration or membrane separation [1], [2], [3]. Ceramic membranes are widely used nowadays in various applications, essentially in the separation 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 thermal stability [2], [4]. However, ceramic membranes show a hydrophilic behaviour due to the presence of the surface hydroxyl (OH) groups [3], [4], [5], [6], [7].
The chemical modification of ceramic membranes has been reported from different research groups. The change of hydrophilic character into the hydrophobic one is nowadays of a particular interest [3], [6], [7], [8], [9], [10], [11], [12].
During the last decade group of Prof. Cohen and co-workers [13], [14], [15], [16], [17], [18], [19], [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] reported the modification of zirconia with terminally grafted poly(vinylpyrrolidone) (PVP). Zirconia surface was modified by a graft polymerisation process consisting of silylation 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], [16], [17] demonstrated that the permeability characteristics of different silica membranes could be altered by graft polymerisation of PVP on the silica membrane surface. Graft polymerisation of PVP and poly(vinylacetate) (PVAc) onto porous silica substrate was used to prepare hydrophobic pervaporation membranes [18], [19], [20].
Fluoroalkylsilanes (FAS) are the group of compounds, which can be efficiently used in the enchancing of the hydrophobic character of different surfaces [21], [22], [23]. Shondelmaier et al. [21] investigated the orientation and self-assembly of different FAS. Fadeev and Yaroshenko [22] performed studies on intrusion and extrusion of water in porous silicas modified with FAS. Akamatsu et al. [23] has reported on the water-repellent coating films prepared from FAS and applied on the glass. Authors examined the influence of polymerisation conditions on the durability of water-repellent glasses for automotive windows. Picard et al. [3] reported the grafting process of FAS on the surface of alumina, titania, zirconia and silica membranes.
Grafting process, leading to the increase of the hydrophobic properties, can be performed by reaction between OH surface groups of the zirconia membrane and ethoxy groups (O–Et) presented in organosilane compounds [3], [16], [24]. Grafting process leads to a monomolecular layer of organosilane compound on the membrane surface [21], [25]. Thus, the hydrophobic character of zirconia membrane can be obtained by using organosilane compounds containing hydrophobic fluorocarbon chains.
This work reports the results of the grafting process of organosilane compounds on the both zirconia powder and zirconia membranes. The main aim of this work was the optimisation the grafting process and the preparation of different new kinds of hydrophobic ceramic membranes by grafting organosilane molecules (FAS) on the membrane surface.
Section snippets
Reagents
All grafting processes were performed using 10−2 mol/dm3 solution of 1H,1H,2H,2H—perfluorodecyltriethoxysilane (denoted hereafter as C8 solution) in chloroform.
C8 was supplied by Lancaster, whereas chloroform (stabilized with ∼1% ethanol) was purchased from CarloErba Reagenti. The preparation of this grafting solution required an argon atmosphere, because a polycondensation process of 1H,1H,2H,2H—perfluorodecyltriethoxysilane is probable in the presence of the traces of humidity from the air.
Zirconia powder and membrane
Results and discussion
The hydrophobic character of the resulting material was tested by measuring the contact angle of water drop. Values of the contact angle were in the range 142°–148° for all prepared membranes (Fig. 2.), what means that all tested membranes possessed the hydrophobic character.
The surface-adsorbed and hydrogen bonded water is released in the temperature range 20–230 °C [5], [14]. Samples contained 1.9 ± 0.3 wt.% of such water molecules and this amount was practically independent on the grafting
Conclusions
The hydrophilic character of ZrO2 membrane can be changed into a hydrophobic one by grafting 1H,1H,2H,2H—perfluorodecyltriethoxysilane on the surface of the membrane. The yield of grafting depends on the ratio of amount of C8 in the grafting solution to the mass of a membrane sample, as well as on temperature and time of grafting process. The performed experiments allowed to determine the optimal conditions of the grafting process.
Obtained membranes show good hydrophobic character suggesting
Acknowledgements
One of the authors (S.R.K.) wishes to express his acknowledgements to the European Community for a Socrates-Erasmus scholarship, at Ecole Nationale Superieure de Chimie de Montpellier and at Institut Européen des Membranes (CNRS-ENSCM-UM II).
References (30)
- et al.
Solid State Sci.
(2000) - et al.
Sep. Purif. Technol.
(2001) - et al.
J. Chromatogr.
(1990) - et al.
J. Membr. Sci.
(1998) - et al.
Microporous Mesoporous Mater.
(1998) - et al.
Colloid Surf. A
(1998) - et al.
J. Membr. Sci.
(2002) - et al.
J. Membr. Sci.
(2001) - et al.
J. Membr. Sci.
(1999) - et al.
J. Membr. Sci.
(1996)
J. Colloid Interface Sci.
J. Colloid Interface Sci.
J. Membr. Sci.
J. Membr. Sci.
J. Membr. Sci.
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