pervaporation properties of fluoroalkylsilane (fas) grafted ceramic membranes

Presented at the EuroMed 2006 conference on Desalination Strategies in South Mediterranean Countries: Cooperationbetween Mediterranean Countries of Europe and the Southern Rim of the Mediterranean. Sponsored by the EuropeanDesalination Society and the University of Montpellier II, Montpellier, France, 21–25 May 2006.

Desalination 205 (2007) 75–86

Pervaporation properties of fluoroalkylsilane (FAS) graftedceramic membranes

Wojciech Kujawskia,b*, Sławomira Krajewskaa, Maciej Kujawskia,Laetitia Gazagnesb, André Larbotb, Michel Persinb

aFaculty of Chemistry, Nicolaus Copernicus University, ul. Gagarina 7, 87-100 Toruń, PolandTel. +48 (56) 611-4315; Fax +48 (56) 654-2477; email: [email protected]

bInstitut Européen des Membranes, UMR 5635, Campus CNRS,1919 route de Mende, 34293 Montpellier cédex 5, France

Received 20 March 2006; Accepted 24 April 2006

Abstract

Changing the hydrophilic character of ceramic membranes into hydrophobic ones is nowadays of particularinterest. The originally hydrophilic character of ceramic membranes can be changed by grafting hydrophobicmolecules on the surface. Fluoroalkylsilanes (FAS) are a group of compounds which can be efficiently used to createthe hydrophobic character of different surfaces. The grafting process can be performed by a reaction between -OHsurface groups of the ceramics and ethoxy groups (-O-Et) presented in organosilane compounds. The aim of this workwas to prepare FAS-modified pervaporation ceramic membranes by grafting alumina and/or titania ceramicnanofiltration membranes with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (C8) molecules and to determine theproperties of such modified hydrophobic ceramic membranes in the pervaporation process used for the desalinationof different salt solutions and for the removal of organic solvents of different hydrophobicity [i.e., ethanol (EtOH)and methyl t-butyl ether (MTBE)] from water. It was found that transport and selective properties of graftedmembranes depended on the type of ceramics and the grafting conditions. In general, FAS grafted titania membraneswere more permeable and more selective than alumina ones. In the case of desalination it was found that salt rejectionwas practically 100%; there was no salt found in the permeate. Pervaporation flux in contact with an aqueous saltsolution was dependent on the kind of salt, its concentration and feed temperature. FAS grafted membranes preparedfrom titania showed much higher permeation fluxes compared with alumina ones. Both membranes showed highselectivity towards the organic component of water–organic mixtures. The selectivity factor of FAS-TiO2 (graftedin 0.1 M C8), FAS-TiO2 (grafted in 0.01 M C8) and FAS-Al2O3 (grafted in 0.01 M C8) membranes in contact withwater–MTBE (2 wt.% MTBE) solution was 95, 45 and 23, respectively. The C8 molecules grafted on the titaniaceramics underwent conformation change from a tangled form into the straightened one when the C8 environmentchanged from pure water to a water–organic or water–electrolyte solution. The concentration range in which thisconformation change occurred was dependent on the hydrophobicity of organic solvent molecules presented in thesolution. In the case of more hydrophobic MTBE molecules the tangled–straightened form change of FAS moleculesoccurred in a concentration range 0–0.1 mol. % MTBE.

0011-9164/07/$– See front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.desal.2006.04.042

W. Kujawski et al. / Desalination 205 (2007) 75–8676

Keywords: Fluoroalkylsilanes grafted ceramic membranes; Pervaporation; Desalination; Water purification

1. IntroductionMembrane separation technologies can offer

energy savings, low-cost modular construction,high selectivity of separated materials, and pro-cessing of temperature-sensitive products. Mem-branes separate mixtures according to physical orchemical attributes of their components such asmolecular size, charge or solubility [1]. Selectedsubstances can be specifically separated from themain streams, either to save raw materials, tominimize the disposal of effluents and/or torecycle the by-products.

Recently, the great increase of interest in thedifferent applications of ceramic membranes hasbeen observed [2–4]. These kinds of membranesopen wide perspectives for commercial applica-tions in many various separation processes suchas ultrafiltration (UF), nanofiltration (NF),reverse osmosis (RO), gas separation (GS) orpervaporation (PV). The major application fieldsfor ceramic membranes are food, biotechnology,water purification and pharmaceutical industries.Ceramic membranes offer several advantagesover polymeric membranes such as mechanicalresistance, chemical inactivity, non-swelling,thermal stability and uncomplicated cleaning.Commercial ceramic membranes are usually pre-pared from metal oxides like alumina, zirconia,silica and/or titania. These materials originallypossess a hydrophilic character due to the pre-sence of surface hydroxyl (-OH) groups, whichcan very easily link water molecules [2–4].

Changing the hydrophilic character of ceramicmembranes into hydrophobic ones is nowadays ofparticular interest. Grafting of hydrophobic mole-cules onto the surface of ceramics can change theoriginally hydrophilic character of ceramic mem-branes. The chemical modification of ceramicmembranes has been reported from differentresearch groups [5–13].

Fluoroalkylsilanes (FAS) are the group ofcompounds which can be efficiently used tocreate the hydrophobic character of different sur-faces [5,7,13–15]. The grafting process can beperformed by reaction between -OH surfacegroups of the ceramics and ethoxy groups (-O-Et)presented in organosilane compounds. Thus thehydrophobic character of ceramic membrane isobtained by formation of the hydrophobic layerof organosilane compound on the membranesurface [7,11,16] (Fig. 1). Larbot and co-workersreported on the grafting process of different FASon the surface of alumina, titania, zirconia andsilica membranes and different applications ofsuch modified ceramic membranes [7,13,17–19].

Pervaporation is recognized as a separationprocess in which a binary or multi-componentliquid mixture is separated by partial vaporiza-tion through a dense lyophilized membrane[20–22]. The feed mixture is in a direct contactwith one side of the membrane whereas permeateis removed in a vapor state from the opposite sideinto a vacuum or sweeping gas (Fig. 2) and thencondensed. The driving force for the masstransfer of permeants from the feed side to thepermeate side of the membrane is a gradient inchemical potential, which is established by apply-ing a difference in partial pressures of thepermeants across the membrane.

Ceramic membranes, both the unmodified orsurface modified, are widely used nowadays indifferent pervaporation processes [6–8,10,11,

Fig. 1. Fluorosilanes grafted on ceramics.

W. Kujawski et al. / Desalination 205 (2007) 75–86 77

(A) (B)

Fig. 2. Scheme of pervaporation (A) and sweeping gas pervaporation (B).

23–26]: (1) splitting of water–organic azeotropesand/or dehydration of aqueous solutions,(2) removal of organics from water streams, and(3) separation of two organic solvents.

The aim of this work was to prepare FASmodified pervaporation ceramic membranes bygrafting an alumina and/or titania ceramic NFmembrane with 1H,1H,2H,2H-perfluorodecyl-triethoxysilane (FAS) molecules and to determinethe properties of such modified hydrophobicceramic membranes in the pervaporation processapplied for the desalination of different saltsolutions and for separation of water–ethanol andwater–MTBE mixtures.

2. Experimental

2.1. Preparation of FAS grafted membranes

In order to prepare the hydrophobic ceramicmembranes, 1H,1H,2H,2H-perfluorodecyltrietho-xysilane molecules C8F17C2H4Si(OEt)3 (C8 solu-tion – Lancaster) were grafted on the surface ofceramic membranes by a condensation reaction.Chloroform (stabilized with 1% ethanol) wasused as a solvent (Carlo Erba Reagenti).

Two types of commercial NF tubular mem-branes with an average pore diameter of 5 nmwere purchased from Pall Exekia. The first mem-brane possessed a selective layer made of alumina(denoted hereafter as FAS-Al/x.). The selective

layer of the other one (FAS-Ti/x) was preparedfrom titania. The thickness of the ceramic separa-tion layer was about 23 µm. The structure of thesupport was macroporous with an average porediameter equal to 800 nm. Tubular membraneswith external/internal diameter of 10/7 mm andthe length of 150 mm were used.

C8 in chloroform was used as the graftingsolution. Both the preparation and use of thisgrafting solution required an argon atmospherebecause a polycondensation process of C8occurred in the presence of the traces of humidityfrom air.

FAS-Al/x and FAS-Ti/x membranes were pre-pared according to the following procedure.Samples of membranes were cleaned with chloro-form and then dried at 150EC. Clean sampleswere immersed in C8 at a temperature of 25ECfor a given period of time (Table 1). To ensurethe continuous mixing of the system, tubes withmembranes and grafting solution were placed onthe BTR5 tube roller (Ratek Instruments). Thistype of mixer provides a rocking as well as arolling motion, ensuring continuous and thoroughmixing action.

2.2. Electrolyte solutions

The NaCl solutions were prepared by usingdeionized water and pure NaCl (ProLabo). Thesolutions in the concentrations ranging from


Table 1Parameters of the grafting process

FAS membrane Grafting time, h C8 conc., mol/L

Al/1Al/2Ti/3Ti/5Ti/6

7272728824

0.010.010.010.10.1

0.001 to 4.7 mol NaCl/kg H2O were prepared.0.5 M solutions of MgCl2 and KCl were alsoprepared from the appropriate pure salts (Pro-labo). Seawater was taken from the Mediter-ranean Sea (Palavas Les Flots). The average saltconcentration in the seawater was around 0.53 M.Presence of the salts in the permeate was testedby using ionic chromatograph analysis (DionexDX-100 ion chromatograph).

2.3. Water–organic solutions

Water–ethanol (0–35 wt.% EtOH) and water-methyl t-butyl ether (0–4 wt.% MTBE) mixtureswere used as feed solutions. Composition of feedand permeate solutions was determined by usinggas chromatography.

2.4. Pervaporation experiments

Pervaporation experiments were performedusing the laboratory set-up schematically pre-sented in Fig. 3. The tubular FAS ceramicmembrane was mounted on the stainless steelmodule. The membrane was sealed by using thetwo-component resin, teflon tape and rubber O-rings. The thermostated feed was circulatedbetween the feed tank and the module by using ateflon head pump. Feed contacted the tubularmembrane from the inner side. Permeate wascollected in the two parallel cold fingers cooledby liquid nitrogen. The vacuum was created by avacuum pump ensuring that pressure on the

Fig. 3. Laboratory set-up for pervaporation experiments.

permeate side was below 4 mbar. Pervaporationexperiments were done at temperatures rangingfrom 18 to 44EC according to the followingschedule: membrane conditioning was performedat 27EC, pervaporation water fluxes were deter-mined at the temperature interval 18 to 44EC,whereas other pervaporation experiments weredone at 40EC.

Performance properties of a given pervapora-tion membrane in contact with the water–organicmixture were defined by the separation factor α[Eq. (1)] and permeate fluxes, J [20].

(1)( )( )org water permeate

org/waterorg water feed

/

/

c c

c cα =

where corg and cwater denote the weight fraction ofthe organic and water components, respectively.

3. Results and discussion

3.1. Membrane conditioning

Prior to use in other pervaporation experi-ments, the newly prepared FAS membranesunderwent conditioning. Pervaporation of purewater at 27EC was performed during severalhours unless a constant flux was attained. As canbe seen from data presented in Fig. 4, the newlyprepared FAS-Al/1 ceramic membrane neededseveral hours to produce the constant permeateflux. The permeate flux increased from about


Fig. 4. Change of permeate flux with time during per-vaporation process of pure water with the new FAS-Al/1membrane.

400 g/(m2 h) to 600 g/(m2 h), that suggested thatat the beginning period of membrane use, someFAS molecules that presented on the surface ofthe ceramic material could be washed out. As wasproved in the detailed studies on grafting effi-ciency [27], during the grafting process thesemolecules were not chemically bonded but ratheradsorbed on the surface of the ceramics. Duringthe conditioning process of freshly prepared FASmembranes, these weakly bonded molecules werehydrolyzed and washed out from the membrane.

3.2. Pervaporation of pure water

Fig. 5 presents the influence of temperature onthe pervaporation flux of pure water. It can beseen that the permeate flux increased exponen-tially with increasing temperature, so the follow-ing Arrhenius-type equation relating flux andtemperature can be written:

(2)0 exp appEJ J

RT⎛ ⎞

= −⎜ ⎟⎝ ⎠

where J and J0 denote fluxes, Eapp is the apparentactivation energy of the transport in pervapo-ration, R is the gas constant and T is temperature.However, one must remember that Eapp is a com-plex relation that includes the influence oftemperature on the driving force in pervaporation

Fig. 5. Temperature dependence of the water pervapo-ration fluxes through the FAS-Al/1 grafted ceramicmembrane.

(i.e., vapor pressure of the feed), as well as theinfluence of temperature on the both solubility ofgiven component in the membrane and diffusivityof this component through the membrane [28,29].

The relation between flux and driving force inpervaporation can be written as follows [30,31]:

(3)PJ pl

= Δ

where P is the permeability coefficient, l themembrane thickness and p the difference of thevapor pressure between feed and permeate. Theterms P and p on the right hand of Eq. (3) aretemperature dependent, so the activation energyof permeation (Ep) in pervaporation should becalculated using the following equation:

(4)/ exp pEJ p A

RT⎛ ⎞

Δ = −⎜ ⎟⎝ ⎠

The apparent activation energy for the watertransport through the FAS-Al/1 membrane(Fig. 6) was equal to 51 kJ/mol, whereas the acti-vation energy of permeation Ep was equal to6.9 kJ/mol. The apparent activation energy found


Fig. 6. Apparent activation energy of water transportthrough the FAS-Al/1 ceramic membrane.

for the FAS-Al/l membrane is at the same rangeas the apparent activation energy of the watertransport through the SBS block copolymermembrane [32]. This value indicates the highenergy required to cross the potential barrier inthe activated state during water transport. Theapparent activation energy found for the watertransport through PDMS membranes was equal to34.4 kJ/mol [33].

3.3. Pervaporation of NaCl solutions

During pervaporation experiments with elec-trolyte solutions, no traces of electrolytes werefound in the permeate. However, it was foundthat electrolyte molecules can diffuse from theliquid feed through the membrane and crystallizeon the permeate side of the membrane, especiallywhen the membrane are in contact with moreconcentrated solutions.

Figs. 7 and 8 present the results of perva-poration of NaCl solutions through FAS-Al/2(Fig. 7) and FAS-Ti/3 (Fig. 8) membranes. It wasfound that water flux through investigatedmembranes decreased with increasing salt

Fig. 7. Pervaporation permeate fux of water through theFAS-Al/2 membrane vs. the concentration of NCl in thefeed solution.

Fig. 8. Pervaporation permeate flux of water through theFAS-Ti/3 membrane vs. the concentration of NaCl in thefeed solution.

concentration. That was caused by the decrease ofpartial pressure of water in NaCl solutions. Thisrelation was practically linear in the case of theFAS-Al/2 membrane whereas for the FAS-Ti/3membrane the relation was much more complex.The pervaporation flux of pure water through theFAS-Ti/3 membrane was about 8700±300 g/m2 h.The concentration dependence of the flux (Fig. 8)shows a sharp decrease of the flux in the


(A) (B)

Fig. 9. Conformation of FAS hydrophobic molecules in the contact with pure water (A) and aqueous solution of electrolyteor organic solvent (B).

concentration region: 0–0.5 M NaCl. At higherconcentrations the decrease of water flux is muchlower (Fig. 8) and linearly proportional to thepartial pressure of water vapors. Such behavior ofthe FAS-Ti/x membranes can be explained byassuming different conformation of C8 moleculesin contact with pure water and in the electrolytesolution. In contact with pure water, the FASmolecules are tangled and located close to thesurface of ceramic; apparent membrane pores arelarger thus allowing for an easier transport ofwater molecules (Fig. 9A). In the presence of ionsin the solutions, the tangled FAS molecules startto straighten and in the external salt concentrationof about 0.5 M NaCl, all FAS molecules arestraightened, forming a brushed layer on theceramic surface and within the pores, thusdecreasing the pore diameter and increasing thewater-repellent properties of membrane (Fig. 9B).

For higher salt concentrations, the decrease ofthe permeate flux is caused only by the decreaseof partial pressure of water [Eq. (3)]. It is alsoworth noting that the permeate flux of water ismuch higher through the FAS-Ti/x membranescompared to that of the FAS-Al/2 one (Figs. 7, 8).

A comparison of the pervaporation waterfluxes through both investigated membranes incontact with different salts and seawater ispresented in Fig. 10. The concentration of NaCl,KCl and MgCl2 was equal to 0.5 M. It can be seenthat water flux is much higher for the titaniamembrane than for the alumina one. The fluxesfound for NaCl and KCl solutions are comparableand smaller than the permeate flux in contact with

Fig. 10. Comparison of water fluxes through FAS graftedceramic membranes in contact with 0.5 M solutions ofdifferent electrolytes and seawater.

the MgCl2 solution. These differences can beexplained comparing the activities of investigatedsalts [34]:

2NaCl KCl MgCla a a≈ >

According to Rault’s Law, the higher activityof salt in the aqueous solution results in lowerpartial pressure of water. The permeate flux ofwater is the smallest when the membranes were incontact with seawater because the partial pressureof water in seawater is much smaller than in the0.5 M aqueous solution of NaCl, KCl and/orMgCl2.


3.4. Pervaporation of water–organic solventmixtures

3.4.1. Water–ethanol mixturesSeparation and transport properties of the FAS

grafted ceramic membranes in contact withwater–ethanol mixtures are presented in Figs. 11–13. It can be seen that both membranes wereselective towards ethanol; however, the selec-tivity of these membranes was not high. Incontact with the feed mixture containing 10 wt.%EtOH, the selectivity coefficient α [Eq. (1)] was

Fig. 11. Separation diagram of FAS grafted ceramicmembranes in contact with water–ethanol mixtures.

Fig. 13. Permeate fluxes through FAS-Ti/3 membrane incontact with water–ethanol mixtures.

equal to 6 for the FAS-Ti/3 membrane but only1.2 for the FAS-Al/2 one.

Comparing the permeate fluxes through bothmembranes, we can state that they were higher inthe case of FAS-Ti/3 (Figs. 12, 13). For bothmembranes, the partial permeate flux of ethanolwas linearly dependent on the concentration ofEtOH in the feed. On the other hand, the concen-tration dependence of water flux was different forthe both membranes. In the case of the FAS-Al/2membrane, water flux decreased proportionally to

Fig. 12. Permeate fluxes through the FAS-Al/2 membranein contact with water–ethanol mixtures.

Fig. 14. Selectivity of FAS grafted ceramic membranes incontact with water–MTBE mixtures.


the decreasing water content in the feed in thewhole concentration range investigated (Fig. 12).In the case of FAS-Ti/3, the concentrationchanges of water permeate flux in contact withthe water–EtOH mixture resembled those in con-tact with the water–NaCl solution (Figs. 8, 13). Inthe concentration range 0–1 wt.% EtOH in thefeed, a sharp decrease of water permeate flux wasobserved (Fig. 13), whereas for the higher ethanolfeed concentrations the flux decline was prac-tically linear. Such behavior of FAS-Ti/x mem-

Fig. 15. Permeate fluxes through the FAS-Al/2 membranein contact with water–MTBE mixtures.

Fig. 17. Permeate fluxes through the FAS-Ti/6 membranein contact with water–MTBE mixtures.

branes confirm our assumptions about differentconformations of FAS molecules on titania incontact with pure water and in contact withelectrolyte or organic solvents aqueous solutions.

3.4.2. Water–MTBE mixturesSelective properties of the membranes studied

in contact with water–MTBE mixtures are pre-sented in Fig. 14. In general, both types ofmembranes were more selective in contact with

Fig. 16. Permeate fluxes through the FAS-Ti/3 membranein contact with water–MTBE mixtures.

Fig. 18. Comparison of water fluxes through FAS graftedceramic membranes in contact with pure water and 1wt.% MTBE aqueous solution.


water–MTBE mixtures than with water–EtOHones (Figs. 11, 14). This was caused by the factthat MTBE is a much more hydrophobic solventthan ethanol. In contact with the feed mixturecontaining 2 wt.% MTBE, the selectivity coeffi-cient α [Eq. (1))] amounted to 23, 45 and 95 forthe FAS-Al/2, FAS-Ti/3 and FAS-Ti/6 mem-branes, respectively. It can be seen that FASgrafted titania membranes were more selectivethan the FAS grafted alumina one. The higherconcentration of C8 in the grafting solution alsoresulted at higher membrane selectivity (Table 1,Fig. 14).

The permeate fluxes for the water–MTBEsystem are presented in Figs. 15–17. Fluxes ofMTBE increased monotonically with increasingMTBE content in the feed solution. MTBE fluxwas the highest for the FAS-Ti/3 membrane andthe smallest for the FAS-Ti/6 one. The smallerflux of MTBE through the FAS-Ti/6 membranecan be explained by a higher C8 concentration inthe grafting solution, which resulted in highergrafting efficiency.

The flux of water through the FAS-Al/2membrane decreased practically linearly (Fig. 15)whereas that through FAS-Ti/x membraneschanged with concentration similarly as in thecase of water–EtOH mixtures, i.e., it was muchlower in contact with aqueous MTBE solutionsthan in contact with pure water (Fig. 18). It wasalso found that the water flux decline dependedon the grafting conditions (Table 1, Fig. 18). Thisbehavior of the FAS-Ti/x membranes resultedfrom the change of FAS molecule con-formationin the presence of electrolytes or hydrophobicsolvents, which seems to be a gene-ral feature forFAS grafted titania membranes. Moreover, theamount of dissolved species (i.e., electrolyte ororganic solvent) that caused this conformationchange was also dependent on the hydrophobicityof organic solvent molecules. The organic solventhydrophobicity can be expressed by using therelative dielectric constant (εr). The lower value

of εr is the more hydrophobic character of thesolvent. It was estimated that for more polarethanol (relative dielectric constant εr = 24.3[35]), the conformation change of FAS moleculesoccurred in the concentration range 0– 0.5 mol. %EtOH, whereas for more hydrophobic MTBE (εr= 2.6 [36]), this change occurred in theconcentration range 0–0.1 mol.% MTBE.

4. Conclusions

Ceramic alumina and titania NF membranesgrafted with perfluoroalkylsilane (1H,1H,2H,2H-perfluorodecyltriethoxysilane) changed the hy-drophilic character into a hydrophobic one. FASgrafted membranes were tested in pervaporationof water–electrolyte and water–organic solventsolutions. In the case of pervaporation of water–electrolyte solutions, only water was found in thepermeate. The pervaporation flux was inverselyproportional to the salt concentration in the feed.

Pervaporation of water–organic solvent(EtOH, MTBE) binary mixtures showed that bothmembranes were selective towards the organiccomponent. Selectivities found for the water–EtOH mixture were smaller than for the water–MTBE one. It was also found that FAS graftedmembrane selectivity was dependent on the con-centration of the grafting solution. In general,FAS grafted titania membranes were more selec-tive than alumina ones.

The C8 molecules grafted on the titaniaceramics undergo the conformation change fromthe tangled from into the straightened one whenthe C8 environment is changed from pure waterto a water–organic or water–electrolyte solution.The concentration range in which this confor-mation change occurred was dependent on thehydrophobicity of organic solvent moleculespresented in the solution. In the case of morehydrophobic MTBE molecules, the tangled–straightened change of FAS molecules occurredin the concentration range 0–0.1 mol.% MTBE.


5. Acknowledgements

The CNRS “post-rouge” research position forWojciech Kujawski at the Institut Européen desMembranes CNRS (UMR5635) in Montpellier iskindly acknowledged.

The authors S.K. and M.K. wish to expresstheir thanks for a Socrates–Erasmus mobilitygrant, which enabled research training at theEcole Nationale Superieure de Chimie deMontpellier and at the Institut Européen desMembranes CNRS-ENSCM-UM II (Montpellier,France).

References

[1] R.W. Baker, Membrane Technology and Applica-tions, Wiley, Chichester, 2004.

[2] A.B. Larbot, Fundamentals on inorganic membranes:Present and new developments, Pol. J. Chem. Tech.,6 (2003) 8–13.

[3] A. Tavolaro and E. Drioli, Zeolite Membranes, Adv.Mat., 11 (1999) 975–996.

[4] L. Cot, A. Ayral, J. Durand, C. Guizard, N.Hovnanian, A. Julbe and A. Larbot, Inorganicmembranes and solid state sciences, Solid State Sci.,2 (2000) 313–334.

[5] S. Alami-Younssi, C. Kiefer, A. Larbot, M. Persinand J. Sarrazin, Grafting γ alumina microporousmembranes by organosilanes: Characterisation bypervaporation, J. Membr. Sci., 143 (1998) 27–36.

[6] J.-D. Jou, W. Yoshida and Y. Cohen, A novelceramic supported polymer membrane for pervapo-ration of dilute volatile organic compounds, J.Membr. Sci., 162 (1999) 269–284.

[7] C. Picard, A. Larbot, F. Guida-Pietrasanta, B.Boutevin and A. Ratsimihety, Grafting of ceramicmembranes by fluorinated silanes: hydrophobicfeatures, Sep. Purif. Technol., 25 (2001) 65–69.

[8] J. Caro, M. Noack and P. Kolsch, Chemically modi-fied ceramic membranes, Micropor. Mesopor. Mat.,22 (1998) 321–332.

[9] W. Yoshida and Y. Cohen, Ceramic-supportedpolymer membranes for pervaporation of binaryorganic/organic mixtures, J. Membr. Sci., 213 (2003)145–157.

[10] W. Yoshida and Y. Cohen, Removal of methyl tert-butyl ether from water by pervaporation usingceramic-supported polymer membranes, J. Membr.Sci., 229 (2004) 27–32.

[11] C. Leger, H. De L. Lira and R. Paterson, Preparationand properties of surface modified ceramic mem-branes. Part II. Gas and liquid permeabilities of 5 nmalumina membranes modified by a monolayer ofbound polydimethylsiloxane (PDMS) silicone oil,J. Membr. Sci., 120 (1996) 135–146.

[12] A. Dafinov, R. Garcia-Valls and J. Font, Modifica-tion of ceramic membranes by alcohol adsorption,J. Membr. Sci., 196 (2002) 69–77.

[13] S.R. Krajewski, W. Kujawski, F. Dijoux, C. Picardand A. Larbot, Grafting of ZrO2 powder and ZrO2

membrane by fluoroalkylsilanes. Coll. Surf. A.Physiochem. Eng. Asp., 243 (2004) 43–47.

[14] D. Schondelmaier, S. Cramm, R. Klingeler, J.Morenzin, Ch. Zilkens and W. Eberhardt, Orien-tation and self-assembly of hydrophobic fluoro-alkylsilanes, Langmuir, 18 (2002) 6242–6245.

[15] Y. Akamatsu, K. Makita, H. Inaba and T. Minami,Water-repellent coating films on glass prepared fromhydrolysis and polycondensation reactions of fluro-alkyltrialkoxysilane. Thin Solid Films, 289 (2001)138–145.

[16] W. Yoshida and Y. Cohen, Topological AFM char-acterization of graft polymerized silica membranes,J. Membr. Sci., 215 (2003) 249–264.

[17] A. Larbot, L. Gazagnes, S. Krajewski, M. Bukowskaand W. Kujawski, Water desalination using ceramicmembrane distillation. Desalination, 168 (2004) 367–372.

[18] C. Picard, A. Larbot, E. Tronel-Peyroz and R.Berjoan, Characterisation of hydrophilic ceramicmembranes modified by fluoroalkylsilanes intohydrophobic membranes, Solid State Sci., 6 (2004)605–612.

[19] P. Janknecht, P.A. Widerer, C. Picard and A. Larbot,Ozone–water contacting by ceramic membranes.Sep. Purif. Technol., 25 (2001) 341–346.

[20] J. Néel, Pervaporation, in: Membrane SeparationsTechnology. Principles and Applications, R.D. Nobleand S.A. Stern, eds., Elsevier, Amsterdam, 1995,pp. 143–211.

[21] H. Brüschke, Industrial application of membraneseparation processes, Pure Appl. Chem., 67 (1995)993–1002.


[22] W. Kujawski, Application of pervaporation andvapor permeation in environmental protection, PolishJ. Environ. Stud., 9 (2000) 13–26.

[23] R.W. van Gemert and F.P. Cuperus, Newlydeveloped ceramic membranes for dehydration andseparation of organic mixtures by pervaporation,J. Membr. Sci., 105 (1995) 287–291.

[24] M. Kondo, M. Komori, H. Kita and K. Okamoto,Tubular-type pervaporation module with zeolite NaAmembrane, J. Membr. Sci., 133 (1997) 133–141.

[25] A. Utriaga, E.D. Gorri, C. Casado and I. Ortiz,Pervaporative dehydration of industrial solventsusing a zeolite NaA commercial membrane, Sep.Purif. Technol., 32 (2003) 207–213.

[26] T. Sano, M. Hasegawa, Y. Kawakami and H. Yana-gishita, Separation of methanol/metyl-tert-butyl ethermixture by pervaporation using silicalite membrane,J. Membr. Sci., 107 (1995) 193–196.

[27] L. Gazagnes, Modification de la surface de mem-branes céramiques par greffage, application audessalement et à la séparation d'émulsions, PhDThesis, Montpellier, 2005.

[28] X. Feng and R.Y.M. Huang, Estimation of activationenergy for permeation in pervaporation processes,J. Membr. Sci., 118 (1996) 127–131.

[29] K.H. Song, J.H. Song and K.R. Lee, Vapor per-meation of ethylacetate, propyl acetate and butylacetate with hydrophobic inorganic membrane,Sep. Purif. Technol., 30 (2003) 169–176.

[30] M. Mulder, Basic Principles of MembraneTechnology, Kluwer Academic, Dordrecht, 2003,pp. 325–339.

[31] W. Kujawski, G. Poźniak, Q.T. Nguyen and J. Neel,Properties of interpolymer PESS ion-exchangemembranes in contact with solvents of differentpolarity, Sep. Sci. Technol., 32 (1997) 16–57.

[32] M. Peng, L.M. Vane and S.X. Liu, Recent advancesin VOCs removal from water by pervaporation,J. Haz. Mat., B98 (2003) 69–90.

[33] P. Wu, R.W. Field, B.J. Brisdon, R. England and S.J.Barkley, Optimisation of organofunction PDMSmembranes for the pervaporative recovery ofphenolic compounds from aqueous streams, Sep.Purif. Technol., 22–23 (2001) 339–345.

[34] R.A. Robinson and R.H. Stokes, Electrolyte Solu-tions, Butterworths, London, 1959.

[35] R.C. Weast, ed., Handbook of Chemistry andPhysics, CRC Press, Boca Raton, FL, 1979.

[36] Lyondell Chemical Company, Product SafetyBulletin, Appendix 15, MTBE, p. 8.

pervaporation properties of fluoroalkylsilane (fas) grafted ceramic membranes

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