Colloids and Surfaces A: Physicochem. Eng. Aspects 443 (2014) 109–117 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects jo ur nal ho me page: www.elsevier.com/locate/colsurfa Investigation of the stability of metal oxide powders and ceramic membranes grafted by perfluoroalkylsilanes Joanna Kujawa a , Sophie Cerneaux b , Wojciech Kujawski a,∗ a Nicolaus Copernicus University, Faculty of Chemistry, 7 Gagarina St., 87-100 Torun, Poland b Institut Europeen des Membranes, UMR 5635, Place Eugene Bataillon, 34095 Montpellier Cedex 5, France h i g h l i g h t s • Metal oxide powders and mem- branes are successfully grafted with PFAS molecules. • Modified hydrophobic powders are thermally stable up to 250 ◦ C. • Hydrophobic nanolayers are stable in organic solvents (e.g. hexane and chloroform). • PFAS nanolayers are partially removed in alkaline media (pH ≥ 12). g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 1 August 2013 Received in revised form 4 October 2013 Accepted 28 October 2013 Available online 5 November 2013 Keywords: Stability Ceramic membrane Hydrophobicity Perfluoroalkylsilanes a b s t r a c t Tubular and planar ceramic titania membranes as well as metal oxide powders (Al 2 O 3 , TiO 2 and ZrO 2 ) were modified by various perfluoroalkylsilanes molecules. During the modification process, the hydrophobic layer on the membrane or powder surface was created. Grafting efficiency was determined by liquid entry pressure (LEP w ), contact angle or FT-MIR analysis. Subsequently grafted samples were exposed to air (2 years) or water (1 year), to evaluate the stability of hydrophobic layer with time. The chemical and thermal stability of modified powders and membranes was also estimated. Moreover, the tubular membranes of various porosity were tested in pervaporation (PV) and air-gap membrane distillation (AGMD) process after 2 years exposure to the air since grafting. The modified powders were thermally stable up to temperature of 250 ◦ C. However, the grafted metal oxide powders were not stable in alkaline solutions at pH ≥ 12. Furthermore, the metal oxide powders and the planar membranes were also stable in organic solvents like hexane or chloroform. Moreover, a significant decrease of contact angle from 132 ◦ to 62 ◦ was observed after 1 year of contact with water for planar membrane grafted by C10 molecules. An important impact on the transport properties of pure water in PV and AGMD after 2 years contact with air was also observed. In PV, the water flux decreased from 1200 g h -1 m -2 to 430 g h -1 m -2 for Ti- 5nm-C8 membrane. AGMD the water fluxes decreased by 21% and 27% for Ti-300kD-C6 and Ti-300kD-C12 membranes, respectively. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Ceramic materials are characterized by high chemical, thermal and mechanical stability and therefore they are ideal materials for ∗ Corresponding author. Tel.: +48 56 611 43 15; fax: +48 56 654 24 77. E-mail address: kujawski@chem.umk.pl (W. Kujawski). many applications in the chemical, biotechnological and pharma- ceutical industries as well as in water and wastewater processing [1–12]. Among ceramic materials, titania is highly desirable due to its stability in organic solvents and caustic media [1]. Titania mem- branes possess numerous potential applications in areas such as food, biotechnology and pharmaceutical industries, where the use of alumina or stainless steel membranes is limited due to their 0927-7757/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.colsurfa.2013.10.059