Novel antibifouling nanofiltration polyethersulfone membrane fabricated from embedding TiO 2 coated multiwalled carbon nanotubes Vahid Vatanpour a , Sayed Siavash Madaeni a,⇑ , Rostam Moradian b , Sirus Zinadini a , Bandar Astinchap b a Membrane Research Center, Department of Chemical Engineering, Razi University, Kermanshah, Iran b Nano Science and Technology Research Center, Physics Department, Razi University, Kermanshah, Iran article info Article history: Received 19 November 2011 Received in revised form 27 January 2012 Accepted 8 February 2012 Available online 16 February 2012 Keywords: Mixed matrix membranes Functionalized MWCNTs Photocatalytic activity Antibiofouling Roughness abstract Multiwalled carbon nanotubes (MWCNTs) coated by anatase titanium dioxide (TiO 2 ) nanoparticles were synthesized via the precipitation of TiCl 4 precursor on the acid oxidized MWCNTs and used in preparation of nanocomposite polyethersulfone (PES) membranes. In this work, the effect of embedding TiO 2 coated MWCNTs in PES matrix on membrane morphology, properties and antibiofouling was presented and the obtained results were compared with the prepared oxidized MWCNTs and TiO 2 blended PES membranes. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses showed that the formed TiO 2 on the surface of MWCNTs had anatase nanostructure with size in the range of 10–20 nm. The scanning electron microscopy (SEM) images displayed a finger-like and porous structure for all NF mem- branes and showed that agglomeration of TiO 2 coated MWCNTs is very low. Contact angle measurements indicated that coating of TiO 2 nanoparticles on the surface of oxidized MWCNTs improved the hydrophi- licity of the obtained membranes. The pure water flux of the blend membranes increased with the content of TiO 2 coated MWCNTs. Fouling resistances of membranes evaluated by whey solution filtration revealed that 0.1 wt.% TiO 2 coated MWCNTs membrane had the best antibiofouling properties due to its lowest surface roughness and synergistic photocatalytic activity induced by incorporated nanoparticles. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Nanofiltration (NF) is a membrane technique that it is becoming progressively universal in water treatment [1,2], desalination [3], concentration and purification [4], pharmaceutical [5] and chemi- cal industries [6]. In NF membranes, both surface charge and siev- ing mechanisms affect the rejection behavior of solutes that are usually characterized using high rejection of divalent ions, lower rejection of monovalent ions, and higher fluxes than reverse osmo- sis (RO) membranes [7]. However, flux decline is an intrinsic event takes place by the limitation of the mass transport throughout the membrane, which hindered wider application of this technology caused by membrane fouling. In such conditions, performance loss from uncontrollable fouling results in higher operating pressure requirement, restricted recoveries, feed water loss, repeated chem- ical cleaning and short lifetimes of membranes [8]. The behavior of membrane fouling depends strongly on mem- brane surface characteristics such as surface porosity, membrane pore size, pore morphology, and hydrophobicity [9]. Fouling by proteins and other organic matter is commonly attributed to the hydrophobic nature of membrane materials that leads to a high interfacial energy with water-rich media, which is decreased upon biomolecules adsorption [10]. For improving hydrophilicity and antifouling properties of polymeric membranes several approaches such as interfacial polymerization with hydrophilic monomers [11], coating of substrate membrane with hydrophilic polymer [12] or nanoparticles [13,14], incorporating in situ hydrophilic sur- face modifying macromolecules [15], grafting [16,17], blending with nanoparticles [18,19] or hydrophilic polymers and monomers [20,21], etc. were used. One of the well-known modification methods of membrane for improving their antifouling properties is blending with inor- ganic nanoparticles such as TiO 2 [22,23], Al 2 O 3 [19,24], SiO 2 [18,25], Fe 3 O 4 [26], and carbon nanotubes [27–29]. Introducing inorganic nanoparticles in the membrane matrix can improve the hydrophilicity, the strength and stiffness, the water perme- ability and the antifouling properties of polymer based nano- composite membranes. Nanosized titanium dioxide (TiO 2 ) and carbon nanotubes (CNTs) are superior candidates as additive for polymer membrane because of theirs high hydrophilicity, good chemical stability, inno- cuity, and high surface area [30]. Some properties of CNTs such as their exceptional mechanical properties, forming highly porous structures, and antibacterial action have been exploited to develop carbon nanotube blended membranes [31]. The CNTs are ideal reinforcing fibers for nanocomposites due to their high aspect ratio and high in axis strength [32,33]. 1383-5866/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2012.02.014 ⇑ Corresponding author. Tel.: +98 831 4274530; fax: +98 831 4274542. E-mail address: smadaeni@yahoo.com (S.S. Madaeni). Separation and Purification Technology 90 (2012) 69–82 Contents lists available at SciVerse ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur