Fabrication of porous polymeric nanocomposite membranes with enhanced anti-fouling properties: Effect of casting composition Alla Alpatova, Eun-Sik Kim, Xiaohui Sun, Geelsu Hwang, Yang Liu, Mohamed Gamal El-Din n Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2W2 article info Article history: Received 8 December 2012 Received in revised form 11 April 2013 Accepted 19 May 2013 Available online 30 May 2013 Keywords: Nanocomposite membrane Anti-fouling Anti-biofouling Antibacterial Nanosilver abstract A mixed matrix porous polymeric membranes with anti-fouling properties were prepared by phase- inversion method from a quaternary system of polysulfone/N,N-dimethylformamide/polyvinilpyrroli- done (PVP)/nanosilver (nAg). The effect of casting mixture composition on the membrane morphology, performance, and anti-fouling (including anti-biofouling) properties was evaluated by microscopic, spectroscopic and surface characterization techniques. The results showed a substantial effect of casting mixture composition on the morphology and selectivity of membranes. The incorporation of nAg to a casting mixture containing 5 wt% PVP induced morphological changes in membrane structure including increase in pore sizes, suppression of macrovoids and thinning of the skin layer. These changes were further resembled in the separation and anti-fouling properties of membranes. The permeate flux of membranes increased regardless of PVP concentration, while the separation properties of membranes formed from a casting mixture containing 5 wt% PVP were significantly compromised as compared to those formed with 1 wt% PVP. Under the same nAg loading, the membrane casted from a mixture contained 1 wt% PVP had better anti-fouling properties with respect to bovine serum albumin. The bioassays with Pseudomonas aeruginosa revealed that anti-biofouling properties of membranes (includ- ing antibacterial and anti-adhesive properties) were significantly induced upon addition of nAg. The findings of this study highlight the importance of casting mixture composition and interactions between its components for the optimization of membrane anti-fouling behavior while maintaining high separation properties. & 2013 Elsevier B.V. All rights reserved. 1. Introduction Membrane separation is an area in water and wastewater treatment which can offer superior economical and technical benefits in order to meet continuously growing requirements to water quality. However, a common drawback that significantly affects the implementation of membrane filtration worldwide is membrane fouling caused by the complex matrices of treated waters [1]. This includes inorganic fouling due to particulate and colloidal material, organic fouling due to proteins, oils, humic acids, and biofouling due to attachment and growth of micro- organisms on the membrane surface [2–5]. As a result, significant decline in process performance and shortened membrane life- span are often the case. The membrane fouling can be classified into reversible fouling which can be removed by backwashing of permeate to the feed site or by chemical cleaning, and irreversible fouling which is permanent [1,6,7]. The biofouling is considered irreversible because bacteria that are adhered to the surface can grow and reproduce to form a confluent lawn, which eventually covers the entire membrane surface [4,8]. One approach to reduce membrane fouling is to change the surface properties of mem- branes through increasing their hydrophilicity [9], decreasing surface roughness [10], increasing surface negative charge [11] or incorporating biocides on the membrane surface to kill attached bacteria [2,12]. The recent developments in nanotechnology have enabled the manufacturing of nanocomposite polymeric membranes in which nanoparticles are blended into a polymeric matrix. Such mem- branes produce surface properties that are significantly different from their nanoparticle-free counterparts. Different nanoparticles such as metal oxides, silica, carbon nanotubes, or silver have been incorporated into polymeric materials, and they show promising results in mitigating membrane fouling and improving quality of permeate [2,12–17]. It was also shown that when incorporated into membrane structure, silver nanoparticles (nAg) successfully improved the anti-biofouling performance of polymeric mem- branes due to antibacterial property of nanosilver [2,4,12]. Silver Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/memsci Journal of Membrane Science 0376-7388/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.memsci.2013.05.034 n Correspondence to: 3-093 Markin/CNRL Natural Resources Engineering Facility, Department of Civil and Environmental Engineering, University of Alberta, Edmon- ton, Alberta, Canada T6G 2W2. Tel.: +1 780 492 5124; fax: +1 780 492 0249. E-mail address: mgamalel-din@ualberta.ca (M. Gamal El-Din). Journal of Membrane Science 444 (2013) 449–460