Improvement of the antifouling potential of an anion exchange membrane by surface modification with a polyelectrolyte for an electrodialysis process Sri Mulyati a,b,1 , Ryosuke Takagi a , Akihiro Fujii a , Yoshikage Ohmukai a , Tatsuo Maruyama a , Hideto Matsuyama a,n a Center for Membrane and Film Technology, Department of Chemical Science and Engineering, Kobe University, Kobe, Japan b Department of Chemical Engineering, Syiah Kuala University, Banda Aceh, Indonesia article info Article history: Received 25 April 2012 Received in revised form 13 June 2012 Accepted 16 June 2012 Available online 26 June 2012 Keywords: Antifouling Electrodialysis Anion exchange membrane Surface modification Polyelectrolyte abstract Membrane fouling by organic solutes during electrodialysis is a well-known problem, especially during water treatment. Fouling causes an increase in membrane electrical resistance, leading to shortened membrane life and increased energy consumption. This article describes an improvement to the antifouling potential for an anion exchange membrane (AEM) by surface modification with poly- (sodium 4-styrene sulfonate) (PSS). The antifouling potential of the AEM was evaluated by the transition time, i.e. the time elapsed before the fouling took place, using sodium dodecylbenzene sulfonate (SDBS) as a model organic foulant. It was shown that the antifouling potential of the AEM was considerably improved by surface modification with PSS. A mechanism for fouling by SDBS is also theoretically discussed and it is concluded that adsorption of SDBS micelles on the AEM surface was prevented by surface modification with PSS and the antifouling potential was improved because both hydrophilicity and the negative charge density were increased on the modified membrane surface. Additionally, it was confirmed that surface modification with PSS scarcely affects the performance of AEM during electrodialysis. & 2012 Elsevier B.V. All rights reserved. 1. Introduction There is an increasing demand for potable water production by treating ground, surface and sea water. Electrodialysis (ED) is a useful technique that has been applied to produce drinking water in addition to reverse osmosis (RO) and nanofiltration (NF) processes. ED is an electrochemical separation process that uses the ion permselectivity of cation and anion exchange mem- branes [1]. In ED processes, ions are selectively transported from one compartment (the diluted compartment) to another compart- ment (the concentrated compartment) through ion exchange membranes under the driving force of an electrochemical potential gradient. One advantage of ED compared to other pro- cesses, such as RO, is that a higher brine concentration can be achieved because there are no osmotic pressure limitations. Also, the chemical and mechanical stability of ion exchange mem- branes in ED guaranties a long useful life, even with feed waters that contain aggressive and oxidizing components [1]. Notably, ED is utilized to remove harmful ions such as F  and NO 3  [2–6]. It also can be used to soften water [7] and to remove heavy metals [8,9]. In spite of such advantages, fouling is a major obstacle in ED process, as it is for other membrane separation processes. It has been reported that fouling takes place mainly on the anion exchange membrane (AEM) surface during ED [10]. This is because AEM has a positive charge and most organic foulants present in natural waters and effluents, such as surfactants, humates, and proteins, are negatively charged [11,12]. Thus, foulants will move towards the AEM by electrophoresis in an ED system and consequently the AEM is fouled by deposition and/ or chemical adsorption of foulants. Fouling causes an increase in membrane electrical resistance, followed by increased energy consumption and shortening of membrane life. Many researchers have focused on fouling of AEMs by organic foulants [10,13–15]. Bovine serum albumin (BSA), humate, carboxylic acids and anionic surfactants such as sodium dodecylbenzene sulfonate (SDBS) are commonly used as model organic foulants [10,13,14]. It is known that SDBS is adsorbed to the AEM surface much more readily than other foulants and has an extreme fouling impact on ED performance. Coating or modification of membrane surfaces is a widely used technique for increasing the antifouling potential of RO and NF membranes [16–21]. It has been widely acknowledged that Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/memsci Journal of Membrane Science 0376-7388/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.memsci.2012.06.024 n Corresponding author. Tel./fax: þ81 78 803 6180. E-mail addresses: takagi@harbor.kobe-u.ac.jp (R. Takagi), matuyama@kobe-u.ac.jp (H. Matsuyama). 1 Tel./fax: þ81 78 803 6610. Journal of Membrane Science 417–418 (2012) 137–143