Electrophoretic deposition of nanosized zeolites in non-aqueous medium and its application in fabricating thin zeolite membranes Wei Shan a , Yahong Zhang a , Wuli Yang b , Chen Ke a , Zi Gao a , Yunfen Ye a , Yi Tang a, * a Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, PR China b Department of Macromolecular Science and Key Laboratory of Molecular Engineering of Polymers, Ministry of Education, Fudan University, Shanghai 200433, PR China Received 25 September 2003; received in revised form 21 January 2004; accepted 24 January 2004 Abstract Thin zeolite films with thicknesses from several hundred nanometers to a few micrometers have been fabricated through elec- trophoretic deposition (EPD) in acetylacetone (Acac) and/or isopropyl alcohol (IPA). Various types of nanosized zeolites with different Si/Al ratios ranging from 1.6 (zeolite LTA) to nearly infinity (silicalite-1) were applied to prepare the EPD suspensions and showed different behaviors in EPD. The EPD rate of zeolite particles in non-aqueous medium was much higher than that in aqueous system mainly due to the high voltage applied, and consequently the whole process was usually completed in a few seconds. It was found that the Al/(Si + Al) ratios of zeolites and the chemical/physical properties of the EPD medium were two crucial factors which affected the thickness and density of the zeolite films prepared by EPD. The zeolite films fabricated through EPD could be effectively densified by secondary growth to prepare compact zeolite membranes. Ó 2004 Elsevier Inc. All rights reserved. Keywords: Zeolite film/membrane; Electrophoretic deposition (EPD); Non-aqueous medium; Secondary growth; Nanosized zeolite 1. Introduction Zeolite membranes or films have been paid much attention in recent years because of their uniform micropore structure, good thermal stability, high mechanical strength and resistance to relatively extreme chemical environment [1–7]. Membranes that are com- posed of different type of zeolites provide different framework structure and pore size, which make them suitable for the application in separating various small molecules [6]. Moreover, the Si/Al ratios of zeolite membranes determine their acidity and hydrophilicity/ hydrophobicity, and consequently their catalytic and separating performance [1,3–5]. In the last few decades, supported zeolite membranes or films have also been adopted as zeolite-modified electrodes [8,9], which mainly relied on the ion-exchange property of zeolites. Practically, thin zeolite membranes or films, especially in submicrometer scale, might be more preferred in appli- cations due to their high fluxes in separation or fast ion transport rate in zeolite-modified electrode. Tavolaro et al. [3] divided the available techniques along the preparation process of zeolite membrane into four cat- egories: (1) pre-treatment of the supports, (2) synthetic methodology, (3) impregnation of the supports, and (4) elimination of small defects. As the key technique, a number of synthetic methods such as in situ synthesis [10], layer-by-layer (LbL) assembly [11] and seed-film method [12] have been successively developed. However, there still existed some defects in most of the synthetic methods. For example, in situ synthesis was a facile method of fabricating zeolite membranes, but the mem- brane thickness could not be precisely adjusted. On the other hand, although LbL assembly of nanosized zeo- lites with electrostatic attraction was considered as one of the most effective ways to control the thickness of zeolite layers, its operation was somewhat time-con- suming. Therefore, a more facile and controllable * Corresponding author. Tel.: +86-21-55664125; fax: +86-21- 65641740. E-mail address: yitang@fudan.edu.cn (Y. Tang). 1387-1811/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2004.01.003 www.elsevier.com/locate/micromeso Microporous and Mesoporous Materials 69 (2004) 35–42