0011-9164/05/$– See front matter © 2005 Elsevier B.V. All rights reserved Desalination 172 (2005) 257–265 Comparative studies on performance of interpolymer and heterogeneous ion-exchange membranes for water desalination by electrodialysis B.G. Shah, Vinod K. Shahi * , S.K. Thampy, R. Rangarajan, P.K. Ghosh Central Salt & Marine Chemicals Research Institute, Bhavnagar-364002 (Gujarat), India Tel. +91 (278) 256-9445; Fax: +91 (278) 256-7562, 256-6970; email: salt@csir.res.in; vinodshahi1@yahoo.com Received 29 January 2004; accepted 28 June 2004 Abstract As the preparation of interpolyme- type anion-exchange membranes involves several steps and the use of hazardous chemicals such as chloromethyl ether and trimethyl amine, it was envisaged to prepare heterogeneous anion-exchange membranes through a simple technique involving casting of a solution containing a binder and a polyelectrolyte. Electrochemical characterization of interpolymer and heterogeneous membranes was carried out by measurement of electrical resistance, counter-ion transport number, ion-exchange capacity and volume fraction of water. Interpolymer ion-exchange membranes exhibited better electrochemical and electrodialytic properties in comparison to a hetero- geneous membrane. In order to develop alternate anion-exchange membranes, a heterogeneous type of anion-exchange membrane was prepared, and its electrodialytic performance in combination with an interpolymer cation-exchange membrane was studied. Electrodialysis experiments in recirculation mode of operation were performed under varied feed concentrations and applied potential gradients in two configurations: (1) interpolymer cation- and anion-exchange membranes and (2) interpolymer cation- and heterogeneous anion-exchange membranes, packed together, in order to assess their comparative efficiencies for water desalination by electrodialysis. Under both configurations energy consumption and current efficiency were similar under comparable experimental conditions, but the rate of desalination from configuration (1) was much faster. Keywords: Electrodialysis; Ion-exchange membrane; Heterogeneous membranes; Water desalination; Electrodialytic rate 1. Introduction Electro-driven membrane separation processes involving ion-exchange membranes are not only *Corresponding author. part of applied electrochemistry but also belong to the field of separation techniques such as electrodialysis, electro-electrodialysis and electro- deionization [1,2]. The most important industrial application of electrodialysis (ED) is the produc-