Metal salt embedded electrodialysis zeolite clay composite membrane has been prepared by in situ hydrothermal crystallization of Analcime-C zeolite over the mesoporous clay support followed by deposition of a suitable salt (FeCl2) inside the pores. To characterize the membrane, it has been used for the electrodialysis of sodium chloride solution in the low current regimen and the results reported in terms of current efficiency and energy requirements. When the membrane is fresh after metal loading, its current efficiency is low (42.8%) which gradually rises and takes a value of 93% asymptotically at room temperature. Once this value is reached, the effect of the current density, flow rate, salt and alkali concentration and temperature on the performance of membrane are measured and reported in this work. The current efficiency of our membrane is found to decrease slightly for higher current densities, increase at higher temperatures and is little affected by flow rate and salt and alkali concentrations. This membrane gives a current efficiency of 93% at room temperature (25 degrees C, 0.1117 kWh/mol NaOH, 275 A m(-2) and 4.2N NaCl solution) which increases with increase in temperature. Impurities, like calcium and magnesium salts, in the feed have small effect on the performance of the membrane and on washing it with dilute HCl, it is restored to the original level. The membrane has been studied over 1 year and its efficiency is not affected with time. (c) 2005 Elsevier B.V. All rights reserved.