Ion-exchange membranes (IEMs) have been used in different processes and applications and have shown the advantages over other comparative processes. The extensive applications of IEMs in many areas have necessitated the improvement in their properties to achieve better performance and lower cost. As the first commercialized IEMs, heterogeneous membranes face the challenge to improve their lower selectivity and conductivity which associated to the higher heterogeneity. Recently, development of

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... e heterogeneous IEMs is steadily growing which is driven by the need to obtain IEMs with better electrochemical properties, lower production cost, and easier preparation procedure. Additive blending, membrane surface modifications, and post-treatment are typical methods used to improve heterogeneous IEMs characteristics. The methods give the improvement in electro-chemical characteristics of heterogeneous membranes and provide the possibility to produce heterogeneous IEMs with comparable performance to homogeneous ones. In this paper, preparation, characterization, and performance of heterogenous IEMs are reviewed. In addition, recent progress on IEMs modifications is pointed out.