1 Korean J. Chem. Eng., 31(4), 1-7 (2014) DOI: 10.1007/s11814-014-0247-4 INVITED REVIEW PAPER pISSN: 0256-1115 eISSN: 1975-7220 INVITED REVIEW PAPER † To whom correspondence should be addressed. E-mail: Sayedmohsen_Hosseini@yahoo.com, S-Hosseini@araku.ac.ir Copyright by The Korean Institute of Chemical Engineers. Electrochemical characterization of mixed matrix heterogeneous cation exchange membranes modified by simultaneous using ilmenite-co-iron oxide nanoparticles Sayed Mohsen Hosseini * ,† , Alireza Hamidi * , Abdolreza Moghadassi * , and Sayed Siavash Madaeni ** *Department of Chemical Engineering, Faculty of Engineering, Arak University, Arak 38156-8-8349, Iran **Membrane Research Centre, Department of Chemical Engineering, Faculty of Engineering, Razi University, Kermanshah 67149, Iran (Received 15 March 2014 • accepted 24 August 2014) Abstract-Mixed matrix heterogeneous cation exchange membranes were prepared by solution casting technique. Ilmenite-co-iron oxide nanoparticle was also employed as inorganic filler additive in membrane fabrication. The effect of the used additives on membrane electrochemical properties was studied. Membrane ion exchange capacity, mem- brane potential, transport number and selectivity all were improved by use of FeTiO 3 /Fe 3 O 4 nanoparticles in mem- brane matrix. Utilizing FeTiO 3 -co-Fe 3 O 4 nanoparticles in the casting solution also led to increase in ionic flux obviously. The modified membranes containing FeTiO 3 -co-Fe 3 O 4 nanoparticles showed higher transport number, selectivity and ionic flux compared to modified membrane containing ilmenite. Electrodialysis experiment in laboratory scale also showed higher cation removal for modified membrane containing FeTiO 3 -co-Fe 3 O 4 nanoparticles compared to other modified membranes and pristine ones. Results showed that membrane areal electrical resistance declined sharply by use of FeTiO 3 -co-Fe 3 O 4 nanoparticles in membrane matrix. Moreover, modified membrane containing ilmenite showed lower electrical resistance compared to others. Results showed that oxidative stability of membranes was decreased slightly by use of FeTiO 3 /Fe 3 O 4 nanoparticles in membrane matrix. The results revealed that modified membranes in this study are comparable with that of other commercial ones. Keywords: Composite Ion Exchange Membrane, Ilmenite-co-iron Oxide Nanoparticles, Synergy, Electrodialysis, Adsorp- tion-ion Exchange, Preparation/Characterization INTRODUCTION Membrane technologies have obtained much attention in diverse industries and human life. Ion exchange membranes have been used widely as active separators in electrically driven processes such as electrodialysis for desalting brackish waters, reconcentrating brine from seawater and production of table salt. Ion exchange mem- branes are also efficient tools in resource recovery, food and phar- macy processing and environmental protection such as treating industrial and biological effluents as well as manufacturing of basic chemical products [1-5]. In IEMs charged groups attached to poly- mer backbone are freely permeable to opposite sign ions under an electrical field influence [6]. In such processes, ion interactions with membrane, water, and with each other occur in complex fash- ions. Knowledge of the electrokinetic properties of ion exchange membranes is a major contributing factor behind decisions about their applicability in specific separation processes and energy stor- age devices [2,7,8]. Preparing inexpensive IEMs with special physico/chemical char- acteristics may be a vital step in future applications [2,4]. Much re- search has already been carried out to improve the IEMs physico- chemical properties. Variation of functional groups type, selection of different polymeric matrices, polymers blending, using of inor- ganic additives/filler, alteration of cross-link density and surface modification are the important techniques to obtain superior IEMs [1,2,9,10]. Utilizing inorganic particles or fillers into polymeric materials has been examined in many applications to enhance the physico-chemi- cal characteristics and separation properties based on the synergism between the organic-inorganic components properties. Magnetic metal oxide (MMO) particles are a new class of advanced materi- als with very interesting features and capacity such as adsorption characteristics in metallic cation adsorption, which can provide unique characteristics for the membranes [1,5,11,12]. FeTiO 3 and Fe 3 O 4 particles are well known magnetic metal oxides which have gained a great deal of attention because of stable chemical prop- erty, safety toward the environment and high adsorption capacity due to valence states of ions in MMO structures [13-15]. The sur- face sites binding, electrostatic interaction and ligand combination are main factors for this adsorptive behavior. This characteristic acts as a driving force for cation transport from solution into membrane matrix, which can improve the ion exchange possibilities. Currently, no reports have considered incorporating magnetic/ adsorptive FeTiO 3 -co-Fe 3 O 4 nanoparticles into ion exchange mem- branes, and the literature is silent on characteristics and functional- ity of electrodialysis IEMs. Preparing heterogeneous cation exchange membranes with spe- cially adapted physico/chemical properties for application in elec-