The transport properties of various anion and cation exchange membranes were studied in different electrolyte solutions using chronopotentiometry technique to get insight about influence of the counter ion on the transport properties of the membranes. The investigated samples include heterogeneous ion exchange membranes varying in the functionality of fixed charged groups, physical properties of the polymer and the preparation procedure. Chloride and nitrate were investigated as counter-ion in their sodium salts for anion exchange membranes while sodium, calcium, potassium and magnesium were selected as counter-ion in their chloride salts to study cation exchange membranes transport properties. First the current – voltage curve of an ion exchange membrane in a given solution was recorded to obtain the limiting current, then a constant current above the limiting current was used for chronopotentiometry measurement. In all the studied membranes the potential across the membrane remained constant for a time interval called the transition time, when a constant current was applied. Then the potential increased rapidly to reach the steady state potential. The permselectivty and the transport number of a membrane were calculated using the corresponding transition time.

An experimental study was carried out on synthesis and performance of the MTES (methyltriethoxysilane) templated and template free nanostructure silica membranes for hydrogen separation. The permeance of hydrogen, carbon dioxide and nitrogen pure gases and permselectivity and separation factor of gas mixtures were investigated at 25 ° C, 100 ° C and 200 ° C. Activated molecular sieve with positive and negative sign and Knudsen diffusion were respectively the dominant transport mechanisms in hydrogen, carbon dioxide and nitrogen gas molecules permeances. Although, the hydrophobic property of templated membrane is a good option for gas separation in hydrothermal conditions, the dense structure of the membrane results in lower permeances and permselectivities in comparison with template free one. Hydrogen permeance at 200 º C and 3 bar which was measured 30. 5×10-8 for template free silica membrane, decreased to 2. 37 for MTES templated silica membrane. Permselectivity and separation factor of H2/N2 at the same conditions, which were 31. 2 and 21 for template free membrane, reached to 21. 5 and 8 for templated membrane. In addition, H2/CO2 permselectivity at the same conditions was measured for template free and templated membranes, 23. 4 and 13. 9, respectively.

In this research, thin film heterogeneous cation exchange membrane was prepared by interfacial polymerization of polyacrylic acid-co-iron nickel oxide nanoparticles on PVC based substrate. Spectra analysis confirmed graft polymerization conclusively. The SEM images showed that polymerized layer covers the membranes by simple gel network entanglement. Results exhibited that membrane water content was decreased by graft polymerization of PAA/Fe2NiO4 nanoparticles on membrane surface.Membrane potential, transport number and permselectivity all were declined initially by PAA interfacial polymerization in NaCl ionic solution and then began to increase. The membrane transport number and permselectivity showed decreasing trend in bivalent (BaCl2) ionic solution. The sodium flux and permeability were improved sharply by PAA graft polymerization on membrane surface and then decreased slightly by graft polymerization of PAA/Fe2NiO4 nanoparticles. Different behavior was found for barium flux and permeability. Membrane areal electrical resistance was also decreased by introducing interfacial graft polymerization on membrane surface.

In this study, ion exchange nanocomposite membranes was prepared by addition of Mg(OH)2 nanoparticles to a blend containing sulfonated polyphenylene oxide and sulfonated polyvinylchloride via a simple casting method. Magnesium hydroxide nanoparticles were synthesized via a facile sono-chemical reaction and were selected as filler additive in fabrication of ion exchange nanocomposite membranes. Nanoparticles and nanocomposites were then characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The effect of nanoparticles loading on physicochemical and electrochemical properties of prepared cation exchange nanocomposite membranes was studied. The membranes performance was evaluated by membrane potential, transport number, permselectivity, ionic permeability, flux of ions and membrane oxidative stability. Various characterizations revealed that the addition of different amounts of inorganic fillers could affect the membrane performance. The inorganic nanoparticles not only created extra pores and water channels that led to ion conductivity enhancement, but also improved transport number, permselectivity and flux of ions.

In this study, graphene oxide (GO) was functionalized by sodium triphosphate (NaTPP) through a physical grafting method and used as a nanofiller to fabricate cation exchange membranes based on polyvinylidene fluoride (PVDF). The influences of the loading percentage of NaTPP in functionalized GO (GON) samples on the hydrophilicity, surface and cross-sectional morphology, permselectivity, and ion transport number of the sodium ion on the fabricated CEMs were explored using different techniques. Adding NaTPP to GO resulted in a more even surface structure, enhanced surface wettability, and decrement of membrane area resistance for the GON-based CEMs compared to GO-containing membranes. The MGON (0.5) membrane showed a high water uptake of 46.2 ± 2.3% and an ion exchange capacity of 3.8 ± 0.1 meq g-1, which facilitated the easier transport of monovalent and divalent ions within the membrane. The results showed that the MGON (0.5) membranes possessed higher permselectivity for monovalent and divalent ions including Na+ (98.3%), K+ (96.4%), Ca2+ (80.2%), and Mg2+(76.3%). Additionally, the membrane area resistance of this optimized membrane was 1.3 ± 0.2 Ω cm2, which was about 87.48% lower than the membrane containing unmodified GO.

Transport studies have been carried out across a newly synthesized inorganic–organic nanocomposite membrane. Membrane potential measurements have been measured in various monovalent electrolyte environments at different concentrations to analyse the relationship between transport properties and fixed charge concentration of the membrane. The charge densities were found to follow the order K+ >Na+ >Li+. The counter-ion transport number, ionic mobility ratio and permselectivity of the nanocomposite membrane have also been calculated which reveal that the inorganic–organic nanocomposite membrane shows a higher selectivity towards K+ ions; however, the selectivity decreases with decrease in dilution for all monovalent electrolytes tested. These membranes were comprehensively characterized for their physicochemical properties, morphology, molecular interactions and crystallinity by sophisticated techniques. The ionexchange capacity, volume void porosity and water uptake of the membrane were found to depend on the polystyrene content in the membrane phase and these properties decreased with increase in the amount of polymer (15–35 % by mass). Moreover, membrane containing 25 % of polystyrene exhibited good selectivity along with moderate ion-exchange capacity, which may be used for their application in electro-driven separation at high temperatures or for other electrochemical processes.

Synthesized poly(2, 6-diphenyl-p-phenylene oxide) ( PPPOdp) and brominated poly(2, 6-diphenyl-p-phenylene oxide) ( BPPPOdp) are identified as new membranes for CO2/ N2 separation and characterized by SEM, FTIR, and 1HNMR. BPPPOdp is known as a flexible membrane with higher permselectivity (  CO2∕ N2 = 30. 53) than PPPOdp membranes. BPPPO and SiO2 nanocomposite membranes display improved CO2 permeability and CO2/ N2 selectivity compared to the pure PPPOdp, and BPPPOdp membranes. The CO2/ N2 separation mechanism in the membranes is related to the amount of gas dissolution than the amount of gas diffusion.