Permselectivity and ion-conductivity of grafted cation-exchange membranes based on UV-oxidized polymethylpenten and sulfonated polystyrene

International audienceIn the present study the properties of novel cation-exchange membranes based on UV-oxidized polymethylpentene (PMP) with grafted sulfonated polystyrene are described. A correlation between the composition of the grafted copolymer (grafting degree, cross-linking degree) and transport properties (Na+-conductivity, permselectivity, diffusion permeability) of resulted membranes are discussed. It is shown that with increasing of grafting degree (GD) and lowering of cross-linking degree (CD) the concentration of functional groups in the inner solution and permselectivity decrease, while ionic conductivity increases. The obtained membranes have the GD ranging from 29 to 120% and CD from 0 to 5%. The best membranes have ionic surface resistance of 0.3–0.6 Ω cm2 in 0.5 M NaCl, apparent cation transport numbers of 0.870–0.998 and NaCl diffusion permeability of 3.3 · 10−8–5.5 · 10−7 cm2 s−1, as well as satisfactory mechanical performance. A comparison of transport properties (conductivity and cation transport number) of the obtained membranes with a properties of number of available samples was made. It is noted that some of the obtained samples are at the level of the best perfluorinated homogeneous membranes in terms of the ratio of conductivity and cation transport numbers. High ionic conductivity and permselectivity make the prepared membranes promising candidates for possible applications in electrodialysis, dialysis, reverse electrodialysis, Red-Ox flow batteries and other membrane processes

Conversion of aliphatic C1 C2 alcohols on In , Nb , Mo-doped complex lithium phosphates and HZr 2 (PO 4 ) 3 with NASICON-type structure

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An approach to increase the permselectivity and mono-valent ion selectivity of cation-exchange membranes by introduction of amorphous zirconium phosphate nanoparticles

International audienceThis paper addresses hybrid ion exchange membranes fabricated by the synthesis of amorphous zirconiumphosphate (dopant contents from 0.5 to 24 wt%) directly in the pore and channel system of heterogeneouscation-exchange membrane RALEX® CM (by in situ technique). The incorporation of zirconium phosphate nanoparticlesinto the membrane system of pores and channels leads to the displacement of the pore water. As aresult, the cation transport numbers increase. The hybrid materials thus obtained are characterized by increasedionic resistance and enhanced monovalent ion selectivity. The former effect was eliminated by fabrication of asurface-modified membrane. The relative simplicity of modification, together with the benefits of the hybridmaterials make them promising for some membrane processes. Using 31P MAS NMR and elemental analysis,considerable difference between the zirconium phosphate composition inside and outside the membrane wasfound

Physicochemical and electrochemical characterization of Nafion-type membranes with embedded silica nanoparticles: Effect of functionalization

International audienceIntroduction of nanoparticles in membranes allows a significant enhancement of their performance in energy production, water treatment and other applications. However, the effect of nanoparticles’ surface functionalization and the mechanism of their impact on membrane properties remain poorly studied. In this paper, we examine a Nafion-based membrane and its modifications, each containing 3 wt% SiO2. The effect of functionalization by propyl, 3-aminopropyl and 3,3,3-trifluoropropyl is investigated. The water uptake, contact angle, conductivity, diffusion permeability to NaCl, current-voltage curves (CVC), chronopotentiograms (ChP), and the difference between the pH of the desalination compartment output and input solutions (characterizing the water splitting rate) are reported. It is found that the doping of the membranes with nanoparticles leads to increasing their conductivity in all cases except 3-aminopropyl, which imparts a positive charge to the nanoparticles; the diffusion permeability decreases and permselectivity increases in all cases. The latter is explained by transformation of the mesoporous membrane structure to the microporous one. The impact of nanoparticles on the membrane conductivity, CVC and ChP is mainly caused by an additional (positive) space charge introduced into the pore solution and at the membrane surface by the electric double layer surrounding the nanoparticles. The greater the surface charge density of the nanoparticles and the smaller their size, the stronger the impact. Accordingly, the highest conductivity, current density at a low fixed voltage and chronopotentiometric transition time are shown by the sample doped with SiO2 and 3,3,3-trifluoropropyl. The interplay between electroconvection and water splitting phenomena is discusse