Ion transport through homogeneous and heterogeneous ion-exchange membranes in single salt and multicomponent electrolyte solutions

The increasing demand for clean industrial processes has intensified the use of electrodialysis in the treatment of metal containing effluents and encourages the investigation of the different phenomena involved in the transport of metal ions through cation-exchange membranes. Ion sorption, chronopotentiometric and current–voltage characteristics have been obtained to characterize the transport of sodium and iron through homogeneous and heterogeneous cation-exchange membranes. The heterogeneous membranes having a broader pore size distribution showed increased electrical resistances with solutions of trivalent iron, which may be caused by the blockage of the smallest pores by multivalent ions. However, for both types of membranes an unexpected decrease of the electrical resistance with increasing current densities was verified with concentrated solutions of Fe2(SO4)3. This behavior was explained to be a consequence of the dissociation of FeSO4+ ions into more conductive Fe3+ and SO42− ions as the depleting solution layer becomes diluted. When tested with multicomponent mixtures, the homogeneous perfluorosulfonic membranes show an increased preference for Na+ ions at low current densities and, once Na+ ions are depleted from the membrane surface Fe3+ ions are transported preferentially at higher current densities. On the contrary, both Na+ ions and Fe(III) species are responsible for the ion transport through the heterogeneous membranes within the ohmic regime of currents.This work was supported by the Ministerio de Economia y Competitividad (Spain) with the Project number CTQ2012-37450-C02-01/PPQ. M.C. Marti-Calatayud is grateful to the Universitat Politecnica de Valencia for a postgraduate grant (Ref. 2010-12). D.C. Buzzi wants to express her gratitude to CAPES (Brazil) for a postgraduate grant (Proc. BEX 8747/11-3).Martí Calatayud, MC.; Buzzi, DC.; García Gabaldón, M.; Bernardes, AM.; Tenório, JAS.; Pérez Herranz, V. (2014). Ion transport through homogeneous and heterogeneous ion-exchange membranes in single salt and multicomponent electrolyte solutions. Journal of Membrane Science. 466:45-57. https://doi.org/10.1016/j.memsci.2014.04.033S455746

Synthesis and electrochemical behavior of ceramic cation-exchange membranes based on zirconium phosphate

Cation-exchange membranes made exclusively from ceramic materials have been synthesized by means of the impregnation of microporous ceramic supports with zirconium phosphate. Changes in the pore size distribution and total pore volume of the supports were provoked by the addition of starch as pore former in the fabrication procedure. This allowed the production of supports with increased effective electrical conductivities and with larger pores available for the zirconium phosphate deposition. An improved functionality for the exchange of cations was given to the ceramic membranes by means of their impregnation with the active particles of zirconium phosphate. The ion-exchange properties of the membranes were increased with further impregnation cycles and the resulting current voltage curves showed a similar shape to that typical of commercial polymeric ion-exchange membranes. The production of ionexchange membranes with increased chemical and radiation stability will broaden their applicability for the treatment of specific industrial waste waters, which are very aggressive for the current commercial ion-exchange membranes.Manuel-Cesar Marti-Calatayud wants to express his gratitude to Universitat Politecnica de Valencia for a postgraduate grant (Ref. 2010-12). S. Sales would like to express her gratitude to Ministerio de Ciencia e Investigacion (Spain) for a postgraduate grant (AP2009-4409). This work was supported by Ministerio de Ciencia e Innovacion (Spain) with the project numbers CTQ2008-06750-C02-01/PPQ and CTQ2008-06750-C02-02/PPQ.Martí Calatayud, MC.; García Gabaldón, M.; Pérez-Herranz, V.; Sales, S.; Mestre, S. (2013). Synthesis and electrochemical behavior of ceramic cation-exchange membranes based on zirconium phosphate. Ceramics International. 39(4):4045-4054. https://doi.org/10.1016/j.ceramint.2012.10.255S4045405439

Study of the effects of the applied current regime and the concentration of chromic acid on the transport of Ni2+ ions through Nafion 117 membranes

In the present work galvanostatic experiments are conducted with an electrodialysis cell in order to study the passage of Ni 2+ ions present in chromic acid solutions through a Nafion cation-exchange membrane. The competing transport between H + and Ni 2+ ions through the membranes has been studied under the imposition of under- and overlimiting currents. Results show an increasing competence between both ions when the concentration of protons exceeds that of the Ni 2+ ions. Increased nickel removal rates and current efficiency values were achieved with intensive current regimes due to the onset of electroconvection. However, at low values of the [Ni 2+]/[H +] ratio, this improved transfer through the membrane implies high values of specific energy consumption due to increased membrane voltage drops, thus decreasing the convenience of applying overlimiting currents. The obtained results are related to the values of plateau length calculated from the polarization curves of this membrane/electrolyte system and prove that Ni 2+ ions promote the arising of electroconvective vortices, whereas H + ions hamper electroconvection. © 2011 Elsevier B.V.The authors of this work would like to express their gratitude to Ministerio de Ciencia e Innovacion (Spain) for their financial support (CTQ2008-06750-C02-01/PPQ) and to Universitat Politecnica de Valencia for a postgraduate grant (Ref. 2010-12).Martí Calatayud, MC.; García Gabaldón, M.; Pérez-Herranz, V. (2012). Study of the effects of the applied current regime and the concentration of chromic acid on the transport of Ni2+ ions through Nafion 117 membranes. Journal of Membrane Science. 392-393:137-149. https://doi.org/10.1016/j.memsci.2011.12.012S137149392-39

Determination of transport properties of Ni(II) through a Nafion cation-exchange membrane in chromic acid solutions

The transport properties of a cation-exchange membrane in the presence of nickel sulphate solutions were investigated by means of chronopotentiometry. The interest of this study relies on the application to the treatment of chromium plating rinse baths. The presence of chromic acid in the solutions and the initial concentration of nickel sulphate affect significantly the shape of the chronopotentiograms. The different shape of chronopotentiograms as well as the values of different parameters is thereby justified by the calculation of the speciation diagrams of Ni(II).Parameters like the limiting current density, resistance of the ohmic region, plateau length, and nickel transport numbers through the cation-exchange membrane were calculated from the chronopotentiometric and the current-voltage curves. The obtained results show an important competence between Ni2+ and H+ ions, with increases of the nickel transport numbers when the [Ni2+]/[H+] ratio corresponding to the initial equilibrium exceeds the unity. The increase in the Ni2+ concentration brings about a facilitated arising of electroconvection, which promotes overlimiting currents and additional mixing at the membrane surface. © 2011 Elsevier B.V.The authors of this work would like to express their gratitude to Ministerio de Ciencia e Innovacion (Spain) for their financial support (CTQ2008-06750-C02-01/PPQ) and to Universitat Politecnica de Valencia for a postgraduate grant (Ref. 2010-12).Martí Calatayud, MC.; García Gabaldón, M.; Pérez-Herranz, V.; Ortega Navarro, EM. (2011). Determination of transport properties of Ni(II) through a Nafion cation-exchange membrane in chromic acid solutions. Journal of Membrane Science. 379(1-2):449-458. https://doi.org/10.1016/j.memsci.2011.06.014S4494583791-