Anion-exchange membranes made from inexpensive ceramic materials were synthesized by using a simple procedure based on incorporating particles of an ion exchanger into a host microporous structure.Microporous ceramics produced from alumina and kaolin were used as supports, and their internal voids were functionalized by direct precipitation of hydrated ZrO 2 . The addition of starch as pore former to the sintering mixture induces the formation of pores within the micrometer range, where the subsequent deposition of hydrated ZrO 2 occurred preferentially. An increase in the loading of hydrated ZrO 2 particles improved the ion exchange capacity (IEC) and induced anion-selective properties on the membranes. However, when more than six infiltration cycles were performed, the membrane porosity was substantially reduced. Electrochemical measurements conducted in acidic and neutral media corroborated the implication of the hydrated ZrO 2 particles on the development of concentration polarization and confirmed the strong relationship existing between the membrane porosity and electrical conductivity. Conversely, chronopotentiometric curves showed that the membranes practically lack of ion-exchange properties when tested under alkaline conditions. The methodology proposed to synthesize ceramic ion-conducting membranes could significantly broaden the utilization of electromembrane processes in industrial applications where the use of polymeric membranes is restricted due to their expensive cost or poor chemical stability.

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 ion

Martí Calatayud, MC.; García Gabaldón, M.; Pérez-Herranz, V.; Sonia; SERGIO MESTRE (2013). Chronopotentiometric study of ceramic cation-exchange membranes based on zirconium phosphate in contact with nickel sulfate solutions. Desalination and Water Treatment. 51(1): 597-605. doi:10.1080/19443994.2012.714629. Chronopotentiometric study of ceramic cation-exchange membranes based on zirconium phosphate in contact with nickel sulfate solutions. Abstract.In this article, the innovative cation-exchange membranes obtained from ceramic materials are presented. Different microporous ceramic supports were obtained from an initial mixture of alumina and kaolin, to which a varying content of starch was added in order to obtain supports with different pore size distributions. The deposition of zirconium phosphate into the porous supports generates membranes with cation-exchange properties. The fabrication of ionexchange membranes which could resist aggressive electrolytes such as strong oxidizing spent chromium plating baths or radioactive solutions would allow the application of electro-dialysis for the decontamination and regeneration of these industrial effluents. The perfor-mance of the manufactured membranes was studied in nickel sulfate solutions by means of chronopotentiometry. An increase of the membrane voltage drop during chronopotentiometric measurements was observed in some membranes, which seems to be a consequence of concentration polarization phenomena resulting from the ionic transfer occurred through the membranes. Current-voltage curves were obtained for the different ceramic membranes, allowing the calculation of their ohmic resistance. The ohmic resistance of the membranes increased when the open porosity (OP) of the samples was incremented up to a value of 50%. For values of OP higher than 50%, the resistance of the membranes decreased significantly with porosity.

Mestre, S.; Sales, S.; Palacios, M.; Lorente, M.; Mallol, G.; Pérez-Herranz, V. (2013). Lowcost inorganic cation exchange membrane for electrodialysis: optimum processing temperature for the cation exchanger. Desalination and Water Treatment. 51(16-18):3317-3324. doi:10.1080/19443994.2012 AbstractThe optimum temperature for fixing zirconium phosphate, obtained by precipitation, on a low-cost ceramic support was determined in order to obtain an inorganic cation-exchange membrane for electrodialysis. Zirconium phosphate ion-exchange capacity maximised between 450ºC and 550ºC, thus it was considered the optimum processing temperature. The origin of this maximum was investigated by means of XRD and TG-EGA. Zirconium phosphate formation by precipitation in the porous network of the support was verified by SEM-EDX and mercury intrusion porosimetry. The membrane obtained after thermal treatment at 450 ºC displayed selectivity to the cations present in the spent rinse water of the chromium plating process. This property allows the recovery of chromium by removing the cations through the cation-exchange ceramic membrane.