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    Electro-deionization of Cr (VI)-Containing Solution. Part I: Chromium Transport through Granulated Inorganic Ion-Exchanger
    (Taylor & Francis Inc, 2009) Dzyazko, Yuliya S.; Rozhdestvenskaya, Ludmila M.; Vasilyuk, Sergey L.; Belyakov, Vladimir N.; Kabay, Nalan; Yuksel, Mithat; Arar, Ozgur; Yuksel, Umran
    Kinetics of Cr (VI) -> OH(-) exchange on both hydrogel and xerogel of hydrated zirconium dioxide was investigated. Self-diffusion coefficient of Cr (VI) species has been determined by analysis of kinetic curves. Transport of Cr (VI) anions through the inorganic ion exchangers under the influence of applied voltage was also researched. In the case of hydrogel, the ions are transported mainly through the solid phase. Diffusion coefficient of chromate anions through this material was estimated as 9.00 x 10(-12) m(2) s(-1). This is in agreement with self-diffusion coefficient of Cr (VI) obtained from kinetic measurements (1.60 x 10(-12)-9.92 x 10(-12) m(2) s(-1)). Owing to the rather high mobility of Cr (VI) through hydrogel of hydrated zirconium dioxide, this material was recommended for electro-deionization processes. On the other hand, the use of polymer anion-exchange membrane must be excluded to prevent poisoning of the inorganic ion exchanger with Cr (III) cations to be formed during chemical interaction of Cr (VI) with organic materials.
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    Electro-deionization of Cr (VI)-Containing Solution. Part II: Chromium Transport through Inorganic Ion-Exchanger and Composite Ceramic Membrane
    (Taylor & Francis Inc, 2009) Dzyazko, Yuliya S.; Vasilyuk, Sergey L.; Rozhdestvenskaya, Ludmila M.; Belyakov, Vladimirn.; Stefanyak, Nikolayv.; Kabay, Nalan; Yueksel, Mithat; Arar, Oezguer; Yueksel, Uemran
    Cr (VI) transport through a composite ceramic membrane containing an ion-exchange component, namely xerogel of hydrated zirconium dioxide, was investigated. The diffusion coefficient of Cr (VI) species through the membrane, which has been determined under open circuit conditions, is 1.80 x 10(-10) m(2) s(-1). The transport number of Cr (VI) species through the ceramic membrane was found to rise with increasing voltage and reached 0.17 under over-limiting current conditions. On the other hand, the transport of chromate ions through hydrogel of hydrated zirconium dioxide becomes more intensive with a decrease in potential drop through the system involving ion-exchanger bed and ceramic membrane due to decrease in the membrane resistance. The diffusion coefficient of Cr (VI) ions in hydrogel of the inorganic ion exchanger was estimated as 4.36 x 10(-12) m(2) s(-1). A possibility of Cr (VI) removal from a weakly acidic diluted solution using an electro-deionization method was shown: the degree of solution purification was found to reach 50%. The transport of species is realized through both the solution and the ion exchanger.