Electro-deionization of Cr (VI)-Containing Solution. Part I: Chromium Transport through Granulated Inorganic Ion-Exchanger

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.