Electro-deionization of Cr (VI)-Containing Solution. Part II: Chromium Transport through Inorganic Ion-Exchanger and Composite Ceramic Membrane

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.