Abstract
An electrodeionization (EDI) apparatus possesses two functions: the “deionization”, where the ion in treated water is captured, and the “electric-regeneration”, where the electric energy is added. In this paper, the arrangement of ion-exchange resin is investigated in order to find the optimum condition of those two functions. Firstly, the relationship between the electric-regeneration function and the arrangement of ion-exchange resin was obtained. Instead of ion-exchange resin, an anion- and cation-exchange non-woven fabric sheet made of ionexchange fibers was examined to compare the effect of position of the sheets on current/voltage measurement curves. It was evident that the most efficient electric regeneration function was generated in the arrangement of resin where only one “reversed-bias” interface exists. Secondly, it was considered that the distribution condition (arrangement) of the anion- and cation-exchange resins, in which the “deionization function” appeared most effectively, was based on the “mixed-bed” to try to increase the nearest neighbor of both resins maintaining the condition of arrangement of the resin cited above. It was also evident that “thin-layered structure”, in which the anion- and cation-exchange groups were stacked on top of each other perpendicular to the membrane in the desalting chamber, was the most optimum structure. Finally, the way to form this structure in the desalting chamber was discussed.
