Formation of Alkaline pH Steps in an Electrodialyzer with a Bipolar and Ion-Exchange Membranes, and its Application to Amino Acids Separation

• Takahashi Hiroshi

  Department of Materials-process Engineering and Applied Chemistry for Environment, Akita University, Japan

• Makita Kengo

  Department of Materials-process Engineering and Applied Chemistry for Environment, Akita University, Japan

• Kikuchi Ken-ichi

  Department of Materials-process Engineering and Applied Chemistry for Environment, Akita University, Japan

Abstract

Bipolar membrane is composed of an anion-exchange layer and a cation-exchange layer, and can produce hydroxide ions and protons in an electrical field. Applications of bipolar membranes to conventional electrodialysis have increased in neutralization of acids or bases, and substitution of salt into acid. However, no applications of generated protons and hydroxide ions to formation of separating zones in electrodialyzer have been found. We have developed a new technique of electrodialysis with a bipolar membrane and ion-exchange membranes. The technique has a separating zone with pH steps between compartments, and may be possible to separate ampholytes by differences of the isoelectric points. The electrodialyzer was composed of six compartments, which were divided by a cation-exchange membrane, a bipolar membrane, and three anion-exchange membranes, respectively. When a voltage was applied to the electrodialyzer, hydroxide ions were electrically generated by the anion-exchange layer in the bipolar membrane, and moved to anode-side compartments through anion-exchange membranes. The hydroxide concentration in each compartment was almost equal to the concentration of coexisting cations, and formed alkaline-pH steps in the electrodialyzer. Moreover, we attempted to apply the technique to separation of L-glutamic acid and L-methionine. In the range of pH steps of 8 to 13, L-glutamic acid permeated through the anion-exchange membranes, and accumulated in the anode compartment, although L-methionine remained in the feed compartment. Thus, the separation by the new technique proceeded well. All the experimental data were simulated by a mathematical model. The model well explained the experimental results of the formation of pH steps in the electrodialyzer, and of the amino acids separation.

Journal

• Asian Pacific Confederation of Chemical Engineering congress program and abstracts

  Asian Pacific Confederation of Chemical Engineering congress program and abstracts 2004 (0), 745-745, 2004

  The Society of Chemical Engineers, Japan

Keywords

• ion-exchange membrane
• bipolar membrane
• electrodialysis

Details

• CRID: 1390001205732969600
• NII Article ID: 130005052824
• DOI: 10.11491/apcche.2004.0.745.0
• Text Lang: en
• Data Source:
  • JaLC
  • CiNii Articles
• Abstract License Flag: Disallowed