Electro-electrodialysis

Onuki, K. et al., Electro-electrodialysis of hydriodic acid in the presence of iodine at elevated temperature, /. Membr. Sci., 192,193, 2001. 

Frenzel, I., Holdik, H., Stamatialis, D.F., Pourcelly, G., and Wessling, A. (2005) Chromic acid recovery by electro-electrodialysis -1. Evaluation of anion-exchange membrane. J. Membr. Sci., 261 (1-2), 49-57. 

Nation membranes have also been used to carry out other concentration schemes. Hwang et al. employed an electro-electrodialysis approach to raise the concentration of HI within the HI, solution at 110°C. Nation acts as a cation exchange membrane in an electrolysis cell in which HI is formed at the cathode. This raises the HI concentration within the HI catholyte (figure 4.23). In addition to this, the increase in HI content helps to break up the azeotropic between HI, I2, and H2O and facilitates the distillation of HI from HI. Researchers at JAERI have taken this concept... 

FIGURE 4.23 Schematic of the electro-electrodialysis process to concentrate the Hl acid feed from the Bunsen reaction. 

Hwang, G.-J., Onuki, K., Nomura, M., Kasahara, S., and Kim, J.-W., Improvement of the thermochemical water-splitting IS (iodine-sulfur) process by electro-electrodialysis, Journal of Membrane Science, 220, 129-136, 2003. 

Electrodialysis can be performed with two main cell types multi-membrane cells for dilution-concentration and water dissociation applications, and electrolysis (or electro-electrodialysis [EED]) cells for oxidoreduction reactions. In multimembrane cells, only the membrane transport phenomena intervene, while electrochemical reactions occurring at the electrodes do not interact with the separation process the electrodes are simple electrical terminals immersed in electrolytes allowing the current transfer. The electrolysis cell operates with only one membrane that separates two solutions circulating in each electrode compartment. This application is based on electrode redox reactions, which are electrolysis specific properties. The anode induces oxidations, and reductions occur at the cathode [4]. 

In the endothermic HI reaction, hydriodic acid Hix from Bunsen reaction is concentrated in a number of steps and the resulting hydrogen iodide concentrate is decomposed into reagent iodine and product hydrogen gas. The HI reaction steps appear to have the largest room for process improvement, for which several innovative process techniques have been incorporated in the present flowsheet. The HI concentration steps combine electro-electrodialysis cell and carbonized osmosis membrane to reduce excess iodine and water prior to final distillation. An iodine absorber is integrated into the HI decomposer to improve decomposition ratio in a newly proposed Co- regenerated process ... 

In KIER, the system of electro-electrodialysis(EED)-distillation-membrane reactor employ in HI decomposition reaction. HI concentrates over 56% by EED Ifom Hix solution, and more concentrate by distillation. Pure HI (include a little H2O) gas come out Ifom the bottom of distillation tower. Pure HI gas decomposes in membrane reactor and produce H2.12 and non-decomposed HI gas go to the HI-12 recovery tower, and separated HI gas and I2 gas. I2 gas recycles to Bunsen reactor and HI gas recycles to vapor tank set the front to membrane reactor. 

S. Mazrou, H. Kerdjoudj, A.T. Cherif, A. Elmidaoni and J. Molenat, Sodium hydroxide and hydrochloric acid generation from sodium chloride and rock salt by electro-electrodialysis, J. Appl. Electrochem., 1997, 27, 558-567 A.T. Cherif, J. Molenat and A. Elmidaoni, Nitric acid and sodium hydroxide generation by electrodialysis using bipolar membranes, J. Appl. Electrochem., 1997, 27, 1069-1074. 

Raucq D, Pourcelly G, Gawich G. Production of sulfur acid and caustic soda from sodium sulfate by electromembrane process. Comparison between electro-electrodialysis and electrodialysis on bipolar membrane. Desalination 1993 91(12) 163—75. 

Electrodialysis (ED) Electrodialysis reversal Electro-electrodialysis Bipolar membrane electrodialysis... 

Membrane processes that use ion-exchange membranes and electric potential difference as the driving force for ionic species transport are referred to as electromembrane processes (Strathmann, 2004). The following electro-membrane separation processes (Scheme 5.1) can be distinguished electrodialysis (ED), including variations such as electrodialysis reversal, electro-electrodialysis and bipolar membrane electrodialysis, electrodeionization (EDI), and Donnan dialysis (DD). 

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