Electrodialysis electrodialyzer

Figure 15.21. Electrodialysis equipment and processes, (a) View of the components of an electrodialysis stack Lacey, 1978). (b) Flow pattern through an electrodialyzer for removal of NaCl from water Ionics Inc.), (c) Electroreduction with the use of an ion exchange diaphragm (d) Flowsketch of a three-stage electrodialysis for treatment of brackish water Rogers, in Belfort, 1984).

Nomura, Y., Iwahara, M., and Hongo, M. 1994. Production of acetic acid by Clostridium thermo-aceticum in electrodialysis culture using a fermenter equipped with an electrodialyzer. World J. Microb. Biotechnol 10, 427 132. 

Figure 5.5 Transport properties of a cation exchange membrane having a cationic polyelectrolyte layer formed by electrodeposition. (A) PNaCa ( ) current efficiency (%) ( ) electrical resistance of the membrane during electrodialysis for 1 h. After solutions containing 0.0416N sodium chloride and poly(3-methylene-N, N-dimethylcyclohexylammonium chloride) of various concentrations had been electrodialyzed, for 60 min at a current density of 10 mA cm 2, as anolyte to electrodeposit the polyelectrolyte on the membrane surface (catholyte was 0.0416N sodium chloride), a 1 1 mixed solution of 0.208N calcium chloride and 0.208 N sodium chloride was electrodialyzed at a current density of 10 mA cmr1 for 60 min (cation exchange membrane NEOSEPTA CH-45T).

Figure 5.14 Change in ratio of calcium ions to sodium ions in the membrane phase during electrodialysis (KNaCa) with polymerization time of aniline. After a 1 1 mixed salt solution of 0.250N calcium chloride and 0.250N sodium chloride (concentration of chloride ions 0.500N) had been electrodialyzed for 1.0 h at 10 mA cm 2 using a membrane with polyaniline layers, the membrane was immediately removed from the cell during electrodialysis and the ratio of calcium ions to sodium ions in the membrane phase was determined (starting membrane NEOSEPTA CM-1).

It is desirable to perform electrodialysis at as high a temperature as possible to save energy, if the membranes and electrodialyzer permit.151 However, when conventional ion exchange membranes are used in high temperature electrodialysis, osmotic water and electro-osmotic water through the membranes increase with increasing temperature. Thus, the amount of water produced decreases in the desalination of saline water and the concentration of the concentrated solution decreases in a concentration processes. On the other hand, a serious problem in electrodialysis is the precipitation of calcium sulfate in the concentrated compartment and the anion exchange membrane. 

Batch wise electrodialysis Circulation in electrodialyzer Circulation in electrodialyzers One electrodialyzer (one stage) Multi-electrodialyzers (multi-stages) Small scale Small scale... 

The effect of the cost of the ion exchange membrane on the total cost of electrodialysis or electrolysis is large because the membrane is relatively expensive. The lifetime of the membrane depends on the purpose and conditions of electrodialysis or electrolysis. A membrane for the electrodialytic concentration of seawater to produce sodium chloride has a lifetime of over 10 years, and that in the chlor-alkali membrane process, which is operated at ten times or more higher current density than that of seawater concentration, is over 5 years. However, in applications for food industries, the lifetime of the membrane is relatively short due to periodical sanitary cleaning of the electrodialyzer by acid or alkali solution, and sometimes oxidizing agents. 

As mentioned above, the efficiency of electrodialysis decreases with increasing desalination of saline water due to a decrease in electrical conductivity of the solution. It was reported that ion exchange resins can be packed in the desalting compartment of an electrodialyzer to increase the conductivity of the... 

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