Electromembrane electrodialysis

Among electrochemical methods of water purification, one can also list the various electromembrane technologies, electrodialysis in particular. The simplest elec-trodialyzer consists of three compartments separated by semipermeable membranes (usually, cation- and anion-exchange membranes). The water to be purified is supplied to the central (desalination) compartment. In the outer (concentration) compartments, electrodes are set up between which a certain potential difference is applied. Under the effect of the electric field, ions pass througfi the membranes so that the concentration of ionic contaminants in the central compartment decreases. 

Lantagne and Velin [267] have reviewed the application of dialysis, electrodialysis and membrane cell electrolysis for the recovery of waste acids. Because of the new trends governed by environmental pressures, conventional treatment methods based on neutralization and disposal are being questioned. Membrane and electromembrane technologies are considered to be potential energy-efficient substitutes for conventional approaches. Paper mills will focus on the application of ion-exchange membranes namely dialysis, electrodialysis and membrane cell electrolysis for recovery of waste acids. 

Electromembrane processes such as electrolysis and electrodialysis have experienced a steady growth since they made their first appearance in industrial-scale applications about 50 years ago [1-3], Currently desalination of brackish water and chlorine-alkaline electrolysis are still the dominant applications of these processes. But a number of new applications in the chemical and biochemical industry, in the production of high-quality industrial process water and in the treatment of industrial effluents, have been identified more recently [4]. The development of processes such as continuous electrodeionization and the use of bipolar membranes have further extended the range of application of electromembrane processes far beyond their traditional use in water desalination and chlorine-alkaline production. 

In this chapter only electromembrane separation processes such as electrodialysis, electrodialysis with bipolar membranes, and continuous electrodeionization will be discussed. 

Unlike electrodialysis, which tends to concentrate and remove or recover species, electromembrane processes transform species present in waste streams by electrolysis and the use of cation and anion exchange membranes. These processes offer chemical cost reduction (by recovery), water consumption reduction, and discharge or reuse of contaminant-free waters. Supplementary gains are also obtained by identifying a market for products obtained from the recovery and transformation processes. 

M. Paleologou, R.M. Berry, R. Thompson, and J.T. Wearing, Electromembrane process for the treatment of Kraft mill electrostatic precipitator catch, US Pat. 5,567, 293 H.-J. Rapp and P.H. Pfromm, Electrodialysis for chloride removal from the chemical recovery cycle of a Kraft pulp mill, J. Membr. Sci., 1998, 146, 247-261 P.H. Pfromm, S.-P. Tsai and M.P. Henry, Electrodialysis for bleach effluent recycling in Kraft pulp reduction Simultaneous control of chloride and other no-process elements, Can. J. Chem. Eng., 1999, 77, 1231-1238. 

D. Raucq, G. Pourcelly and C. Gavach, Production of sulfuric acid and caustic soda from sodium sulfate by electromembrane processes. Comparison between electroelectrodialysis and electrodialysis on bipolar membrane, Desalination, 1993, 91, 163— 175 S. Mazrou, H. Kerdjoudi, A.T. Cherif and J. Molenat, Sodium hydroxide and hydrochloric acid generation from sodium chloride and rock salt by electroelectrodialysis, J. Appl. Electrochem., 1997, 27, 558 A.T. Cherif, J. Molenat and A. Elmidaoui, Nitric acid and sodium hydroxide generation by electrodialysis using bipolar membranes. J Appl. Electrochem., 1997, 27, 1069-1074. 

Electrodialysis (ED) is used to remove ionized substance from hquids through selective ion-permeable membranes. ED is the most widely commercialized electromembrane technology. Desalination of brackish water is the area of electrodialysis application with the largest number of installations. This chemical-free technology competes with reverse osmosis. Electrodialysis shows better resistance to fouling and scaling. It also has an economical advantage in desalination of low-salinity solutions [13]. Also, it should be kept in mind that because of small material consumption ED is the most environmental friendly process for solution desalination [14]. 

Grebenyuk VD (1976) Electrodialysis Technic Kiev, p 160 (in Russian). Grebenyuk VD, Ponomarov MI (1992) Electromembrane separation of mixtures Naukova Dumka, Kiev, p 184 (in Russian). Gnusin NP, Grebenyuk VD (1972) Electrochemistry of granulated ion exchangers, Naukova Dumka, Kiev, 180 (in Russian). 

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. 

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). 

Grebenyuk, VD., Chebotareva, R.D., Linkov, N.A. Linkov, VM. (1998) Electromembrane extraction of Zn from Na-containing solutions using hybrid electrodialysis-ion exchange method. Desalination, 115, 255-263. 

---