Electrodialysis water recovery

Cooling Water Salinity and Brine Disposal Optimized with Electrodialysis Water Recovery/Brine Concentration System... 

Likewise, nanofiltration can be integrated into waste water treatment. Combined reverse osmosis/nanofiltration processes can offer higher water recovery than either process alone [122]. Moreover, nanofiltration can be combined with other membrane filtration processes [123], electrodialysis [124], or other waste water treatment processes such as ozonation [125]. 

Electrodialysis/electrodialysis reversal (ED/EDR) represents 3% of aU the desalination capacity in the world [48]. It is, however, used mainly for desalinating brackish water. It can achieve 95% water recovery with minimal chemical feed. However, it can only reject ionised matter. Substances such as colloids, silica and boron at pH <8.0 are not removed. A triple-membrane system using UF-EDR-RO has been very effective in producing purified water for power plants [50]. In this integrated system, UF is used for removing suspended solids and macromolecules ... 

Electrodialysis is a particularly economic process for low-salinity waters when compared to RO because, although the initial capital cost may be 10 to 15% higher, it generally requires no pretreatment, it produces a higher recovery rate (around 80-85%), it has a lower operating and maintenance cost, and the membranes last twice as long (up to 10 years). 

Reverse Osmosis/Electrodialysis. Very recently, Perdue and co-workers have developed a novel process in which reverse osmosis (RO) is used to remove water from seawater and electrodialysis (ED) is used to desalt seawater. The coupled RO/ED process was developed initially by Koprivnjak et al. (2006) to purify RO-concentrated samples of DOM from freshwaters, which are nearly always contaminated with sulfuric acid (H2S04) and silicic acid (H4Si04). It was possible to remove nearly all H2S04 and H4Si04 from such samples with an average 85% overall recovery of DOC. 

Water Splitting A modified electrodialysis arrangement is used as a means of regenerating an acid and a base from a corresponding salt. For instance, NaCl may be used to produce NaOH and HCl. Water splitting is a viable alternative to disposal where a salt is produced by neutralization of an acid or base. Other potential applications include the recovery of organic acids from their salts and the treating of effluents from stack gas scrubbers. The new component required is a bipolar membrane, a membrane that splits water into H and OH . At its simplest, a bipolar membrane may be prepared by... 

Wisniewski, J. and G. Wisniewska (1997). Application of electrodialysis and cation exchange technique to water and acid recovery. Environ. Protection Eng., 23, 3-4, 35-45. 

Chiapello and Gal [93] studied the recovery of cyanide electroplating rinse waters by electrodialysis. The transfer rates of the ionic species present in a copper or zinc cyanide rinse bath was limited by the high resistance of the anion exchange membrane used. The presence of highly charged cyano complexes of copper increased the resistance of the anion exchange membrane. The transfer of zinc was easier at higher... 

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. 

Electrodialysis. In electrodialysis, separation of an aqueous stream is achieved through the use of synthetic membranes and an electric field. The membrane allows only one type of ions to pass through and may be chosen to remove other ions that move in the opposite direction. Therefore, it produces one stream rich in particular ions and another stream depleted of those ions. The two streams can be recycled or disposed off. This technique is commonly used in the desalination of brackish water. The other uses are in acid mine drainage treatment, the desalting of sewage-plant effluents, and in sulfite-liquor recovery. 

Like many other specialities, electrodialysis plants are purchased as complete packages from a few available suppliers. Membrane replacement is about 10% per year. Even with prefiltering the feed, cleaning of membranes may be required at intervals of a few months. The comparative economics of electrodialysis for desalting brackish waters is discussed by Belfort (1984) for lower salinities, elecfrodialysis and reverse osmosis are competitive, but for higher ones elecfrodialysis is inferior. Elecfrodialysis has a number of important unique applications, for removal of high contents of minerals from foods and pharmaceuticals, for recovery of radioactive and other substances from dilute solutions, in electro-oxidation reduction processes and others. 

The procedure of electrodialysis 7) proposed for recovery of Na2CO, uses sea water purified from magnesium, which is fed to the anode while sodium bicarbonate is supplied to the cathode. The two electrodes are separated by a sulfonated anion resin. The net transfer of sodium to the cathode produces a saturated solution of Na2C03. Bicarbonate is regenerated and recycled from a portion of the carbonate product 28,29). 

A process for recovery of uranium from sea water comprises the regeneration of the sorbent by elution of uranium. Elution should proceed rapidly and with high yield in order to maximize the overall eficiency of the recovery process, which is measured in terms of the increase of the effective concentration, i.e. the concentration of uranium in the eluate compared to the initial concentration in the sea water. Finally, a high selectivity of the elution process is desirable 107,130). A further concentration of uranium in the eluate up to the precipitability in the form of yellow cake can be attained by ion exchange, ion flotation, or electrodialysis. 

Electrodialysis uses stacks of pairs of anion- and cation-exchange membranes in deionizing water and in recovery of formic, acetic, lactic, gluconic, citric, succinic, and glutamic acids from their sodium and potassium salts in fermentation broths.114 This may have an advantage over processes that involve purification through calcium salts. Electrodialytic bipolar membranes have been used to recover concentrated mineral acids from dilute solution.115 They can be used to convert sodium chloride to hydrogen chloride and sodium hydroxide in a process that avoids the use of chlorine.116 Soy protein has been precipitated by... 

H. Takahashi, S. Hirawatari and K. Kikuchi, Recovery of rare-metal elements from their EDTA complex solution by means of electrodialysis accompanied by metal substitution reaction, Nippon Kaisui Gakkashi (Bull. Soc. Sea Water Sci. Jpn.) 1997, 51, 219. 

Electrodialysis is also effective in remediation of pollution by heavy metal ions, and recovery of valuable materials from the waste. Water containing heavy metal ions such as the waste solution and effluent from galvanizing plating baths can be... 

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