Abstract: An electrodialysis water splitting processes incorporates a chromatographic separation step using an amphoteric ion exchange resin to remove contamination salts from a salt solution feedstream and a base product solution. When the chromatographic column is subsequently eluted with water an effective separation of the components is achieved. The separated pure salt stream is forwarded to an electrodialysis water splitter cell for conversion to acid and base. The base product solution (sodium hydroxide, potassium hydroxide) may be similarly purified by passing through a second chromatographic column also containing an amphoteric resin to separate the base from the salt (recovered salt). The process is also applicable in a chlor-alkali process for acidifying the brine feed to the electrolysis cell and for producing high purity caustic from salt.

Abstract: The present invention provides an improved process for the regeneration of ion exchange gels and resins. Exhausted regenerating solutions from a either a cationic or anionic exchange column are converted into fresh regenerating solutions via one or a combination of electrodialysis units having at least one bipolar membrane. The spent regenerants may be treated in an electrodialytic water splitter, an acid or base purification unit, or any combination thereof, to reclaim as much or as little of the regenerating solution as is required by the particular process.

Abstract: The present invention comprises an improved electrodialytic cell and closed loop process for removing SO.sub.2 from SO.sub.2 containing gases. An aqueous scrubbing medium is used to remove the SO.sub.2 from the gas. A two compartment electrodialytic water splitter and a means for stripping is used to isolate the SO.sub.2 and regenerate the aqueous scrubbing medium. Use of univalent cation selective membranes, recycling of the acid product to the base loop of the water splitter, and a prescrubber allow high concentrations of scrubbing solution to be treated without significant fouling inside the membranes. The above process embodiments may be used either alone or in combination.

Abstract: The present invention is an improved process for electrodialytically generating salts of volatile acids and/or bases from a salt stream. The salt of the volatile base may either be generated from a similar salt, or may be recovered from a mixed salt solution containing the salt of a volatile base and other similar salts. The salt solution is treated in a two or three compartment electrodialytic water splitter. The acid formed in the acid compartment of the electrodialytic unit is neutralized as it is formed by adding the volatile base directly to the acid loop. Neutralization of the acid in the acid loop minimizes the acid concentration in the electrodialytic unit, thereby increasing the efficiency of the membranes, and the cell stack. The electrodialytic unit may be run in either batch or continuous mode.

Abstract: The present invention relates to a method and related apparatus useful to electrodialytically convert salt to acid and/or base of improved purity. The apparatus comprises an electrodialytic water splitting apparatus comprised of at least one unit cell. Each cell comprises at least two means for splitting water. An intermediate compartment is between the two adjacent means for splitting water. At least one ion selective means is adjacent to at least one of the means for splitting water. An acid or base product compartment is between the ion selective means and the means for splitting water. There is an aqueous salt feed compartment, the ion selective means being between the salt feed compartment and the water splitting means.

Abstract: The present invention relates to a method and related apparatus useful to electrodialytically convert the salt of a strong base and a weak acid to base with improved purity; or the salt of a weak base and a strong acid to acid with improved purity.

Abstract: A method of separating acid from an aqueous feed stream comprising acid and salt. The method is conducted in an apparatus comprising a bipolar membrane between at least one first anion membrane and at least one second anion membrane.

Abstract: A process for recovering concentrated mixed acids comprising HF from mixed salts at a high efficiency is disclosed. The process comprises the steps of providing an electrodialytic water splitter comprising at least one unit cell, each cell comprising a first compartment and a second compartment, feeding an aqueous solution comprising at least two salts formed from at least two different anions to the first compartment, one of said anions being fluoride, feeding a liquid comprising water to the second compartment, passing current through said electrodialytic water splitter to produce an aqueous product comprising mixed acids formed from the different anions in the second compartment, and an aqueous salt-containing product comprising a reduced concentration of said anions in the first compartment, and recovering aqueous products from the second compartment. The process is particularly useful in the production of concentrated HNO.sub.

Abstract: The present invention is a method of recovery of base from material comprising base or acid and salt. The method is conducted in an apparatus comprising a cation membrane between two bipolar membranes.

Abstract: A process for recovering concentrated mixed acids comprising HF from mixed salts at a high efficiency is disclosed. The process comprises the steps of providing an electrodialytic water splitter comprising at least one unit cell, each cell comprising a first compartment and a second compartment, feeding an aqueous solution comprising at least two salts formed from at least two different anions to the first compartment, one of said anions being fluoride, feeding a liquid comprising water to the second compartment, passing current through said electrodialytic water splitter to produce an aqueous product comprising mixed acids formed from the different anions in the second compartment, and an aqueous salt-containing product comprising a reduced concentration of said anions in the first compartment, and recovering aqueous products from the second compartment. The process is particularly useful in the production of concentrated HNO.sub.

Abstract: The present invention is a method and apparatus of controlling a raw salt stream to be treated in an electrodialytical water splitter. An aqueous salt feed stream is fed to an electrodialysis water splitter and a dilute salt stream is withdrawn from the water splitter. The dilute salt stream is fed to an electrodialysis unit comprising a concentration compartment and a diluting compartment, at least part of the dilute salt stream being fed to the concentration compartment. An electrodialysis product stream is withdrawn from the concentration compartment. The product stream and the raw salt stream are controllably combined to form the aqueous feed stream. In accordance with the method of the present invention the salt concentration of the product stream can be maintained below the salt concentration of the raw salt stream. The pH of aqueous salt feed stream can be controlled based on the pH of electrodialysis unit product stream.

Abstract: The present invention is a method of recovery of base from material comprising base or acid and salts. The method is conducted in an apparatus comprising a cation membrane between two bipolar membranes.

Abstract: We have discovered an improved, energy efficient method for recovering and regenerating acid from a solution comprising acid and salt.

Abstract: A process employing two- and three-compartment electrodialytic water splitting for conversion of basic sodium material such as dry-mined or subterranean deposits of trona or nahcolite into a liquid comprising aqueous sodium base such as NaOH and/or Na.sub.2 CO.sub.3. The basic sodium material is contacted with a liquid comprising aqueous hydrogen ions for a time sufficient to produce a liquid comprising aqueous sodium ions. A liquid comprising water is introduced into each base compartment and the liquid comprising aqueous sodium ions is introduced into each remaining compartment of a two- or three-compartment water splitter. Direct current is passed through said water splitter to produce, a liquid comprising an aqueous sodium base in the base compartment and a liquid comprising aqueous hydrogen ions in an acid compartment of said water splitter. At least a portion of the liquid comprising aqueous hydrogen ions is used in the initial contacting step.

Abstract: An electrodialytic water splitting process for recovering SO.sub.2 -containing gases for converting the spent materials used in alkaline sodium scrubbing of SO.sub.2 -containing gases into NaOH. The alkaline sodium scrubbing materials such as Na.sub.2 CO.sub.3, NaHCO.sub.3 or mixtures thereof are used in the form of an aqueous slurry or aqueous solution to scrub SO.sub.2 from gases containing same to form a reaction mixture comprising Na.sub.2 SO.sub.3, Na.sub.2 SO.sub.4, and possibly NaHSO.sub.3, and a gas depleted in SO.sub.2. The reaction mixture is contacted with an aqueous hydrogen ion solution comprising Na.sub.2 SO.sub.4 and H.sub.2 SO.sub.4 formed in an acid compartment of a two- or three-compartment electrodialytic water splitter to form a solution comprising aqueous SO.sub.2 values and aqueous Na.sub.2 SO.sub.4. Contact of the reaction mixture with the aqueous hydrogen ion solution may be performed externally, of the water splitter or internally, in an acid compartment of the water splitter.

Abstract: A basified aqueous salt solution and an aqueous acid are generated in a multichamber two-compartment electrodialytic water splitter having unit cells comprised of a bipolar membrane, a first anion permselective membrane and at least one additional substantially non-porous, water-swollen non-cation permselective membrane disposed between an anion face of the bipolar membrane and a face of said first anion membrane thereby forming at least two base compartments and an acid compartment, positioned between an anode and a cathode.

Abstract: The present invention provides an improved electrodialytic water splitting process that may be operated in two- or three-compartment cells to recover valuable metal or ammonium values from materials comprising a salt of a first acid while avoiding formation of gas bubbles in the two- or three-compartment electrodialytic water splitting cells. The process comprises contacting a material comprising a salt of a first acid e.g. Na.sub.2 SO.sub.3, Na.sub.2 CO.sub.3 /NaHCO.sub.3, wherein the first acid is capable of generating a gas upon acidification of the salt of the first acid with a hydrogen ion-enriched aqueous solution comprising a second acid, e.g. Na.sub.2 SO.sub.4 /H.sub.2 SO.sub.4 which is generated and withdrawn from a two- or three-compartment electrodialytic water splitter. The gas generated e.g. CO.sub.2, SO.sub.2 is released external to the water splitter where it can be easily removed by conventional techniques such as application of vacuum.

Abstract: A process and a system for converting materials comprising sodium carbonate and sodium bicarbonate, such as dry-mined or subterranean deposits of trona, into a liquid comprising sodium carbonate substantially free of sodium bicarbonate. The process and the system incorporate the features of: (a) forming an aqueous solution comprising sodium carbonate and sodium bicarbonate; (b) removing a portion of said sodium bicarbonate from said solution to form a mother liquor comprising sodium carbonate and a reduced amount of sodium bicarbonate; (c) subjecting the mother liquor to electrodialytic water splitting by circulating the water liquor through an electrodialytic water splitter to produce a liquid reaction product comprising sodium carbonate substantially free of sodium bicarbonate; and (d) withdrawing the liquid reaction product comprising sodium carbonate substantially free of sodium bicarbonate from the electordialytic water splitter.

Abstract: An apparatus is disclosed for generating an acidified aqueous salt solution and an aqueous base in a multichamber two-compartment electrodialytic water splitter which comprises alternating bipolar and first cation permselective membranes and at least one additional substantially non-porous, water-swollen cation permselective or neutral membrane disposed between a cation face of the bipolar membrane and a face of said first cation membrane thereby defining at least two acid compartments and a base compartment positioned between an anode and a cathode.

Abstract: A process and apparatus for converting alkali metal sulfate values, such as sodium or potassium sulfate values in spent rayon spin bath liquors, into alkali metal hydroxide and alkali metal sulfate/sulfuric acid by using two- or three-compartment electrodialytic water splitter cells. The process and apparatus incorporate the features of: (a) feeding a liquid comprising water to the base compartment of an electrodialytic water splitter, (b) feeding a liquid comprising alkali metal sulfate values to the remaining compartments of the electrodialytic water splitter (c) passing current through said electrodialytic water splitter to produce liquid comprising alkali metal sulfate and sulfuric acid in one of the remaining compartments and a liquid comprising alkali metal hydroxide in said base compartment. The liquid fed to the acid compartments of two- and three-compartment cells may contain H.sub.2 SO.sub.4. When more than about 5 weight percent H.sub.2 SO.sub.