Alliedsignal Inc.

Allied Corporation

Archer Daniels Midland Company

Krishnamurthy N Mani

Frederick P Chlanda

Yu-Chih Chiao

Carolyn Byszewski

John C McArdle

James M DiPalma

Yu-Chin Chiao

Yu C Chiao

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.

Electrodialysis water splitting process

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.

Ion exchange resin regenerant waste recovery and recycling via bipolar

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.

Electrodialytic water splitting process for removing SO.sub.2 from gases

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.

Separation/recovery of ammonium salts via electrodialytic water splitting

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.

Apparatus and method for electrodialytic treatment of salts to produce

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.

Electrodialysis of salts of weak acids and/or weak bases

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.

Method for purification of acids from materials comprising acid and salt

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.3 at unexpectedly high current efficiencies, and has particular utility in the area of regenerating stainless steel pickling acid mixtures comprising HF and HNO.sub.3.

Recovery of mixed acids from mixed salts

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.

Method for purification of bases from materials comprising base and salt

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.

Method and apparatus to control a salt stream to be treated in an

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.

We have discovered an improved, energy efficient method for recovering and regenerating acid from a solution comprising acid and salt. The process comprises of the steps of supplying a solution comprising salt and a first concentration of acid to a first compartment of an electrodialysis apparatus comprising a first compartment and a second compartment, supplying a liquid comprising water to the second compartment, applying a direct current to the electrodialysis apparatus to form, in the first compartment, a first product comprising salt and a second concentration of acid, the second concentration of acid being less than the first concentration of acid, and, in the second compartment, a second product comprising water and enriched in acid by a proportionate amount, recovering the first product, recovering the second product, recovering acid from the first product using electrodialytic water splitting to convert at least a portion of the salt to a third product comprising acid, and recovering the third product. The process has particular utility for the recovery and regneration of mixed acids from spent pickle liquors containing free nitric acid and salts of an anion other than nitrate anion.

Recovery of acids from materials comprising acid and salt

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. In preferred embodiments, a subterranean deposit of trona is solution mined with a Na.sub.2 SO.sub.4 /H.sub.2 SO.sub.4 solution thereby converting the trona into CO.sub.2 and an aqueous solution (reaction liquid) of Na.sub.2 SO.sub.4, optionally containing NaHCO.sub.3, which is pumped to the surface and supplied to a water splitter to wherein a Na.sub.2 SO.sub.4 /H.sub.2 SO.sub.4 solution is regenerated and aqueous NaOH is produced. The regenerated Na.sub.2 SO.sub.4 /H.sub.2 SO.sub.4 may be reinjected into the trona deposit and the NaOH may be concentrated or optionally used to convert trona into soda ash.

Solution mining of sodium minerals with acids generated by

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. Gaseous SO.sub.2 can then be recovered from the aqueous SO.sub.2 values. A liquid comprising water and at least a portion of the aqueous sodium values in the aqueous Na.sub.2 SO.sub.4 is transfered to a base compartment of the electrodialytic water splitter to produce a liquid comprising aqueous NaOH. The aqueous solution comprising NaOH can then be recovered from the base compartment.

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Basking Ridge, NJ, United States of America

Krishnamurthy N Mani