Allied Corporation

Alliedsignal Inc.

Allied Chemical Corporation

The Graver Company

Frederick P Chlanda

Krishnamurthy N Mani

Kang-Jen Liu

Yu-Chih Chiao

Krishnamurthy Nagasubramanian

Lester T Lee

Jian-Ping Huang

Gerald J Dege

Robert S Cooke

Christopher Andreola

Yu-Chin Chiao

Ming J Lan

The present invention relates to ion exchange membranes comprising soluble graft copolymer comprising a backbone of a first polymer having a main chain containing aromatic rings and a polymerizable vinyl or ring containing compound which contains at least one functional group which displays ion exchange functionality or may be converted to display ion exchange functionality, which is grafted onto said first polymer on at least one of said aromatic rings or on at least one benzylic carbon atom of said aromatic rings. The copolymer components may be selected to produce membranes for a variety of uses including electrodialytic processes such as electrodialytic concentration and separation processes, electrodialytic water splitting, electrolysis or electrolytic splitting of water and fuel cells for electrical generation; and pressure or chemical potential driven membrane processes such as ultrafiltration, reverse osmosis, piezodialysis, diffusion dialysis and pervaporation. The ion exchange membranes of the present invention display excellent mechanical properties, electrical and mechanical stability to oxidizing acids, good permselectivity and resistance to fouling. Process for making said graft copolymers, and process for making specific graft copolymers are also disclosed.

Process for producing ion exchange membranes, and the ion exchange

The present invention discloses permselective membranes comprising at least one layer formed from an arylenedialkylidene polymer at least a portion of which is sulfonated, said arylenedialkylidene polymer comprising recurring monomeric units as shown by the formula: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are alkyl having one to four carbon atoms; wherein A and B are different; A is selected from the group consisting of ##STR2## wherein R.sub.x is hydrogen or an alkyl having 1 to 4 carbon atoms, R.sub.5 is alkylidene of 1-4 carbon atoms or oxyalkylene of 1-4 carbon atoms; B is derived from the group consisting of benzene, naphthalene, thiophene, and aromatic compounds of the formula ##STR3## wherein R.sub.6 is selected from the group consisting of alkylidene of 1-4 carbon atoms, oxyalkylene of 1-4 carbon atoms, --O--, --S--; R.sub.7 and R.sub.8 may be the same or different and may be H or methyl; and n is a number sufficient to provide a copolymer having a molecular weight sufficient to form a film. Processes for making said membranes and their use as ion exchange membranes are also disclosed.

Arylenedialkylidene polymers for high performance ion exchange membranes

The present invention relates to an improved apparatus of the type containing membranes which are selectively permeable to ion transport and a related method. The apparatus comprises at least one guard membrane located adjacent to a first membrane. A conductive bridge is formed between the guard and first membrane, either by adding an adhesive layer between the membranes or by treating the surface of the guard membrane. The adhesive layer between the guard and first membranes is preferably highly water swollen. The apparatus comprises at least one unit cell comprising at least one first membrane and one guard membrane which are held together by a static ionically conductive layer or interface. The guard membranes of the present invention are particularly useful in weak acid systems and prevent the formation of a non-conducting layer which greatly increases potential across the cell.

Guard membranes for use in electrodialysis cells

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 relates to an improved apparatus of the type containing membranes which are selectively permeable to ion transport and a related method. The apparatus comprises at least one guard membrane located adjacent to a first membrane. The apparatus comprises at least one unit cell comprising at least one first membrane having at least one ion selective layer selected from the group consisting of an anion selective layer and cation selective layer. There is at least one separate guard membrane adjacent to at least one first membrane.

The present invention is directed to a process for the separation of an aqueous solution of at least one amphoteric compound from an aqueous feed comprising the amphoteric compound including amino acids, and at least one salt. The process is conducted in an apparatus comprising at least one cell. The cell comprises at least one bipolar membrane each of which comprises a cation layer and an anion layer. Cells useful in the process of the present invention include arrangements with the bipolar membrane in combination with at least one cation membrane and/or at least one anion membrane.

Electrodialytic treatment of aqueous solutions containing amino acids

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.

Bipolar membranes are disclosed which exhibit high permselectivity, good mechanical strength, ability to operate at high current density, low potential drop and long-term stability. Essential to the production of bipolar membranes with these properties is the construction of the interface layer, which includes a matrix material containing quaternary and non-quaternary amine groups and having dispersed therein a cation exchange resin. A number of additional important characteristics are disclosed directed to the construction of the anion and cation layers of the bipolar membranes. A preferred method for forming bipolar membranes by casting layers on top of one another is also disclosed.

Bipolar membranes and methods of making same

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.

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Rockaway, NJ, United States of America

Frederick P Chlanda