Abstract: 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.

Abstract: 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.

Abstract: 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.

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: 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.

Abstract: 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.

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 salts. The method is conducted in an apparatus comprising a cation membrane between two bipolar membranes.

Abstract: 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.

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

Abstract: Permselective membranes are disclosed which comprise a layer comprising polystyrene, at least a portion of which is sulfonated, and between about 10 wt. % and about 35 wt. % monovinyl arene-hydrogentated diene block copolymer, at least a portion of which is sulfonated. The membranes exhibit a resistance of less than about 8 .OMEGA.-cm.sup.2 in 7 wt. % Na.sub.2 SO.sub.4 and an ion exchange capacity of between about 1.0 meq/g and about 1.6 meq/g. Monopolar and bipolar membranes comprising the layer are disclosed. A preferred process for forming the membranes comprises the steps of sulfonating polystryene and monovinyl arene-hydrogenated diene block copolymer, forming a mixture of the materials in a solvent, forming a layer of the mixture and drying the layer to form at least a portion of the membrane.

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.