초록

Improved electrodialysis (ED) stacks are disclosed having one or more components selected from the group:

대표청구항 ▼

[ What is claimed is:] [1.] An electrodialysis stack comprising one or more components selected from the group consisting of:(a) cation exchange membranes comprising as exchange groups, in at least the surface portions of the cation exchange membranes which surface portions contact the fluid in the

[ What is claimed is:] [1.] An electrodialysis stack comprising one or more components selected from the group consisting of:(a) cation exchange membranes comprising as exchange groups, in at least the surface portions of the cation exchange membranes which surface portions contact the fluid in the diluting compartments of said stack, a predominant amount of sulfonic acid moities and a minor amount of weakly acid and/or weakly basic moities and anion exchange membranes comprising as exchange groups in at least the surface portions of the anion exchange membranes which surface portions contact the fluid in the diluting compartments of said stack, substantially only quaternary ammonium and/or quaternary phosphonium groups and substantially no primary, secondary and/or tertiary amine and/or no primary, secondary and/or tertiary phosphine groups and in which solvolytic and/or Lewis base decomposition of said quaternary ammonium and/or quaternary phosphonium groups leaves substantially no primary, secondary and/or tertiary amine and/or no primary, secondary and/or tertiary phosphine groups bound to said anion exchange membranes in at least said surface portions thereof;(b) cation exchange membranes comprising as exchange groups, in at least the surface portions of the cation exchange membranes which surface portions contact the fluid in the diluting compartments of said stack, a predominant amount of sulfonic acid moieties and a minor amount of weakly acid and/or weakly basic moieties and as a packing in at least some of the dilute compartments of said stack, ion exchange granules comprising in whole or in part cation exchange granules comprising as exchange groups in at least the surface portions thereof a predominant amount of sulfonic acid moieties and a minor amount of weakly acid and/or weakly basic moieties;(c) anion exchange membranes comprising as exchange groups in at least the surface portions of the anion exchange membranes which surface portions contact the fluid in the diluting compartments of said stack, substantially only quaternary ammonium and/or quaternary phosphonium groups and substantially no primary, secondary and/or tertiary amine groups and/or substantially no primary, secondary and/or tertiary phosphine groups and in which solvolytic and/or Lewis base decomposition of said quaternary ammonium and/or quaternary phosphonium groups leaves substantially no primary, secondary and/or tertiary amine groups and/or substantially no primary, secondary and/or tertiary phosphine groups bound to said membranes in at least said surface portions thereof and as a packing in at least some of the dilute compartments of said stack, anion exchange granules wherein the exchange groups which are in at least the surface portions of said anion exchange granules comprise substantially only quaternary ammonium and/or quaternary phosphonium groups and substantially no primary, secondary and/or tertiary amine and/or phosphine groups and in which solvolytic and/or Lewis base decomposition of said quaternary ammonium and/or phosphonium groups leaves substantially no primary, secondary and/or tertiary amine and/or phosphine groups bound in said surface portions of said granules;(d) as a packing in at least some of the dilute compartments of said stack, ion exchange granules comprising in whole or in part anion exchange granules consisting of one or more polymers having as anion exchange groups in at least the outer portions of said anion exchange granules moieties having the formula: [ STR 3 ] where R.sub.1 is an acryloxy ethyl, methacryloxy ethyl, 2-hydroxy-3-methacryloxy propyl, acrylamido neopentyl, methacrylamido neopentyl, acrylamido ethyl, methacrylamido ethyl, vinyl benzyl, methyl vinyl benzyl, ethyl vinyl benzyl, vinyl phenethyl, vinyl phenyl and/or vinyl menapthyl residue polymerized as part of said one or more polymers and where [ STR 4 ] is not a member of the group consisting of trimethyl ammonium, methyl diethanol ammonium, ethyl diethanol ammonium, triethanol ammonium, dimethyl ethanol ammonium and diethyl ethanol ammonium;(e) as a packing in at least some of the dilute compartments of said stack, ion exchange granules comprising in whole or in part ion exchange granules prepared from a mixture of non-polymerizable diluent and monomers having a relatively high proportion of crosslinking monomer and wherein water content of said granules is primarily determined by said non-polymerizable diluent in said mixture;(f) as a packing in at least some of the dilute compartments of said stack, ion exchange granules comprising in whole or in part anion exchange granules in which the concentration of anion exchange moieties is substantially greater in outer regions of said anion exchange granules than in inner regions and said anion exchange granules are selective to nitrate and/or chloride ions compared to sulfate ions in dilute solutions during electrodialysis at current densities substantially less than the limiting current density of said anion exchange granules in said dilute compartments;(g) as a packing in at least some of the dilute compartments of said stack, ion exchange granules comprising in whole or in part cation exchange granules in which the concentration of cation exchange moieties is substantially greater in the outer regions of said cation exchange granules than in the inner regions and said cation exchange granules are selective to sodium ions compared to calcium ions in dilute solutions during electrodialysis at current densities substantially less than the limiting current density of said cation exchange granules in said dilute compartment;(h) as a packing in at least some of the dilute compartments of said stack, ion exchange granules comprising in whole or in part cation exchange granules in which the concentration of ion exchange moieties is substantially greater in the outer regions of said cation exchange granules than in the inner regions, said cation exchange granules comprising as exchange groups in at least the surface portions of said outer regions a predominant amount of sulfonic acid moieties and a minor amount of weakly acid and/or weakly basic moieties.