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US 5,006,211 AGranted
Electrodialylic water splitting process for the treatment of aqueous electrolytes
AssigneePulp and Paper Research Institute of Canada
InventorsMichael Paleologou, Richard M. Berry
Life of this patent
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Abstract
A process for dealkalization or acidification of aqueous salt solutions or for the splitting of the salt of such solutions employs a water splitting system of bipolar membranes in conjunction with ion selective membranes; a two component cell employs cation permselective membranes to define acid and base compartments with the bipolar membranes, and a three compartment cell employs anion permselective and cation permselective membranes to define with the bipolar membrane salt, acid and base compartments; the process has particular applicability to the dealkalization of a monosodium peroxide solution containing sodium hydroxide produced in a hydrogen peroxide generator.
Claims34
a process which comprises the steps of
- (a) providing a cell comprising an anode, a cathode and at least two compartments therebetween defined at least in part by a cation permselective membrane and at least a pair of bipolar membranes, said bipolar membranes having an anion side facing said anode and a cation side facing said cathode,
- (b) feeding an aqueous alkaline solution comprising monosodium peroxide and sodium hydroxide into a first of said compartments to contact a first side of said cation permselective membrane,
- (c) feeding a liquid comprising water into a second of said compartments to contact an anion side of a said bipolar membrane,
- (d) passing a direct current through said cell between said anode and cathode to effect:
- (i) migration of sodium cations from said first compartment through said cation permselective membrane into said second compartment, and
- (ii) splitting of water by said bipolar membrane of said second compartment with accumulation of hydroxide ions of the water in said second compartment and removal of hydrogen ions of the water from aid second compartment,
- (e) removing accumulated NaOH from said second compartment, and
- (f) removing accumulated dealkalized monosodium peroxide solution from said first compartment.
5 more elements
A process for the dealkalization of an aqueous alkaline alkali metal peroxide solution comprising:
- (a) establishing an electrolytic cell comprising an anode, a cathode and a plurality of membranes therebetween, said plurality of membranes including spaced apart bipolar membranes and a cation permselective membrane disposed between each pair of bipolar membranes, said bipolar membranes each having an anion side facing said anode and a cation side facing said cathode, and a plurality of side-by-side compartments defined between adjacent membranes of said plurality,
- (b) feeding an aqueous alkaline solution of a salt MX and a hydroxide MOH, in which M is an alkali metal cation and X is an anion of an acid into a first compartment of said plurality to contact a first side of a said cation permselective membrane,
- (c) feeding a liquid comprising water into a second compartment of said plurality to contact an anion side of a said bipolar membrane,
- (d) passing a direct current through said cell between said anode and cathode to effect:
- (i) migration of said cation M from said first compartment through said cation permselective membrane into said second compartment,
- (iii) splitting of water by said bipolar membrane of said second compartment with accumulation of hydroxide ion of the water in said second compartment and removal of hydrogen ions of the water from said second compartment
- (e) removing accumulated MOH from said second compartment, and
- (f) removing accumulated dealkalized MX from said first compartment.
5 more elements
A process which comprises the steps:
- (a) feeding an aqueous alkaline alkali metal salt solution of NaHO.sub.2 and NaOH into each acid compartment between a cation membrane and a cation side of a bipolar membrane of an electrodialytic water splitter comprised of alternating cation and bipolar membranes positioned between an anode and a cathode;
- (b) feeding into each base compartment between a cation membrane and an anion side of a bipolar membrane, a liquid comprising water;
- (c) passing a direct current through said water splitter thereby causing dealkalization or acidification of said aqueous alkaline alkali metal salt solution and basification of said liquid comprising water through transfer of sodium cations from said aqueous alkaline alkali metal salt solution to said liquid comprising water,
- (d) bleeding form the base compartments a liquid comprising aqueous sodium hydroxide,
- (e) bleeding from the acid compartments a dealkalized or acidified aqueous NaHO.sub.2 solution.
2 more elements
A process which comprises the steps:
- (a) feeding an aqueous alkaline or nonalkaline solution of an alkali metal and/or non-metal salt into a three compartment water splitter composed of alternating cation, bipolar and anionic membranes, said solution being introduced into each salt compartment between a cation membrane and an anion membrane;
- (b) feeding a liquid comprising water into each base compartment, between a cation membrane and an anion side of a bipolar membrane,
- (c) feeding into each acid compartment, between an anion membrane and a cation side of a bipolar membrane, a solution of alkali metal and/or non-metal hydroxide of a concentration equivalent to a desired concentration of a salt to be produced;
- (d) passing a direct current through said water splitter thereby causing transfer of alkali metal cations from said solution of a salt to the base compartment thereby causing basification of said liquid comprising water and in addition causing the transfer of hydroxide anions and anions of the salt to the acid compartment thereby causing the formation of water and the acid of the anion of the salt, said acid reacting with the added alkali metal hydroxide in said acid compartment to produce the salt of the anion and water;
- (e) bleeding from the salt compartments a partially dealkalized and depleted aqueous salt solution,
- (f) bleeding from the base compartments a liquid comprising aqueous alkali metal hydroxide;
- and
- (g) bleeding from the acid compartments a dealkalized salt solution.
5 more elements
Dependencies are inferred from the claim text.