US3748238A - Electrolytic process for the preparation of sodium hydrosulfite - Google Patents

Electrolytic process for the preparation of sodium hydrosulfite Download PDF

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US3748238A
US3748238A US00251293A US3748238DA US3748238A US 3748238 A US3748238 A US 3748238A US 00251293 A US00251293 A US 00251293A US 3748238D A US3748238D A US 3748238DA US 3748238 A US3748238 A US 3748238A
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catholyte
chamber
sodium
anolyte
cathode
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A Heit
J Williamson
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Lanxess Sybron Chemicals Inc
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/14—Alkali metal compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/64—Thiosulfates; Dithionites; Polythionates
    • C01B17/66—Dithionites or hydrosulfites (S2O42-)

Definitions

  • the spongy, porous lead electrode which makes the cathodic reduction of the bisullite ion feasible in the electrodialytic apparatus, is produced from the alkali metal plumbities in an electrodialytic apparatus having an anode chamber and at least one cathode chamber adjacent the anode chamber with designated ion migrating means (membranes) positioned between the anode and cathode chambers.
  • the bisuliite ion reduction to hydrosultite anion is carried out in the same electrodialysis apparatus as, or an electrodialysis apparatus similar to, the apparatus used to produce the spongy, porous lead electrode.
  • This invention relates generally to electrodialysis, and more particularly, to a method and apparatus for the electrodialytic preparation of hydrosultes from bisultes. It also relates to a new and novel electrode and to an electrodialytic method of producing an electrode from plumbite anion.
  • hydrosulites a term which is interchangeable herein with the term dithionites, hydrosulte salts or dithionite salts, have found great commercial use due to their powerful reducing action ⁇ on many materials.
  • the dithionites readily reduce several metal ions to the metal, disulde linkages in wool and hair, many nitro compounds and many dyes. Principal applications are in various textile operations, such as dyeing, printing and stripping. Dithionites are also used for bleaching of ground wood pulp, soap, sugar, molasses and glue.
  • the ionic equation for the electrodialytic preparation of hydrosulte ion from bisulite ion is wherein H803- represents bisulte ion and S2052 represents hydrosulte ion.
  • the chemical equation for the electrodialytic preparation of sodium hydrosuliite is One chemical method for the production of sodium hydrosulte is carried out in accordance with the following two equations where liquid sulfur dioxide is reacted with zinc dust slurried in water to produce zinc hydrosuliite which is converted to the sodium salt by means of caustic soda:
  • the chemical method is characterized by an excessive number of steps which are uneconomical to carry out and which tend to expose the sodium dithionite, Na2S2O'4, to air and thereby cause rapid oxidation of the dithionite to the metabisuliite since the dihydrate is generally the form which crystallizes from solution and since the dihydrate rapidly yoxidizes in air to the metabisulte.
  • the preferred cathode is a mercury cathode which is continuously stirred (Patel et al., Proc. Natl. Inst. Sci. India 15, 131 (1949)).
  • Electrodialytic cells having cation permselective membranes dividing the cell into an anolyte chamber and a catholyte chamber are known in the art.
  • U.S. Pat. No. 2,731,408 and U.S. Pat. No. 2,978,402 disclose such electrodialytic cells. These electrodialytic cells are characterized by the presence of graphite and/ or steel electrodes. Silver-lead electrodes are disclosed in U.S. Pat. No. 3,607,694. Lead electrodes are commonly used and prepared in electrolytic lead rening by the Betts process wherein base lead bullion is electrolytically refined to produce a pure lead cathode.
  • the anodes are the cast lead bullion, the electrolyte is a solution of lead uosilicate and tluosilicic acid.
  • cathode starting sheets are made from pure electrolytic lead, and the lead is deposited upon the cathodes in the electrolytic chamber.
  • the cathode starting sheet made from pure lead and the electrolytically deposited lead are solid, non-porous lead bodies. This type of electrode is a standard electrode.
  • standard electrode we mean those electrodes which are found in the prior art and which are made from such materials as steel, zinc, tin, mercury, graphite, non-porous lead, silver-lead alloy, platinum-lead alloy and the like.
  • the apparatus is adapted for passage of di-rect electric current between the anode and the lead shot cathode, and the apparatus has been specifically adapted to the production of adiponitrile from acrylonitrile.
  • the surface area of the electrode is increased by the addition of conductive bodies thereto, the area of the electrodes and in particular the area of the cathode is insuliicient to provide a suicient current density for certain applications where a low unit area current density is required, such as, in the electrodialytic preparation of dithionites from bisultes.
  • the electrode formed thereby is not essentially a single, unit electrode body, but is a conglomeration of small electrode bodies the effectiveness of which depends upon the contact each particle thereof establishes with every other particle and with the standard electrode body.
  • particulate bodies when particulate bodies are used in chambers as electrodes, they have diminished conductivity of electrical current due to dependence upon contact of particle with particle and particle with standard electrode when compared with the conductivity of a continuous or non-particulate conductive body.
  • Still another object of this invention is to provide a single, continuous lead electrode capable of substantially filling an electrolytic or electrodialytic chamber.
  • Another object of this invention is to provide a continuous lead electrode which will permit the circulation of electrolyte within the chamber of an electrolytic or electrodialytic apparatus, said chamber being substantially filled With the lead electrode.
  • dithionite may be prepared from bisullte in an electrodialytic apparatus having at least one anolyte (anode) chamber, at least one catholyte (cathode) chamber adjacent said anolyte chamber, a cation permselective membrane between said anolyte chamber and said catholyte chamber, said catholyte chamber having a spongy, porous, continuous lead cathode substantially defined by the Walls of said catholyte charnber and said anolyte chamber having an anode, and a suitable power source.
  • Each chamber has inlet and outlet means and means for circulating a Huid medium therethrough.
  • a bisulte-containing solution maintained at less than about 30 C. is circulated through the catholyte chamber of the electrodialytic apparatus, and an acid electrolyte solution is circulated through the anolyte chamber.
  • hydrosulite dithionite
  • hydrosulite cathodically produced from the bisulte in the bisulite-containing solution in the catholyte chamber having the continuous, spongy, porous lead electrode.
  • the continuous, spongy, porous lead electrode is formed as a cathode in an electrodialytic cell having at least one anolyte chamber, at least one catholyte chamber adjacent said anolyte chamber and ion migrating means acting as a barrier to fluid media between said anolyte and catholyte chambers.
  • a plumbite or plumbate salt solution is circulated through the catholyte chamber, and a caustic solution capable of supplying an alkali metal cation to the catholyte chamber is circulated through the anolyte chamber.
  • a spongy, porous lead metal is electrolytically deposited at the cathode until the catholyte chamber is substantially filled with a porous, spongy lead metal.
  • this deposited electrode is a continuous body with the standard electrode initially placed within the chamber, the deposit is suciently porous to permit the passage or circulation of solution through the chamber Without interruption of the ilow therethrough.
  • substantially lled we mean placing or forming the electrode in the chamber in such a way that the spongy, porous lead electrode occupies either all or nearly all the volume of the chamber.
  • the continuous, porous lead electrode (cathode) deposited in the catholyte chamber may be left in situ, properly washed, and the apparatus may be used for electrodialytic synthesis, purification and/or separation.
  • the continuous, porous lead deposit although somewhat fragile, may be carefully removed from the catholyte chamber of the electrodialytic apparatus and may be used as an electrode in various other chambers as a substitute for a standard electrode or in another electrodialytic apparatus for the preparation of dithionites.
  • a spongy, porous lead electrode is defined herein as the electrode prepared by the electrodialytic process of this invention.
  • porous lead electrode of the present invention may be regenerated by electrodialytic treatment with caustic solutions when the porous lead electrode becomes fouled and thereby reduces the eiective surface area of the electrode which in turn increases the unit area current density.
  • the contents of the reservoir in communication with the catholyte chamber may be protected from atmospheric oxidation effects by establishing a layer of inert liquid hydrocarbon on the surface of the contents of the reservoir vessel.
  • FIG. 1 is a diagrammatic representation of a longitudinal cross-section of an electrodialytic cell illustrating pertinent ion formation and transfer for the formation of dithionite ion therein.
  • FIG. 2 is a diagrammatic representation of a longitudinal cross-section of a two-chambered electrodialytic cell illustrating the formation and transfer of ions pertinent to the formation of the spongy, porous lead cathode.
  • FIG. 3 is a diagrammatic representation of longitudinal cross-section of a tWo-chambered electrodialytic cell illustrating the spongy, porous lead cathode formed in the catholyte chamber.
  • PIG. 4 is a diagrammatic representation of a longitudinal cross-section of a three-chambered electrodialytic cell having two spongy, porous lead cathodes in two catholyte chambers and one anolyte chamber.
  • FIG. 5 is a diagrammatic representation of a longitudial cross-section of an electrodialytic cell having multiple anolyte and catholyte chambers sharing anode and cathodes respectively.
  • FIG. 6 is a diagrammatic representation of a longitudinal cross-section of a two-chambered electrodialytic cell in communication with a circulating system including pumps and reservoirs.
  • FIGS. 1-6 in the accompanying drawings there is shown a cell frame, 2, preferably of plastic construction, which partially defines the outer portions of the appaartus.
  • Numerals 4 and 6 represent electrodes, the numeral 4 being used to designate the cathode and the numeral 6 being used to designate the anode.
  • both the anode and the cathode are prepared from lead sheet material which partially defines the respective chambers in which they are located.
  • Ion migrating means designated by numeral 8 is an ion exchange membrane of the type which will permit the passage of cations therethrough and is located between cathode 4 and anode 6 in such a way that it separates the cell into chambers designated as catholyte chamber and anolyte chamber 22.
  • the cell construction of a two-chambered apparatus as shown in FIGS. 1, 2, 3 and 6 comprises a cathode, catholyte chamber, ion migrating means, anolyte chamber and an anode within a suitable cell frame. Provisions must be made in each chamber for the entrance and exit of the circulating electrolyte.
  • catholyte chamber 20 catholyte enters the chamber at inlet or opening 12 and leaves the chamber at opening or outlet 14.
  • Anolyte enters the anolyte chamber 22 at inlet 10 and leaves chamber 22 at outlet 16.
  • hydrosulite or dithionite formation is shown in ionic form when a bisuliite-containing solution is used as the catholyte, and sulfuric acid is used as the acid anolyte solution. Ionic decomposition of water is also shown in the chambers of the apparatus of FIG. 1.
  • FIG. 2 the ionic formation of the spongy, porous lead electrode is shown when plumbite ion-forming solutions are reduced to elemental lead at the cathode.
  • the plumbite-containing solution is circulated in the presence of a caustic solution in the catholyte chamber while a caustic solution such as an aqueous alkali metal hydroxide solution is circulated in the anolyte chamber.
  • Ionic decomposition of water is shown in both chambers of FIG. 2.
  • aqueous sodium plumbite is circulated in the anolyte chamber while a dilute aqueous sodium hydroxide solution is circulated in the contiguous anode chamber.
  • a suitable power source such as a direct current source
  • a mass of spongy, porous lead is deposited at the cathode until the catholyte chamber is substantially filled with the spongy, porous lead. It is important in the practice of the present invention that substantially uninterrupted circulation of the catholyte liquor be carried out while the current is imposed across the electrodes.
  • This electrolytic deposition of spongy, porous lead upon the initial single sheet-like rod, disc or strip electrode greatly increases the cathodic area beyond the planar or cylindrical nature of the original electrode. Due to the nature of the deposition of the lead in the catholyte chamber the deposited lead is also characterized by porosity which permits the flow of catholyte or any electrolyte liquor therethrough and gives the electrode a spongy property.
  • FIG. 3 illustrates an electrodialytic apparatus having a spongy, porous lead electrode designated by numeral 18 deposited throughout catholyte chamber 20.
  • the spongy, porous nature of the lead deposited at the cathode and substantially lling the catholyte chamber permits catholyte liquor or any other suitable electrolyte to pass through opening 12 into catholyte chamber 20 and out opening 14.
  • Lead may be deposited at the cathode in the form of a spongy, porous deposit until the current imposed across the electrodes ceases.
  • By control of current, deposit of spongy, porous lead can be stopped at any time during deposition to provide an electrode body having any amount of spongy, porous lead deposited thereon.
  • a porous lead electrode having almost any shape or form desired can be produced by varying the shape of the catholyte chamber in the electrodialytic cell. This may be accomplished in view of the fact that the spongy, porous lead electrode is defined by the walls of the catholyte chamber when the electric current is imposed across the electrodes for a sufiicient time, and there is suicient catholyte liquor circulated through the catholyte chamber during the imposition of current.
  • the plumbite-containing solution can be drained from the catholyte chamber, and the spongy, porous lead electrode can be removed from the chamber.
  • the porous lead cathode prepared in the catholyte chamber remain in situ and that the catholyte solution as well as the anolyte solution be removed from the respective chambers followed by suitable rinsing of the chambers with water to remove residual electrolytes.
  • a bisuliite salt containing solution is circulated in the catholyte chamber and an acid electrolyte solution is circulated through the anolyte chamber.
  • Dithionites are formed when an electrical current is imposed across the spongy, porous lead cathode and the anode.
  • the spongy, porous lead electrode which substantially fills the catholyte chamber.
  • the spongy, porous lead cathode permits high planar current density and consequently, short residence time of the circulating liquor.
  • the sponge lead electrode may accumulate lead sulfide formed as a side reaction, and thereby decrease the activity of the dithionate formation within the chamber.
  • circulation of a sodium hydroxide solution through the catholyte compartment under an imposed potential will remove the lead sulfide and restore full activity in situ, without necessity of cell disassembly.
  • About a 2 N aqueous solution of sodium hydroxide is suitable for removing the lead sulfide accumulation.
  • This regeneration of the sponge lead electrode is represented by the reaction of sodium hydroxide and lead sullide to form sodium plumbite which under the imposed potential re-deposits the lead at the cathode.
  • Any suitable caustic solution which forms a soluble plumbite salt, in the presence of lead sulfide may be used as cathode regenerant.
  • One skilled in the art can select a suitable concentration range for the caustic solution.
  • sodium bisulfite is circulated in an aqueous solution at less than about 30 C. in the catholyte chamber of the electrodialytic apparatus containing the spongy, porous lead cathode.
  • the sodium bisuliite may be made available by either dissolution of sodium metabisultite in water in accordance with the following equation:
  • bisulfite or sodium metabisulte are the preferred bisultite salts for the formation of dithionite salts of the present invention
  • other bisulfite salts such as, the potassium salt, the magnesium salt, the zinc salt, and the like or mixtures thereof may be converted to their corresponding hydrosulites or dithionites.
  • the bisuliite salt of the present invention must be water-soluble or partially soluble in water and when used as catholyte, it is used as an aqueous solution.
  • a bisuliite salt-containing solution is any bisulte salt or bisulte salt precursor capable of forming a bisulfite salt, dissolved completely or partially in fwater.
  • the pH of the circulating bisuliite salt-containing solution may be of from about 2.5 to 6.0, it is preferred that the pH be from about 3.0 to about 4.5 for the cathodic reduction of the bisuliite ion to the hydrosulte ion.
  • the hydrosulfite or dithionite is totally unstable at a pH below about 2.0 having a half-life depending upon the degree of acidity, measurable in minutes or seconds.
  • the hydrosulte exhibits maximal Istability at a pH range of from about 7 to l0, but at a pH of about 7 to 10 the catholyte solution is essentially a solution of sodium sulte which is cathodically reduceable, but yields substantial quantities of sodium sulfide. Accordingly, to prevent high yields of sodium sulfide the pH of the circulating catholyte solution should be less than about 7.0.
  • the anolyte liquor used in the preparation of the dithionites is preferably a dilute sulfuric acid solution containing about (by Weight) sulfuric acid in water.
  • suitable concentrations of sulfuric acid which may be used as the anolyte liquor may be selected by one skilled in the art.
  • sulfuric acid When sulfuric acid is used as the anolyte, the sulfuric acid breaks down into hydrogen ion, bisulfate ion and sulfate ion.
  • the hydrogen ion migrates from the anolyte chamber into the catholyte chamber through the cation permselective membrane disposed between the two chambers.
  • aqueous sulfuric acid solution is the preferred anolyte liquor in the preparation of the dithionites
  • other aqueous acid electrolyte solutions such as phosphoric acid
  • One ,skilled in the art can select a suitable acid electrolyte solution and concentration for circulation as anolyte liquor.
  • the temperature of the catholyte liquor be maintained at temperatures of about 20-25 C. and at no time in excess of 30 C. Although temperatures lower than 20 C. may be used, it is preferred that the lowest operating tem perature be about 20 C. At temperatures in excess of 25 C., and particularly in excess of 30 C., extreme precaution must be exercised because of the thermal instability of the dithionites, particularly at the membrane interface where hydrogen ion enters the catholyte liquor and forms hydrosulfurous acid. At temperatures of 25 C. or less the possibility of thermal instability is substantially decreased.
  • hydrosuliite or dithionite salt formed by the cathodic reduction of the aqueous bisuliite salt-containing solution is designated herein as hydrosulte, hydrosulite salt or aqueous hydrosulte salt solution.
  • sodium plumbite be circulated as the catholyte liquor in the presence of an aqueous solution of sodium hydroxide or other suitable alkali metal, alkaline earth metal hydroxide or caustic solution and the like.
  • Sodium plumbite Na2PbO2 or Na2[Pb(OH)4] can be formed or prepared from lead monoxide and sodium hydroxide.
  • any of the other corresponding alkali metal hydroxides or alkaline earth metal hydroxides and the like may be used with lead monoxide (litharge), PbO, to form the corresponding water-soluble plumbite salt.
  • any water-soluble plumbite salt, plumbate salt, or a suitable source therefor and mixtures thereof may be used in the formation of the sponge lead electrode of the present invention and as used herein a plumbite salt, alkali metal plumbite salt, alkaline earth metal plumbite salt or any other plumbite salt source is designated as a plumbite salt.
  • Alkali metal plumbate salt, alkaline earth metal plumbate, plumbate salt or any other plumbate salt source is referred to herein as plumbate salt.
  • Critical to the process of the present invention is the 'water solubility or partial water solubility of the plumbite or plumbate salt.
  • the anolyte solution used in the apparatus during the preparation of the spongy, porous lead electrode is preferably an alkali metal hydroxide, or carbonate, such as,
  • caustic solution refers to any suitable alkali or alkaline earth metal hydroxide or carbonate and the like, including mixtures thereof normally used in electrodialysis as electrolyte solutions.
  • a dilute aqueous solution of the caustic material may be used in the anolyte solution, it being preferred that about 2 N sodium hydroxide solution (in water) be used as the anolyte liquor, when sodium hydroxide is used as the anolyte liquor.
  • a concentration of the caustic lsolution or alkali metal hydroxide suitable for use in the anolyte liquor may range from about 0.5 N to 3.0 N, it being within the purview of one skilled in the art to select the proper caustic solution at the proper concentration.
  • the ion migrating means which separates anolyte and catholyte chambers used in the preparation of the dithionites can be any material which selectively permits the passage of cations in the direction of the cathode and rejects the passage of anions in the direction of the anode. This role is filled by cation exchange membranes. Cation exchange (cation permselective) membranes are also preferred and recommended as the ion migrating means in the production of the spongy, porous lead electrodes. Cation permselective membranes minimize excessive diffusion of the oxidation sensitive dithionite (hydrosulte) and bisulte anions and yet permit hydrogen ion or other cation to reach the catholyte chamber.
  • the ion migrating means used to separate the anode and cathode chambers of the electrodialytic apparatus used to prepare the spongy lead electrode may be cation permselective or non-selective (neutral).
  • the ion migrating means can be any material which selectively permits the passage of cations in the direction of the cathode and may be designated as cation migrating means.
  • a neutral membrane is a membrane Which permits the migration of anions and cations.
  • the neutral membrane is the ion migrating means between anode and cathode chambers in the electrodialytic apparatus used to prepare the spongy, porous lead electrode
  • the predominance of hydroxyl ion and its superior mobility in the catholyte solution there is a preferential transport of the hydroxyl ion and an opportunity for a significant amount of reduction of the plumbite or plumbate ion to elementary lead.
  • the standard electrodes provided in the electrodialytic apparatus of the present invention may be any suitable conductive material and may be selected by one skilled in the art.
  • Examples of electrode material are graphite, several lead alloys including a silver-lead and a platniumlead alloy, lead, steel, zinc and the like.
  • the cathode upon which the spongy, porous lead electrode is deposited from the plumbite-containing solution can be any conductive material which will form an intimate contact with the spongy, porous lead which deposits thereon.
  • the electrodes may assume several varying shapes such as sheets, strips or cylinders it is preferred in the practice of the present invention that the electrodes assume the shape of rectangular sheets and thereby deline one Wall of the chamber in which it is located.
  • Cell construction may be varied such that a single electrode series as the electrode for two contiguous or adjacent chambers having electrodes of the opposite charge, such as, the single anode source shown in the three-chambered cell of FIG. 4.
  • FIG. 4 Another embodiment of the present invention is represented in FIG. 4 where a three-chambered apparatus having two catholyte chambers designated by numeral 20 which are filled with a porous lead cathode designated by numeral 18 previously deposited upon cathodes designated by numeral 4 a-nd one anolyte chamber designated by the numeral 22 having an anode designated by number 6,
  • the two catholyte chambers are separated from the centrally located single anolyte chamber by two ion migrating means designated by numeral 8 which are preferably a cation permselective membrane, and a single anode serves as the anode source for two cathodes.
  • anolyte is circulated in anolyte chamber 22 while catholyte is circulated in catholyte chambers 20.
  • the electrical current is imposed across the electrodes cathodic reduction of the bisulte takes place in the two catholyte chambers.
  • the spongy, porous lead cathodes are formed in the three chambered apparatus of FIG.
  • anolyte chamber 22 is common to both of the adjacent catholyte chambers designated by numeral 20, and when an electrical current is imposed across the electrodes the spongy, porous lead deposits upon the cathodes by cathodic reduction of the plumbite salts, in both chambers simultaneously.
  • FIG. 5 represents still another embodiment of the present invention showing a stack of two-chambered electrodialytic cells in which, except for the end chambers, a single electrode is common to two chambers.
  • an apparatus such as the one designated in FIG. 5, there is a maximum utilization of the electrode surfaces of all electrodes except those positioned at both ends of the cell where only one surface of the electrode is used, and as shown in FIG. 5, cathode 4 is the electrode positioned at each end of the stack.
  • FIG. 5 may be stacked to include up to 3() or more chambers having the configuration of cathode, catholyte chamber, cation permselective membrane, anolyte chamber, anode, anolyte chamber, cation permselective membrane, catholyte chamber, cathode, catholyte chamber, cation permselective membrane, anolyte chamber, etc.
  • FIG. 5 illustrates a stack of two-chambered electrodialytic cells starting with the cathode and catholyte chamber, it is within the purview of one skilled in the art to produce a stack of two-chambered cells wherein the first members of the stack are an anode and anolyte chamber.
  • a single anode is common to two anolyte chambers and a single cathode source serves two catholyte chambers having spongy, porous lead electrodes.
  • a cathode source is used herein to define the standard cathode upon which the spongy, porous lead metal is deposited.
  • FIG. 6 we have shown a complete circulating system feeding a two-chambered electrodialytic apparatus, the numerals of which designate the same elements of the cells in FIGS. 1-5 above.
  • two reservoirs are provided one for the anolyte chamber designated as reservoir 30, and one for the supply of the catholyte chamber designated as reservoir 40.
  • Reservoir 30 contains water and sulfuric acid during the cathodic reduction of the bisulfite containing solution and reservoir S) contains water, the bisulte containing solution such as sodium bisulfite, and the dithionite produced as a result of the cathodic reduction of bisulte and shown in reservoir 40 as sodium dithionite.
  • a pump designated by numeral 42 removes the aqueous solution from reservoir 40 by a conduit 41 and forces the solution removed from reservoir 40 into catholyte chamber 20 at inlet 12 through conduit 44.
  • This catholyte solution or liquor comprising water and sodium bisulte initially, and, after cathodic reduction, water, sodium bisulfite and sodium dithionite, passes through the catholyte chamber containing the sponge lead cathode where it is subjected to cathodic reduction.
  • the electrolyte liquor from reservoir 40 then passes from catholyte chamber 20 through catholyte chamber outlet 14 into conduit 46 where it returns to reservoir 40 for recirculation and further cathodic reduction.
  • a layer designated by numeral 48 is shown covering the catholyte liquor of reservoir 40'.
  • Layer 48 represents a hydrocarbon or other inert material which will not react with the catholyte liquor but which will prevent air from entering or contacting the catholyte liquor.
  • Kerosene is one of the preferred hydrocarbons which may be used in layer 48.
  • Other hydrocarbons which may be used in the layer are mineral oil, number 2 fuel oil, and the like.
  • One skilled in the art can select a suitable hydrocarbon to prevent exposure of the liquor to air.
  • Catholyte liquor passing from catholyte chamber 20 through conduit 46 into reservoir 40 is preferably admitted to reservoir 40 beneath layer 48 so that the catholyte liquor is not exposed to air. It is also deemed within the purview of one skilled in the art to use an inert atmosphere above the catholyte liquor to prevent exposure of the liquor to air.
  • the anolyte liquor comprising water and an acid solution, such as sulfuric acid, is removed by pump 32 from reservoir 30 by conduit 31 and passes by means of conduit 34 into opening 10 of anolyte chamber 22.
  • the anolyte liquor passes from anolyte chamber 22 through opening 16 and is recirculated back into reservoir 30 by means of conduit 36.
  • Any circulating means may be used to cause a flow of electrolyte solutions through the respective chambers, and for continuous operation of the apparatus of this invention it is preferred that a mechanical pump be used for such circulating means. It is within the-purview of one skilled in the art to select suitable means for circulating the electrolyte solutions.
  • reservoir 30 or an alternative reservoir may be lled with a caustic solution, such as sodium hydroxide, and reservoir 40 or an alternative reservior may be lled with a plumbite salt solution and an alkali metal hydroxide or carbonate solution, alkaline earth metal hydroxide or carbonate solution, or other caustic solution.
  • a caustic solution such as sodium hydroxide
  • reservoir 40 or an alternative reservior may be lled with a plumbite salt solution and an alkali metal hydroxide or carbonate solution, alkaline earth metal hydroxide or carbonate solution, or other caustic solution.
  • the catholyte liquors can be circulated to and from a single reservoir or each catholyte chamber can utilize its own reservoir and pumping system. Furthermore, when there is more than one catholyte chamber the eiuent from one catholyte chamber can be circulated to one of the other catholyte chambers and used as the influent in that particular catholyte chamber. The efliuent from the second catholyte chamber can be used as the inuent of a third catholyte chamber, etc.
  • catholyte liquors can be returned at any point in the systern to the catholyte reservoir where it will be recirculated.
  • Anolyte liquors may be circulated from chamber to chamber as described above for the catholyte liquor, or the anolyte liquor can be returned to the reservoir and recirculated. It is within the purview of one skilled in the art to replenish the anolyte liquor with acid when the acid concentration of the anolyte liquor becomes diminished to the point where it is no longer effective as an anolyte (electrolyte).
  • the concentration of the dithionite in the catholyte liquor increases as the concentration of the bisulte decreases.
  • Recirculation of the catholyte liquor is generally terminated when the dithionite concentration reaches the desired level. This generally may be determined by the darkening of a lead acetate test solution which is an indicator for sullite ion.
  • a lead acetate test solution which is an indicator for sullite ion.
  • sodium sulfite forms and is cathodically reduci- 5E to sodium sulde.
  • the sodium sulde causes the darkening of the lead acetate test solution.
  • the terminal point of the cathodic reduction of the bisulte has been reached. This is generally defined as the desired level of dithionite salt.
  • the invention is not limited to the direction of the ow of the anolyte and catholyte liquors, and accordingly, there may be a downward ow of the liquors or there may be a combination of upward and downward flow of the liquors (in separate chambers).
  • the power source for the apparatus of the present invention may be any suitable rectifier capable of delivering sufficient direct current for the cathodic reduction of the plumbite or plumbate salts and the bisulte or metabisulflte salts, and can be selected by one skilled in the art.
  • pretreat the anode it is preferred to pretreat the anode to build an adherent lead oxide, PbO2, coating on the anode.
  • This is preferably done by imposing an electrical potential across the electrodes when the anolyte is an acid solution, prefearbly a 10% (by weight) sulfuric acid solution, and the catholyte is a salt of a sulfate, such as sodium sulfate, or similar salt in a concentration of about 15% by weight in an aqueous solution.
  • electrolyte liquors are circulated for approximately 24 hours under an imposed potential to coat the anode properly.
  • Suitable anolyte acids, catholyte salt solutions and concentrations thereof for this purpose can be determined by those skilled in the art.
  • the process of the present invention can be carried out in the presense of electrolyte impurities and adjuvants which do not adversely effect the cathodic reduction of the bisulte or metabisulte in the preparation of the dithionite.
  • Valves, vents, gauges, meters, conduits and the like can be used in the process and apparatus of the present invention, and it is within the purview of one skilled in the art to utilize such equipment and devices.
  • a sulfonated, polystyrene cation exchange membrane manufactured by Ionac Chemical Company and designated as Ionac MC 3470 was mounted between neoprene gaskets and sandwiched in turn bewvecn a pair of gasketed, perforated, rigid PVC anti-billow sheets which were 1/3 inch thick. Electric connections were made to the lead sheets by 1/16 inch thick by 1/2 inch wide copper strips to a rectifier capable of furnishing a maximum of 10 amperes at a maximum of 20 Volts.
  • the cell was terminated at each end by 1/2 inch thick rigid PVC 8 inch by 8 inch end plates, and the entire assemblage comprising end plate, anode, anti-billow sheet, membrane, anti-billow sheet, cathode, and end plate with included gaskets, was compressed by suitably spaced C clamps.
  • the cell frames were also included in the assemblage of the other elements. Each of the cell frames was tubulated at the center of the base and the top with rigid PVC nipples of yf; inch inner diameter, and plastic tubing was attached to these nipples to provide upflow circulation of anolyte and catholyte by means of two pumps connected to aspirator bottles.
  • the anolyte reservoir was a single-necked aspirator bottle of one-liter capacity.
  • the catholyte reservoir was a threenecked aspirator bottle of 2-1iter capacity. Both anolyte and catholyte reservoirs were mounted inside stainless steel trays of 4 inch depth and equipped with spouts at their base, and a rapid stream of cold tap water was circulated in the trays. This permitted maintenance of a temperature in the anolyte and catholyte reservoirs of 20 to 25 C.
  • EXAMPLE 1 Preparation of dithionite An anolyte solution or liquor comprising 700 ml. of 5% (by volume) sulfuric acid in water was placed in the anolyte reservoir. A catholyte liquor comprising 600 ml. of 20% (by weight) sodium metabisulte, Na2S2O5 (anhydride form of sodium bisulfite, NaHSOg), in Water and 350 ml. of deodorized, colorless kerosene were placed in the catholyte reservoir. The kerosene formed a layer on the top of the sodium metabisullite solution and protected both the bisulfte and the ultimately formed hydrosulte or dithionite from atmospheric oxidation. Tubing leading into the reservoir from the catholyte chamber was adjusted so that it extended beneath the kerosene layer. Table I below shows the time of operation of the cell, amperage, voltage and percentage of sodium dithionate obtained in Example 1.
  • the amount of sodium dithionite was determined by an yIndigo Carmine test adapted with some minor modifications from the method disclosed in Scotts Standard Methods of Chemical Analysis (5th edition), vol. '1, page l930.
  • the Indigo Carmine (3.732 grams) is dissolved in strong sulfuric acid solution (75 ml. H2504/ 1500 H2O) and diluted with Water to a volume of 2.0 liters. Twentyve milliliters of this solution is placed in a ask.
  • Sodium bicarbonate (about 4 to 5 grams) is placed in a convenient vessel for immediate use. The sodium bicarbonate is quickly added to the 25.0 ml.
  • catholyte liquor was required to convert the blue color of the indigo solution to the desired yellowish-green color.
  • 5.44% of the catholyte liquor was sodium dithionite after 1.75 hours of operation under the designated conditions.
  • EXAMPLE 3 Using the electrodialytic apparatus disclosed above, anolyte liquor of 30 m1. concentrated sulfuric acid in 970 ml. of water and a catholyte liquor of 850 ml. of a 20% (by weight) sodium metabisulte under the conditions set forth in Table Ill below, after 2.35 hours of operation it was determined that the catholyte liquor contained 6.74% sodium dithionite.
  • EXAMPLE 4 A two-chambered electrodialytic apparatus was assembled in accordance with the description given above.
  • the anode was prepared in accordance with the process described above, and the spongy, porous, lead cathode was made in accordance with the process of this invention. After the system was drained, the cell was disassembled carefully and the spongy, lead cathode was removed from the chamber. The electrode was soft and spongy to the touch and appeared to have a ne porosity capable of permitting the passage of fluid therethrough.
  • the spongy, porous lead electrode was deiined by the space of the chamber walls and adhered to the original lead electrode sheet which had been inserted in the catholyte chamber.
  • an electrodialytic apparatus and process have been termed for the preparation of dithionites from bisultes.
  • a spongy, porous lead electrode has been prepared in an electrodialytic apparatus by an electrodialytic process, and said spongy, porous lead electrode has been utilized in the electrodialytic preparation of dithionites from bisuliites.
  • a process for the electrodialytic formation of a hydrosulte salt comprising:
  • an electrolytic cell having an anolyte chamber, at least one catholyte chamber adjacent said anolyte chamber, a cation permselective membrane between said chambers, said catholyte chamber having a spongy, porous lead cathode substantially defined by the walls of said chamber, said cathode being of the type prepared by the cathodic reduction of plumbite or plumbate salt sources in the catholyte chamber of an electrodialytic apparatus while catholyte comprising plumbite or plumbate salt sources is circulated through the chamber, and said anolyte chamber having an anode, inlet and outlet means in each chamber and means for imposing an electrical current across said cathode and said anode;
  • a process for the electrolytic formation of sodium hydrosulte comprising:
  • an electrolytic cell having an anolyte chamber, at least one catholyte chamber adjacent said anolyte chamber, a cation permselective membrane between the anolyte and catholyte chambers, said catholyte chamber having a cathode and said anolyte chamber having an anode, inlet and outlet means in each chamber and means for applying a difference in potential to the anode and cathode;
  • a process for the electrolytic formation of sodium hydrosulfte comprising:

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980534A (en) * 1973-04-11 1976-09-14 The Electricity Council Electrochemical fluorination and an electrode for use therein
US4692229A (en) * 1983-06-17 1987-09-08 Electrocell Ab Electrode chamber unit for an electro-chemical cell having a porous percolation electrode
EP0257815A1 (en) * 1986-08-04 1988-03-02 Olin Corporation Electrochemical process for producing hydrosulfite solutions
US4740287A (en) * 1986-12-19 1988-04-26 Olin Corporation Multilayer electrode electrolytic cell
US4761216A (en) * 1987-04-01 1988-08-02 Olin Corporation Multilayer electrode
US4770756A (en) * 1987-07-27 1988-09-13 Olin Corporation Electrolytic cell apparatus
EP0332394A1 (en) * 1988-03-08 1989-09-13 Hoechst Celanese Corporation Electrosynthesis of sodium dithionite
US4976835A (en) * 1988-03-08 1990-12-11 Hoechst Celanese Corporation Electrosynthesis of sodium dithionite
US4992147A (en) * 1986-08-04 1991-02-12 Olin Corporation Electrochemical process for producing hydrosulfite solutions

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0284527A (ja) * 1988-02-29 1990-03-26 Toray Ind Inc 炭素繊維の処理方法

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980534A (en) * 1973-04-11 1976-09-14 The Electricity Council Electrochemical fluorination and an electrode for use therein
US4692229A (en) * 1983-06-17 1987-09-08 Electrocell Ab Electrode chamber unit for an electro-chemical cell having a porous percolation electrode
EP0257815A1 (en) * 1986-08-04 1988-03-02 Olin Corporation Electrochemical process for producing hydrosulfite solutions
US4743350A (en) * 1986-08-04 1988-05-10 Olin Corporation Electrolytic cell
US4793906A (en) * 1986-08-04 1988-12-27 Olin Corporation Electrochemical process for producing hydrosulfite solutions
US4992147A (en) * 1986-08-04 1991-02-12 Olin Corporation Electrochemical process for producing hydrosulfite solutions
US4740287A (en) * 1986-12-19 1988-04-26 Olin Corporation Multilayer electrode electrolytic cell
US4761216A (en) * 1987-04-01 1988-08-02 Olin Corporation Multilayer electrode
US4770756A (en) * 1987-07-27 1988-09-13 Olin Corporation Electrolytic cell apparatus
EP0332394A1 (en) * 1988-03-08 1989-09-13 Hoechst Celanese Corporation Electrosynthesis of sodium dithionite
US4976835A (en) * 1988-03-08 1990-12-11 Hoechst Celanese Corporation Electrosynthesis of sodium dithionite

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FR2183861A1 (show.php) 1973-12-21
AT329592B (de) 1976-05-25
AU5481173A (en) 1974-10-31
FR2183861B3 (show.php) 1976-04-23
ZA731737B (en) 1973-12-19
CA1020902A (en) 1977-11-15
DE2322294A1 (de) 1973-11-29

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