Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
  • C25C7/04—Diaphragms; Spacing elements
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
  • C25C1/16—Electrolytic production, recovery or refining of metals by electrolysis of solutions of zinc, cadmium or mercury
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• This invention relates to an improvement in the cell assembly used in the electrolytic deposition of metals such as zinc.
• roasted zinc ore is leached with a sulfuric acid solution to dissolve the zinc and form a solution of zinc sulfate.
• the pure zinc is then recovered from the zinc sulfate solution by electrolysis, the zinc being deposited on the cathode plates which form part of a series circuit through the electrolyte to the anode plates.
• the electrolysis is complete, the zinc is stripped from the plates and processed to prepare the bulk metal.
• Aluminum cathodes pose several problems.
• Aluminum cathodes have a high initial cost due to the fact that a specially refined metal must be employed in their
• U.S. Patent No. 2,058,259 to Ralston et al disclose the substitution of zinc cathodes for the aluminum cathodes and suggests that the problems of solution line corrosion can be solved by attaching a film or coating of a protective material to the starting sheet prior to commencement of the electrolytic operation to effectively inhibit corrosion of the cathode at the solution line.
• U.S. Patent No. 3,579,431 to Jasberg relates to a specific cell design for the deposition of metal and incidentally discloses the application of a coating of material, preferably polyvinyl chloride resin approximately four inches wide, to the aluminum cathodes to provide a coating about two inches above and two inches below the solution line.
• SUMMARY OF THE INVENTION The present invention is directed to a method for eliminating attack on the cathode of a cell used for electrolytically depositing metals from an electrolyte in which a barrier structure that is not attacked by the electrolyte solution is positioned between the anode and the cathode.
• the barrier extends a distance of about one to ten centimeters below and one to ten centimeters above the solution line depending on the size of the cell being used in the process.
• the instant invention relates to a method of improving the process of recovering zinc metal from zinc ore.
• prior art processes consist of roasting sulfidetype ores to prepare a zinc calcine that contains 50 to 65 percent zinc. More than 90 percent of the zinc is present as the oxide, with up to four percent present as a sulfate and a few percent present as zinc ferrite.
• the calcine is leached with dilute sulfuric acid obtained from electrolytic cells.
• the .zinc sulfate is then purified to remove other elements such as arsenic, antimony, copper, cadmium, iron, nickel, tin, germanium, selenium, tellurium, silicon, and aluminum.
• the purified zinc sulfate solution is then electrolyzed, the electrolysis being represent by the reaction:
• the problems inherent in the use of aluminum cathodes can be solved by the use of zinc cathodes.
• the use of zinc cathodes not only eliminates the sticking, but also enables processing of zinc concentrates containing flourides and eliminates the necessity for the edge strips conventionally used to facilitate the stripping of the zinc deposits from the aluminum.
• the present invention is an improvement over the processes of the prior art in that it solves the problems inherent in the use of aluminum cathodes by substitution of zinc cathodes without encountering the problems that are caused by the application of paint or other coatings to the zinc cathodes.
• the barrier structure of this invention can be fabricated from any substance that is not attacked by the electrolyte.
• a sheet of . plastic material such as the material currently available under the trade name "Plexiglass” (poly-methyl methacrylate), is suspended from the structure that holds the electrodes and extends into the solution of the electrolyte between cathode and anode.
• the barrier structure preferably extends across the width of the electrolytic cell and extends into the electrolyte solution a distance of about one to ten centimeters and above the electrolyte solution a distance of about one to ten centimeters depending on the size of the cell.
• These barriers must be of sufficient vertical height to cover variations in the height of solution in the cell.
• a barrier having a vertical height of 20 centimeters is generally adequate.
• the barrier can be of any thickness that can be handled conveniently, a thickness of about two centimeters normally being adequate.
• the invention is described as an electrolytic system that is designed for the electrowinning of zinc, it can obviously be used for other electrolysis systems where the cathode is attacked at the solution level.
• This mple illustrates the problem normally encountered when zinc is deposited on a zinc cathode from a zinc sulfate solution.
• a solution of zinc sulfate was prepared by dissolving zinc oxide in sulfuric acid to prepare a solution have a Zn++ concentration of 65 grams per litre and a sulfuric acid concentration of 200 grams per litre.
• the solution was transferred to a cell having a capacity of four litres and a lead oxide- coated titanium anode having a dimension of 3" x 9" and a rolled zinc cathode 3" x 9" x 0.032" thick.
• the electrodes were spaced 1.5 inches apart.
• the solution was electrolyzed using a current density of 50 amps per square foot which was supplied by 40 amp, 50 volt power supply as a constant source of direct current.
• the cell temperature was maintained at 35 - 45 o C., and the electrolysis was carried out for a period of 24 hours. At the end of this time the zinc electrode was examined and found to be almost completely dissolved at the solution line.
• EXAMPLE II This example illustrates the improvement when the cell is operated with a barrier positioned between the anode and the cathode.
• a zinc sulfate solution was made up to have the same concentration as in Example I.
• the cell was operated under exactly the same conditions with the exception that "Plexiglass" strips were placed between the anode and the cathode. These strips extended across the width of the cell and were attached to a bar supporting the electrodes. The "Plexiglass” strips extended about one centimeter below and above the level of the solution. After 24 hours of operation, the cathode was examined. There was no detectable indication of solution level attack on the zinc cathode.
• the examples illustrate the preferred embodiment of the disclosed invention, other materials which have sufficient rigidity to be handled conveniently and are not attacked by the electrolyte can be substituted for "Plexiglass" in fabricating the barrier.
• the barrier can be attached to the sides of the cell or can be attached to the structure supporting the electrodes or suspended therefrom.
• the only requirement as to the dimensions of the barrier is that it extend beyond the width of the electrodes a sufficient distance to prevent oxygen transport from the anode to the cathode and that it extend above and below the solution a sufficient distance to compensate for variations in the solution level in the cell. Modifications and variations can be made without departing from the inventive concept.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)

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Applications Claiming Priority (2)

Publications (1)

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Citations (5)

• 1977
  • 1977-07-22 US US05/818,183 patent/US4104132A/en not_active Expired - Lifetime
• 1978
  • 1978-07-20 BE BE2057157A patent/BE869147A/xx unknown
  • 1978-07-21 JP JP8931778A patent/JPS5460205A/ja active Pending
  • 1978-07-21 GB GB7908950A patent/GB2036080B/en not_active Expired
  • 1978-07-21 CA CA000307882A patent/CA1149771A/en not_active Expired
  • 1978-07-21 FR FR7821771A patent/FR2398117B3/fr not_active Expired
  • 1978-07-21 WO PCT/US1978/000046 patent/WO1979000059A1/en not_active Ceased
  • 1978-07-24 ZA ZA00784185A patent/ZA784185B/xx unknown
  • 1978-07-24 AU AU38302/78A patent/AU517014B2/en not_active Expired

Patent Citations (5)

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