Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
  • C25C3/26—Electrolytic production, recovery or refining of metals by electrolysis of melts of titanium, zirconium, hafnium, tantalum or vanadium
• • 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
  • C25C7/06—Operating or servicing

Definitions

• the present invention which results from work carried out in the laboratories of the concluded Nationale Su Southerneure d'Electrochimie et d'Electrométallurgie de Grenoble, relates to a process for improving the purity of transition metals obtained by continuous electrolysis from of their halides dissolved in a bath of molten salts constituted by alkali and / or alkaline-earth halides.
• the subsequent contributions of salts intended to compensate for the losses caused by the extraction of the metal and the common impurities contained in the halide of the metal to be produced such as, for example, iron, aluminum, oxygen, etc., constitute a permanent source of pollution in these various impurities.
• the purity can be improved by a prior electrolytic treatment called pre-electrolysis, during which between two electrodes immersed in the molten bath which does not yet contain halides of the metal to be deposited, a DC voltage slightly lower than that necessary to obtain the easiest reduction of the alkali or alkaline earth halide.
• the density of the current which results therefrom is a function of the concentrations of elements to be eliminated: but it is generally very low, of the order of 10 -3 A / cm 2 , and it decreases further during the operation. Therefore, the duration of the preelectrolysis is very long.
• the invention therefore applies to electrolysis cells in which the metal cell containing the bath of molten salts is devoid of internal refractory lining and is therefore in direct contact with said bath.
• the metal which constitutes the tank is chosen from those of metals having good chemical resistance to the salts and halides of the transition metals. It can in particular be nickel and its alloys or more simply a stainless steel.
• This tank is connected in a known manner to an electrical circuit so that a bias current is established in contact with the bath and the tank.
• the applied potential makes it possible to establish a bias current with a density of between 0.5 10 -4 and 5 10 -4 A / cm 2 .
• a bias current with a density of between 0.5 10 -4 and 5 10 -4 A / cm 2 .
• the electrolysis carried out according to the usual voltage and current density criteria between anode and cathode. leads to a metal of improved purity compared to that obtained without polarization of the tank; this. improvement being obtained at the expense of a slight loss of highly polluted metal deposited on the wall of the tank.
• the density range used is explained by the fact that below 0.5 10- 4 A / cm 2 the polarization is no longer sufficiently effective and that above 5.10- 4 A / cm it s turns out to be superfluous because it leads to an unnecessary loss of metal without appreciable improvement in the purity of the metal collected at the cathode.
• the Applicant has also found that it is possible to impose on the cell a cathodic potential with respect to the anode, but with a higher current density, as a means of preelectrolysis at the start of the cell. Indeed, if before starting the actual electrolysis between anode and cathode, and while the molten bath is loaded with halide of the metal to be produced, the cell is polarized so as to have a current density between 1.10- 2 A / cm 'and 5.10-' A / cm 2 , there occurs on the walls of the tank a deposit of metal polluted in oxygen and in foreign metallic elements less electro-negative than the metal to be produced which are therefore quickly eliminated from the bath.
• the present invention finds its application in the manufacture by continuous electrolysis in a bath of molten salts of transition metals with a low oxygen content and of foreign metallic elements.

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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)
• Manufacture And Refinement Of Metals (AREA)

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Publications (2)

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ID=9317652

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Citations (1)

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• 1985
  • 1985-03-19 FR FR8504596A patent/FR2579230B1/fr not_active Expired - Fee Related
• 1986
  • 1986-02-18 US US06/829,937 patent/US4675084A/en not_active Expired - Lifetime
  • 1986-03-14 JP JP61056744A patent/JPS61217592A/ja active Granted
  • 1986-03-17 CA CA000504243A patent/CA1268446A/fr not_active Expired - Fee Related
  • 1986-03-17 AT AT86420077T patent/ATE38693T1/de active
  • 1986-03-17 EP EP86420077A patent/EP0197867B1/de not_active Expired
  • 1986-03-17 DE DE8686420077T patent/DE3661203D1/de not_active Expired

Patent Citations (1)

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