Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G53/00—Compounds of nickel
  • C01G53/04—Oxides; Hydroxides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity

Definitions

• the present invention relates to a novel method of manufacturing nickel hydroxide by an electrochemical process whereby this substance can be obtained directly from nickel mat (preferably refined by a metallurgical process) and from which any impurities detrimental to its subsequent applications (notably as an additive to nickelplating baths) have been removed.
• high-purity nickel hydroxide is obtained from nickel sulfate or nickel chloride :by lime or soda transfer, the salts, sulfate or chloride themselves being obtained heforehand according to conventional methods notably from pure nickel or nickel oxide.
• pure nickel or nickel oxide may be prepared from nickel mat by applying various known refining processes, whether of the dry or moist type.
• this invention is concerned with a method capable of producing nickel hydroxides having the lowest possible contents of alkaline or alkaline-earth metal residues.
• the present invention relates to a method of producing nickel hydroxide by an electrolytic process comprising the following steps:
• An anodic corrosion of nickel-mat anodes by exerting a direct electrolytic action in the anode compartments of an electrolysis cell divided into compartments and containing as the electrolyte an aqueous solution of a water-soluble chloride or sulfate of an alkaline or alkaline-earth metal such as notably sodium, potassium, magnesium, calcium, to produce a high nickelchloride, or nickel-sulfate, anolyte in an acid medium having a pH value of 2 to 4.
• a water-soluble chloride or sulfate of an alkaline or alkaline-earth metal such as notably sodium, potassium, magnesium, calcium
• this method is carried out continuously.
• the nickel-mat anodes comprise mainly nickel and sulfur, 76% to 83% by Weight of nickel and 23% to 16% by weight of sulfur.
• the contents of elements other than nickel and sulfur lie within the following limits, by weight:
• the corrosion of the immersed portions of the anodes takes place regularly and uniformly. The dissolution is stopped when the current rises. Then, only a stump of anode (undissolved mat) and a sponge of sulfur remain.
• the sulfur sponge contains from 2% to 3% of the total initial nickel.
• a complete method of continuously manufacturing nickel hydroxide according to this invention is described hereinafter, by way of example, by using a sodium sulfate electrolyte.
• Nickel-mat anodes are anodically corroded in anode compartments filled with a sodium sulfate, Na SO electrolyte, the Na SO concentration ranging from to g./liter. This electrolyte becomes charged with Ni to form a mixture of nickel sulfate and sodium sulfate.
• the nickel concentration maintained by continuous circulation ranges from 4 to 8 g./liter of nickel.
• the pH in the anode compartment is kept at a value of 2 to 4.
• the electrolytic dissolution takes place at between 100 to 150 a./sq. m. of anode current density consistent with an adequate anode efficiency and the absence of oxygen release.
• a difference in level of 4 to 6 cm. is maintained between the anode and the cathode compartments by proper partitioning and the use of partition fabric elements, whereby the anolyte will flow continuously towards the cathode compartments.
• the cathode compartment is kept at a pH value of 8 to 10 and the nickel sulfate is precipitated therein in the form of nickel hydroxide within these pH limit values.
• the cathodes consist of stainless steel or nickel sheets and are the seat of a release of hydrogen.
• the bath is kept at a temperature ranging from 45 to 55 C., and the cathode compartment is stirred by using compressed air to keep the hydroxide in suspension and continuously sweeping the cathodes to avoid any undesired or parasitic deposit.
• the hydroxide suspension flowing continuously from the electrolytic cells is decanted in a static decanter in order to raise the nickel concentration to about 25-30 g./liter.
• This suspension is subsequently filtered on a drum-type rotary filter and then washed over the filter.
• three filtration steps are carried out and followed by a Washing step and two inter-mediate repulping steps with water by using 8 to 10 volumes of water per volume of hydroxide.
• These repulping steps should be effected in a minimum time, of the order of half an hour, to ensure an eflicient Washing of the hydroxide, in a lukewarm medium, the same applying to the filtration steps.
• a temperature of 45 to 55 C. is adequate for performing these steps.
• hydroxide manufactured according to the method of this invention by using a Na SO electrolyte and from mat anodes having the composition set forth hereinabove assays as follows (the percentages being by weight):
• the present invention has been described hereinabove with particular reference to the electrolysis of mat anodes in a sodium sulfate electrolyte, but it applies as well to 'any electrolysis of mat anodes in any type of alkaline or alkaline-earth salt electrolyte providing a cathode basic medium having a pH value ranging from 8 to 10.
• a method of manufacturing pure nickel hydroxide which comprises the steps of effecting the anodic corrosion of nickel mat anodes having the following contents by weight: nickel 76% to 83%, sulfur 23% to 16%, cobalt 0.30% to 0.40%, iron 0.04% to 0.08%, copper 0.050% to 0.065%, by direct electrolytic action in anode compartments of an electrolysis cell divided into compartments which contains as an electrolyte an aqueous solution of a water-soluble salt selected from the group consisting of the chlorides and sulfates of sodium, potassium, magnesium and calcium, to form an anolyte having a high-nickel salt content selected from the group consisting of the chloride and sulfate, in an acid medium having a pH value ranging from 2 to 4, diffusing the anolyte towards the anode compartments of the electrolysis cell through fabric partitions separating the anode compartments from the cathode compartments, precipitating the nickel in the cathode compartments in the form of nickel hydroxide,

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Citations (2)

• 1965
  • 1965-04-30 FR FR15327A patent/FR1441749A/fr not_active Expired
  • 1965-10-22 US US502434A patent/US3414494A/en not_active Expired - Lifetime
  • 1965-11-18 CH CH1588665A patent/CH437235A/fr unknown
  • 1965-11-19 NO NO160556A patent/NO115735B/no unknown
  • 1965-11-19 GB GB49310/65A patent/GB1080119A/en not_active Expired
  • 1965-11-22 BE BE672641D patent/BE672641A/xx unknown
  • 1965-11-30 NL NL6515547A patent/NL6515547A/xx unknown
  • 1965-12-10 DE DEN27747A patent/DE1265153B/de not_active Withdrawn
  • 1965-12-20 AT AT1146065A patent/AT262934B/de active
  • 1965-12-29 ES ES0321567A patent/ES321567A1/es not_active Expired
  • 1965-12-30 FI FI653119A patent/FI45649C/fi active

Patent Citations (2)

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