Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Patent
1990-05-14
1992-12-29
Willis, Jr., Prince
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
423139, 423143, 75626, C22B 300
Patent
active
051748126
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a novel process for the separation and recovery of nickel and cobalt. More specifically, it relates to the separation and recovery of nickel and cobalt values when present in aqueous ammoniacal solution by solvent extraction and the recovery of the isolated nickel by aqueous ammonium carbonate stripping of the nickel-organic reagent complex.
Nickel and cobalt are valuable metals and their recovery from ores containing these metals is the basis of widespread Industrial Processes of considerable importance. A common process for the recovery of nickel and cobalt from ores and concentrates is to use a reduction roast followed by an ammonia-ammonium carbonate leach process.
In such processes it is desirable to produce a basic nickel carbonate to allow for further processing. In order to produce a basic nickel carbonate of suitable purity, it is necessary to first remove the associated dissolved cobalt.
This is normally achieved by injection of a suitable sulphiding agent, for example, gaseous hydrogen sulphide or ammonium hydrosulphide solution. This procedure results in some dissolved cobalt remaining in solution as well as the removal of some dissolved nickel, both of which are undesirable.
In addition, the mixed nickel-cobalt sulphide formed, and other metal impurities that are concurrently precipitated, have to be subjected to a complex series of digestion, separation and recovery processes before metallic cobalt and metallic nickel, or suitable salts thereof, can be obtained.
The sulphiding process also introduces sulphur anions into the essentially cobalt-free nickel-rich process stream. The sulphur anions are difficult to remove and contaminate the basic nickel carbonate when it is precipitated. The presence of sulphur compounds in the basic nickel carbonate requires high calcination temperatures to produce a suitable low sulphur content nickel oxide product.
Liquid-liquid extraction processes are now well established in processing a wide range of metallic and non-metallic compounds. The application of such a process to the present problem avoids the use of a sulphiding compound, but it is often difficult to achieve the desired result.
In particular, nickel-cobalt separation by liquid-liquid extraction is relatively difficult but can be effected under certain conditions, for example, a suitable extraction can be achieved by contacting the organic reagent tri-iso-octylamine with a strongly acidic chloride solution of nickel and cobalt in oxidation state II. Another example of the extraction is the application of di-2-ethylhexyl phosphoric acid or similar reagents, such as bis-(2,4,4-trimethylpentyl) phosphonic acid and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester to acidic sulphate solutions containing nickel and cobalt in oxidation state II.
Further examples of the extraction step involve the application of oxime type reagents such as 2-hydroxy-5-t-nonyl acetophenone oxime and 2-hydroxy-5-dodecyl benzophenoneoxime to ammoniacal ammonium sulphate or carbonate solutions of nickel and cobalt, the latter in oxidation state III. An additional example of another type of reagent is the contacting of substituted beta-diketone reagents with ammoniacal ammonium carbonate or sulphate solutions of nickel and cobalt in oxidation state III.
During liquid-liquid extraction of nickel and cobalt using organic solvents the aqueous phase that separates from the organic phase is usually termed the raffinate and contains the majority of the cobalt, while the organic phase contains the majority of the nickel. In order to recover the nickel, the nickel-rich organic phase is reacted (stripped) with a suitable aqueous acid, for example sulphuric acid, to return the nickel to an aqueous phase, the resulting aqueous solutions are fed to conventional metal winning circuits, e.g. electrowinning, to recover nickel and the cobalt.
Acid stripping of the nickel-containing organic layer should be avoided if a basic nickel carbonate product is required. Prior to the present invention, a suitable non-acidic
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Price Malcolm J.
Reid John G.
MEQ Nickel Pty., Ltd.
Squillante Edward
Willis Jr. Prince
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