Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Patent
1993-07-08
1995-06-27
Andrews, Melvyn J.
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
423 29, 4236585, C22B 1108
Patent
active
054276063
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a system and method for recovering metal(s) from pulp material which has particular, although not exclusive utility, in the extraction and recovery of noble metals from ores containing the same.
In this specification, noble metals are defined to include gold, and base metals are defined to include metals other than gold which are comparatively aesthetically less valuable, such metals including nickel and copper. In particular, the invention has application in the extraction process of gold from aurous material, commonly known as the carbon-in-pulp or carbon-in-leach process.
The carbon-in-pulp and the carbon-in-leach process for the recovery of gold and silver from cyanide leaching of ores is widespread in the noble metals mining industry. However, existing plants are considerably expensive to construct and run, and accordingly any improvement in the efficiency and construction of the plant, and in the method of running the same, can lead to major savings in costs.
The carbon-in-pulp (CIP) process or the carbon-in-leach (CIL) process generally consists of the steps of feed preparation of the ore to form a pulp, leaching with cyanide solution, adsorption of the resulting cyano-gold complex onto activated carbon, stripping the cyano-gold complex from the carbon using elution and recovering the gold from the eluate by electrowinning or other suitable process.
The CIP process is characterised by the adsorption stage occurring separately from the leach stage and the CIL process is generally characterised by combining the leaching and adsorption steps or stages so that these are performed concurrently; both processes having the stripping and recovering steps performed as a subsequent step.
It is an object of certain aspects of the present invention to provide a system and method which improves the efficiency of a CIP and/or CIL process by effectively operating or performing the metal stripping step or stage concurrently with the adsorption step or stage, either as an adjunct to all of the steps of a conventional CIP or CIL plant, or as an alternative to such plants.
The presence of various base metals in the ore can also have a detrimental effect of great proportions on the efficiency and economics of a CIP or CIL process due to the high consumption of cyanide, and a reduction in the leaching and adsorption rates and also in the recovery rate of the noble metals. Furthermore, the presence of a fast leaching and adsorbing base metal such as copper can significantly reduce the carbon loading capacity for the noble metals, thereby necessitating more frequent stripping and a higher carbon inventory resulting in higher production costs.
Hitherto, known processes for dealing with base metals contained in noble metal bearing ores have concentrated on minimising the formation of copper cyanide complexes during the leach process by such methods as operating the chemical environment to minimise the formation of base metal cyanide complexes, or pretreating the ore to render the base metals relatively inert to cyanide ions so that cyano-base metal complexes do not form; or have got around the problem by ignoring it, merely expending larger quantities of cyanide or carbon in order to recover the required noble metals.
Accordingly, it is an object of certain other aspects of the present invention to provide a system and method to mitigate the aforementioned detrimental effects of base metal laden feed and also, in certain instances, to provide for the recovery of the base metals in a saleable form.
In accordance with a first aspect of the present invention there is provided a method of recovering base metal values from material containing said base metal values and noble metal values, comprising: metal complex including a cyano-base metal complex anion anion having the stoichiometry M(CN).sub.x.sup.y-, where M is a base metal cation, x is 2 or 3 or 4, and y is 1 or 2 or 3; by adjusting the amount of available cyanide anion to said base metal cation to favour formation of said cyano-base metal complex
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Andrews Melvyn J.
Bruno Sceresini Holding Pty. Ltd.
Fersayth N.L.
Forsayth (Gibson) Ltd.
Reynolds Australia Metals, Ltd.
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