Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group ib metal
Patent
1998-06-16
2000-11-07
Bos, Steven
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group ib metal
423110, 423153, 423154, C22B 1100, C22B 1500, C22B 1900, C22B 2300
Patent
active
061432598
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method to enhance the extraction of valuable metals, such as gold and silver, from sulphide minerals.
The present invention relates particularly, although by no means exclusively, to a method to enhance the extraction of valuable metals from sulphide minerals that include iron or which form part of ore bodies that include iron.
The present invention relates more particularly, although by no means exclusively, to a method to enhance the extraction of gold from iron sulphide minerals, such as pyrite (FeS.sub.2) and arsenopyrite (FeAsS).
A large part of the accessible gold mineral reserves and resources are associated with sulphide minerals, such as pyrite and arsenopyrite. In many cases, these sulphides yield gold recoveries below 80% using conventional cyanidation methods and, as a consequence, the sulphide minerals are classified as refractory. The main reason for the low gold recoveries is that it is common to find some of the gold as very finely disseminated particles inside the sulphide crystal matrix and therefore the gold is not readily accessible by conventional cyanidation methods. The particle size of the gold inside the sulphide matrix can range from a few microns to submicrons.
In order to efficiently recover gold (as well as other metals) from refractory sulphide minerals it is first necessary to break down the sulphide minerals, for example by oxidising the sulphide minerals. The gold can then be recovered by conventional gold recovery methods, such as cyanidation treatment.
It is known to oxidise sulphide minerals by roasting and by a range of hydrometallurgical methods including pressure leaching and bioleaching.
It is an object of the present invention to provide an alternative method of treating refractory gold-containing sulphide minerals based on hydrometallurgical oxidation of sulphide minerals to improve the recovery of valuable metals from the sulphide minerals.
According to the present invention there is provided a method of treating a mined material or a concentrate of the mined material to improve the recovery of a valuable metal from the mined material, the mined material including a sulphide mineral which contains the valuable metal, and the mined material including iron, which method comprises: produce ferrous ions, the purpose being to make the valuable metal in the sulphide mineral more accessible to extraction; and mined material with a mixture of sulphur dioxide and oxygen to produce ferric ions for use in oxidising the sulphide mineral in step (i).
The present invention is based on the realisation that: ions to break down the sulphide mineral and produce ferrous ions; ions; and sulphide mineral as a source of the ferrous/ferric ions; mineral to improve subsequent recovery of a valuable metal from the sulphide mineral.
The valuable metal may be any metal, such as gold, nickel, copper and zinc.
It is noted that oxidation step (i) may make the valuable metal more accessible to extraction from the sulphide mineral by releasing solid particles of the valuable metal from the sulphide mineral structure or exposing the valuable metal in the structure for dissolution of the valuable metal. In either case, the valuable metal (in solid or dissolved form) can then be extracted by any suitable means. For example, in the case of gold in a sulphide mineral, oxidation step (i) typically would release the entrapped gold particles for extraction by conventional treatments, such as cyanidation. In addition, in the case of nickel in a sulphide mineral, oxidation step (i) typically would break-down the sulphide mineral and expose nickel particles which would then pass into solution and be extracted thereafter from the solution.
It is preferred that the concentration of ferric ions be maintained above a minimum level.
It is preferred that the ratio of the concentrations of ferric to ferrous ions be maintained above a minimum level.
It is preferred that the method comprises oxidising the sulphide mineral in step (i) in the presence of a catalyst.
The catalyst may
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Tiwari, et al., "Leaching of high-solids, attritor-ground chalcopyrite concentrate by in situ generated ferric sulfate solution" Metallurgical Trans. B vol. 11B, pp. 89-93, Mar. 1980.
Bos Steven
Kao Dolly
Moss Dennis
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