Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1987-05-18
1989-08-15
Dixon, Jr., William R.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75100, 75118R, 75 93R, C22C 300, C22C 1104
Patent
active
048571075
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to methods for the separation of precious metals from other metals and in particularly methods of refining gold.
Conventional refining methods for refining gold involves the use of aqua regia for parting whereby the gold is dissolved by the aqua regia and the dissolved gold is then recovered from solution by way of chemical precipitation, or electrolysis.
Both of these systems are expensive and are usually unsuitable for the refining of smaller quantities, due to the number of steps required to collect the gold.
Conventional refining methods, such as aqua regia parting and the like only refine gold to a level in the vicinity of 95%, and usually below this. However, Bullion is classified as gold having a purity in excess of 96% and fine Bullion being in excess of 99%. Thus to further refine gold which has been first refined by aqua regia parting, requires a further step of electrolytic parting or other process. This usually means the sending away of the gold to be refined, which increases costs, involves security risks, and takes one to two weeks before the final product results.
Other systems for the refining of gold require the shipment of the gold to places other than the miner's premises. This outside refining can take weeks to perform with various hazards and costs in the shipment of the product to the refinement site.
Further, the refinement area or site also knows the exact amount of gold being refined.
It is an object of the present invention to provide a single step method of refining precious metals which will substantially overcome or ameliorate the abovementioned disadvantages, by producing bullion grade precious metals in said single step.
According to one form of the present invention there is provided a method of refining a precious metal comprising the steps of:
(a) assaying the material, containing the precious metal to be extracted, to determine the concentration of the precious metal in the material;
(b) inquarting the material containing the precious metal to be extracted into an alloy with a known quantity of a base metal, such as copper, to form an alloy of a known concentration of the precious metal to be extracted;
(c) dissolving the base metal in acid to leave the refined precious metal; and
(d) filtering the precious metal from the thus formed solution.
According to another aspect of the present invention there is disclosed a method of refining a precious metal, said method being a single process including at least the following steps:
(a) granulating a precious metal bearing ore;
(b) inquarting said granulated ore with a base metal; and
(c) subjecting said inquarted material to nitric acid parting.
Preferably the precious metal being refined is gold whilst the inquarting is performed so that the resultant material has a precious metal content of 15% to 40% and most preferably 25%.
The present invention will now be described by way of example only with reference to the following examples and the figures of the drawings in which:
FIG. 1 illustrates a schematic view of the equipment set up for the disolution stage of nitric acid parting; and
FIG. 2 illustrates a schematic view of the refining process.
The following are examples of several methods used to extract gold from the prepared alloy.
EXAMPLE 1
Nitric Acid Parting
The method of this example was performed on 498 g of granulated alloy with the composition:
100 g of the 498 g of granulated alloy were treated with 500 ml of nitric acid, diluted to the ratio of 1:1, to obtain a fine gold residue and a parting solution containing the silver, palladium and base metals. Silver and palladium were readily recovered by precipitation on copper wire. Assays performed on the gold and silver products and barren liquor gave the following results: ppm Pt Pt gold were very low, totalling less than 0.035%.
EXAMPLE 2
Aqua Regia Parting
Aqua regia parting is a well known process and to compare performance of nitric acid parting to aqua regia parting the first mentioned alloy was treated by aqua regia parti
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Brunsman David M.
Dixon Jr. William R.
Fine Metals Export Corporation Limited
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