CA1148748A - Recovery of precious metals from difficult ores - Google Patents
Recovery of precious metals from difficult oresInfo
- Publication number
- CA1148748A CA1148748A CA000359836A CA359836A CA1148748A CA 1148748 A CA1148748 A CA 1148748A CA 000359836 A CA000359836 A CA 000359836A CA 359836 A CA359836 A CA 359836A CA 1148748 A CA1148748 A CA 1148748A
- Authority
- CA
- Canada
- Prior art keywords
- sulfite
- precious metals
- ore
- recovery
- copper
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B11/00—Obtaining noble metals
- C22B11/04—Obtaining noble metals by wet processes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE Precious metals such as gold and silver are recovered from difficult-to-treat ores, particularly those containing manganese, by lixiviating using an ammonium thiosulfate leach solution containing copper, sufficient ammonia to maintain a pH of at least 7.5, and at least 0.05% sulfite ion.
Description
~1~8~48 ' RECOVERY OF PRECIOUS ME~ALS
~ ~RO~ DIFFICULT ORES
FIELD O~ THE INVENTION
The present invention relates to the recovery of minerals from ores and, more particularly, to the extrac~ion of precious metals by lixi~iation, particularly from ores which are otherwise;difficult to handle.
BACKGROUND OF THE INVENTION
Lixiviation is a technique used to extract a soluble component from a solid mixture by washing or per-colation, i.e. leaching. World-wide present practise for extracting precious metals by lixiviation is carried out using cyanide solutions, m~inly sodium cyanide. ~ecause cyanides are so highly toxic, and because they cause substan--tial environmental problems, the use of cyanides is now ~alling into disfavor. Moreover, cyanides are costly materials, which makes their use economically diæadvantageous. Moreover, the use of cyanlde solutions is at best difficult and at ~orst impossible with respect to some-ores, especially those containing copper and/or manganese, since these materials easily contamina~e the cyanide; and such materials are requently present to the extent that poor recoveries of the precious metals are obtained using cyanide solutions.
Indeed, with respect to the last problem mentioned immediately above, there are many difficult-to-treat ores in existence which contain manganese and significant quantities of silver and/or gold, and from which it would be desirable to --1-- .
'..
extract these precious metals, and i a sui~able and suffic~ently inexpensive technique existed for such recovery.
However, present techniques are simply not adequate and these ores remain an untapped mineral resource, Copper-bearing sulphur-containing ores, such as chalcopyrite, often contain small quantities of gold and silver which, desirably, should be recovered, Although the problem of recovering such precious metals, as well as the copper, has received considerable attention in the past, much of the work carried out in this connection, insofar as com-mercial processing is concerned, has involved the recovery of precious metals using pyrometallurgical processes ~or the recovery of the copper, One attempt to solve the above identified problems is disclosed in the Genik-Sass-Berecowsky et al patent 4,070,182.
This patent ~roposes the use of ammonium thiosulate as a secondary leach for the recovery o~ silver and gold, in con-junction with a hydrometallurgical process ~or the recovery of copper ~rom the copper-bearing sulphidic ore. Fig, 3 o~
this patent shows a flow diagram or the extraction of precious metals from chalcopyrite concentrate be~ore the main leaching step for extraction of copper~ However, this patent appears to provide no instruction as to how to maintain the thiosulfate radical s~able, and does no~ even appear to recognize ~he problem o4 thiosulfate instability. This patent also does not clearly teach the necessity of maintaining an alkaline pH in the thiosul~ate leach liquor when starting with a raw ore, although ` the need or an alkaline pH is mentioned in conjunction ~ith thiosul4ate extraction following a copper recovery leach.
Furthermore, this patent provides no guidance with respect to the extraction ol precious metals from difficult ores containing manganese.
~87~8 S~RY OF T~ INVENTION
I~ is, accordingly, an object o:~ the instant inven,ion to overcome de~iciencies in the prior ar'L, such as indicated above.
It is another object to provide ~ror the improved extrackion Of precious metals r~rom ores by lixiviation.
It is a further object to provide an improved process ~or extracting precious metals, such as gold and silver, by lixiviation, using an ammonium thiosuli~ate leach liquor It is yet another object of the instant invention - 10 to provide for ~he extraction of precious metals rom dificult-to-treat ores, and particularly such ores containing copper and/or manganese, and most particularly such ores containing manganese ' It is yet a further object to provide a method ~or recovery of precious metals from an ore contàining same, which method comprises lixiviating the precious metals, using an ammonium thiosulate leach liquor at an alkaline p~ and containing copper and sulfite ions.
These and other objec~s and the nature and a~vantages of the ins~ant invention will be more apparent from the ollow-ing detailed description of various embodiments, such detailed description being offered illustratively and not limitatively~
. DE~AILED DESCRIPTION-OF I~E E~ODI~ENTS
. .: . - -~ In accordance.wi~h the instanb invention, it~has been fo'und that t~e pxo~lems extant in the prior'art, including those .
.indicated ab'ove, are largely-over;come by lixiviation in -am~oniu~ thiosulfate solutions.containing'copper and.at-le'ast a trace of sulfite ions. With the use o~ such a leach liquor .
. , ,._, .
.' .
~4~748 good recoveries are achieved in less time compared with the prior art use o cyanide, and without the possibility of con'amination of streams and surroundings. Moreover, the process constitutes an improvement o the thiosulf.ate leaching of Patent 4,070,182 by providing better control o~ the S stability o the thiosulfate radical.
A~ter the liYiviation has been completed, recovery of the precious metals from ~he leach liquor can be carried out in the same ways as are conventionally used for recovering such metals from cyanide solutions, namely by the use of metallic ~inc, iron or copper; by electrolysis; or by the addition of soluble sulfides to recover a sulfide precipitate.
The stripped ammonium thiosulfate solution is thereby rejuven-ated and can be recycled for reuse in the instant process, The present process is especially advantageous *or the recovery of precious metals from difficult-to-treat ores, namely those which are contaminated by copper and/or manganese, and possibly other base metals as well. Copper and manganese, and particularly manganese, are especially poisonous to cyanide solutions, and because thiosulfate is much less expensive, stronger leach solutio~ may be used, which will overcome the disadvantages of such poisons as manganese and lead. A
particular problem exists with manganese ores, as many such ores presently exist which, under previous technology, are simply unusable. The inst~nt invention overcomes the dis-advantages o~ high manganese content, and good recoveries areobtained merely at the expense of the use o more reagent and, at times, maintaining a higher quantity of sulfi~e in the leach solu~ion than would othe~ise be needed in accordance with the instant invention~
8 7~
In any lixivia.ion procefis, the strength of the leach solution is an important consideration. However, with cyanide lixiviation the high to~icity and the high cost of the chemical prohibit consideration of using re than about 1-2% solutions, thereby requiring long reten~ion times and resul~ant large solution tanks. These problems are eliminated by the instant invention; thus, in the present invention ammonium thiosullate, which is a relatively low cost and non-toxic material, can be used in much stronger solutions than is permissible with cyanide, namely as high 2S 60%o Solu~ions in the range o 12-25% are particularly satisfactory, it being understood that the higher the solution strength, the less the time needed for completing the leaching. In some ores, as little as 2%
ammonium thiosul~ate gives adequate results.
An impor~ant aspect of the present invention is the inclusion of copper in the leach solution or lixiviation liquor.
This, o~ course, presents no problem if the ore l~sel contains copper, such as the ores treated in accordance with patent 4,070,182. Some copper must be present for good recovery, ~nd i the ore itsëlf contains copper, this will most generally suffice.~ If not, a copper salt or copper-containing ore should be added to supplement and maintain the concentration required for best results~ In general, and consistent with patent 4,070,182, it has been found that a copper concen-tration of 1-4 g/~ is desirable, although this will vary - -somewhat rom ore to ore.
~nother important requirement is to maintain the pH o~
the leach solution in the alkaline range, preerably at least 705 and most preferably at least 8. Ammonium hydroNde (ammonia titrable with dilute standard acid) is the preerred means for maîntaining the desired pH. Available ammonia not only _5_ 87~8 accelerates the rate oE solution of the precious metal in the leach liquor, but also helps to stabilize the ammonium thio-sulate.
The presence of sulfite ions in the leach solution is an essential aspect of the invention. The sulfite ion is necessary to inhibit the decomposition of the thiosul~ate which, i permitted to occur, would result in precipiation of silver sulfide with resultant loss of recovery, While the quantity of sulfite present need not be great~ as noted below, it is essential that the sulfite be present throughout the lixiviation process. Quantities as little as trace amounts of sulfite will assure stability of the solution, but in view of the continuously changing conditions which inherently occur in the lixiviation process, it is desirable that the sulfite ion be present in a quantity o at least 0,05%0 In the case where the ores being treated are refractory ores, in particular ores containing significant quantities of manganese, up to three or four percent of sulfite ions are desirable to main-tain stability of the ammonium thiosulfate.
Su~ite ions can be provided in a nwmber of ways, The most direct is by simply adding ammonium sulfite or ammonium bisulfite to the leaching s~lution; other sulfite salts may also be used. In some cas~s it is desirable to ~aintain sulfite concentrations by adding sulfur dioxide to the ammoniacal leach solution, but if this method is chosen, - precaution must be taken to assure that the solution does not become acid and that the pH is preferably maintained at 8 or above, it being understood that sulfur dioxide is an acid source The importance of maintaining at least a trace of sul-- fite anion (S03) in the leaching liquor during lixivia-ion is , ~
mportant because without the presence of sulfite the thio-sulfate radical becomes unstable, resulting in the production of sulfide and the precipitation of silver, as represented by the following equation:
(1) CaO + (Ag)2S2O3 ~ Ag2S + CaSO4 This equation is representative of the irreversible reactions which take place not only in the presence of calcium oxide, but also with the oxides of iron, aluminum, manganese and copper; and such reaction may even take place with ammonium hydroxide in the absence of the sulfite anion. The sulfite ion prevents the formation of any free divalent sulfur necessary for the formation and precipitation of silver, and automatic entrainment and loss of gold. In treating raw ores containing oxides of the metals listed above, which serve to poison the extraction process, particularly manganese, the conditions are quite variable depending on the ore and thus it is essential to prevent decomposition of the thiosulfate following the general mechanism of formula (1), above. ~laintaining at least a trace of sulfite ion, preferably at least 0.05~ and most preferably 0.1-2~ sulfite ion, has been found to stabilize ` the thiosulfate and thereby present precipitation of already ; dissolved precious metal.
An equilibrium reaction occurs in the thiosulfate leach ~; liquor, as represented by the following equation:
~ ~RO~ DIFFICULT ORES
FIELD O~ THE INVENTION
The present invention relates to the recovery of minerals from ores and, more particularly, to the extrac~ion of precious metals by lixi~iation, particularly from ores which are otherwise;difficult to handle.
BACKGROUND OF THE INVENTION
Lixiviation is a technique used to extract a soluble component from a solid mixture by washing or per-colation, i.e. leaching. World-wide present practise for extracting precious metals by lixiviation is carried out using cyanide solutions, m~inly sodium cyanide. ~ecause cyanides are so highly toxic, and because they cause substan--tial environmental problems, the use of cyanides is now ~alling into disfavor. Moreover, cyanides are costly materials, which makes their use economically diæadvantageous. Moreover, the use of cyanlde solutions is at best difficult and at ~orst impossible with respect to some-ores, especially those containing copper and/or manganese, since these materials easily contamina~e the cyanide; and such materials are requently present to the extent that poor recoveries of the precious metals are obtained using cyanide solutions.
Indeed, with respect to the last problem mentioned immediately above, there are many difficult-to-treat ores in existence which contain manganese and significant quantities of silver and/or gold, and from which it would be desirable to --1-- .
'..
extract these precious metals, and i a sui~able and suffic~ently inexpensive technique existed for such recovery.
However, present techniques are simply not adequate and these ores remain an untapped mineral resource, Copper-bearing sulphur-containing ores, such as chalcopyrite, often contain small quantities of gold and silver which, desirably, should be recovered, Although the problem of recovering such precious metals, as well as the copper, has received considerable attention in the past, much of the work carried out in this connection, insofar as com-mercial processing is concerned, has involved the recovery of precious metals using pyrometallurgical processes ~or the recovery of the copper, One attempt to solve the above identified problems is disclosed in the Genik-Sass-Berecowsky et al patent 4,070,182.
This patent ~roposes the use of ammonium thiosulate as a secondary leach for the recovery o~ silver and gold, in con-junction with a hydrometallurgical process ~or the recovery of copper ~rom the copper-bearing sulphidic ore. Fig, 3 o~
this patent shows a flow diagram or the extraction of precious metals from chalcopyrite concentrate be~ore the main leaching step for extraction of copper~ However, this patent appears to provide no instruction as to how to maintain the thiosulfate radical s~able, and does no~ even appear to recognize ~he problem o4 thiosulfate instability. This patent also does not clearly teach the necessity of maintaining an alkaline pH in the thiosul~ate leach liquor when starting with a raw ore, although ` the need or an alkaline pH is mentioned in conjunction ~ith thiosul4ate extraction following a copper recovery leach.
Furthermore, this patent provides no guidance with respect to the extraction ol precious metals from difficult ores containing manganese.
~87~8 S~RY OF T~ INVENTION
I~ is, accordingly, an object o:~ the instant inven,ion to overcome de~iciencies in the prior ar'L, such as indicated above.
It is another object to provide ~ror the improved extrackion Of precious metals r~rom ores by lixiviation.
It is a further object to provide an improved process ~or extracting precious metals, such as gold and silver, by lixiviation, using an ammonium thiosuli~ate leach liquor It is yet another object of the instant invention - 10 to provide for ~he extraction of precious metals rom dificult-to-treat ores, and particularly such ores containing copper and/or manganese, and most particularly such ores containing manganese ' It is yet a further object to provide a method ~or recovery of precious metals from an ore contàining same, which method comprises lixiviating the precious metals, using an ammonium thiosulate leach liquor at an alkaline p~ and containing copper and sulfite ions.
These and other objec~s and the nature and a~vantages of the ins~ant invention will be more apparent from the ollow-ing detailed description of various embodiments, such detailed description being offered illustratively and not limitatively~
. DE~AILED DESCRIPTION-OF I~E E~ODI~ENTS
. .: . - -~ In accordance.wi~h the instanb invention, it~has been fo'und that t~e pxo~lems extant in the prior'art, including those .
.indicated ab'ove, are largely-over;come by lixiviation in -am~oniu~ thiosulfate solutions.containing'copper and.at-le'ast a trace of sulfite ions. With the use o~ such a leach liquor .
. , ,._, .
.' .
~4~748 good recoveries are achieved in less time compared with the prior art use o cyanide, and without the possibility of con'amination of streams and surroundings. Moreover, the process constitutes an improvement o the thiosulf.ate leaching of Patent 4,070,182 by providing better control o~ the S stability o the thiosulfate radical.
A~ter the liYiviation has been completed, recovery of the precious metals from ~he leach liquor can be carried out in the same ways as are conventionally used for recovering such metals from cyanide solutions, namely by the use of metallic ~inc, iron or copper; by electrolysis; or by the addition of soluble sulfides to recover a sulfide precipitate.
The stripped ammonium thiosulfate solution is thereby rejuven-ated and can be recycled for reuse in the instant process, The present process is especially advantageous *or the recovery of precious metals from difficult-to-treat ores, namely those which are contaminated by copper and/or manganese, and possibly other base metals as well. Copper and manganese, and particularly manganese, are especially poisonous to cyanide solutions, and because thiosulfate is much less expensive, stronger leach solutio~ may be used, which will overcome the disadvantages of such poisons as manganese and lead. A
particular problem exists with manganese ores, as many such ores presently exist which, under previous technology, are simply unusable. The inst~nt invention overcomes the dis-advantages o~ high manganese content, and good recoveries areobtained merely at the expense of the use o more reagent and, at times, maintaining a higher quantity of sulfi~e in the leach solu~ion than would othe~ise be needed in accordance with the instant invention~
8 7~
In any lixivia.ion procefis, the strength of the leach solution is an important consideration. However, with cyanide lixiviation the high to~icity and the high cost of the chemical prohibit consideration of using re than about 1-2% solutions, thereby requiring long reten~ion times and resul~ant large solution tanks. These problems are eliminated by the instant invention; thus, in the present invention ammonium thiosullate, which is a relatively low cost and non-toxic material, can be used in much stronger solutions than is permissible with cyanide, namely as high 2S 60%o Solu~ions in the range o 12-25% are particularly satisfactory, it being understood that the higher the solution strength, the less the time needed for completing the leaching. In some ores, as little as 2%
ammonium thiosul~ate gives adequate results.
An impor~ant aspect of the present invention is the inclusion of copper in the leach solution or lixiviation liquor.
This, o~ course, presents no problem if the ore l~sel contains copper, such as the ores treated in accordance with patent 4,070,182. Some copper must be present for good recovery, ~nd i the ore itsëlf contains copper, this will most generally suffice.~ If not, a copper salt or copper-containing ore should be added to supplement and maintain the concentration required for best results~ In general, and consistent with patent 4,070,182, it has been found that a copper concen-tration of 1-4 g/~ is desirable, although this will vary - -somewhat rom ore to ore.
~nother important requirement is to maintain the pH o~
the leach solution in the alkaline range, preerably at least 705 and most preferably at least 8. Ammonium hydroNde (ammonia titrable with dilute standard acid) is the preerred means for maîntaining the desired pH. Available ammonia not only _5_ 87~8 accelerates the rate oE solution of the precious metal in the leach liquor, but also helps to stabilize the ammonium thio-sulate.
The presence of sulfite ions in the leach solution is an essential aspect of the invention. The sulfite ion is necessary to inhibit the decomposition of the thiosul~ate which, i permitted to occur, would result in precipiation of silver sulfide with resultant loss of recovery, While the quantity of sulfite present need not be great~ as noted below, it is essential that the sulfite be present throughout the lixiviation process. Quantities as little as trace amounts of sulfite will assure stability of the solution, but in view of the continuously changing conditions which inherently occur in the lixiviation process, it is desirable that the sulfite ion be present in a quantity o at least 0,05%0 In the case where the ores being treated are refractory ores, in particular ores containing significant quantities of manganese, up to three or four percent of sulfite ions are desirable to main-tain stability of the ammonium thiosulfate.
Su~ite ions can be provided in a nwmber of ways, The most direct is by simply adding ammonium sulfite or ammonium bisulfite to the leaching s~lution; other sulfite salts may also be used. In some cas~s it is desirable to ~aintain sulfite concentrations by adding sulfur dioxide to the ammoniacal leach solution, but if this method is chosen, - precaution must be taken to assure that the solution does not become acid and that the pH is preferably maintained at 8 or above, it being understood that sulfur dioxide is an acid source The importance of maintaining at least a trace of sul-- fite anion (S03) in the leaching liquor during lixivia-ion is , ~
mportant because without the presence of sulfite the thio-sulfate radical becomes unstable, resulting in the production of sulfide and the precipitation of silver, as represented by the following equation:
(1) CaO + (Ag)2S2O3 ~ Ag2S + CaSO4 This equation is representative of the irreversible reactions which take place not only in the presence of calcium oxide, but also with the oxides of iron, aluminum, manganese and copper; and such reaction may even take place with ammonium hydroxide in the absence of the sulfite anion. The sulfite ion prevents the formation of any free divalent sulfur necessary for the formation and precipitation of silver, and automatic entrainment and loss of gold. In treating raw ores containing oxides of the metals listed above, which serve to poison the extraction process, particularly manganese, the conditions are quite variable depending on the ore and thus it is essential to prevent decomposition of the thiosulfate following the general mechanism of formula (1), above. ~laintaining at least a trace of sulfite ion, preferably at least 0.05~ and most preferably 0.1-2~ sulfite ion, has been found to stabilize ` the thiosulfate and thereby present precipitation of already ; dissolved precious metal.
An equilibrium reaction occurs in the thiosulfate leach ~; liquor, as represented by the following equation:
(2) 4SO=3 + 2S= < > 3S2O3 + 3H2O
It is clear that without the sulfite ion being present, the equilibrium would move to the left, thereby producing di-- valent sulfide sulfur (S ), which precipitates metal sulfides, thereby losing them from the leaching solution. Equilibrium reaction (2) thereby readily illustrates the need for continued presence of some sulfite to drive the reaction (2) to the right ~ .
~L
thereby preventing ~he decomposition o the thiosulfate with loss of not only reagents but loss of values from the leaching solution.
Manganese containing precious metal ores have an unusually high requirement for sulfite ion, because of the oxy-- dizing capabili~y of various manganic compounds, especially pre~
valent among which is manganese oxide (~2)- This high requirement for sulfite is demonstrated by equation ~3) below:
It is clear that without the sulfite ion being present, the equilibrium would move to the left, thereby producing di-- valent sulfide sulfur (S ), which precipitates metal sulfides, thereby losing them from the leaching solution. Equilibrium reaction (2) thereby readily illustrates the need for continued presence of some sulfite to drive the reaction (2) to the right ~ .
~L
thereby preventing ~he decomposition o the thiosulfate with loss of not only reagents but loss of values from the leaching solution.
Manganese containing precious metal ores have an unusually high requirement for sulfite ion, because of the oxy-- dizing capabili~y of various manganic compounds, especially pre~
valent among which is manganese oxide (~2)- This high requirement for sulfite is demonstrated by equation ~3) below:
(3) ~n2 ~ 2(NH4)2S03 ~ 2 ~ 0 3 ~S~06 ~ 4NH~0H
The reaction demonstrated'by equation (3~ is beneficial with many ores, because the metals are in a complex - combination with manganese, and such reaction serves to free the desirable metals from the ~anganese so that such desirable metals can then be lixiviated. However, the undesirable aspect 15 of this reaction is that it consumes sulfite anion and it is therefore important that when acting on manganese containing ores in accordance with the present invention, special pre-- cautions be taken to assure the continued presence o~ sul-fite, thereby'preventing'equation (2) from going to the ~et 20 ' wit~ the resultant loss of these desired precious metals ` from the ieaching solution. ' .
- 'The lLxiviation is preferably c æ ried out at a tem-~ ~ 'perature of 40-60C, preferab~y- 50-60C. Temperatureæ much -'' '' ' greater tban 60C m~ke i~ difficult to retain the ammonium hydroxide content needed for best results. Temperatures below -40C adversely affect the speed of the proce8s~ i.e. the ~me - it takes for the desired precious metals to become solublized is undesirably extended.
A~ noted above, after recovery of the dissolved pre-cious metals, such as by precipitation from the leaching ~ liquor, the ammonium thiosulfate con~aining liquor is desirably .
- - -' 37~8 ecycled for reuse. However, there are likely to be certain losses of chemicals, including thiosulfate, both due to side reactions and to mechanical losses. In such a case additional ammonium thiosulfate to make up for the losses is manufactured ln situ by the reaction between extra sulfite, i.e. an amount of sulfite above and beyond that otherwise needed, and soluble sulfide. Thus, at the conclusion of the recovery stage, ammonium thiosulfate may be internally manufactured in the liquor by the addition of extra sulfite, either as ammonium sulfite, or sulphur dioxide and ammonia, and the addition to the filtered liquor of soluble sulfide, preferably as ammonium polysulfide or ammonium sulfide. Addition of the soluble sulfide will first precipitate metals from solution, and the remaining soluble sulfide will then react with sulfide present to produce the desired thiosulfate. This technique can be used to restore only the thiosulfate lost during the prior lixiviation and/or recovery stage, or it can be used to bring the solution to the desired strength. The mechanism of the reaction is according to equation (2), above.
The following examples will illustrate the manner in which the invention can be practiced. It is to be understood that the specific conditions set forth in the examples are not to be considered limiting to the invention.
Example l A manganese containing ore from the State of Sonora, Mexico, in the Guereguito region, was obtained, the ore having the following assay: Gold 0.014 oz per ton; Silver, 12.1 oz.
per ton; Manganese, 2.1~. This is a very difficult-to-treat ore, the owner having attempted for many years without success to have the ore commercially treated to recover the gold and silver.
g _ X
~ ~ ~8 74 ~ ' The ore was split into seven equal parts of 500 grams each. The first 500 gram portion of the lot was ground fifteen minutes in a solution containing 200 grams of ammonium thiosulfate, 12 grams of ammonium sulfite, fifty grams of ammonium hydroxide, and sufficient water to bring the solution to 1/2 liter. hfter grinding in this solution, the slurry was transferred to a 2,000 ml beaker along with additional water~ added whi.le washing the mill, to ~n~ the total to 1,200 cc. This was placed - on a hotplate with stirring and the temperature raised and maintained while stirring to between 50 and 60C. After one and one half hours of this heating and stirring, suf~icient copper sulfate was added to make 4 grams per liter of copper in solution. Stirring and heating continued for an additional six hours, adding every hour an additional amount of ammonium hydroxide to maintain the volume at a total of 1,200cc. ~t the end of this period the slurry was filtered and the solids washed twice with 250 cc of water, after which the solids were ; dried and sent for assay.
The solution from the above test was analyzed for free ammonia, ammonium thiosulfate and sulfite ion, as well as for . .
~! precious metals content. Sufficient ammonium sulfide was . .. .
added to this solution to precipitate the silver content on~y, - ; according to the following equation:
. . g2523 ~ (NH4)2S ~ Ag2S ~ (NH4~2S203 - If there is any lead in the solution which has been leached from the ore, it too would be precipitated along with the silver and therefore additional suLfide to precipitate the lead must be added in order to precipitate the silver. Some copper also precipitates and some silver will remain in the solution. However, if 80% of the silver is precipitated and the residual solution containing a little silver but most of the copper is recycled to the process, reagent costs are kept low.
.
~ ~ ~87 ~
After removing the silver precipitate, the leaching solution was recycled to the second 500 gram lot of ore~ and the above procedure repeated adding only sufficient ammonium thio-sulfate, ammonium sulfite and copper to maintain opti~um strength of the solution. Anhydrous ammonia was used in all cycles subsequent to the first, instead of ammonium hydroxide, so as to be able to use more water and better wash the values from the leached solids.
For this series, the solution analysis was brought 10 back with each cycle to the approximate analysis as follows:
Ammonium thiosulfate 18%
Ammonium sulfite 3%
Ammonium hydroxide 2%
- Copper about 4 grams per liter This process was continued as above for the seven cycles with an average of 93.2% recovery for the silver and 86.7%
of the gold. Consumption was approximately eight pounds of , ammonium thiosulfate and three pounds of ammonium sulfite per ton of ore. Copper loss was about a pound per ton.
It is therefore seen that excellent results were achieved-demonstrating the successful-and economical recovery - of gold and silver from this ~ifficult-to-treat manganese . . .
- containing ore.
.
` Example 2 - Six different "difficult" ores as identified in the tables below were split into du~licate 500 gram samples, and two series of lixviations were carried out, each series with one of the duplicates from each of the six samples. The A series of samples were treated in accordance with the present invention with 180 grams of ammonium thiosulfate> plus 9 grams of ammonium sulfite, and 4 grams of copper (as copper sulfate) and - . ' . . .
-- . . -- . , .
~ 4~
made up with water to one liter of slurry. The ~ series were treated with precisely the same 7eaching liquor, except that n~ sulfite was used. The samples were all placed on a heated-agitator and 4 grams o~ copper were added ~o each S slurry while injecting ammonla to bring the pH ~o ~.0 and the ~emperature to 50C. Every two hours throughout ~he eight hcur ~eaching, a sample was taken from the solution and in the case o ~he A series sufficient ammonium sul*ite - ~7as added to maintain the sulfite analysis at about 1/~.
~mmonia was also added to maintain the pH above 7,5, The results are given in the table below in which the identi*ication of the ore is given in the left hand column, with the gold and silver assays being presented in ounces per ton, and ~he other important ingredients are given in percent; gold and silver recoveries are reported in two series: See chart, next page.
- It will be obvious to those skilled in the art that various changes may be made without departing ~rom the scope of the invention and the invention is not to be considered -limited to what is described in the specification.
- . .
-, ' , 8'7~8 _ ._ . . ~ _ .. _ ~, ~ . . . o~o ~ o\
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C ~ ~ _ _ N o o\O ~ ~ ~1 r-l ~ CO . O ~i O
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~ ~ 3 ~ 3 _ ~
~ .
37~
Oo\o ~oo\o ~ ~ Ln o N 11~ Il) O
, . .___ .
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__ ~ -.-~
.~ . ~
Z;
_ . _ . - . _ ,,,_, ~ ' ~
~ : ,~
. o\O o\O o\O o\O
O ~ ~ O
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. ~ ~ ~C ~
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O O , O O
. _ .. . _ o O ' O
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.
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-x ~5 ~ ~ h ~ ~ ~ o ~
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`~ 14
The reaction demonstrated'by equation (3~ is beneficial with many ores, because the metals are in a complex - combination with manganese, and such reaction serves to free the desirable metals from the ~anganese so that such desirable metals can then be lixiviated. However, the undesirable aspect 15 of this reaction is that it consumes sulfite anion and it is therefore important that when acting on manganese containing ores in accordance with the present invention, special pre-- cautions be taken to assure the continued presence o~ sul-fite, thereby'preventing'equation (2) from going to the ~et 20 ' wit~ the resultant loss of these desired precious metals ` from the ieaching solution. ' .
- 'The lLxiviation is preferably c æ ried out at a tem-~ ~ 'perature of 40-60C, preferab~y- 50-60C. Temperatureæ much -'' '' ' greater tban 60C m~ke i~ difficult to retain the ammonium hydroxide content needed for best results. Temperatures below -40C adversely affect the speed of the proce8s~ i.e. the ~me - it takes for the desired precious metals to become solublized is undesirably extended.
A~ noted above, after recovery of the dissolved pre-cious metals, such as by precipitation from the leaching ~ liquor, the ammonium thiosulfate con~aining liquor is desirably .
- - -' 37~8 ecycled for reuse. However, there are likely to be certain losses of chemicals, including thiosulfate, both due to side reactions and to mechanical losses. In such a case additional ammonium thiosulfate to make up for the losses is manufactured ln situ by the reaction between extra sulfite, i.e. an amount of sulfite above and beyond that otherwise needed, and soluble sulfide. Thus, at the conclusion of the recovery stage, ammonium thiosulfate may be internally manufactured in the liquor by the addition of extra sulfite, either as ammonium sulfite, or sulphur dioxide and ammonia, and the addition to the filtered liquor of soluble sulfide, preferably as ammonium polysulfide or ammonium sulfide. Addition of the soluble sulfide will first precipitate metals from solution, and the remaining soluble sulfide will then react with sulfide present to produce the desired thiosulfate. This technique can be used to restore only the thiosulfate lost during the prior lixiviation and/or recovery stage, or it can be used to bring the solution to the desired strength. The mechanism of the reaction is according to equation (2), above.
The following examples will illustrate the manner in which the invention can be practiced. It is to be understood that the specific conditions set forth in the examples are not to be considered limiting to the invention.
Example l A manganese containing ore from the State of Sonora, Mexico, in the Guereguito region, was obtained, the ore having the following assay: Gold 0.014 oz per ton; Silver, 12.1 oz.
per ton; Manganese, 2.1~. This is a very difficult-to-treat ore, the owner having attempted for many years without success to have the ore commercially treated to recover the gold and silver.
g _ X
~ ~ ~8 74 ~ ' The ore was split into seven equal parts of 500 grams each. The first 500 gram portion of the lot was ground fifteen minutes in a solution containing 200 grams of ammonium thiosulfate, 12 grams of ammonium sulfite, fifty grams of ammonium hydroxide, and sufficient water to bring the solution to 1/2 liter. hfter grinding in this solution, the slurry was transferred to a 2,000 ml beaker along with additional water~ added whi.le washing the mill, to ~n~ the total to 1,200 cc. This was placed - on a hotplate with stirring and the temperature raised and maintained while stirring to between 50 and 60C. After one and one half hours of this heating and stirring, suf~icient copper sulfate was added to make 4 grams per liter of copper in solution. Stirring and heating continued for an additional six hours, adding every hour an additional amount of ammonium hydroxide to maintain the volume at a total of 1,200cc. ~t the end of this period the slurry was filtered and the solids washed twice with 250 cc of water, after which the solids were ; dried and sent for assay.
The solution from the above test was analyzed for free ammonia, ammonium thiosulfate and sulfite ion, as well as for . .
~! precious metals content. Sufficient ammonium sulfide was . .. .
added to this solution to precipitate the silver content on~y, - ; according to the following equation:
. . g2523 ~ (NH4)2S ~ Ag2S ~ (NH4~2S203 - If there is any lead in the solution which has been leached from the ore, it too would be precipitated along with the silver and therefore additional suLfide to precipitate the lead must be added in order to precipitate the silver. Some copper also precipitates and some silver will remain in the solution. However, if 80% of the silver is precipitated and the residual solution containing a little silver but most of the copper is recycled to the process, reagent costs are kept low.
.
~ ~ ~87 ~
After removing the silver precipitate, the leaching solution was recycled to the second 500 gram lot of ore~ and the above procedure repeated adding only sufficient ammonium thio-sulfate, ammonium sulfite and copper to maintain opti~um strength of the solution. Anhydrous ammonia was used in all cycles subsequent to the first, instead of ammonium hydroxide, so as to be able to use more water and better wash the values from the leached solids.
For this series, the solution analysis was brought 10 back with each cycle to the approximate analysis as follows:
Ammonium thiosulfate 18%
Ammonium sulfite 3%
Ammonium hydroxide 2%
- Copper about 4 grams per liter This process was continued as above for the seven cycles with an average of 93.2% recovery for the silver and 86.7%
of the gold. Consumption was approximately eight pounds of , ammonium thiosulfate and three pounds of ammonium sulfite per ton of ore. Copper loss was about a pound per ton.
It is therefore seen that excellent results were achieved-demonstrating the successful-and economical recovery - of gold and silver from this ~ifficult-to-treat manganese . . .
- containing ore.
.
` Example 2 - Six different "difficult" ores as identified in the tables below were split into du~licate 500 gram samples, and two series of lixviations were carried out, each series with one of the duplicates from each of the six samples. The A series of samples were treated in accordance with the present invention with 180 grams of ammonium thiosulfate> plus 9 grams of ammonium sulfite, and 4 grams of copper (as copper sulfate) and - . ' . . .
-- . . -- . , .
~ 4~
made up with water to one liter of slurry. The ~ series were treated with precisely the same 7eaching liquor, except that n~ sulfite was used. The samples were all placed on a heated-agitator and 4 grams o~ copper were added ~o each S slurry while injecting ammonla to bring the pH ~o ~.0 and the ~emperature to 50C. Every two hours throughout ~he eight hcur ~eaching, a sample was taken from the solution and in the case o ~he A series sufficient ammonium sul*ite - ~7as added to maintain the sulfite analysis at about 1/~.
~mmonia was also added to maintain the pH above 7,5, The results are given in the table below in which the identi*ication of the ore is given in the left hand column, with the gold and silver assays being presented in ounces per ton, and ~he other important ingredients are given in percent; gold and silver recoveries are reported in two series: See chart, next page.
- It will be obvious to those skilled in the art that various changes may be made without departing ~rom the scope of the invention and the invention is not to be considered -limited to what is described in the specification.
- . .
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o oo~ ~ ~ ~ ~
_ ~ ~ 0~ oLr) oO\O o~
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. ........... _ ~ .
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O ~. . O ~ O u~) O N
U~ ~0 ~1 0 ~i 0 0 0 0 ~ _ $ -- ------ ------I
~ ~ ~i o ~ o ~ b ~ .
~0 ~\o~ ~r 1_ [_ o~
C ~ ~ _ _ N o o\O ~ ~ ~1 r-l ~ CO . O ~i O
O ~ r~ O N P~ 1-- 0 ~ O O 0~ ~ \ N i--~a~O ~I N ~; O ~1 o\ o\ ZO O ~1 o\ o\O ~ O o\
~ ~ 3 ~ 3 _ ~
~ .
37~
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`~ 14
Claims (6)
1. In a method for the recovery of precious metals including gold and silver from an ore containing same, comprising lixiviating said precious metals from said ore using an ammonium thiosulfate liquor as the lixiviating agent in the presence of copper, followed by recovering said precious metals from said ammonium thiosulfate liquor, the improvement comprising:
maintaining the pH of said liquor during lixiviation at a value of at least 7.5 with ammonia, and simultaneously main-taining a sulfite ion concentration of at least 0.05%.
maintaining the pH of said liquor during lixiviation at a value of at least 7.5 with ammonia, and simultaneously main-taining a sulfite ion concentration of at least 0.05%.
2. A method in accordance with Claim 1,wherein said ore is a manganeses containing ore and said sulfite ion concentration is maintained at a level of at least 0.1%.
3. A method in accordance with Claim 1, wherein said ore contains at least 0.5% manganese and said sulfite ion concentration is maintained at 1-4%.
4. A process in accordance with Claim 1, wherein the sulfite ion concentration is maintained by generation in situ from the addition of sulfur dioxide.
5. A method in accordance with claim 1, wherein the temperature is maintained at 40 - 60°C.
6. A method in accordance with claim 1, wherein after said recovery of said precious metals, said ammonium thiosulfate liquor is recycled and additional thiosulfate is generated in situ by adding extra sulfite and sulfide and reacting the same to form the additional thiosulfate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US108,168 | 1979-12-28 | ||
| US06/108,168 US4269622A (en) | 1979-12-28 | 1979-12-28 | Recovery of precious metals from difficult ores |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1148748A true CA1148748A (en) | 1983-06-28 |
Family
ID=22320690
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000359836A Expired CA1148748A (en) | 1979-12-28 | 1980-09-08 | Recovery of precious metals from difficult ores |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4269622A (en) |
| CA (1) | CA1148748A (en) |
| ZA (1) | ZA807196B (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4369061A (en) * | 1979-12-28 | 1983-01-18 | Kerley Jr Bernard J | Recovery of precious metals from difficult ores |
| CA1188522A (en) * | 1982-03-11 | 1985-06-11 | Eberhard Krause | Recovery of silver from precious metal-containing intermediates |
| US4654078A (en) * | 1985-07-12 | 1987-03-31 | Perez Ariel E | Method for recovery of precious metals from difficult ores with copper-ammonium thiosulfate |
| GB2181722B (en) * | 1985-08-15 | 1989-08-02 | Roger Harper Little | Method for the recovery of precious metals from ores |
| US4645535A (en) * | 1985-08-15 | 1987-02-24 | Little Roger H | Method for the recovery of precious metals from ores |
| US4738718A (en) * | 1985-10-28 | 1988-04-19 | Freeport Minerals Company | Method for the recovery of gold using autoclaving |
| US4904358A (en) * | 1988-02-16 | 1990-02-27 | Inland Aqua-Tech Co., Inc. | Gold and silver recovery processes by electrolytic generation of active bromine |
| GB9002311D0 (en) * | 1990-02-02 | 1990-04-04 | Rio Tinto Minerals Dev | Separation process |
| US5114687A (en) * | 1990-12-14 | 1992-05-19 | South Dakota School Of Mines & Technology | Ammonia extraction of gold and silver from ores and other materials |
| US6482373B1 (en) | 1991-04-12 | 2002-11-19 | Newmont Usa Limited | Process for treating ore having recoverable metal values including arsenic containing components |
| US6696283B1 (en) | 1991-07-10 | 2004-02-24 | Newmont Usa Limited | Particulate of sulfur-containing ore materials and heap made therefrom |
| US5332559A (en) * | 1991-07-10 | 1994-07-26 | Newmont Gold Co. | Biooxidation process for recovery of metal values from sulphur-containing ore materials |
| US6383458B1 (en) | 1991-07-10 | 2002-05-07 | Newmont Mining Corporation | Biooxidation process for recovery of metal values from sulfur-containing ore materials |
| US5354359A (en) * | 1992-04-01 | 1994-10-11 | Newmont Gold Co. | Hydrometallurgical process for the recovery of precious metal values from precious metal ores with thiosulfate lixiviant |
| US5328669A (en) * | 1993-01-26 | 1994-07-12 | South Dakota School Of Mines And Technology | Extraction of precious metals from ores and other precious metal containing materials using halogen salts |
| US5308381A (en) * | 1993-04-15 | 1994-05-03 | South Dakota School Of Mines & Techology | Ammonia extraction of gold and silver from ores and other materials |
| US5542957A (en) * | 1995-01-27 | 1996-08-06 | South Dakota School Of Mines And Technology | Recovery of platinum group metals and rhenium from materials using halogen reagents |
| US5785736A (en) * | 1995-02-10 | 1998-07-28 | Barrick Gold Corporation | Gold recovery from refractory carbonaceous ores by pressure oxidation, thiosulfate leaching and resin-in-pulp adsorption |
| US5536297A (en) * | 1995-02-10 | 1996-07-16 | Barrick Gold Corporation | Gold recovery from refractory carbonaceous ores by pressure oxidation and thiosulfate leaching |
| GB2310424B (en) * | 1996-02-22 | 1999-09-29 | Finch Limited | Process for recovering gold from oxide-based refractory ores |
| US6251163B1 (en) | 1998-03-04 | 2001-06-26 | Placer Dome, Inc. | Method for recovering gold from refractory carbonaceous ores |
| US6368381B1 (en) | 1998-03-11 | 2002-04-09 | Placer Dome Technical Services, Ltd. | Autoclave using agitator and sparge tube to provide high oxygen transfer rate to metal-containing solutions |
| AUPQ456299A0 (en) * | 1999-12-09 | 2000-01-13 | Geo2 Limited | Recovery of precious metals |
| US6344068B1 (en) | 2000-04-04 | 2002-02-05 | Barrick Gold Corporation | Process for recovering gold from thiosulfate leach solutions and slurries with ion exchange resin |
| US6660059B2 (en) | 2000-05-19 | 2003-12-09 | Placer Dome Technical Services Limited | Method for thiosulfate leaching of precious metal-containing materials |
| US6632264B2 (en) | 2001-04-17 | 2003-10-14 | The University Of British Columbia | Gold recovery from thiosulfate leaching |
| US7722840B2 (en) * | 2002-11-15 | 2010-05-25 | Placer Dome Technical Services Limited | Method for thiosulfate leaching of precious metal-containing materials |
| EP1433860A1 (en) * | 2002-12-23 | 2004-06-30 | Paques B.V. | Process for regenerating thiosulphate from a spent thiosulphate gold leachant |
| US20040237721A1 (en) * | 2003-05-29 | 2004-12-02 | Morteza Baghalha | Anoxic leaching of precious metals with thiosulfate and precious metal oxidants |
| AU2003904385A0 (en) * | 2003-08-18 | 2003-08-28 | Murdoch University | Improved Thiosulphate Leach Process |
| US7604783B2 (en) * | 2004-12-22 | 2009-10-20 | Placer Dome Technical Services Limited | Reduction of lime consumption when treating refractor gold ores or concentrates |
| US7572317B2 (en) * | 2005-11-10 | 2009-08-11 | Barrick Gold Corporation | Thiosulfate generation in situ in precious metal recovery |
| CN101421426B (en) * | 2006-03-03 | 2015-05-27 | 鑫亚国际有限公司 | Process for extracting gold from gold-bearing ore |
| US8061888B2 (en) * | 2006-03-17 | 2011-11-22 | Barrick Gold Corporation | Autoclave with underflow dividers |
| WO2007115399A1 (en) * | 2006-04-07 | 2007-10-18 | Queen's University At Kingston | Precious metal recovery from solution |
| US8252254B2 (en) * | 2006-06-15 | 2012-08-28 | Barrick Gold Corporation | Process for reduced alkali consumption in the recovery of silver |
| WO2009037596A2 (en) * | 2007-09-17 | 2009-03-26 | Barrick Gold Corporation | Method to improve recovery of gold from double refractory gold ores |
| JP5792284B2 (en) | 2010-04-15 | 2015-10-07 | アドバンスド テクノロジー マテリアルズ，インコーポレイテッド | How to recycle an aged printed circuit board |
| PE20171794A1 (en) | 2010-12-07 | 2017-12-28 | Barrick Gold Corp | METHODS AND SYSTEM FOR LEACHING WITH THOSULFATE A MATERIAL CONTAINING GOLD AND / OR SILVER IN RESIN CIRCUITS THAT INCLUDE PARALLEL AND COUNTERCURRENT CURRENTS |
| AR086933A1 (en) | 2011-06-15 | 2014-01-29 | Barrick Gold Corp | METHOD FOR RECOVERING PRECIOUS METALS AND COPPER OF LIXIVIATE SOLUTIONS |
| BR112014014495A2 (en) | 2011-12-15 | 2017-06-13 | Advanced Tech Materials | apparatus and method for stripping weld metals during recycling of waste electrical and electronic equipment |
| US8931642B2 (en) | 2013-01-14 | 2015-01-13 | William D. Simmons | Activated flotation circuit for processing combined oxide and sulfide ores |
| US10161016B2 (en) | 2013-05-29 | 2018-12-25 | Barrick Gold Corporation | Method for pre-treatment of gold-bearing oxide ores |
| PE20211512A1 (en) | 2019-01-21 | 2021-08-11 | Barrick Gold Corp | METHOD FOR CARBON-CATALYZED THOSULFATE LEACHING OF MATERIALS CONTAINING GOLD |
| PE20220206A1 (en) | 2019-06-03 | 2022-02-01 | Barrick Gold Corp | METHOD FOR RECOVERING PRECIOUS METALS FROM THIOSULFATE LEACHING SOLUTIONS |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US296709A (en) * | 1884-04-08 | Xpf s seraratigg precious w etals frofvl ores | ||
| US296710A (en) * | 1884-04-08 | Tbeeitoey | ||
| US295815A (en) * | 1884-03-25 | Teeeitoet | ||
| US381849A (en) * | 1888-04-24 | Teeeitoey | ||
| US320590A (en) * | 1885-06-23 | Teeeitoey | ||
| US366103A (en) * | 1887-07-05 | Process of extracting silver from its ores by lixlviation | ||
| US295816A (en) * | 1884-03-25 | Teeeitoey | ||
| US1627582A (en) * | 1922-09-07 | 1927-05-10 | Thomas H Sherian | Process for treatment of ores |
| BE380028A (en) * | 1929-11-29 | 1900-01-01 | ||
| US1870703A (en) * | 1931-04-17 | 1932-08-09 | Allingham John | Metallurgical process |
| US2693404A (en) * | 1951-01-18 | 1954-11-02 | Sherritt Gordon Mines Ltd | Method of separating metal values from ammoniacal solutions |
| US2822263A (en) * | 1954-09-01 | 1958-02-04 | Sherritt Gordon Mines Ltd | Method of extracting copper values from copper bearing mineral sulphides |
| US2928732A (en) * | 1957-08-20 | 1960-03-15 | Bethlehem Steel Corp | Use of so2 in ammonia leaching mayari ore |
| US3848054A (en) * | 1972-06-02 | 1974-11-12 | Freeport Minerals Co | Recovery of cobalt values from the leached ore tailings of a conventional ammoniacal leaching process |
| US3983017A (en) * | 1972-12-01 | 1976-09-28 | Kennecott Copper Corporation | Recovery of metal values from manganese deep sea nodules using ammoniacal cuprous leach solutions |
| JPS5316761B2 (en) * | 1974-05-23 | 1978-06-03 | ||
| US3953200A (en) * | 1975-03-27 | 1976-04-27 | Ethyl Corporation | Nickel extraction process |
| CA1073681A (en) * | 1976-02-20 | 1980-03-18 | Roman M. Genik-Sas-Berezowsky | Recovery of precious metals from metal sulphides |
-
1979
- 1979-12-28 US US06/108,168 patent/US4269622A/en not_active Expired - Lifetime
-
1980
- 1980-09-08 CA CA000359836A patent/CA1148748A/en not_active Expired
- 1980-11-19 ZA ZA00807196A patent/ZA807196B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| US4269622A (en) | 1981-05-26 |
| ZA807196B (en) | 1981-08-26 |
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