CA1145951A - Process for beneficiating gold - Google Patents
Process for beneficiating goldInfo
- Publication number
- CA1145951A CA1145951A CA000342807A CA342807A CA1145951A CA 1145951 A CA1145951 A CA 1145951A CA 000342807 A CA000342807 A CA 000342807A CA 342807 A CA342807 A CA 342807A CA 1145951 A CA1145951 A CA 1145951A
- Authority
- CA
- Canada
- Prior art keywords
- gold
- mixture
- iron
- iron carbonyl
- carbonyl
- 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
Links
Abstract
PROCESS FOR BENEFICIATING GOLD JAMES K. KINDIG
RONALD L. TURNER
ABSTRACT
A process for beneficiating particulate gold from non-magnetic foreign material with which it is mixed which comprises contacting the mixture with an iron carbonyl in order to selectively enhance the magnetic susceptibility of the gold particles so that a magnetic separation between the gold and foreign material may be effected.
RONALD L. TURNER
ABSTRACT
A process for beneficiating particulate gold from non-magnetic foreign material with which it is mixed which comprises contacting the mixture with an iron carbonyl in order to selectively enhance the magnetic susceptibility of the gold particles so that a magnetic separation between the gold and foreign material may be effected.
Description
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BACI'~G~OU~D OF T~ NV~NTION
As is well known, since the qovernment has lifted the price on gold from $35.00 an ounce, the price of yold has multiplied. As a result, many gold mines ~hich were forced out of operation by the $35.00 an ounce-ceiling have now resumed operations, and gold exploration and mining has greatly increased.
Because most gold ores contain less than a few ounces of gold per ton of ore, large amounts of gangue must be processed in order to recover the gold. In addition to the low grade of gold ores, the gold is usually present as very fine particles.
Thus, gravity processes for the separation of gold from gangue are inefficient. This is due to the high viscous drag forces acting on small particles in water relative to the force of gravity.
Typically, large amounts of water are needed for bene-ficiating gol~ ores, particularly placer gold ores. This is a significant problem in recovering gold from low , ~, , '' , ' .
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grade ores particularly plac-~rs existing in arid areas su-~h as deserts. There is, therefore, considerable time and expense involved in recovering gold from its ores.
The above conditions have created a need for improved and more efficient beneEiciating procedures for the recovery of gold from low grade ores, i.e., gold - associated Wit}l ~oreign materials with which the gold exists in small percentages. Also, a process which operates dry would be especially useful, because it would provide a method for recovering gold which is located in deserts.
Accordingly, it is a principal object of this invention to provide an economically feasible method for separating gold rom foreign material by selectively enhancing the magnetic susceptibility of the gold particles so that they may be successfully separated from the foreign material by magnetic separation.
SUMI~ARY OF Tll~ INVENTION
The magnetic susceptibility of gold associate~
with oreign materials is increased to the point where magnetic separation of gold particles from the foreign material is feasil~le. The magnetic susceptibility of the gold particles is increased by contacting a mixture of particulate gold ~nd foreign materials, such as occurs with placer deposits, with an iron carbonyl like iron pentacarbonyl under conditions at which general decompo-sition of the iron carbonyl into metallic iron and carbon .
monoxide is not appreciable. ~he carbonyl-treated mixture is then passed through a ma~netic separator for removal of the gold particles.
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Placer ~old ores usually do not require grinding to achieve liberation; however, if required~ they may be ground. The liberated ore is then contacted with carbonyl vapors in a gas treating chamber, either alone or by means of a gas that is inert to the process, which is used to carry the iron carbonyl vaporsO Physical separation between gold and forei~n material follows in a magnetic separator.
DESCI~IPTION O~ THE; PREF13RRED E:~5BODIMENTS
The invention is particularly useful for re-covering gold from placer type gold deposits wherein gold particles which are either free or have an e~posed surface exist in small percentages with large amounts of sand and other particulate material including dolomite, albite, muscovite, gypsu~, and calciteO In the case o placer gold, grinding can ordinarily be dispensed with. The invention i5 apylicable to recoverin~ gold from quartz, granite, other type rocks, and other mat~rial to which it is attached;
however, in the case of these materials it is ordinarily first necessary to grind the material to a sufficiently fine particle si~e to liberate particulate gold. This process also includes the recovery of more than one metal value at a time from an ore or mixture. The terrn "mixture"
- as used herein includes ore.
It is not known why the process of the invention énhances l:he magnetic susceptibility of the gold particles.
It is well known that neither gold nor iron carbonyl are magnetic. It is probable that the ~old is coated with a thin shell oE metallic iron, which, of course, is magnetic.
What is not known is why there should be a selective deposi-tion of a film of magnetic material on the gold while under . ~ . . .
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essentially the same conditions there i5 not decomposition of iron carbonyl producing a magnetic ilm on all ~he ore - particles. Of course, a rapid and complete decompositicn of iron carbonyl would ~esult in coating partic}es of both gold and the fo~eign material with iron so tha~ an effective magnetic separation would be obviated. Other metal car-~onyls may be used such as those o~ the Group ~III metals nickel and cobalt.
Iron carbonyl decomposes under the proper tempera-ture conditions in accordance with the following reaction:Fe(CO)5 ~_ Fe ~ 5C~
The process is applied by contacting the mi~ture of gold and foreign material with iron carbonyl under conditions wherein the iron carbonyl decomposes to form a magnetic skin on the gold particles but not on the foreign material. These conditions are determined ~y the temperature, the type of carbonyl used, pressure, gas composition, etc.
ordinarily~ th~ reaction occurs at a teraperature just below the substantial decomposition temperature of the ~ carbonyl in the presence of an ore. Various types of available equipment can be used for contacting the gold and foreign material with iron carbonyl vapors, such as, a rotating kiln used as B reaction vessel with the material being contacted directly with iron carbonyl vapors or the ~5 vapors carried into contact with the tumbling contents of the kiln by a gas such as nitroc3en which is inert to the j reaction process. It has been found that the material : which enhances the magnetic susceptibility of the gold particles exercises a preferential selectivity for the ~¦ gold particles over the particles of the foreign material.
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The process must be carried out at a tempexature below the temperature o major decomposition of the carbonyl under the reaction conditions so that there is no opportunity or decomposition o~ the carbonyl on a nonselective basis or, ~erhaps, for its reaction with some material to produce the magnetic material with which the gold particles are coated. Obviously, if ~he temperature is allowed ~o rise above thc decomposition temperature of the carbonyl for sufficient time, complete decomposition of the carbonyl will occur with the result that the particles of the foreign material as well as the gold will be coated with metallic iron to give both types of particles an enhanced ¦ magnetic suscep~ibility, thus preventing their effective separation magnetically.
The amount of carbonyl used and the time of treat-ment can be varied to efect substantially complete magneti-zation of the gold presentO l`he time, temperature and injection rate o the treatment is a balance between the reaction rate and the economics of the magnEtic separation ' process. Carbonyl will be added in an amount of from about 0.1 to about 128 kilograms per metric ton of feed with from about 0.25 to about 8 ]cilograms per metric _ ~ ton o feed being preferred and from about 0.5 to about 4.0 kilograms per metric ton of feed being more preferred.
~dditionally, it is preferred to in~ect the carbonyl into I the reactor durin~ the first ha].f of the roast period ¦ and it is more preferred if it is injected during the j~ first quarter of the roast and most preferred if injected during the first tenth of the roast period~
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Generally, a reaction time not in excess of about two hours is adequate, with a reaction time not in excess of one hour being preferxed and a reaction time not in excess of a hal~ hour being most preferredO The temperature at which the reaction is formed at atmospheric pressure can vary between about 100-250C, a preferred temperature rang?e is from about 100 to about 150C and a more preferred temperature ran~e is from about 110 to about 130C.
Generally, the higller the temperature, the more complete the gold recovery with lower gold concentration in both the tails and the magnetic concentrate and the larger the amount of magnetic concentrate. Therefore, for any feed material, the economics of the situation will have to be consi~ered and conditions set to produce the most favorable balance between the grade and recovery.
If desired, prior to treating the gold and foreign material with iron carbonyl, the mixture of gold and foreign material can be magnetically cleaned to remove any magnetlc impurities. Thereafter, the non magnetic fraction o~ the ~0 mixture is treated wlth the iron carbonyl. After the feed mixture containing the gold has been treated with a metal carbonyl, it is then subjected to a magnetic separation process to efEect the separation of gold. Any of many comrnercially available magnetic separators can be used to remove the gold from the gangue. Por example, low or medium intensity separations can be made with a permanent magnetic drum separator (field strengths up to about
BACI'~G~OU~D OF T~ NV~NTION
As is well known, since the qovernment has lifted the price on gold from $35.00 an ounce, the price of yold has multiplied. As a result, many gold mines ~hich were forced out of operation by the $35.00 an ounce-ceiling have now resumed operations, and gold exploration and mining has greatly increased.
Because most gold ores contain less than a few ounces of gold per ton of ore, large amounts of gangue must be processed in order to recover the gold. In addition to the low grade of gold ores, the gold is usually present as very fine particles.
Thus, gravity processes for the separation of gold from gangue are inefficient. This is due to the high viscous drag forces acting on small particles in water relative to the force of gravity.
Typically, large amounts of water are needed for bene-ficiating gol~ ores, particularly placer gold ores. This is a significant problem in recovering gold from low , ~, , '' , ' .
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grade ores particularly plac-~rs existing in arid areas su-~h as deserts. There is, therefore, considerable time and expense involved in recovering gold from its ores.
The above conditions have created a need for improved and more efficient beneEiciating procedures for the recovery of gold from low grade ores, i.e., gold - associated Wit}l ~oreign materials with which the gold exists in small percentages. Also, a process which operates dry would be especially useful, because it would provide a method for recovering gold which is located in deserts.
Accordingly, it is a principal object of this invention to provide an economically feasible method for separating gold rom foreign material by selectively enhancing the magnetic susceptibility of the gold particles so that they may be successfully separated from the foreign material by magnetic separation.
SUMI~ARY OF Tll~ INVENTION
The magnetic susceptibility of gold associate~
with oreign materials is increased to the point where magnetic separation of gold particles from the foreign material is feasil~le. The magnetic susceptibility of the gold particles is increased by contacting a mixture of particulate gold ~nd foreign materials, such as occurs with placer deposits, with an iron carbonyl like iron pentacarbonyl under conditions at which general decompo-sition of the iron carbonyl into metallic iron and carbon .
monoxide is not appreciable. ~he carbonyl-treated mixture is then passed through a ma~netic separator for removal of the gold particles.
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Placer ~old ores usually do not require grinding to achieve liberation; however, if required~ they may be ground. The liberated ore is then contacted with carbonyl vapors in a gas treating chamber, either alone or by means of a gas that is inert to the process, which is used to carry the iron carbonyl vaporsO Physical separation between gold and forei~n material follows in a magnetic separator.
DESCI~IPTION O~ THE; PREF13RRED E:~5BODIMENTS
The invention is particularly useful for re-covering gold from placer type gold deposits wherein gold particles which are either free or have an e~posed surface exist in small percentages with large amounts of sand and other particulate material including dolomite, albite, muscovite, gypsu~, and calciteO In the case o placer gold, grinding can ordinarily be dispensed with. The invention i5 apylicable to recoverin~ gold from quartz, granite, other type rocks, and other mat~rial to which it is attached;
however, in the case of these materials it is ordinarily first necessary to grind the material to a sufficiently fine particle si~e to liberate particulate gold. This process also includes the recovery of more than one metal value at a time from an ore or mixture. The terrn "mixture"
- as used herein includes ore.
It is not known why the process of the invention énhances l:he magnetic susceptibility of the gold particles.
It is well known that neither gold nor iron carbonyl are magnetic. It is probable that the ~old is coated with a thin shell oE metallic iron, which, of course, is magnetic.
What is not known is why there should be a selective deposi-tion of a film of magnetic material on the gold while under . ~ . . .
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essentially the same conditions there i5 not decomposition of iron carbonyl producing a magnetic ilm on all ~he ore - particles. Of course, a rapid and complete decompositicn of iron carbonyl would ~esult in coating partic}es of both gold and the fo~eign material with iron so tha~ an effective magnetic separation would be obviated. Other metal car-~onyls may be used such as those o~ the Group ~III metals nickel and cobalt.
Iron carbonyl decomposes under the proper tempera-ture conditions in accordance with the following reaction:Fe(CO)5 ~_ Fe ~ 5C~
The process is applied by contacting the mi~ture of gold and foreign material with iron carbonyl under conditions wherein the iron carbonyl decomposes to form a magnetic skin on the gold particles but not on the foreign material. These conditions are determined ~y the temperature, the type of carbonyl used, pressure, gas composition, etc.
ordinarily~ th~ reaction occurs at a teraperature just below the substantial decomposition temperature of the ~ carbonyl in the presence of an ore. Various types of available equipment can be used for contacting the gold and foreign material with iron carbonyl vapors, such as, a rotating kiln used as B reaction vessel with the material being contacted directly with iron carbonyl vapors or the ~5 vapors carried into contact with the tumbling contents of the kiln by a gas such as nitroc3en which is inert to the j reaction process. It has been found that the material : which enhances the magnetic susceptibility of the gold particles exercises a preferential selectivity for the ~¦ gold particles over the particles of the foreign material.
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The process must be carried out at a tempexature below the temperature o major decomposition of the carbonyl under the reaction conditions so that there is no opportunity or decomposition o~ the carbonyl on a nonselective basis or, ~erhaps, for its reaction with some material to produce the magnetic material with which the gold particles are coated. Obviously, if ~he temperature is allowed ~o rise above thc decomposition temperature of the carbonyl for sufficient time, complete decomposition of the carbonyl will occur with the result that the particles of the foreign material as well as the gold will be coated with metallic iron to give both types of particles an enhanced ¦ magnetic suscep~ibility, thus preventing their effective separation magnetically.
The amount of carbonyl used and the time of treat-ment can be varied to efect substantially complete magneti-zation of the gold presentO l`he time, temperature and injection rate o the treatment is a balance between the reaction rate and the economics of the magnEtic separation ' process. Carbonyl will be added in an amount of from about 0.1 to about 128 kilograms per metric ton of feed with from about 0.25 to about 8 ]cilograms per metric _ ~ ton o feed being preferred and from about 0.5 to about 4.0 kilograms per metric ton of feed being more preferred.
~dditionally, it is preferred to in~ect the carbonyl into I the reactor durin~ the first ha].f of the roast period ¦ and it is more preferred if it is injected during the j~ first quarter of the roast and most preferred if injected during the first tenth of the roast period~
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Generally, a reaction time not in excess of about two hours is adequate, with a reaction time not in excess of one hour being preferxed and a reaction time not in excess of a hal~ hour being most preferredO The temperature at which the reaction is formed at atmospheric pressure can vary between about 100-250C, a preferred temperature rang?e is from about 100 to about 150C and a more preferred temperature ran~e is from about 110 to about 130C.
Generally, the higller the temperature, the more complete the gold recovery with lower gold concentration in both the tails and the magnetic concentrate and the larger the amount of magnetic concentrate. Therefore, for any feed material, the economics of the situation will have to be consi~ered and conditions set to produce the most favorable balance between the grade and recovery.
If desired, prior to treating the gold and foreign material with iron carbonyl, the mixture of gold and foreign material can be magnetically cleaned to remove any magnetlc impurities. Thereafter, the non magnetic fraction o~ the ~0 mixture is treated wlth the iron carbonyl. After the feed mixture containing the gold has been treated with a metal carbonyl, it is then subjected to a magnetic separation process to efEect the separation of gold. Any of many comrnercially available magnetic separators can be used to remove the gold from the gangue. Por example, low or medium intensity separations can be made with a permanent magnetic drum separator (field strengths up to about
2,500 gauss), electromagnetic drum separators (field strengths up to about 7,000 gauss), induced roll separators (field strengths of about 11,000 gauss) or other confi~-urations known to those skilled in the art. Additionally, newer high-~Jradierlt magnetic separators are espacially good .
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for separating ~ines, although they are generally operated wet. A dry matJnetic separation process for gold iB
generally preferrcd. This avoids the exp~nse o~ de-waterin~ and also allo~s for the reco~ery of gold from deserts.
The invention is illustrated by the examples I presented below in which samples of placer gold and associated foreign material were treated by the process . of the invention. The examples are illustrative of the invention bu~ not limiting thereofO
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~X~MPL~ 1 In this example, a sample of placer gold concen-trate was diluted with gangue of essentially silicon dioxide and aluminum dioxide. The resultant sample con-tained 4050 grams gold per metric ton of placer ore. ~or - ~ the purpose of a blank, a comparative magnetic separation ~ was made on an untreated portion of the sample. Rnother ~~ ! portion of the sample was treated with the process of the ? invention at 135C and a third portion of the sample was ;~t , z~ treated by the process of the invention at temperatures up to 145 C. Both of the treated samples were subjected to magnetic separation as in the first test, and the magnetit, and nonmagnetic ractions of each test were analy~ed as , to ~old content with the gold distributlon for the magnetic and nonmagnetic fractions of each test cGmputed. By "Gold Distribution" is meant the percentage of gold in the entire ,; ~ beginning sample which is partitioned to the specified final ~ fraction. The following table sets forth the results obtaint .. 1 . - ~
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'I'ABI,E 1 Weight Gold Gold Treatment % of AssayDistri-of_Samplt~ FractionsSample oz/tonbution No Treatment Magnetic 11.54 21~26 1.92 Non-Mat7netic 88.46142 04 98.08 Low TempeOa-turc 135 C, 30 min Magnetic11.95 132.8713.29 32 kgfm. ton Fe(CO)5 Non-Magnetic 88.05117.68 86.71 High Tempera-turQ up to 145~C in 23 min Magnetic14.18 200.8326.79 ~otal 23 kg/
m.ton FetCO)5 Non-Magnetic85.82 90.70 73.21 EX~MPLE 2 To provide a test sample for this example, 4.7 grams of the non-magnetic fraction of a placer gold con-centrate was blended with 195 grams of sandO Analysis of this material showed a gold content of 84 grams per metric ton. A one-~tn~ split of the above material (52 grams) was placed in a rotating glass reactor and heated to 150C under nitrogen. At this temperature, the mixture was exposed to vapors of iron carbonyl ~or one half hour at an amount equal to about 32 kilograms of carbonyl per metric ton oE material. Cool down was under nitrogen.
After treatment, magnetic separation was efEected by using a Dings crossbelt separator with a 4.5 amp setting. Two recleanings of the magnetic material were made.
The results of the above tests are set forth in the following table:
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col.cent~:a~e a8 3 5(~agnetic) ~o96 225O
[Non-Magnetic) 99.04 0.29 11.7 ?
EX~MP~E 3 The sample of Clear Creek placer gold from Colorado was diluted with silica to yield a gold content of 1.0 kilogram per metric ton. This placer yold ore 1 was treated with 1 kilogram of iron pentacarbonyl per ¦ metric ton feed at a temperature of 122C for 15 minutes.
The iron carbonyl was injected in l.S minutes coincident 1~ with the start of the lS minute roast and the reaction chamber was purged with nitrogen during heating and cool down. The reactor product was magnetically separated 1 yielding a magnetic con~centrate of 57O4 kilograms per $1 metric ton of gold (1676 ounce per ton~ and 1.6~ of the . 20 feed. The non-magnetic tails contained 660 9 grams per / metric ton gold (1.95 ounce per ton). The overall gold ~, I recovery was 93.3%.
EXJ~/IPLE 4 To several non-magnetic fractions of 28- x lS0-mesh Vulture placer from Arizona spiked with non-magnetic 28- x 150-mesh Clear Cxeek gold concentrate to a total of 891 grams per metric ton (26 ounce per ton) wexe added various co~mon mineralsO Several samples were made from this mixture by adding an eYcess of loe of each of the ~ '.'.,>~
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gangue minerals so that the gold content oE the composited placer ore was approximately 823 grams per metric ton (24 ounce per ton). Each of the mixtures was then treated with 1 kilogram of iron pentacarbonyl per metric ton of feed for 15 minutes at 122C in a small glass rotary reactor. The treated ore was then separated usin~ an induced magnetic roll (IMR) separator and the products assayed for gold.
The results are glven below in Table 3.
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TA~L13 3 . Gold Gold Added .M~q etic ~t % o~ ~ of Total Muscovite Nonma3netic 278 6 ,82 698 ag.3 Calc head 100.026.5 Gypsum No~magnedic 100 0 26.6 llen~atite ~agnet;lCtic 48 7 310 8 76.5 Calc head 100.022.3 Albite l~onmat3netiC lloO.. 82o 125.0 87.4 J Dolomite ~laynetic 19.0 91.2 85.9 Nonmagnetlc 81.
Calc head 100.020.2 ",~ 20 Calcite Nogmay letlc 810 o 92330 9367 86.7 '~ Silioal Nonmagnctic 98 4 1 95 Calc head 100.028.7 ¦ Vulture Nonmaylletic 79 6 ~ 78.0 Vulture~ gnetict 729 82 106 0 ~ 82.0 Nonrna~i1nead100 0 26.0 Clear Creek yold collcentrate added to silica sand, :
no Vulture placer.
Assay data not available ~or tails.
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EX~MPLE S
~ synth~tic placer containing 891 grams of gold per metric ton (26 ounce per ton) was diluked with magnetically sc,alped Vulture placer to 27.1 grams of gold per metric ton of feed ~0.79 once per ton)O The gold particles con~ained in this feed material were 28- x 150-mesh. A second sample of a placer containing a low gold content was prepared by adding 49 flakes of 65- x 100-mesh gold ~hand picked from Clear Creek concentrate) to one kiloyram of magnetically scalped Vulture placer. This resulted in a placer ore contain-ing 3.4 grams of gold per metric ton of feed (0.098 ounce per ton). One kilogram samples of each of these mixtures was then separately treated at 122C for 15 minutes with an iron pentacarbonyl dosage of one kilogram pex metric ton of feed. The carbonyl was injected into the reactor by a syringe pump calibrated to deliver the required amount oE iron carbonyl in the first 1.5 minutes of the roast. The test~results are presented in Table 4.
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2 O , T2~BLE
Gold Yield, Gold ~ssay, Recovery PractionWt ~i _ oz/ton ~i of ~'otal Magnt-3tic11.6 5.82 85.7 25 . Nonmaglletic 88.4 0.127 Calc head100.0 0.787 Mac3netic14.1 0.49 69.9 Nonmagnetic 85.1 0.034 Calc head100.0 0.098 , . 1~ ' ' .
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Eight 90 gram samples of a simulated gold placer ore with a si~e range of 28- x 150-mesh were subjected to two different ~oast d~rations, iOe~ 15 minutes and 60 minutes. For each of these times two injection rates were used, additionally ~he effec~ of varying roast time and injection rates were analy~ed with respect to different size fractions. All of the samples were treated with 4 kilograms of iron carbonyl per metric ton at a tempera-ture of 120-122C. ~or the "slow" injection rate, the iron carbonyl was injected during the entire run, while for the "fast" injection rate, all the iron carbonyl was injected in the first 11% of the roast time, i.e.
1.65 minutes for the 15 minute run and 6.6 minutes for the 60 minute run. The results are given below in Tables 5 and 6. ~
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~X~MPLE 7 ~ synthetic gold placer ore was prepared from the nonmagnetic fraction of Vulture placer spiked to ap-proximately 920 grams gold per metric ~on f~ed with the nonmagnetic portion of Clear Creek gold concentrate. The size range o the feed was 28- x 150-meshO Four dif-ferent samples were treated with 4 kilograms iron penta-ca~bonyl per metric ton of feed for a period of 15 minutes - at various temperatures. The results are given below in Table 7.
~ - T~LE 7 ¦ Treatment Gold Gold Distri-Tempgratu~e Yield ~ssay, bution C Fraction W _ oz/ton 110 Magnet.ic 9.42245. 86.2 No~lmaanetic 90.58 4.09 13.8 Calc head 100.0 26.8 115 Ma~netic 9.37 276.93.7 Nonmaanetic 90.63 1.93 6.3 Calc head 100.0 27.6 125 Maqnetic, 25.42 93.0 99.2 Nonma(Jnetic 74.58 0.26 0.8 - Calc head 100.0 23.8 135 Ma~ne-tic 73.42 39.299.98 N nmahnadic 100 0 28 82 ~0,02 :~ , ' ' :
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A synthetiC 9 pi~od to ap-OnmagnetiC ~aCtion tric ~on o~ feed (2 pro .th a nonmagnetic P
ullce p ~he Size range of ctor for lS ml 5 ~ rlbed irOn ~sr 130oc at a pr6 tacarbonyl per 'i~1 ox 4 kilograms 5 minute5 of the roa t c 5~paratin ~
d r With the ma9 n i e raction5 being Carried i fractin three PasSes d ~ver an indUced ma9n h e testS are an the cOmposited~size marlze _'3 ~.." ' .''','',^" ~ ' .
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R p~acer ore containing 446 grams gold per ~etric ton of fee,d (13 ounces per ton) which had been treated with 4 ki.lograms of iron pentacarbonyl per metric ton of ~eed for one hour at a temperature o~
125 to 130C in a large reacto~ was subje,ctecd to abr~sive and weathering conclitions prior to magnetic separation o~
the gold. The results are given below in Table 9.
T ~
Gold Gold Sam~]e Treatment Yield ~ssay, Recovery Be~ore t on ~ oz/Ton Magnetic Separation Frac 1 _ ' ' in Dry ~ir , Nonmagnetic 60 3 0.78 ~ged lwo~iMro NonmacJnctic 64 1 0 87 ~cJ d T~o Month'din24 yonmaqnetic 65 1 11 9 D1y ~ir, ~Y~l~osed 48 Nonmaclnet~jic 62 8 30 5 91,4 '.^~ llumidity, Stored ' ~ 24 llours in Vial ~:~ . , . .:
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~X~ML'LE 10 Sam~les oE a non-magnetic fraction o~ 28-x 65-mesh Vulture placer were spiked ~ith non-magnetic 28- x 65-mesh Clear Creek gold concentrate ~o ob~ain 1.99 kilograms of gold per metric ton of synthetic placer (58 oz/ton~. The synthetic placer was then wet-screened at 55-mesh to remove fines. Thereafter, each sample was treated with iron carbonyl at varying levels at a 122C in a small glass rotary reactor for 15 minutes.
In each case, the carbonyl was injected during the first 1.5 minute of the roast. Results are given below.
I ~ TABLe 10 ¦ Carbonyl Yield, Wt. % ~ Recovery, k/a9ton Maqnetic magnetic Magnetic mag ~
1 9.3 90.7 5608.14 59.5 87.6 2 9.6 90.4 ~915.06 51.7 91.2 a lo.l as.o 36:2.59 60 3 94.2 I
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for separating ~ines, although they are generally operated wet. A dry matJnetic separation process for gold iB
generally preferrcd. This avoids the exp~nse o~ de-waterin~ and also allo~s for the reco~ery of gold from deserts.
The invention is illustrated by the examples I presented below in which samples of placer gold and associated foreign material were treated by the process . of the invention. The examples are illustrative of the invention bu~ not limiting thereofO
e~ .
~X~MPL~ 1 In this example, a sample of placer gold concen-trate was diluted with gangue of essentially silicon dioxide and aluminum dioxide. The resultant sample con-tained 4050 grams gold per metric ton of placer ore. ~or - ~ the purpose of a blank, a comparative magnetic separation ~ was made on an untreated portion of the sample. Rnother ~~ ! portion of the sample was treated with the process of the ? invention at 135C and a third portion of the sample was ;~t , z~ treated by the process of the invention at temperatures up to 145 C. Both of the treated samples were subjected to magnetic separation as in the first test, and the magnetit, and nonmagnetic ractions of each test were analy~ed as , to ~old content with the gold distributlon for the magnetic and nonmagnetic fractions of each test cGmputed. By "Gold Distribution" is meant the percentage of gold in the entire ,; ~ beginning sample which is partitioned to the specified final ~ fraction. The following table sets forth the results obtaint .. 1 . - ~
~"~ 7 .-9 . ,..... ;., . . . - :
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595~L
'I'ABI,E 1 Weight Gold Gold Treatment % of AssayDistri-of_Samplt~ FractionsSample oz/tonbution No Treatment Magnetic 11.54 21~26 1.92 Non-Mat7netic 88.46142 04 98.08 Low TempeOa-turc 135 C, 30 min Magnetic11.95 132.8713.29 32 kgfm. ton Fe(CO)5 Non-Magnetic 88.05117.68 86.71 High Tempera-turQ up to 145~C in 23 min Magnetic14.18 200.8326.79 ~otal 23 kg/
m.ton FetCO)5 Non-Magnetic85.82 90.70 73.21 EX~MPLE 2 To provide a test sample for this example, 4.7 grams of the non-magnetic fraction of a placer gold con-centrate was blended with 195 grams of sandO Analysis of this material showed a gold content of 84 grams per metric ton. A one-~tn~ split of the above material (52 grams) was placed in a rotating glass reactor and heated to 150C under nitrogen. At this temperature, the mixture was exposed to vapors of iron carbonyl ~or one half hour at an amount equal to about 32 kilograms of carbonyl per metric ton oE material. Cool down was under nitrogen.
After treatment, magnetic separation was efEected by using a Dings crossbelt separator with a 4.5 amp setting. Two recleanings of the magnetic material were made.
The results of the above tests are set forth in the following table:
.
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.
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T~BL~ 2 yio~d ~ (Oz/Ton~ D~
col.cent~:a~e a8 3 5(~agnetic) ~o96 225O
[Non-Magnetic) 99.04 0.29 11.7 ?
EX~MP~E 3 The sample of Clear Creek placer gold from Colorado was diluted with silica to yield a gold content of 1.0 kilogram per metric ton. This placer yold ore 1 was treated with 1 kilogram of iron pentacarbonyl per ¦ metric ton feed at a temperature of 122C for 15 minutes.
The iron carbonyl was injected in l.S minutes coincident 1~ with the start of the lS minute roast and the reaction chamber was purged with nitrogen during heating and cool down. The reactor product was magnetically separated 1 yielding a magnetic con~centrate of 57O4 kilograms per $1 metric ton of gold (1676 ounce per ton~ and 1.6~ of the . 20 feed. The non-magnetic tails contained 660 9 grams per / metric ton gold (1.95 ounce per ton). The overall gold ~, I recovery was 93.3%.
EXJ~/IPLE 4 To several non-magnetic fractions of 28- x lS0-mesh Vulture placer from Arizona spiked with non-magnetic 28- x 150-mesh Clear Cxeek gold concentrate to a total of 891 grams per metric ton (26 ounce per ton) wexe added various co~mon mineralsO Several samples were made from this mixture by adding an eYcess of loe of each of the ~ '.'.,>~
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gangue minerals so that the gold content oE the composited placer ore was approximately 823 grams per metric ton (24 ounce per ton). Each of the mixtures was then treated with 1 kilogram of iron pentacarbonyl per metric ton of feed for 15 minutes at 122C in a small glass rotary reactor. The treated ore was then separated usin~ an induced magnetic roll (IMR) separator and the products assayed for gold.
The results are glven below in Table 3.
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TA~L13 3 . Gold Gold Added .M~q etic ~t % o~ ~ of Total Muscovite Nonma3netic 278 6 ,82 698 ag.3 Calc head 100.026.5 Gypsum No~magnedic 100 0 26.6 llen~atite ~agnet;lCtic 48 7 310 8 76.5 Calc head 100.022.3 Albite l~onmat3netiC lloO.. 82o 125.0 87.4 J Dolomite ~laynetic 19.0 91.2 85.9 Nonmagnetlc 81.
Calc head 100.020.2 ",~ 20 Calcite Nogmay letlc 810 o 92330 9367 86.7 '~ Silioal Nonmagnctic 98 4 1 95 Calc head 100.028.7 ¦ Vulture Nonmaylletic 79 6 ~ 78.0 Vulture~ gnetict 729 82 106 0 ~ 82.0 Nonrna~i1nead100 0 26.0 Clear Creek yold collcentrate added to silica sand, :
no Vulture placer.
Assay data not available ~or tails.
~ . . . .
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EX~MPLE S
~ synth~tic placer containing 891 grams of gold per metric ton (26 ounce per ton) was diluked with magnetically sc,alped Vulture placer to 27.1 grams of gold per metric ton of feed ~0.79 once per ton)O The gold particles con~ained in this feed material were 28- x 150-mesh. A second sample of a placer containing a low gold content was prepared by adding 49 flakes of 65- x 100-mesh gold ~hand picked from Clear Creek concentrate) to one kiloyram of magnetically scalped Vulture placer. This resulted in a placer ore contain-ing 3.4 grams of gold per metric ton of feed (0.098 ounce per ton). One kilogram samples of each of these mixtures was then separately treated at 122C for 15 minutes with an iron pentacarbonyl dosage of one kilogram pex metric ton of feed. The carbonyl was injected into the reactor by a syringe pump calibrated to deliver the required amount oE iron carbonyl in the first 1.5 minutes of the roast. The test~results are presented in Table 4.
.
2 O , T2~BLE
Gold Yield, Gold ~ssay, Recovery PractionWt ~i _ oz/ton ~i of ~'otal Magnt-3tic11.6 5.82 85.7 25 . Nonmaglletic 88.4 0.127 Calc head100.0 0.787 Mac3netic14.1 0.49 69.9 Nonmagnetic 85.1 0.034 Calc head100.0 0.098 , . 1~ ' ' .
_ , .... . ... . . . _ ._,.. ~__._.. ..
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.
Eight 90 gram samples of a simulated gold placer ore with a si~e range of 28- x 150-mesh were subjected to two different ~oast d~rations, iOe~ 15 minutes and 60 minutes. For each of these times two injection rates were used, additionally ~he effec~ of varying roast time and injection rates were analy~ed with respect to different size fractions. All of the samples were treated with 4 kilograms of iron carbonyl per metric ton at a tempera-ture of 120-122C. ~or the "slow" injection rate, the iron carbonyl was injected during the entire run, while for the "fast" injection rate, all the iron carbonyl was injected in the first 11% of the roast time, i.e.
1.65 minutes for the 15 minute run and 6.6 minutes for the 60 minute run. The results are given below in Tables 5 and 6. ~
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~X~MPLE 7 ~ synthetic gold placer ore was prepared from the nonmagnetic fraction of Vulture placer spiked to ap-proximately 920 grams gold per metric ~on f~ed with the nonmagnetic portion of Clear Creek gold concentrate. The size range o the feed was 28- x 150-meshO Four dif-ferent samples were treated with 4 kilograms iron penta-ca~bonyl per metric ton of feed for a period of 15 minutes - at various temperatures. The results are given below in Table 7.
~ - T~LE 7 ¦ Treatment Gold Gold Distri-Tempgratu~e Yield ~ssay, bution C Fraction W _ oz/ton 110 Magnet.ic 9.42245. 86.2 No~lmaanetic 90.58 4.09 13.8 Calc head 100.0 26.8 115 Ma~netic 9.37 276.93.7 Nonmaanetic 90.63 1.93 6.3 Calc head 100.0 27.6 125 Maqnetic, 25.42 93.0 99.2 Nonma(Jnetic 74.58 0.26 0.8 - Calc head 100.0 23.8 135 Ma~ne-tic 73.42 39.299.98 N nmahnadic 100 0 28 82 ~0,02 :~ , ' ' :
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A synthetiC 9 pi~od to ap-OnmagnetiC ~aCtion tric ~on o~ feed (2 pro .th a nonmagnetic P
ullce p ~he Size range of ctor for lS ml 5 ~ rlbed irOn ~sr 130oc at a pr6 tacarbonyl per 'i~1 ox 4 kilograms 5 minute5 of the roa t c 5~paratin ~
d r With the ma9 n i e raction5 being Carried i fractin three PasSes d ~ver an indUced ma9n h e testS are an the cOmposited~size marlze _'3 ~.." ' .''','',^" ~ ' .
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~ L59~
R p~acer ore containing 446 grams gold per ~etric ton of fee,d (13 ounces per ton) which had been treated with 4 ki.lograms of iron pentacarbonyl per metric ton of ~eed for one hour at a temperature o~
125 to 130C in a large reacto~ was subje,ctecd to abr~sive and weathering conclitions prior to magnetic separation o~
the gold. The results are given below in Table 9.
T ~
Gold Gold Sam~]e Treatment Yield ~ssay, Recovery Be~ore t on ~ oz/Ton Magnetic Separation Frac 1 _ ' ' in Dry ~ir , Nonmagnetic 60 3 0.78 ~ged lwo~iMro NonmacJnctic 64 1 0 87 ~cJ d T~o Month'din24 yonmaqnetic 65 1 11 9 D1y ~ir, ~Y~l~osed 48 Nonmaclnet~jic 62 8 30 5 91,4 '.^~ llumidity, Stored ' ~ 24 llours in Vial ~:~ . , . .:
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9~
~X~ML'LE 10 Sam~les oE a non-magnetic fraction o~ 28-x 65-mesh Vulture placer were spiked ~ith non-magnetic 28- x 65-mesh Clear Creek gold concentrate ~o ob~ain 1.99 kilograms of gold per metric ton of synthetic placer (58 oz/ton~. The synthetic placer was then wet-screened at 55-mesh to remove fines. Thereafter, each sample was treated with iron carbonyl at varying levels at a 122C in a small glass rotary reactor for 15 minutes.
In each case, the carbonyl was injected during the first 1.5 minute of the roast. Results are given below.
I ~ TABLe 10 ¦ Carbonyl Yield, Wt. % ~ Recovery, k/a9ton Maqnetic magnetic Magnetic mag ~
1 9.3 90.7 5608.14 59.5 87.6 2 9.6 90.4 ~915.06 51.7 91.2 a lo.l as.o 36:2.59 60 3 94.2 I
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Claims (19)
1. A process for beneficiating particulate gold from foreign material with which it is mixed which comprises con-tacting the mixture with an iron carbonyl under conditions which cause the iron carbonyl to react substantially at the surface of the gold particles to the substantial exclusion of the foreign material so as to alter the surface character-istics of the gold particles thereby causing a selective en-hancement of the magnetic susceptibility of the gold particles to the substantial exclusion of the foreign material so that a magnetic separation between the gold and foreign material may be effected.
2. The process of Claim 1 in which the treated mixture is subjected to a magnetic field to remove gold particles from the foreign material.
3. The process of Claim 1 in which the iron carbonyl is iron pentacarbonyl.
4. The process of Claim 3 in which the carbonyl is in gaseous form and is contacted with the mixture in an inert carrier gas.
5. The process of Claim 1 wherein the foreign material is selected from the group consisting of granite, quartz, muscovite, alumina, gypsum, albite, dolomite, calcite, hematite and silica.
6. The process of Claim 1 wherein the mixture is magnetically cleaned and the non-magnetic fraction of the mixture is then contacted with iron carbonyl.
7. The process of Claim 1 wherein the mixture of gold and foreign material is contacted with iron carbonyl at a temperature between 110° C and 250° C.
8. A process for beneficiating gold mixed with foreign material, which comprises the steps of:
(a) reducing the mixture to a particulate form;
(b) placing the particulate mixture in a gas treatment chamber;
(c) introducing iron carbonyl vapor into said chamber under conditions which preclude substantial non-selective decomposition of the iron carbonyl, and (d) maintaining the iron carbonyl vapor in contact with said mixture for a sufficient time for the iron carbonyl to selectively enhance the magnetic sus-ceptibility of substantially all of the gold particles in the mixture.
(a) reducing the mixture to a particulate form;
(b) placing the particulate mixture in a gas treatment chamber;
(c) introducing iron carbonyl vapor into said chamber under conditions which preclude substantial non-selective decomposition of the iron carbonyl, and (d) maintaining the iron carbonyl vapor in contact with said mixture for a sufficient time for the iron carbonyl to selectively enhance the magnetic sus-ceptibility of substantially all of the gold particles in the mixture.
9. The process of Claim 8 wherein the iron is iron pentacarbonyl.
10. The process of Claim 8 wherein the temperature of the chamber is not in excess of about 250° C.
11. The process of Claim 8 wherein the iron carbonyl vapor is contacted with said mixture at a temperature between 110° C and 130° C.
12. The process of Claim 8 wherein from about 0.25 to about 8 kilograms of iron carbonyl per metric ton of mixture are introduced into said chamber.
13. The process of Claim 8 wherein the iron carbonyl vapor is maintained in contact with said mixture for less than one-half hour.
14. The process of Claim 8 wherein the iron carbonyl gas is first contacted with an inert carrier gas and then introduced into said chamber.
15. A process for recovering gold from a mixture of gold with other material which comprises contacting the mixture with a carbonyl of a Group VIII metal under condi-tions which cause the metal carbonyl to decompose and then cause a coating at the surface of the gold to the substantial exclusion of the other material so as to alter the surface characteristics of the gold thereby causing a selective enhancement of the magnetic susceptibility of the gold to the substantial exclusion of the other material so that a magnetic separation between the gold and said other material may be effected.
16. The process of Claim 15 in which the Group VIII
metal is a member selected from the group consisting of iron, nickel and cobalt.
metal is a member selected from the group consisting of iron, nickel and cobalt.
17. The process of Claim 16 in which the metal is iron.
18. A process for beneficiating gold mixed with foreign material, comprising:
(a) reducing the mixture to a particulate form;
(b) placing the particulate mixture in a gas treatment chamber;
(c) contacting an inert carrier gas with iron carbonyl vapor to incorporate the iron carbonyl vapor in the carrier gas;
(d) introducing the iron carbonyl vapor carried in the carrier gas into said chamber at a rate of from about 0.5 to about 4.0 kilograms of iron carbonyl per metric ton of particulate material and at a temperature from about 110°
C to about 130° C.
(e) maintaining the iron carbonyl vapor in contact with said mixture for less than one-half hour to selectively enhance the susceptibility of substantially all of the gold particles in the mixture;
(f) separating the gold particles from the mixture by magnetic separation.
(a) reducing the mixture to a particulate form;
(b) placing the particulate mixture in a gas treatment chamber;
(c) contacting an inert carrier gas with iron carbonyl vapor to incorporate the iron carbonyl vapor in the carrier gas;
(d) introducing the iron carbonyl vapor carried in the carrier gas into said chamber at a rate of from about 0.5 to about 4.0 kilograms of iron carbonyl per metric ton of particulate material and at a temperature from about 110°
C to about 130° C.
(e) maintaining the iron carbonyl vapor in contact with said mixture for less than one-half hour to selectively enhance the susceptibility of substantially all of the gold particles in the mixture;
(f) separating the gold particles from the mixture by magnetic separation.
19. The process of Claim 18 wherein the iron carbonyl is iron pentacarbonyl.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000342807A CA1145951A (en) | 1979-12-31 | 1979-12-31 | Process for beneficiating gold |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000342807A CA1145951A (en) | 1979-12-31 | 1979-12-31 | Process for beneficiating gold |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1145951A true CA1145951A (en) | 1983-05-10 |
Family
ID=4115931
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000342807A Expired CA1145951A (en) | 1979-12-31 | 1979-12-31 | Process for beneficiating gold |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1145951A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4726895A (en) * | 1986-03-28 | 1988-02-23 | Edward Martinez | Process for concentration of gold and uranium magnetically |
-
1979
- 1979-12-31 CA CA000342807A patent/CA1145951A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4726895A (en) * | 1986-03-28 | 1988-02-23 | Edward Martinez | Process for concentration of gold and uranium magnetically |
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