189:
551:
515:) - converts cyanide to cyanate. Cyanate then hydrolyses to ammonium and carbonate ions. The Caro's acid process is able to achieve discharge levels of Weak Acid Dissociable" (WAD) cyanide below 50 mg/L, which is generally suitable for discharge to tailings. Hydrogen peroxide and basic chlorination can also be used to oxidize cyanide, although these approaches are less common. Typically, this process blows compressed air through the tailings while adding
200:
122:
85:, the process is controversial and its use is banned in some parts of the world. Cyanide can be safely used in the gold mining industry. A key feature for safe use of cyanide is to ensure adequate pH control at an alkaline pH level above 10.5. At industrial scale, pH control is mainly achieved using lime, as an important enabling reagent in gold processing.
1537:
566:
cyanide spills can have a devastating effect on rivers, sometimes killing everything for several miles downstream. The cyanide is soon washed out of river systems and, as long as organisms can migrate from unpolluted areas upstream, affected areas can soon be repopulated. According to
Romanian authorities, in the
565:
due to the toxic nature of cyanide. Although aqueous solutions of cyanide degrade rapidly in sunlight, the less-toxic products, such as cyanates and thiocyanates, may persist for some years. The famous disasters have killed few people â humans can be warned not to drink or go near polluted water, but
346:
slows leaching rate. Air or pure oxygen gas can be purged through the pulp to maximize the dissolved oxygen concentration. Intimate oxygen-pulp contactors are used to increase the partial pressure of the oxygen in contact with the solution, thus raising the dissolved oxygen concentration much higher
842:
Under
Article 14, companies must also put in place financial guarantees to ensure clean-up after the mine has finished. This in particular may affect smaller companies wanting to build gold mines in the EU, as they are less likely to have the financial strength to give these kinds of guarantees.
1357:
Al, Tom A.; Leybourne, Matthew I.; Maprani, Antu C.; MacQuarrie, Kerry T.; Dalziel, John A.; Fox, Don; Yeats, Phillip A. (2006). "Effects of acid-sulfate weathering and cyanide-containing gold tailings on the transport and fate of mercury and other metals in Gossan Creek: Murray Brook mine, New
506:
The Inco process can typically lower cyanide concentrations to below 50 mg/L, whereas the Caro's acid process can lower cyanide levels to between 10 and 50 mg/L, with the lower concentrations achievable in solution streams rather than slurries. Caro's acid â peroxomonosulfuric acid
531:
is added as a catalyst if there is insufficient copper in the ore extract. This procedure can reduce concentrations of WAD cyanide to below the 10 ppm mandated by the EU's Mining Waste
Directive. This level compares to the 66-81 ppm free cyanide and 500-1000 ppm total cyanide in the pond at
152:, Scotland, developed the MacArthurâForrest process for the extraction of gold from gold ores. Several patents were issued in the same year. By suspending the crushed ore in a cyanide solution, a separation of up to 96 percent pure gold was achieved. The process was first used on the
420:
The cyanide remaining in tails streams from gold plants is potentially hazardous. Therefore, some operations process the cyanide-containing waste streams in a detoxification step. This step lowers the concentrations of these cyanide compounds. The INCO-licensed process and the
536:. Remaining free cyanide degrades in the pond, while cyanate ions hydrolyse to ammonium. Studies show that residual cyanide trapped in the gold-mine tailings causes persistent release of toxic metals (e.g. mercury ) into the groundwater and surface water systems.
167:
in Utah, "the first mining plant in the United States to make a commercial success of the cyanide process on gold ores." In 1896, BodlÀnder confirmed that oxygen was necessary for the process, something that had been doubted by MacArthur, and discovered that
1039:
367:(prior to the introduction of cyanide) of the ore in water at high pH can render elements such as iron and sulfur less reactive to cyanide, therefore making the gold cyanidation process more efficient. Specifically, the oxidation of iron to
76:
for mineral processing to recover gold represents more than 70% of cyanide consumption globally. Other metals are recovered from the process include copper, zinc, and silver, but gold is the main driver of this technology. Due to the highly
839:", and at most all mines started after 1 May 2008 may not discharge waste containing over 10ppm WAD cyanide, mines built or permitted before that date are allowed no more than 50ppm initially, dropping to 25ppm in 2013 and 10ppm by 2018.
816:(Directive 80/68/EEC) which bans any discharge of a size which might cause deterioration in the quality of the groundwater at the time or in the future. The Groundwater Directive was largely replaced in 2000 by the
755:. Challenges include reagent cost and the efficiency of gold recovery. Thiourea has been implemented commercially for ores containing stibnite. Yet another alternative to cyanidation is the family of glycine-based
835:
on the management of waste from extractive industries. Article 13(6) requires "the concentration of weak acid dissociable cyanide in the pond is reduced to the lowest possible level using
395:
In order of decreasing economic efficiency, the common processes for recovery of the solubilized gold from solution are (certain processes may be precluded from use by technical factors):
727:
Although cyanide is cheap, effective, and biodegradable, its high toxicity has incentivized to alternative methods for extracting gold. Other extractants have been examined including
1314:
Maprani, Antu C.; Al, Tom A.; MacQuarrie, Kerry T.; Dalziel, John A.; Shaw, Sean A.; Yeats, Phillip A. (2005). "Determination of
Mercury Evasion in a Contaminated Headwater Stream".
812:(82/501/EEC brought in after the 1976 dioxin disaster. "Free cyanide and any compound capable of releasing free cyanide in solution" are further controlled by being on List I of the
798:
1625:
Directive 2000/60/EC of the
European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (the
1392:"Long Term persistence of cyanide species in mine waste environments", B. Yarar, Colorado School of Mines, Tailings and Mine Waste '02, Swets & Zeitlinger,
1037:, MacArthur, John Stewart; Forrest, William & Forrest Robert, Robert, "Process of Obtaining Gold and Silver from Ores", published 1889-05-14
832:
793:
rejected a proposal for such a ban, noting that existing regulations (see below) provide adequate environmental and health protection. Several attempts to ban
574:, the plankton returned to 60% of normal within 16 days of the spill; the numbers were not confirmed by Hungary or Yugoslavia. Famous cyanide spills include:
813:
1680:
176:(1869â1956) and his engineer Thomas Bennett Crowe improved the treatment of the cyanide leachate, by using vacuum and zinc dust. Their process is the
1576:
1238:
Teixeira, Luiz
Alberto Cesar; Montalvo, Javier Paul; Yokoyama, Andia, LĂdia; da Fonseca AraĂșjo, Fabiana ValĂ©ria; Sarmiento, Cristian Marquez (2013).
872:
1502:
1284:
1713:
1007:
Gray, J. A.; McLachlen, J. (Jun 1933). "A history of the introduction of the MacArthur-Forrest cyanide process to the
Witwatersrand goldfields".
1301:
1184:
1641:
Directive 2006/21/EC of the
European Parliament and of the Council of 15 March 2006 on the management of waste from extractive industries.
1613:
Council
Directive 80/68/EEC of 17 December 1979 on the protection of groundwater against pollution caused by certain dangerous substances.
797:
were rejected by the
Romanian Parliament. There are currently protests in Romania calling for a ban on the use of cyanide in mining (see
938:
2183:
140:. The gold could not be extracted from this compound with any of the then available chemical processes or technologies. In 1887,
1520:
1401:
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Council Directive 96/82/EC of 9 December 1996 on the control of major-accident hazards involving dangerous substances.
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256:
Gold is one of the few metals that dissolves in the presence of cyanide ions and oxygen. The soluble gold species is
2347:
1656:
International Cyanide Management Code For The Manufacture, Transport, and Use of Cyanide In The Production of Gold
156:
in 1890 and, despite operational imperfections, led to a boom of investment as larger gold mines were opened up.
17:
870:
Rubo, Andreas; Kellens, Raf; Reddy, Jay; Steier, Norbert; Hasenpusch, Wolfgang (2006). "Alkali Metal Cyanides".
1813:
1808:
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Greenwood, N. N. & Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.), Oxford:Butterworth-Heinemann.
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1973:
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281:
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Council Directive 82/501/EEC of 24 June 1982 on the major-accident hazards of certain industrial activities.
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850:" that aims to reduce environmental impacts with third party audits of a company's cyanide management.
315:) is added to the extracting solution to ensure that the acidity during cyanidation is maintained over
173:
1034:
836:
817:
429:, which is not as toxic as the cyanide ion, and which can then react to form carbonates and ammonia:
409:
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177:
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of South Africa began to slow down in the 1880s, as the new deposits being found tended to contain
1860:
1191:
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Du Plessis, C. A.; Lambert, H.; GĂ€rtner, R. S.; Ingram, K.; Slabbert, W.; Eksteen, J. J. (2021).
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422:
1209:"The absorption of gold cyanide onto activated carbon. I. The kinetics of absorption from pulps"
1982:
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125:
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1577:
European Commission rejects proposed ban on using cyanide in extractivism|extractive industry
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Such spills have prompted fierce protests at new mines that involve use of cyanide, such as
379:
minimizes loss of cyanide from the formation of ferrous cyanide complexes. The oxidation of
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8:
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1978:
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La Brooy, S.R.; Linge, H.G.; Walker, G.S. (1994). "Review of gold extraction from ores".
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consumed during cyanidation, accepting the electrons from the gold, and a deficiency in
276:
using grinding machinery. Depending on the ore, it is sometimes further concentrated by
2033:
1930:
1742:
1428:
La politica es la politica: "After cyanide spill, can First Majestic clean up its act?"
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109:(1847), it was determined that each atom of gold required two cyanide ions, i.e. the
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304:
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The chemical reaction for the dissolution of gold, the "Elsner equation", follows:
102:
98:
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327:
speed and quantity recovered, particularly in processing partially oxidized ores.
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In the EU, industrial use of hazardous chemicals is controlled by the so-called
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2012:
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Truck leaked 200 liters of cyanide solution into the Piaxtla River in Durango
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The Citizens Initiative banning of cyanide mining in the State of Montana, US
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881:
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110:
65:. Cyanidation is also widely used in the extraction of silver, usually after
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188:
144:, working in collaboration with brothers Robert and William Forrest for the
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1998:
1988:
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260:. from which it can be recovered by adsorption onto activated carbon.
199:
172:
was formed as an intermediate. Around 1900, the American metallurgist
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1993:
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1213:
Journal of the Southern African Institute of Mining and Metallurgy
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Journal of the Southern African Institute of Mining and Metallurgy
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Despite being used in 90% of gold production: gold cyanidation is
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786:
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426:
339:
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82:
73:
1302:"UN assessment mission â Cyanide Spill at Baia Mare, March 2000"
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In some ores, particularly those that are partially sulfidized,
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1798:
383:
compounds to sulfate ions avoids the consumption of cyanide to
380:
335:
137:
78:
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A different commercial method that does not use toxic cyanide
1356:
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1653:
46:
1313:
390:
288:. The basic ore slurry can be combined with a solution of
128:
developed the cyanide process for gold extraction in 1887.
1771:
269:
50:
799:
2013 Romanian protests against the RoÈia MontanÄ Project
203:
Cyanide leaching "heap" at a gold mining operation near
316:
869:
195:
of the aurocyanide or dicyanoaurate(I) complex anion,
751:), iodine/iodide, ammonia, liquid mercury, and alpha-
554:
Sodium cyanide drum at the abandoned Chemung Mine in
1558:
Zöld siker: törvényi tilalom a cianidos bånyåszatra!
1643:
For the modifications see the consolidated version.
1631:
For the modifications see the consolidated version.
1591:
For the modifications see the consolidated version.
1439:
1296:
1294:
351:. Oxygen can also be added by dosing the pulp with
1240:"Oxidation of cyanide in effluents by Caro's Acid"
1538:"Czech Senate bans use of cyanide in gold mining"
905:Etris, S. F. (2010). "Silver and Silver Alloys".
808:(Directive 96/82/EC, which replaced the original
2329:
1291:
415:
27:Technique for extracting gold from low-grade ore
907:Kirk-Othmer Encyclopedia of Chemical Technology
527:is added to maintain the pH at around 8.5, and
358:
253:are sometimes used in place of sodium cyanide.
873:Ullmann's Encyclopedia of Industrial Chemistry
1707:
1006:
539:
330:
1687:How gold is extracted by cyanidation process
1283:: CS1 maint: multiple names: authors list (
915:10.1002/0471238961.1909122205201809.a01.pub3
2242:
846:The industry has come up with a voluntary "
1714:
1700:
1091:The alumni quarterly and fortnightly notes
722:
53:by converting the gold to a water-soluble
1721:
1094:. University of Illinois. January 1, 1921
980:
865:
863:
687:Helicopter dropped crate into rainforest
957:"Lime use in gold processing â A review"
549:
284:. Water is added to produce a slurry or
198:
187:
120:
1527:regarding the use of cyanide in mining.
719:in Chile, and Bukit Koman in Malaysia.
391:Recovery of gold from cyanide solutions
14:
2330:
1316:Environmental Science & Technology
1002:
1000:
860:
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904:
183:
116:
1415:BBC: "Cyanide seeps into PNG rivers"
132:The expansion of gold mining in the
1190:. Multi Mix Systems. Archived from
997:
282:centrifugal (gravity) concentration
24:
1138:. Elsevier. pp. XXXVIIâXLII.
1071:Recent Advances in Gold Metallurgy
789:, have banned cyanide mining. The
97:discovered that gold dissolved in
25:
2359:
1735:Non-ferrous extractive metallurgy
1663:
898:
669:Collapse of containment dam (see
303:To prevent the creation of toxic
307:during processing, slaked lime (
300:, which is more cost effective.
101:of cyanide. Through the work of
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1136:Advances in Gold Ore Processing
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1106:
425:process oxidise the cyanide to
163:had refined the process at his
57:. It is the most commonly used
1082:
1046:
1027:
948:
931:
762:
263:
13:
1:
2088:Bottom-blown oxygen converter
1540:. Nl.newsbank.com. 2000-08-10
1134:Adams, Mike D. (2005-12-02).
853:
546:List of gold mining disasters
416:Cyanide remediation processes
347:than the saturation level at
159:By 1891, Nebraska pharmacist
1670:Efforts at a cleaner process
1480:Mining and Process Solutions
1462:10.1016/0892-6875(94)90114-7
1264:10.1016/j.mineng.2013.01.008
1054:"Methods to recover Gold II"
982:10.1016/j.mineng.2021.107231
825:2000 Baia Mare cyanide spill
671:2000 Baia Mare cyanide spill
622:Unrestrained waste discharge
359:Pre-aeration and ore washing
7:
1300:UNEP/OCHA Environment Unit
1219:(2): 50â54. February 1984.
795:gold cyanidation in Romania
105:(1844), Elsner (1846), and
10:
2364:
766:
543:
540:Effects on the environment
331:Effect of dissolved oxygen
174:Charles Washington Merrill
88:
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2011:
1944:
1898:
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1741:
1729:
1627:Water Framework Directive
1505:October 21, 2007, at the
837:best available techniques
818:Water Framework Directive
637:Collapse of tailings dam
113:of the soluble compound.
45:technique for extracting
39:MacArthurâForrest process
1814:Underground in soft rock
1809:Underground in hard rock
944:. Australian Government.
882:10.1002/14356007.i01_i01
831:and the Council adopted
653:Truck drove over bridge
2348:Metallurgical processes
1575:International Mining -
876:. Weinheim: Wiley-VCH.
723:Alternatives to cyanide
605:Leakage from leach pad
319:10.5 - strongly basic.
1563:July 21, 2011, at the
1225:10520/AJA0038223X_1427
1185:"Technical Bulletin 1"
1021:10520/AJA0038223X_5033
558:
296:; many operations use
207:
196:
142:John Stewart MacArthur
129:
126:John Stewart MacArthur
2142:(by aqueous solution)
1974:Gravity Concentration
1723:Extractive metallurgy
1681:Cyanide Uncertainties
814:Groundwater Directive
553:
410:MerrillâCrowe process
202:
191:
178:MerrillâCrowe process
124:
2257:HallâHĂ©roult process
1936:Mechanical screening
1518:2001 Senate Bill 160
1476:"Glycine lixiviants"
1442:Minerals Engineering
1360:Applied Geochemistry
1358:Brunswick, Canada".
1244:Minerals Engineering
961:Minerals Engineering
939:"Cyanide Management"
833:Directive 2006/21/EC
769:Gold cyanidation ban
517:sodium metabisulfite
349:atmospheric pressure
193:Ball-and-stick model
95:Carl Wilhelm Scheele
55:coordination complex
1979:Magnetic separation
1926:Cyclonic separation
1747:(by physical means)
1732:Metallurgical assay
1454:1994MiEng...7.1213L
1372:2006ApGC...21.1969A
1328:2005EnST...39.1679M
1256:2013MiEng..45...81T
973:2021MiEng.17407231D
829:European Parliament
823:In response to the
806:Seveso II Directive
791:European Commission
556:Masonic, California
519:, which releases SO
33:(also known as the
2060:Refractory linings
1931:Gyratory equipment
1743:Mineral processing
1523:2006-10-10 at the
1076:2008-03-30 at the
559:
208:
197:
184:Chemical reactions
130:
117:Industrial process
43:hydrometallurgical
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2231:Electrometallurgy
2225:
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2184:Gold chlorination
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2018:
2007:
2006:
1969:Jig concentrators
1767:Natural resources
1762:Geological survey
1748:
1448:(10): 1213â1241.
1417:, March 23, 2000.
1366:(11): 1969â1985.
1336:10.1021/es048962j
1145:978-0-444-51730-2
909:. pp. 1â43.
773:The US states of
705:
704:
684:Papua New Guinea
618:Papua New Guinea
387:(SCN) byproduct.
353:hydrogen peroxide
323:can improve gold
309:calcium hydroxide
294:potassium cyanide
247:Potassium cyanide
170:hydrogen peroxide
161:Gilbert S. Peyton
99:aqueous solutions
16:(Redirected from
2355:
2240:
2239:
2235:(by electricity)
2234:
2217:Pan amalgamation
2189:Gold cyanidation
2179:In situ leaching
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2016:
1777:Economic geology
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369:iron (III) oxide
344:dissolved oxygen
313:sodium hydroxide
305:hydrogen cyanide
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31:Gold cyanidation
21:
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2098:IsaKidd process
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2015:
2003:
1954:Froth flotation
1940:
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1654:cyanidecode.org
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371:and subsequent
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298:calcium cyanide
278:froth flotation
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251:calcium cyanide
239:
235:
233:
227:
225:
219:
215:
186:
146:Tennant Company
119:
91:
67:froth flotation
63:gold extraction
49:from low-grade
35:cyanide process
28:
23:
22:
18:Cyanide process
15:
12:
11:
5:
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2083:Parkes process
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2049:Flash smelting
2046:
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2019:
2013:Pyrometallurgy
2009:
2008:
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1792:Precious metal
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1664:External links
1662:
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1426:Wilson, T. E.
1419:
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1197:on 2009-10-23.
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924:978-0471238966
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820:(2000/60/EC).
783:Czech Republic
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400:Carbon in pulp
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360:
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338:is one of the
332:
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290:sodium cyanide
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72:Production of
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2194:Bayer process
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2174:Tank leaching
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2169:Dump leaching
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1056:. 2013-05-14.
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373:precipitation
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258:dicyanoaurate
254:
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175:
171:
166:
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111:stoichiometry
108:
104:
100:
96:
86:
84:
80:
75:
70:
68:
64:
60:
56:
52:
48:
44:
40:
36:
32:
19:
2244:Electrolysis
2204:Amalgamation
2188:
1959:Jameson cell
1916:Hydrocyclone
1648:
1636:
1626:
1620:
1608:
1596:
1584:
1579:, July, 2010
1571:
1553:
1542:. Retrieved
1532:
1513:
1495:
1483:. Retrieved
1479:
1470:
1445:
1441:
1435:
1422:
1409:
1402:Google Books
1388:
1363:
1359:
1352:
1319:
1315:
1309:
1279:cite journal
1267:. Retrieved
1247:
1243:
1233:
1216:
1212:
1203:
1192:the original
1179:
1162:
1135:
1129:
1117:. Retrieved
1114:"Mercur, UT"
1108:
1096:. Retrieved
1090:
1084:
1048:
1029:
1012:
1008:
964:
960:
950:
933:
906:
900:
871:
848:Cyanide Code
847:
845:
841:
822:
803:
772:
753:cyclodextrin
726:
711:in Romania,
706:
570:river below
560:
505:
419:
394:
362:
334:
321:Lead nitrate
302:
285:
267:
255:
245:
209:
205:Elko, Nevada
158:
131:
92:
71:
61:process for
38:
34:
30:
29:
2280:Co-products
2114:Calcination
2078:Cupellation
1994:Dry washing
1983:Magnetation
1906:Ore sorting
1871:Pebble mill
1838:Comminution
763:Legislation
729:thiosulfate
717:Pascua Lama
650:Kyrgyzstan
598:Summitville
423:Caro's acid
385:thiocyanate
311:) or soda (
264:Application
165:Mercur Mine
138:pyritic ore
2332:Categories
2317:Stamp sand
2267:Downs cell
1999:Buddle pit
1989:Rocker box
1846:Stamp mill
1787:Base metal
1755:Extraction
1544:2013-01-03
1413:BBC News,
967:: 107231.
854:References
767:See also:
757:lixiviants
713:Lake Cowal
695:San Dimas
594:1985â1991
544:See also:
355:solution.
274:comminuted
81:nature of
2159:Lixiviant
2124:Liquation
2017:(by heat)
1878:Ball mill
1821:Recycling
1250:: 81â87.
1154:0167-4528
1035:US 403202
991:240128866
779:Wisconsin
681:Tolukuma
662:Baia Mare
589:Incident
572:Baia Mare
534:Baia Mare
103:Bagration
93:In 1783,
79:poisonous
2287:Tailings
2151:Leaching
2119:Roasting
2070:Refining
2054:ISASMELT
2026:Smelting
1883:Rod mill
1866:SAG mill
1851:Arrastra
1561:Archived
1521:Archived
1503:Archived
1485:23 April
1344:15819225
1074:Archived
741:thiourea
666:Romania
586:Country
365:aeration
340:reagents
325:leaching
222:NaCN + O
74:reagents
59:leaching
2312:Red mud
2302:Clinker
2056:furnace
1964:Panning
1921:Trommel
1911:Vanning
1888:IsaMill
1861:AG mill
1856:Crusher
1804:Surface
1782:Mineral
1675:Yestech
1450:Bibcode
1368:Bibcode
1324:Bibcode
1252:Bibcode
969:Bibcode
787:Hungary
775:Montana
698:Mexico
634:Guyana
614:Ok Tedi
427:cyanate
150:Glasgow
107:Faraday
89:History
83:cyanide
41:) is a
37:or the
2292:Gangue
2093:Poling
1899:Sizing
1799:Mining
1396:
1342:
1170:
1152:
1142:
1119:May 1,
1098:May 1,
1041:
989:
921:
888:
827:, the
781:, the
743:(SC(NH
646:Kumtor
381:sulfur
336:Oxygen
280:or by
240:
238:Na + 4
236:
228:
220:
218:Au + 8
216:
2107:Other
1826:Scrap
1683:(PDF)
1652:ICMI
1269:2 May
1195:(PDF)
1188:(PDF)
987:S2CID
942:(PDF)
692:2018
678:2000
658:2000
642:1998
631:Omai
628:1995
583:Mine
580:Year
568:SomeÈ
443:+ â
234:O â 4
2338:Gold
2307:Chat
2297:Slag
1487:2021
1394:ISBN
1340:PMID
1285:link
1271:2021
1168:ISBN
1150:ISSN
1140:ISBN
1121:2016
1100:2016
919:ISBN
886:ISBN
777:and
525:Lime
466:+ 2
286:pulp
268:The
249:and
242:NaOH
154:Rand
134:Rand
47:gold
1772:Ore
1458:doi
1376:doi
1332:doi
1260:doi
1221:hdl
1017:hdl
977:doi
965:174
911:doi
878:doi
801:).
739:),
602:US
481:HCO
457:OCN
445:OCN
375:as
292:or
272:is
270:ore
226:+ 2
148:in
51:ore
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1277:{{
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959:.
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884:.
862:^
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759:.
731:(S
673:)
523:.
511:SO
507:(H
493:NH
491:+
479:â
434:CN
317:pH
180:.
69:.
1985:)
1981:(
1715:e
1708:t
1701:v
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1464:.
1460::
1452::
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1378::
1370::
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1326::
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1262::
1254::
1227:.
1223::
1174:.
1156:.
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1019::
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894:.
880::
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747:)
745:2
737:3
735:O
733:2
521:2
513:5
509:2
498:3
486:3
477:O
473:2
468:H
232:2
230:H
224:2
214:4
20:)
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