Thiosulphate as an alternative to cyanide for gold processing

Abstract

Thiosulphate is an attractive alternative reagent to cyanide for processing gold ores. It is relatively cheap and non-toxic, forms relatively strong gold and silver complexes, and readily leaches gold ores in ammoniacal solutions, catalysed by Cu(II). It is particularly suited to carbonaceous ores where the recovery of gold by cyanide is poor. However, research over the past 20 years has identified a number of issues and impediments that must be understood or overcome before an overall process can be demonstrated as practical and economic for typical oxidised gold ores. This paper reviews the current understanding of thiosulphate chemistry and mechanism of gold dissolution, and discusses the stability of thiosulphate and polythionates. It then reviews the results of leaching various gold ores that have been reported in the literature, discusses gold recovery options, and considers environmental and toxicity issues. Some of the issues that require further research include decreasing the oxidation of thiosulphate by Cu(II) or other oxidants, increasing the extraction of gold compared to cyanide, and understanding the variation in gold recovery between ores. More work is also required to minimise the effect of polythionates on gold recovery using resins or alternative absorbents, to improve the elution of copper and gold from resins, and to recycle or minimise the concentration of reagents.

Keywords

THIOSULPHATE CYANIDE GOLD PROCESSING

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References

MCNULTY

: ‘Cyanide substitutes’, Mining Magazine, May 2001, 256–260.

SPARROW

G. J.

and WOODCOCK

J. T.

: ‘Cyanide and other lixiviant leaching systems for gold with some practical applications’, Min. Process. Extract. Metal. Rev., 1995, 14, 193–247.

SMITH

R. M.

and MARTELL

A. E.

(eds.): ‘Critical stability constants’, vol. 5, 1st suppl., Oxford, Plenum, 1989.

WANG

X-H.

: ‘Electrochemistry in mineral and metal processing III’, The Electrochemical Society, Inc., Pennington, NJ, 1992, 452–477.

MARSDEN

and HOUSE

: ‘The Chemistry of Gold Extraction’, London. Ellis Horwood, 1993.

ABBRUZZESE

, FORNYARI

, MASSIDDA

, VEGLIO

and UBALDINI

: ‘Thiosulfate leaching for gold hydrometallurgy’, Hydrometallurgy, 1995, 39, 265–276.

WAN

R-Y

: ‘Importance of solution chemistry for thiosulfate leaching of gold’, Proc. World Gold ‘97, 25. Singapore, Society for Mining, Metallurgy and Exploration, Inc. Littleton, 1997, 159–162.

AYLMORE

M. G.

and MUIR

D. M.

: ‘Thermodynamic analysis of gold leaching by ammoniacal thio sulfate using Eh/pH and speciation diagrams’, J Min. Metal. Process., 2001, 18, 221–227.

I M. I., BREUER

and CHOO

w L.

: ‘How rapidly do alternative lixiviants leach gold?’ (eds. Young

C. A.

, Twidwell

L. G.

and Anderson

C. A.

) Cyanide: social, industrial and economic aspects, Warrendale, TMS, 2001, 441-454.

10.

I M. I., P BREUER and W. L. CHOO: ‘A kinetic study comparing gold leaching in the cyanide, thiosulfate and chloride systems’, Metal. Mater. Trans. B, 2001, 32, 979–986.

11.

BREUER

P L.

, JEFFREY

M. I.

and CHOO

W. L.

: ‘Fundamental aspects of the gold thio sulfate leaching process’, (eds. Young

C. A.

, Twidwell

L. G.

and Anderson

C. A.

) Cyanide: social, industrial and economic aspects, Warrendale, TMS, 2001, 455-468.

12.

BREUER

P L.

and JEFFREY

M. I.

: ‘Electrochemical study of gold leaching in thiosulphate solutions containing ammonia and copper’, Hydrometallurgy 2002, 65, 145–157.

13.

JEFFREY

M. I.

: ‘Kinetic aspects of gold and silver leaching in ammonia-thiosulfate solutions’, Hydrometallurgy, 2001, 60, 7–16.

14.

AYLMORE

M. G.

and RAE

: ‘Factors affecting the rate of leaching of gold in ammoniacal thiosulfate and the stability of the leach solution’, CSIRO Report DMR-1493, 2001, 1–36.

15.

DHAWALE

S. W.

: ‘Thiosulfate’, J Chem. Ed., 1993, 70, 12–14.

16.

KAMETANI

and AOKI

: Potential-pH diagrams of the 502-H20 and 5203-H20 systems at 90 degrees’, Trans. Natl. Inst. Metals, 1976, 18, 20–30.

17.

WAN

R. Y

: ‘Importance of solution chemistry for thiosulfate leaching of gold’, Proceedings of the ‘World Gold ‘97’, Singapore, Society for Mining, Metallurgy and Exploration, Inc., Littleton, 1997, 159–162.

18.

BYERLEY

J. J.

, FOUDA

and REMPEL

G. L.

: ‘Kinetics and mechanism of the oxidation of thiosulfate ions by copper (II) ions in aqueous ammonia solution’, J Chem. Soc. Dalton Trans., 1973, 889–893.

19.

BYERLEY

J. J.

, FOUDA

and REMPEL

G. L.

: ‘The oxidation of thiosulfate in aqueous ammonia by copper (II) oxygen complexes’, Inorg. Nuclear Chem. Lett., 1973, 9, 879–883.

20.

BYERLEY

J. J.

, FOUDA

and REMPEL

G. L.

: ‘Activation of copper(II) amine complexes by molecular oxygen for the oxidation of thiosulfate ions’, J Chem. Soc. Dalton Trans., 1975, 1329-133 8.

21.

, MILLER

J.D.

and WAN

R-Y.

: ‘Importance of solution chemistry Factors that influence the ammonium thiosulfate leaching of gold’, Paper presented at SME Annual Meeting, Feb, 1996, Phoenix, Arizona.

22.

NAITO

, SHEH

and OKABE

: The chemical behaviour of low valence sulfur compounds V. Decomposition and oxidation of tetrathionate in aqueous ammonia solution’, Bull. Chem. Soc. Jpn., 1970, 43, 1372–1376.

23.

ROLLA

and CHAKRABARTI

C. L.

: ‘Kinetics of decom-position of tetrathionatg trithionate and thiosulfate in alkaline media’, Environ. Sci. Technol, 1982, 16, 852–857.

24.

AYLMORE

M. G.

and MUIR

D. M.

: ‘Thiosulfate leaching of gold - a review’, Min. Eng., 2001, 14, 135–174.

25.

TOZAWA

, INUI

and UMETSU

: ‘Dissolution of gold in ammoniacal thio sulfate solution’, 110th Annual Meeting of AIME, Chicago, Illinois, USA TMS paper, 1981, A81-25.

26.

KERLEY

B. J.

: Recovery of precious metals from difficult ores, 1981, US Patent 4, 269, 622.

27.

KERLEY

B. J.

: Recovery of precious metals from difficult ores, 1983, US Patent 4, 369, 061.

28.

BLOCK-BOLTEN

, TORMA

M. S.

, TORMA

A. E.

and STEENAMA

: ‘Gold and silver extraction from from complex sulfide wastes’, (ed. Taylor

P. R.

) Conference on Recycle and Secondary Recovery of Metals, Metallurgy Society, AIME, Warrendale, USA, 1985, 715-726.

29.

BLOCK-BOLTEN

, TORMA

M. S.

, TORMA

A. E

and S'TEENAMA

: ‘New possibilities in the extraction of gold and silver from zinc and lead sulfide flotation wastes’, paper submitted to the Extractive and Process Metallurgy Fall Meeting AIME-CIM Nov 10-13, San Diego, CA, USA, 1985.

30.

ZIPPERIAN

, RAGHAVAN

and WILSON

J. P.

: Gold and silver extraction by ammoniacal thiosulfate leaching from a rhyolite ore. Hydrometallurgy, 1988, 19, 361–375.

31.

HEMMATI

, HENDRIX

J. L.

, NELSON

J. H.

and B

, MILOSAVLJEVIC: ‘Study of the thiosulphate leaching of gold from carbonaceous ore and the quantitative determination of thiosulphate in the leached solution’, Extraction Metallurgy ‘89 symposium. Inst. Min. Metall, London, UK, 1989, 665-678

32.

CAIXIA

and QIANG

: ‘Research and optimisation of thiosulfate leaching tecgnology of gold. Rare Metals, 1991, 10, 275–280

33.

and GONG

: Recovery of gold from thiosulphate solution. Huagong Yejin (Eng Chem. Metall.), 1989, 10, 45-50 (Abstract)

34.

MURTHY

D. S. R.

: ‘Some studies on the extraction of gold and silver from lead-zinc sulfide flotation tailings through non-cyanide leachants’, Trans. Indian Inst. Metals, 1991, 44, 349–354

35.

CAO

, HU

, GONG

,: ‘Leaching of gold by low concentration thiosulfate solution’, Randol Gold Forum, Vancouver ‘92, Randol International, Colorado, USA, 1992, 293–298.

36.

LANGHANS

J. W.

, LEI

K. P. V.

and CARNAHAN

T. G.

: ‘Copper-catalysed thiosulfate leaching of low grade gold ores’, Hydrometallurgy, 1992, 29, 191–203.

37.

WAN

R. Y.

, LEV IER

K. M.

and CLAYTON

R. B.

: ‘Hydro-metallurgical process for the recovery of precious metal values from precious metal ores with thiosulfate lixiviant’, 1994, US Patent 5, 354, 359.

38.

GROUDEV

S. N.

, SPASOVA

I. I.

and IVANOV

I. M.

: ‘Two-stage microbial leaching of a refracrory gold-bearing pyrite ore’, Miner. Eng., 1996, 9, 707–713

39.

MARCHBANK

A. R.

, THOMAS

K. G.

, DREISINGER

and FLEMING

: Gold recovery from refractory carbonaceous ores by pressure oxidation and thiosulfate leaching, U. S. Patent 1996, 5, 536, 297.

40.

w T. YEN, K. Strogan and T. Fujita: ‘Gold extraction from a copper bearing ore by thiosulfate leaching’, Resources Treat. Technol., 1996, 43, 83–87.

41.

WAN

R. Y.

and BRIERLY

J. A.

: ‘Thio sulfate leaching following biooxidation pretreatment for gold recovery from refractory carbonaceous-sulfidicore’, Min. Eng., 1997, 76, 76–80.

42.

YEN

W. T.

, AGHAMIRIAM

, DESCHENES

and THEBEN

: ‘Gold extraction from mild refractory ore using ammonium thiosulfate’, Proceedings of the International Symposium on Gold Recovery Montreal, Canada, May 3-6, CIM, 1998.

43.

THOMAS

K. G

, FLEMING

, MARCHBANK

A. R.

and DREISINGER

: ‘Gold recovery from refractory carbonaceousores by pressure oxidation, thio sulfate leaching and resin-in-pulp adsorption’, 1998, US Patent 5, 785, 736.

44.

FREITAS

L. R.

, TRINDADE

R. B. E.

and CARAGEORGOS

: ‘Thiosulfate leaching of gold-copper ores from Igarape Bahia mine (CVRD)’, VI SHMMT/XVIII ENTMH Conference, Rio de Janeiro, 2001.

45.

BAGDASARYAN

K. A.

, EPISKOPOSYAN

M. L.

, TER-ARAKELYAN

K. A.

and BABAYAN

G. G.

: The kinetics of the dissolution of gold and silver in sodium thiosulfate solutions’, Soy. J Non-Ferrous Met., 1983, 376, 64–68.

46.

PEDRAZA

A. M.

, VILLEGAS

, FREUND

P L.

and CHORNIK

: ‘Electro-oxidation of thiosulfate ion on gold: study by means of cyclic voltammetry and Auger electron spectroscopy’, J Electroanal. Chem. Interfacial Electrochem., 1988, 250, 443–449.

47.

MACDONALD

D. D.

: ‘Review of mechanistic analysis by electrochemical impedance spectroscopy’, Electrochim Acta, 1990, 35, 1509.

48.

BRIONES

and LAPIDUS

G. T.

: The leaching of silver sulphide with the thiosulfate-ammonia-cupricion system’, Hydrometallurgy, 1998, 50, 243–260.

49.

PEREZ

A. E.

and GALAVIZ

H. D.

: ‘Method of recovery of precious metals from difficult ores with copper-ammonium thiosulfate’. US Patent 4, 654, 078, 1987.

50.

MIURA

and KOH

: ‘Spectroscopic determination of tetrathionate by means of its alkaline decomposition’, Nippon Kagaku Kaishi, 1983, 11, 1597-160 1.

51.

RUBAI

and EPSTEIN

I. R.

: ‘Equilibria and kinetics of the fast interaction between copper(II) and thiosulfate ions in aqueous solution’, Inorg. Chem., 1992, 31, 3239–3242.

52.

RITCHIE

I. M.

, NICOL

M. J.

and STAUNTON

W. P

: ‘Are there realistic alternatives to cyanide as a lixiviant for gold at the present time?’ (eds. Young

C. A.

, Twidwell

L. G.

and Anderson

C. A.

) Cyanide: social, industrial and economic aspects, Warrendale, TMS, 2001, 427-440.

53.

LULHAM

J. P

and LINDSAY

: ‘Separation process’, International Patent WO 91/11539, 1991.

54.

GUERRA

and DREISINGER

D. B.

: ‘A study of the factors affecting copper cementation of gold from ammoniacal thiosulfate solution’, Hydrometallurgy, 1999, 51, 155–172.

55.

NICOL

and O'MALLEY

G. P

: ‘Recovery of gold from thiosulfate solutions and pulps with ion-exchange resins’, (eds. Young

C. A.

, Twidwell

L. G.

and Anderson

C. A.

) Cyanide: social, industrial and economic aspects, Warrendale, TMS, 2001, 469-483.

56.

WAN

R-Y.

, LEVIER

K. M.

and MILLER

J. D.

: ‘Research and development activities for the recovery of gold from non-cyanide solutions’, Hydrometallurgy: fundamentals, technology and innovations, SME, Littleton Co., 1993, 415-43 6.

57.

FLEMING

C. A.

: ‘The potential role of anion exchange resins in the gold industry’, (ed. Mishra

), EPD Congress, Minerals, Metals and Materials Soc., 1998, 95-11 7.

58.

VIRNIG

M. J.

and SEROKOWSKI

J. M.

: ‘Process for the recovery of precious metal values from aqueous ammoniacal thio sulfate leach solutions’, International Patent WO 97/49474, 1997.

59.

O'MALLEY

G. P

: ‘The elution of gold from anion exchange resins’. Australian Patent, WO 0123626,2001.

60.

FLEMING

C. A.

: ‘Recent advances in the development of an alternative to the cyanidation process based on thiosulfate leaching and resin in pulp’, Unpublished paper presented to AMIRA Gold Conference, Ballarat, 2000.

61.

GOS

and RUBO

: ‘Alternative lixiviants for gold leaching. A comparison’, Proc. Randol Gold & Silver Forum 2000, 271–281.

Thiosulphate as an alternative to cyanide for gold processing – issues and impediments

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Keywords

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