Bio-extraction of metals: from the acid rock drainage to the production scale

1. Bio-extraction of metals: from the acid rock drainage to the production scale XXI CIME (Mexico) Luis Sobral & Débora Monteiro Centre for Mineral Technology - CETEM/MCTI Maio/2012

2. Conventional metal extraction processes Pyrometallurgicalprocess Flash Smelt Blistercopper Eletrorefining • SO2 • Metal impurities (Cd, As, Te, Bi, Hg)

3. Conventional metal extraction processes Hidrometallurgical processes Directchemicalleaching Pressureleaching

4. Acid rock drainage Microorganismisolation(ARD, sludgesand ore) • Strainsfromculturecollection • (ATCC/USAand DSMZ/Germany) • In vitrocultivation • (contactingtheM-oswithnutrientsandenergy sources)

5. Bioleachingtests Amenabilitytesting Cominution Caracterization Acid consumption In vitro bioleaching tests • Results to be expected: • To evaluate the maximum metals extraction as well as the toxic effect of those metals and other heavy metals should they are present and at what concentration; • Evaluate the maximum acid consumption.

6. Bioleachingtests Semi-pilotscale • Results to be expected: • To foreseen the efficiency of the bioleaching process on each operating temperatures; • The viability of the used microorganisms during the bioleaching process and the influence of the heterotrophic microorganisms during the bioleaching process; • The maximum extraction of the metals of interest bearing in mind the ore particle size range used and the acid consumption in such operating conditions, taking into consideration that not all the gangue minerals will be available to such acid digestion; • The evaluation of the metals extraction efficiencies bearing in mind the different two ways of crushing the ore under study (Jaw crusher, HPGR and Selfrag).

7. Bioleachingtests Pilotscale • Results to be expected: • The behaviour of used microorganisms in diverse pH, Eh and temperature for different height of the ore bed; • Identification of predominant microorganisms in the above mentioned heights through molecular biology techniques; • Whether or not will be necessary to re-inoculate the ore body as the bioleaching process goes on; • The leaching solution percolation and air blowing efficiencies while running the bioleaching process; • The necessity or not of an extra offer of CO2; • The influence of the ever increasing metals concentration being released into solution while running the bioleaching process through the dynamic evaluation of the extraction of metals of interest (chemical analysis); • The evaluation of axial flow of liquor and possible slumping of the ore bed.

8. Important parameters during sulphide bioleaching

9. Semi-pilotScale - CETEM GEOCOATTM Process Solution Irrigation Flotation concentrate coating Support rock Void Air flow

10. Semi-pilotScale - CETEM

11. PilotScale - CETEM

12. ProcessParametersMonitoring

13. MCSA – pilotscale Columntemperature(ºC) Set pointtemperature(ºC) Copperextraction (%) Copperextraction(%) TemperatureºC Time(days) Copper extraction vs.Time Copperextraction: 90.06% (74 days)

14. Demonstrationand Industrial application - Bioleaching • Caraíba Mining – Brazil • Quebrada Blanca - Chile • Talvivaara - Finland • Agnes Gold Mine – SouthAfrica

15. Caraíba Mining Co. - Brazil

16. Caraíba Mining Co. - Brazil – GEOCOAT™ Demonstration Plant • Design – 10,000 tpa crushed ore - Sulphide copper Concentrate (28 % Cu) – 4 months operation up to 80 % Cu extraction – 40 m x 40 m x 6 m heap Concentrate Chalcopyrite (58%) CuFeS2 Bornite (38%) Cu5FeS4 Pyrite (2% ) FeS2

17. Caraíba Mining Co. - Brazil Demonstration Plant

18. Quebrada Blanca - Chile

19. Quebrada Blanca - Chile – GEOLEACH™ Demonstration Plant • Design – 40,000 tpa crushed ore • 1.35% Cu • 2.8 % S(T) – Chalcocite and Chalcopyrite – 250 day demonstration 75% extraction – $1.0 million capital investment – 60 m x 60 m heap

20. Quebrada Blanca - Chile

21. Quebrada Blanca - Chile

22. Talvivaara - Finland

23. Talvivaara - Finland Internationally significant base metals producer with primary focus on nickel and zinc. • Targeted full scale production from 2012 – Nickel 50,000 tonnesp.a. – Zinc 90,000 tonnesp.a. – Copper 15,000 p.a. – Cobalt 1,800 tonnesp.a. • Estimated mine life approx. 46 years

24. Talvivaara - Finland • The bacteria used in the Talvivaara process grow naturally in the ore, and the company reports recovery rates of up to 98% of metal from ore to solution. Reserves 257 Mt 0.27% Ni 0.02% Co 0.14% Cu 0.55% Zn 600 – 1200 m3/h

25. Talvivaara - Finland Source: www.talvivaara.com

26. Talvivaara - Finland

27. Talvivaara - Finland Raising the heap Stacking operation

28. Agnes Gold Mine – South Africa

29. Agnes Gold Mine – South Africa Heap 50m x 40m x 8m 65000 t ofconcentrate per year

30. Agnes Gold Mine – South Africa

31. Agnes Gold Mine – South Africa Cil – Carbon in leaching Gold-bearingactivatedcarbon (to elutionprocess)

32. In progressbioleachingprojects in CETEM • Low grade zinc ore (Zn + Pb) • Low grade zinc ore (Zn, Cu andpreciousmetals) • Low grade copper ore (CuFeS2) • Low grade nickel ore (Ni + Cu) • Andbioleachingofflotationprocessresidue

33. Way to improvingthe ore bioleaching • Highpressuregrindingrolls (HPGR) • Polysius, Germany

34. Way to improvingthe ore bioleaching • HPGR • HPGR Product BaumandAusburn/MineralsandMetallurgicalProcessing 28 (2011) 77-81 • JawCrusher Ghorbaniet al./Minerals Engineering 24 (2011) 1249-1257

35. Way to improvingthe ore bioleaching Selfrag- Electro-dynamicFragmentation www.selfrag.com

36. Waysofimprovingthe ore bioleaching Selfrag www.selfrag.com SelfragLab, 2012

37. Way to improvingthe ore bioleaching Selfrag www.selfrag.com Capacity: 35000 t/a Value proposition: Selectivity continuous in modules Application: Mining, E-scrap Recycling, Concrete Recycling etc.

38. Final Remarks • Before such possibilities of bio-extracting metals out of ores, concentrates and tailings one can mention that: • The bioleaching process is far more environmentally friendly as the metals are put into solution, which is easier to control their issues to ground water, although safety measures have to be taken so as to avoid releasing metal ions to water streams; • As far as the use of autotrophic microorganisms is concerned we can assure that they do not pose any risk for the human being and to any other living species; • Taking into consideration that the PLS being continuously produced has to go through solvent extraction process, in order to get a metal of interest concentrated and free of metallic impurities solution and ready for the electrowinning process, the raffinate can return to the bioleaching process as it contains high acidity and high microorganisms population. However, should such raffinate carries much extractant micro-droplets it can be detrimental for its percolation down the heap as its top layer can acts as a coalescence surface for such droplets causing the leaching solution to by-pass the heap.

39. Biohydrometallurgical Processes: A Practical Approach is a book that deals with the practical aspects of the biohydrometallurgical processes, such as the bioleaching of sulphide minerals, the bio-extraction of nutrients out of agro-minerals, the bio-remediation of crude oil bearing soils, among others.

40. ¡MuchasGracias! Luis Gonzaga Santos Sobral Ph.D Head of the Metallurgical and Biotechnological Processes DivisionLsobral@cetem.gov.br Débora Monteiro de Oliveira M.Sc. Service of the Metallurgical and Biotechnological Processes dmonteiro@cetem.gov.br Centre for Mineral Technology CETEM/MCTAv. Pedro Calmon, 900Cidade UniversitáriaRio de Janeiro - RJCEP: 21941-908Tel: 55 21 3865-7246Fax: 55 21 3865-7232