Copper ores bioleaching

Lecture #6

Copper extraction technology

• World copper production has increased steadily in the period 1964-2007 from 9 Mt to 16 Mt per year.

• In 2008 the copper production will be close to 18 Mt.

• More than 20-25 % of that copper is produced via biohydrometallurgy

BioCOP technology

High concentrations of Cu (20-25g/L) are required if iron cementation is used, midrange concentrations (10-12 g/L) are used in solvent extraction.

Copper bioleaching plants

Region /mine Ore processed [t/day] Cu production [t/year] Cerro Colorado, Chile 1993 Chalcocite, covellite [16 103] 100 103

Quebrado Blanc, Chile 1994 Chalcocite, [17.3 103] 75 103

Zaldivar, Chile 1998 Chalcocite [20 103] 150 103 Lomas Bayas, Chile 1998 Oxides/sulfides [36 103] 60 103 Cerro Verde, Peru 1977 Oxides/sulfides [32 103] 54.2 103 Escondida, Chile 1995 Oxides/ sulfides 200 103 Morenci, Arizona 2001 Calcocite, pyrite [75 103] 380 103 S&K Copper, Monywa

Myanmar 1999 Chalcocite [18 103] 40 103

Jinchuan Copper, China 2006 Chalcocite, covellite 10 103

Copper ore bioleaching

• Copper sulfide ore bioleaching processes are currently under full development in Chile.

• Bioleaching processes are realized as:Treatment of secondary sulfide in heapsLow-grade ores in dumpsBioleaching of concentrates in reactors at

high temperature

Significant processes occur at heap bioleaching

Equipment flow diagram for heap bioleaching of chalcopyrite (CaFeS2) ores

Copper minerals for bioleaching

• Chalcopyrite CuFeS2 is the most abundant copper mineral in nature. (70% of copper reserves in the world).

• Covellite CuS

• Chalcocite CuS2

• Bornite Cu5FeS2

Copper biooxidation processes

Chalcopyrite bioleaching

• Chalcopyrite dissolves in the presence of ferric ion (Fe3+) according to the following reaction:

CuFeS2+ 4Fe3+Cu2+ + 5Fe2+ + 2S0

CuFeS2+ 4Fe3+ + 3O2+ 2H2O Cu2+ +5Fe2+ + 2H2SO4

Silver-catalyzed chalcopyrite leaching

• In the presence of silver ions the leaching of chalcopyrite takes place according to the following reactions:

• CuFeS2 + 4Ag+ Cu2+ + Fe2+ + 2Ag2S

• Ag2S + 2Fe3+ 2 Ag+ + Fe2+ + S0

The rate of copper extraction is a faster in the presence of silver ions.

Ag2S layer is porous.

Microorganisms

• Amongst the microorganisms participating in copper bioleaching are:

Iron-oxidising bacteriaSulfur-oxidising bacteriaHeterotrophic bacteria

(Iron–oxidising bacteria are critical for keeping a high oxidising potential in solutions)

BacteriaMesophiles -30-42oC, rod-shaped bacteria with diameter of about 0.5-2.0 m

Moderate thermophiles,

45 – 55oC

similar morphology

Extreme thermophiles 60 – 90oC

Spherical shape, diameter 1-2

Copper bioleaching

Particle size effect

Heap bioleaching

• Copper is the metal recovered i the largest quantity by the heap bioleaching.

• The large copper leaching operation are those by Sociedad Contractual Minera El Abra and the Codelco Division Radimiro Tomic both in Chile producing 225 000 and 180 000 tonnes Cu per annum respectively.

• Gold ore is also preatreated by bioleaching in heaps by Newmont Mining in the Carlin Trend region, Nevada.

Heap creation

• Copper ores containing such minerals as chalcocite (Cu2S) or covellite (CuS) are crushed, acidified with sulfuric acid and agglomerated in rotating drums to bind fine material to coarser agglomerates.

• These agglomerates are stacked in the heaps onto lined pads on the aeration pipes are placed.

• The stacked heaps are irrigated with an iron-containing solution through a second system of pipes laid on the heap surface.

Heap preparation(segregation process)

The flow in the dump of Dexing Copper Mine

Heap leaching of low-grade copper ores (drainage system)

Drainage system

Top of heap

Bioleaching of flotation tailings

Heap bioleaching

Heap

Leaching solution pool

Inoculum preparation station

Bottom of heap

Leaching solution

Copper heap bioleaching

Heap model

Copper bioleaching

Copper recovery from Escondida dump

Effect of particle size

• In China, the first commercial plant of bio-heap leaching with a capacity of 10,000 t Cu/a at the Zijinshan Copper Mine started operation by the end of 2005.

• The ore contained the relative high proportion of pyrite (up to 5.8%)

Zijinshan Copper Mine-China

Bioleaching and EX-EW flowsheet in Dexing Copper Mine (China)

Bioleaching of a complex polymetallic sulfide concentrate at Monterrey, Mexico

Recovery of other metals by bioleaching

Base metals bioleaching

• Bioleaching may be used as an alternative process for extraction and recovery of other metals like:

NickelZincCobaltMolybdenumThese metals occur in significant quantities

in sulfidic ores (polymetallic ores)

The companies have developed biooxidatio process for use in metal extraction

Newmount

mining

BIOPROTR Process – heap leaching of refractory gold ore

BHP Billiton Ltd.

BioCOPTM Process –agitated tank oxidation and bioleaching of copper sulfide

BioNICTM Process – agitated tank oxidation and leaching of nickel sulfides

BioZINCTM Process – agitated tank oxidation and leaching zinc sulfides

Godl FieldsnLtd.

BIOXTM Process – agitated tank oxidation and leaching of copper sulfides

Bac Tech Environmet

BacTech/Mintek Process – agitated tank oxidation and leaching of copper sulfides

Geo Biotics Inc.

GEOCOATTM Process – heap leaching sulfide mineral concentrates

Nickel

• The nickel mineral most commonly mined is pentlandite (Fe,Ni)9S8. Nickel sulfide –millerite NiS.

• Billiton developed a process named BioNICTM to treat low-grade nickel ores, based on the gold bioleaching.

• Nickel could be recovery from lateritic ores using heterotrophic microorganism such as Aspergillus niger and Penicillium.

Talvivaara dopsit

• The Talvivara deposit is the largest in the world nickel deposit with 340 Mt of ore with an average contents of 0.27% Ni, 0.02% Co and 0.56% Zn.

• Heap bioleaching would make Talvivaara

the most attractive source of Ni in the whole of Europe.

Zinc

Sphalerite ore bioleachingThe ore contained sphalerite (ZnS) and pyrite FeS2

Variation of the ferrous (Fe2+) and ferric (Fe3+) concentration

Variation of zinc (Zn2+) ion concentration

Flow sheet of Tamboraque plant - Peru

Cobalt

• Bioleaching of cobalt-containing pyrite from KCC Kasese industrial operation.

• The amount of flotation concentrate was approximately 900 000t and contained approximately 80% pyrite and 1.38 % cobalt.

• The gangue minerals are mostly quartz, silicates and gypsum.

• The predominat organisms:Letospirillum (tow different strains), Acidithiobacillus thiooxidans, Acidithiobacillus caldus, Sulfobacillus thermosulfidooxidans.

Kasese Cobalt Company

Optimum growth temperature: 35OC

Solids concentration: 10-15 % by weight

Particle size: all particles ground to smaller than 63m

pH in the tanks : between 1.3 and 2.0