Cynthia Torres

7/23/2019 Cynthia Torres

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Possible role of copper species

in enhanced chalcopyritedissolutionPhD. Cynthia Torres Godoy



TEAM

• Cynthia Torres• Maria Elisa Taboada• Teófilo Graber

• Osvaldo Herreros• Pía Hernandez• Helen Watling• Denis Shiers



OUTLINE

• RELEVANCE OF THIS RESEARCH

• OBJECTIVES

• EXPERIMENTAL PROCEDURE

•RESULTS AND CONCLUSIONS



RELEVANCE OF THIS RESEARCH

•In recent years several processes have been proposed for leachingof chalcopyrite concentrates in chloride media.

• However, there is very little information in the public domain

about the role of copper species in enhanced chalcopyrite

dissolution.

• Focused studies simulating different unit processes will become

the foundation for optimising those processes and/or describing

the possible role of copper species for the chalcopyrite

concentrate study.



KEY OBJECTIVE

• The primary goal of this research is to understand the

formation of chlorocomplexes mechanisms (the

concentration of copper monochloride ion (+1) (CuCl+)

correlated directly with extraction.



EXPERIMENTAL EQUIPMENTS

Leaching reactors

Shaker Shaker with temperature control



• In the present study, copper extraction from chalcopyriteconcentrate was investigated using:

A suite of solutions acidified with H2SO4 and encompassing

five chloride concentrations,

three cupric ion concentrations and,

two initial solution pH set points. Soluble copper was measured during the leaching

experiments.

The extraction data were analysed in respect of the roles of

major copper species present in initial acidified leach media.

METHODOLOGY



Mineral phase Content Ideal formula Mineral phase Content Ideal formula

Chalcopyrite 74 CuFeS2 Hematite 1 Fe2O3

Melanterite 5 FeSO4.7H2O Bernalite 1 Fe(OH)3

Calcite 4.5 CaCO3 Magnesioferrite 1 MgFe3+2O4

Quartz 2.5 SiO2 Siderite 0.5 FeCO3

K-Jarosite 2.5 KFe3(SO4)2(OH)6 Ferrihydrite 0.5 Fe5O3(OH)9

Pentlandite 2 (Fe,Ni)9S8 Talc 0.5 Mg3(Si2O5)2(OH)2

Römerite 2 Fe3(SO4)4.14H2O Dwornikite 0.5 NiSO4.H2O

Pyrite 2 FeS2 Magnesite 0.5 MgCO3

Table Mineralogical analysis of chalcopyrite concentrate [%]

Cu Fe S As Si Na K Al Mg Zn Pb

24.5 25.9 28.6 0.126 5.19 0.036 <0.05 0.323 0.950 0.106 0.094

Table Chemical analysis of chalcopyrite concentrate [%]

INFORMATION OF CPY CONCENTRATE



RESULTS AND CONCLUSIONS

0

20

40

60

80

100

0 50 100 150

E s t i m a t e d C u e x t r a c t i o n

[ % ]

Time [hours]

Cu 0.0234 M pH 1

Cu 0.0234 M pH 2

Cu 0.0391 M pH 1

Cu 0.0391 M pH 2

Effect of initial solution pH on copper extraction.The media were 0.143 M chloride.

• Copper extraction was faster in chloride media initially pH 1 compared with pH 2.• The results are consistent with those of Velásquez-Yévenes et al. (2010) who reported that extractionrates are almost independent of pH in the range 0.5-2.0, but that a “fairly low pH is necessary to keepiron(III) in solution”.




-20

0

20

40

60

80

100

0 50 100 150

E

s t i m a t e d C u e x t r a c t i o n

[ % ]

Time [hours]

Cu 0.0078 M

Cu 0.0234 M

Cu 0.0391 M

Cu 0.0078 Madjusted fo r adsorption

Initial copper concentration effect in leach medium on

copper extraction. The media were 0.2 M chloride at pH 1.

• While an initial copper concentration 0.0078 M was limiting, copper extractions were not affected

greatly at higher initial copper concentrations.• Thus the presence of cupric ions is necessary for accelerated chalcopyrite dissolution,• but above the limiting concentration, rates of dissolution are not enhanced for increased copperconcentration.




0

20

40

60

80

100

0 50 100 150

E s t i m a t e d C u e x t r a c t i o n

[ % ]

Time [hours]

Cl 0 M

Cl 0.143 M

Cl 0.200 M

Cl 0.286 M

Effect of chloride concentration on copper extraction from

chalcopyrite. Initial copper concentration was 0.0391 M in media at pH

1.

• The presence of chloride in the initial leach medium resulted in increased copper extraction,compared with the chloride-free medium.• However, the rate of chalcopyrite dissolution is not greatly affected by the chloride concentration




Predicted copper speciation [M] as a function of chloride

concentration. Initial copper concentration was 0.0234 M in media pH

1.

Reaction ∆G (kJ/mol) K

Cu2+ + Cl – CuCl+ -2.198 K1=2.426

CuCl+ + Cl –

CuCl2(aq) 6.653 K2=0.068

CuCl2(aq) + Cl – CuCl3 – 9.131 K3=0.025

CuCl3 – + Cl – CuCl4

2– 13.142 K4=0.005

•A model of copper speciation in the experimental range predicted that, increased Cl – concentration,Cu+2 concentration decreased significantly while the chlorocomplex species CuCl+ concentrationincreased



Total Cl–

[M]

Total Cu

[M]

Cu+2

[M]

CuCl+

[M]

Extraction

[%]

0 0.0078 0.0078 0 16

0 0.0234 0.0234 0 24

0 0.0391 0.0391 0 30

0.143 0.0078 0.0058 0.0020 39

0.200 0.0078 0.0053 0.0025 55

0.286 0.0078 0.0046 0.0032 57

0.143 0.0234 0.0176 0.0058 60

0.200 0.0234 0.0159 0.0074 67

0.286 0.0234 0.0139 0.0093 67

0.143 0.0391 0.0295 0.0095 57

0.200 0.0391 0.0267 0.0122 58

0.286 0.0391 0.0234 0.0153 57

Table 4. Copper extraction [%] at pH 1 correlated with predicted copper speciation at different chloride

and copper concentrations.



SUMMARY AND CONCLUDING REMARKS

•

At low initial copper concentration and pH 1, copper was removed from solution inthe first 24 hours of leaching. This could be due to adsorption of cupric ions or the

formation of a disordered bornite-like phase on the chalcopyrite surface.

• This phenomenon was not discerned at pH 2 or in higher-concentration copper

solutions.

• An increase in the initial copper concentration resulted in increased copper

extraction from chalcopyrite. Copper extraction was faster in media initially pH 1

compared with pH 2.

• Copper extraction increased with increase chloride concentration but chloride itself

was not the key component.

• Using a thermodynamic model, it was predicted that CuCl+ was the dominant copper

species in the system at the concentrations studied



ACKNOWLEDGEMENTS

•

The authors are grateful for the financial support provided by CICITEM R04I1001,CSIRO–Chile International Centre of Excellence, and CONICYT through Fondecyt

Project 1140169 (Director: Maria Elisa Taboada)

Cynthia Torres

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