Effects of enhanced pyrite on the Galvanox process

Transcription

1 Effects of enhanced pyrite on the Galvanox process Ghazaleh Nazari Supervisors: Dr. Dixon and Dr. Dreisinger The University of British Columbia

2 Outline Chalcopyrite Leaching The Galvanox Process Motivations and Objectives Experiments and Results Conclusions

3 Chalcopyrite Leaching Chalcopyrite, CuFeS 2, the most abundant source of copper in the world Various hydrometallurgical processes: Sulfate Chloride Ammonia Nitrate

4 Sulfate Processes Advantages: Simplicity of the leaching reactions Low capital cost Low operating cost Conventional SX/EW Disadvantages Slow leaching rates Low copper recoveries

5 The Galvanox Process Pyrite-catalyzed atmospheric leaching Low-cost atmospheric leaching tanks Low oxygen consumption Low sulfuric acid generation Safe disposal of iron (as hematite) to tails No chloride, nitrate, or ammonia No surfactants No microbes No ultrafine grinding

6 Motivation In the Galvanox process, pyrite samples from various sources can influence the rate of chalcopyrite leaching differently The effectiveness of pyrite on the kinetics of chalcopyrite leaching has a strong correlation with the amount of silver on pyrite

7 Objectives 1. To investigate the use of silver enhanced pyrite in the Galvanox process to improve the extraction of copper from chalcopyrite 2. To develop a comprehensive understanding of the mechanism of this process

8 Experimental Apparatus

9 Silver Enhanced Pyrite 0.5 L of solution containing the desired amount of silver is prepared Silver is added as silver nitrate solution The solution is well mixed using a magnetic stirrer Fifty grams of pyrite are added and allowed to react with the silver until no silver is detected in the solution Pulp density is held at 1 to ensure a high degree of mixing by the magnetic stirrer in the glass beaker the solid residue is filtered and rinsed several times with water

10 Experiments Investigating the effect of various parameters on the kinetics of chalcopyrite leaching: Silver concentration on pyrite Solution potential Pyrite recycle Pulp density Comparison of silver-catalyzed leaching and silverenhanced pyrite-catalyzed leaching

11 Mineralogy Mineral Copper Conc (%) Pyrite #1 (%) Pyrite #2 (%) Pyrite #3 (%) Pyrite Chalcopyrite Quartz Biotite Dolomite Plagioclase 2.2 Anhydrite 1.8 Gypsum Calcite 1.6 Pyrrhotite 2.1 Clinochlore 2.2 Muscovite 3.4

12 Elemental composition Element Copper Conc Pyrite #1 Pyrite #2 Pyrite #3 Cu % 0.13 % 1.8 % 9 ppm Fe % % % % S % % 45.3 % % Mg 0.27 % 0.04 % 1.88 % < 0.01 % Co 0.16 % 68 ppm Pb 0.14 % 48 ppm < 2 ppm As 130 ppm 49 ppm 10 ppm Ag 15.5 ppm 21 ppm 2 ppm < 0.5 ppm Ca 0.47 % 0.56 % 4.05 % 0.69 % Al 0.51 % 0.02 % 0.41 % 0.18 % Zn 0.01 % 441 ppm 71 ppm Si 1.14 % 0.28 % 1.18 % 1.2 %

13 Unassisted chalcopyrite leaching Potential set point = 470 mv (vs. Ag/AgCl), T = 80 C

14 Natural pyrite addition Pyrite #1, Py/Cp = 6 Pyrite #2, Py/Cp = Pyrite #3, Py/Cp = 6 Potential set point = 470 mv (vs. Ag/AgCl), T = 80 C

15 Silver-enhanced pyrite addition Pyrite #3, Py/Cp = 6, Ag/Py = 100 ppm Pyrite #1,Py/Cp = 6, Ag/Py = 100 ppm Pyrite #2,Py/Cp = 6, Ag/Py = 100 ppm Potential set point = 470 mv (vs. Ag/AgCl), T = 80 C

16 Comparison Pyrite #3, Py/Cp = 6, Ag/Py = 100 ppm Pyrite #1, Py/Cp = 6 Pyrite #2, Py/Cp = 6 Pyrite #1,Py/Cp = 6, Ag/Py = 100 ppm Pyrite #3, Py/Cp = Pyrite #2,Py/Cp = 6, Ag/Py = 100 ppm Potential set point = 470 mv (vs. Ag/AgCl), T = 80 C

17 Natural pyrite addition C o p p e r E x tra ctio n 6 4 C o p p e r E x tra ctio n 6 4 Py/Cp = 6, Ag/Py = 0, E = 470 mv Py/Cp = 4, Ag/Py = 0, E = 470 mv Py/Cp = 6, Ag/Py = 0, E = 470 mv, Py Recycle Py/Cp = 4, Ag/Py = 0, E = 470 mv, Py Recycle Fresh pyrite Recycled pyrite Potential set point = 470 mv (vs. Ag/AgCl), T = 80 C

18 Silver-to-pyrite ratio Py/Cp = 4, Ag/Py = 200 ppm Py/Cp = 4, Ag/Py = 100 ppm Py/Cp = 4, Ag/Py = 50 ppm Potential set point = 470 mv (vs. Ag/AgCl), T = 80 C

19 Solution potential set point 450 mv 420 mv 450 mv 420 mv Py/Cp = 4, Ag/Py = 100 ppm, E = 450 mv Py/Cp = 4, Ag/Py = 100 ppm, E = 440 mv Py/Cp = 4, Ag/Py = 100 ppm, E = 470 mv Py/Cp = 4, Ag/Py = 100 ppm, E = 420 mv Fresh pyrite Py/Cp = 4, Ag/Py = 100 ppm, E = 450 mv, Py Recycle Py/Cp = 4, Ag/Py = 100 ppm, E = 440 mv, Py Recycle Py/Cp = 4, Ag/Py = 100 ppm, E = 470 mv, Py Recycle Py/Cp = 4, Ag/Py = 100 ppm, E = 420 mv, Py Recycle Recycled pyrite Py/Cp = 4, Ag/Py = 100 ppm, T = 80 C

20 Recycled pyrite at low pulp density Py/Cp = 4, Ag/Py = 100 ppm, E = 450 mv Py/Cp = 4, Ag/Py = 100 ppm, E = 440 mv Py/Cp = 4, Ag/Py = 100 ppm, E = 470 mv Py/Cp = 4, Ag/Py = 100 ppm, E = 420 mv Py/Cp = 4, Ag/Py = 100 ppm, E = 450 mv, Py Recycle Py/Cp = 4, Ag/Py = 100 ppm, E = 440 mv, Py Recycle Py/Cp = 4, Ag/Py = 100 ppm, E = 470 mv, Py Recycle Py/Cp = 4, Ag/Py = 100 ppm, E = 420 mv, Py Recycle Fresh pyrite Recycled pyrite 10 g/l Cu concentrate, T = 80 C

21 High pulp density Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mv, 2nd Py Recycle Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mv, Fresh Py Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mv, 1st Py Recycle g/l Cu concentrate, T = 80 C

22 Silver Catalyzed Leaching The copper extraction from chalcopyrite in ferric sulfate solution increases by addition of silver as a soluble silver salt. Formation of an intermediate Ag 2 S film CuFeS Ag + 2 Ag 2 S (chalcopyrite surface) + Cu 2+ + Fe 2+ Ag 2 S + 2 Fe 3+ 2 Ag Fe 2+ + S 0

23 Comparison of silver-catalyzed leaching and enhanced pyrite-catalyzed leaching Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mv Same Silver Added, No Pyrite Added, E = 450 mv Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mv, Py Recycle Same Silver Added, No Pyrite Added, E = 450 mv Fresh pyrite Recycled pyrite 0.61 g Ag/kg Cu, E = 450 mv, T = 80 C

24 Conclusions An improvement to the UBC Galvanox process has been developed Pyrite, enhanced with as little as 60 mg of silver per kg of copper, is sufficient to ensure complete copper extraction typically within 10 hours of leaching The silver enhanced pyrite can be recycled and reused with minimal loss and no need for a separate silver recovery step The fastest rate was observed at a solution potential of 450 mv Recycled pyrite is equally as effective as freshly enhanced pyrite as a catalyst Both weaknesses of silver catalyzed leaching, silver availability and toxicity, are overcome in this process

25 Thank You! Questions?