PROCESS FOR METAL RECOVERY IN FLOTATION OPERATIONS

Abstract

The present invention is related to a process for increasing copper or metal recovery in flotation processes, specially of minerals that are dissolved during the grinding stage, by the use of any sulfidizing agent or ionizing sulfide such as, but not limited to, sodium hydrogen sulfide, sodium sulfide, potassium hydrogen sulfide, potassium sulfide, ammonium hydrogen sulfide or ammonium sulfide, hydrogen sulfide (H2S), polysulfides of potassium, calcium, magnesium or ammonium to precipitate during the grinding stage or immediately after the grinding stage, metals that have been dissolved prior or during the milling or grinding stage prior to normal flotation.

Claims

1. Process for improving recovery of metals in mineral flotation operations or metal mineral pulps containing easily soluble metal sulfides and/or metal oxides or metals in solution in the case of pulps from reprocessed tailings, characterized in that it comprises adding a ionizing sulfide or sulfurizing agent in the grinding step or in a prior step, so as to precipitate as insoluble sulfides the dissolved metal ions of interest or being dissolved in the grinding step prior to flotation, in order to recover them by a conventional flotation process.

2. The process according to claim 1, characterized in that the ionizing sulfide or sulfidizing agent is selected form the group comprising sodium hydrogen sulfide, sodium sulfide, potassium hydrogen sulfide, potassium sulfide, ammonium hydrogen sulfide or ammonium sulfide, hydrogen sulfide (H2S), polysulfides of potassium, sodium, calcium, magnesium or ammonium, or a mixture of thereof

3. The process according to claim 1, characterized in that the pH is adjusted with lime or another modifying agent to a pH of 6.0 to 8.0 or more preferably to 6.5 to 7.5 during the grinding stage, to neutralize the generation of acid caused by the precipitation reaction.

4. The process according to claim 1, characterized in that the pH is not adjusted during the grinding stage.

5. The process according to claim 1, characterized in that the sulfidizing agent is added after grinding but before the actual flotation, and also prior to the addition of lime to adjust pH.

6. The process according to claim 1, characterized in that the dose of sulfidizing agent is such that the pulp will achieve an electrochemical potential of 50 mV to 250 mV, or more preferably of 100 mV to 200 mV.

7. The process according to claim 6, characterized in that the sulfidizing agent is added at a dose close to the stoichiometric rate of dissolved metal to obtain a floatable metal sulfide.

8. The process according to claim 7, characterized in that the sulfidizing agent is added at a dose slightly below the stoichiometric dose of dissolved metal.

9. The process according to claim 7, characterized in that the sulfidizing agent is added at a rate slightly above the stoichiometric rate of dissolved metal.

10. The process according to claim 1, characterized in that in the subsequent flotation steps a sulfidizing agent dosage is maintained as well as a normal sulfidizing process so as to maintain an electrochemical potential allowing the precipitated sulfides to be recovered.

11. The process according to claim 1, characterized in that the metal to be recovered is copper.

12. The process according to claim 11, characterized in that copper minerals containing brocantite, chalcanthite and atacamite ore similar species are processed.

13. The process according to claim 1, characterized in that through the addition of a sulfidizing agent, a reduction in grinding steel consumption is obtained.

14. The process according to claim 1, characterized in that the ionizing sulfide or sulfidizing agent is added during the grinding step of the ores containing soluble metal minerals.

15. The process according to claim 1, characterized in that the ionizing sulfide or sulfidizing agent is added into an ore pulp containing sulfides, soluble sulfides and dissolved metals, such as mineral pulps recovered from tailings.

16. The process according to claim 1, characterized in that through the precipitation of copper in solution during the grinding step, pyrite activation is avoided.

17. The process according to claim 16, characterized in that through the precipitation of copper in solution, grinding steel consumption is reduced since the presence of copper in solution is avoided, which dissolves steel by electrochemical processes.

18. The process according to claim 16, characterized in that through the reduction in activation of pyrite minerals the selectivity in copper recovery is increased in flotation operations.

19. Process for increasing selectivity in copper recovery in flotation operations due to reduction of activation of pyrite minerals, characterized in that it comprises the following steps: adding a ionizing sulfide or sulfurizing agent in the step of grinding an ore containing soluble copper or an ore pulp containing sulfides or dissolved copper, besides pyrite; grinding the mixture obtained in the previous step so that the dissolved copper precipitates immediately by conversion into insoluble sulfides, and avoids activation of pyrite; and recovering the copper precipitated in the previous step with sulfides from the mineral by conventional flotation processes with sulfide collectors.

20. Process for decreasing grinding steel consumption in flotation operations through the reduction in the presence of copper cations, characterized in that it comprises the following steps: adding a ionizing sulfide or sulfurizing agent in the step of grinding an ore containing soluble copper or an ore pulp containing sulfides and dissolved copper; grinding the mixture obtained in the previous step so that the dissolved copper precipitates immediately by conversion into insoluble sulfides, and avoids dissolution of steel; and recovering the copper precipitated in the previous step with sulfides from the mineral by conventional flotation processes with sulfide collectors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0041] The present invention is carried out by a process that comprises adding a ionizing sulfide or sulfurizing agent in the grinding step or in a prior step, so as to precipitate as insoluble sulfides the dissolved metal ions of interest or being dissolved in the grinding step prior to flotation, in order to recover them by a conventional flotation process.

[0042] In a preferred embodiment, the ionizing sulfide or sulfidizing agent is selected form the group comprising sodium hydrogen sulfide, sodium sulfide, potassium hydrogen sulfide, potassium sulfide, ammonium hydrogen sulfide or ammonium sulfide, hydrogen sulfide (H.sub.2S), polysulfides of potassium, sodium, calcium, magnesium or ammonium or a mixture of thereof.

[0043] In another preferred embodiment, during grinding, the pH is adjusted with lime or another modifying agent to a pH of 6.0 to 8.0 or more preferably to 6.5 to 7.5 during the grinding stage, to neutralize the generation of acid caused by the precipitation reaction.

[0044] In another preferred embodiment, the pH is not adjusted during the grinding stage.

[0045] In another preferred embodiment, the sulfidizing agent is added after grinding but before the actual flotation and also prior to the addition of lime to adjust pH.

[0046] In a preferred embodiment, the dose of sulfidizing agent is such that the pulp will achieve an electrochemical potential of 50 mV to 250 mV, or more preferably of 100 mV to 200 mV.

[0047] In a preferred embodiment, the sulfidizing agent is added at a dose close to the stoichiometric rate of dissolved metal to obtain a floatable metal sulfide. This dose can be slightly below the stoichiometric or above the stoichiometric dose of dissolved metal.

[0048] In another preferred embodiment, in the subsequent flotation steps a sulfidizing agent dosage is maintained as well as a normal sulfidizing process so as to maintain an electrochemical potential allowing the precipitated sulfides to be recovered.

[0049] In a preferred embodiment, the metal to be recovered is copper.

[0050] In another preferred embodiment, copper minerals containing brocantite, chalcanthite and atacamite ore similar species are processed.

[0051] In a preferred embodiment of the invention, the ionizing sulfide or sulfidizing agent is added during the grinding step of the ores containing soluble metal minerals.

[0052] In another preferred embodiment of the invention, the ionizing sulfide or sulfidizing agent is added into an ore pulp containing sulfides, soluble sulfides and dissolved metals, such as mineral pulps recovered from tailings.

[0053] The present invention is further directed to a process for increasing selectivity in copper recovery in flotation operations due to reduction of activation of pyrite minerals, comprising the following steps:

[0054] adding a ionizing sulfide or sulfurizing agent in the step of grinding an ore containing soluble copper or an ore pulp containing sulfides or dissolved copper, besides pyrite;

[0055] grinding the mixture obtained in the previous step so that the dissolved copper precipitates immediately by conversion into insoluble sulfides, and avoids activation of pyrite; and

[0056] recovering the copper precipitated in the previous step with sulfides from the mineral by conventional flotation processes with sulfide collectors.

[0057] Lastly, the present application is also focused on a process for decreasing grinding steel consumption in flotation operations through the reduction in the presence of copper cations, which comprises the following steps:

[0058] adding a ionizing sulfide or sulfurizing agent in the step of grinding an ore containing soluble copper or an ore pulp containing sulfides and dissolved copper;

[0059] grinding the mixture obtained in the previous step so that the dissolved copper precipitates immediately by conversion into insoluble sulfides, and avoids dissolution of steel; and

[0060] recovering the copper precipitated in the previous step with sulfides from the mineral by conventional flotation processes with sulfide collectors.

EXAMPLE

[0061] A mineral pulp obtained from an old tailings dam in central Chile containing about 0.3% copper and with a content of 50% solids was tested at laboratory conditions. The fraction of water contained 130 ppm Cu prior to grinding and the pH value of the pulp was 5.

[0062] A standard grinding with addition of lime and following flotation with collector and frother was performed obtaining a recovery of 62% of the contained copper. Flotation pH was 9.

[0063] Then, using the same grinding time with addition of lime during grinding, a flotation was performed adding sodium hydrogen sulfide prior to flotation at a dose of 80 g/ton, obtaining an EV of 80 mV. Under this condition, 72% of the copper was recovered. This would correspond to a traditional sulfidization process used normally at mine sites where oxide minerals are present.

[0064] A third test was made, adding sodium hydrogen sulfide at a dose of 80 g/ton to the mill and the amount of lime needed to adjust pH to 7. After grinding, a normal flotation with the same dose of collector and frother was performed at a pH of 9, adjusting pH with additional lime prior to flotation. Under these conditions, a copper recovery of 79% of the contained copper was obtained under laboratory flotation conditions.

[0065] The results show that the addition of the sodium hydrogen sulfide to the mill in the presence of a mineral pulp that also contains dissolved copper results in a significantly improved recovery of copper than the traditional sulfidization process, where the sulfidizing agent is added after the grinding stage.