ZA200201534B - Base metal recovery from a tailings dump by bacterial oxidation. - Google Patents
Base metal recovery from a tailings dump by bacterial oxidation. Download PDFInfo
- Publication number
- ZA200201534B ZA200201534B ZA200201534A ZA200201534A ZA200201534B ZA 200201534 B ZA200201534 B ZA 200201534B ZA 200201534 A ZA200201534 A ZA 200201534A ZA 200201534 A ZA200201534 A ZA 200201534A ZA 200201534 B ZA200201534 B ZA 200201534B
- Authority
- ZA
- South Africa
- Prior art keywords
- surface layer
- tailings
- slurry
- adjusted
- dump
- Prior art date
Links
- 230000001580 bacterial effect Effects 0.000 title claims description 14
- 239000010953 base metal Substances 0.000 title claims description 14
- 230000003647 oxidation Effects 0.000 title claims description 14
- 238000007254 oxidation reaction Methods 0.000 title claims description 14
- 238000011084 recovery Methods 0.000 title claims description 12
- 239000002344 surface layer Substances 0.000 claims description 35
- 238000000034 method Methods 0.000 claims description 31
- 239000002002 slurry Substances 0.000 claims description 15
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 11
- 229910052802 copper Inorganic materials 0.000 claims description 11
- 239000010949 copper Substances 0.000 claims description 11
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 11
- 239000011707 mineral Substances 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 239000007787 solid Substances 0.000 claims description 8
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 7
- 230000002349 favourable effect Effects 0.000 claims description 4
- 238000005342 ion exchange Methods 0.000 claims description 4
- 238000000638 solvent extraction Methods 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 3
- 238000005188 flotation Methods 0.000 claims description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L sulfate group Chemical group S(=O)(=O)([O-])[O-] QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 3
- 235000011149 sulphuric acid Nutrition 0.000 claims description 3
- 239000001117 sulphuric acid Substances 0.000 claims description 3
- 238000000227 grinding Methods 0.000 claims description 2
- 238000013019 agitation Methods 0.000 claims 2
- 239000000243 solution Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 7
- 239000011435 rock Substances 0.000 description 4
- 241000894006 Bacteria Species 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 3
- 229910052737 gold Inorganic materials 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 238000002386 leaching Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000005273 aeration Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 239000005569 Iron sulphate Substances 0.000 description 1
- 229910052770 Uranium Inorganic materials 0.000 description 1
- 229910052948 bornite Inorganic materials 0.000 description 1
- 229910052947 chalcocite Inorganic materials 0.000 description 1
- 229910052951 chalcopyrite Inorganic materials 0.000 description 1
- DVRDHUBQLOKMHZ-UHFFFAOYSA-N chalcopyrite Chemical compound [S-2].[S-2].[Fe+2].[Cu+2] DVRDHUBQLOKMHZ-UHFFFAOYSA-N 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 229910001779 copper mineral Inorganic materials 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 238000010908 decantation Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000008774 maternal effect Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000005325 percolation Methods 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- NIFIFKQPDTWWGU-UHFFFAOYSA-N pyrite Chemical group [Fe+2].[S-][S-] NIFIFKQPDTWWGU-UHFFFAOYSA-N 0.000 description 1
- 229910052683 pyrite Inorganic materials 0.000 description 1
- 239000011028 pyrite Chemical group 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 229910021653 sulphate ion Inorganic materials 0.000 description 1
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical group [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 239000010878 waste rock Substances 0.000 description 1
Landscapes
- Manufacture And Refinement Of Metals (AREA)
Description
LE » BASE METAL RECOVERY FROM A TAILINGS DUMP BY BACTERIAL OXIDATION
This invention relates to the recovery of base metals from tailings and is more particularly concerned with the oxidation of sulphide minerals in tailings dams or dumps.
A substantial amount of literature exists relating to the heap leaching of waste rock by natural oxidation through bacterial action. Oxidation of this type requires that air can freely penetrate the rock. This is usually the case for the rock is relatively coarse and the air can easily penetrate into the interior of a pile of rock. The bacteria are then capable of oxidising the sulphide minerals and the base metals may be dissolved by solution percolation through a rock pile. | ]
If a tailings dump is formed from material with a fine particle size, for example with a particle size which is less than 100 microns, then the dump is normally naturally compacted and the ability of air to penetrate to the interior of the dump is at best restricted but more generally prevented.
Two publications have addressed the problem of bacterial leaching of tailings with fine particle size, i.e. slime, for the recovery of gold. Reference is made in this regard to: 1. Livesey-Goldblatt E. Bacterial leaching of gold, uranium, pyrite bearing compacted mine tailing slime. In: Lawrence RW, Branion RMR, Ebner GH, eds. Fundamental and Applied Biohydrometallurgy. New York: Elsevier, 1986:89-96; 2. Lawson EN, Taylor JL, Hulse GA. Biological pre-treatment for the recovery of gold from slime dams. Journal of South African Institute of Mining and Metallurgy, 1990;
Py BE
In the processes described in the these publications oxidised minerals in the form of soluble iron and sulphate are dissolved. These processes are not however directed to the recovery of base metals.
The invention provides a method of recovering base metal from a tailings dump which includes the steps of: : 15 (a) aerating a surface layer of the dump; _ (b) adjusting the pH and the moisture content of the surface layer to provide conditions oo ® favourable for bacterial oxidation of sulphide minerals; (c) allowing bacterial oxidation to take place for a controlled period; (d) after the controlled period removing the oxidised surface layer and adding water thereto to form a slurry; (e) separating the slurry into solids and a solution; and 4) recovering base metal from the solution.
The aforementioned method lends itself particularly to the recovery of copper from a tailings dump.
The aeration of the surface layer may be achieved in any appropriate manner for example by agitating or mechanically loosening the surface layer. This may be done by ploughing the surface layer to a required depth which may be of the order of from 0,5 to 1,0 metres.
~ WO 01/16385 PCT/ZA00/00155 5: <« The pH of the surface layer may be adjusted by adding acid e.g. sulphuric acid thereto.
The pH may be brought to a level in the range of from 1,3 to 2,0. ~The moisture content of the surface layer may be adjusted to a value in the region from 16% to 20% and preferably to a value of the order of 18%.
The duration of the controlled period during which bacterial oxidation takes place should be sufficient to ensure that substantially all of the sulphide minerals are oxidised. The duration of this period is dependent on physical conditions and on the nature of minerals.
Thus, for example, the duration of the period may be temperature dependent and may also be affected by the depth of the surface layer, the degree of aeration which is achieved and the recovery figure which is being aimed at. Thus the duration of the controlled period may be at least four weeks. . The oxidised surface layer may be removed using any appropriate technique. Thus the oxidised surface layer may be removed mechanically and water may then be added to the surface layer. One may also make use of water jets which are emitted by water guns or the like and which washes the surface layer from the tailings dump. Additional water, or a suitable aqueous solution, may be added to the material which is washed away to form a slurry of a desired consistency.
The slurry may be agitated. This step may be carried out in a tank.
The base metal in sulphate form in solution may be separated from the slurry. The remaining solids may be washed to ensure effective recovery of the base metal sulphates.
Solids remaining after the separation step may be directed to waste. «a
The desired base metal or metals may be recovered from solution using any appropriate technique such as solvent extraction or ion exchange techniques.
RI CRIPTION OF THE DRAWING
The invention is further described by way of example with reference to the accompanying drawing which is a flow chart representation of a method of recovering copper from a tailings dump, according to the invention. - 15 5 DESCRIPTION OF PREFERRED EMBODIMENT
The accompanying flow chart illustrates a copper recovery process according to the invention. :
The method of the invention applies particularly to the treatment of tailings which result from the grinding of copper ores followed by a flotation process. The tailings are usually pumped into a tailings pile. The particles in the tailings are fine and normally compact automatically to such an extent that penetration of air into the tailings dump is not possible unless such penetration is assisted by external means.
In accordance with the invention a tailings pile 10, of the aforementioned kind, is adjusted in a step 12 to have a moisture content in the range of from 16% to 20% and preferably of the order of 18%. Thereafter, in a step 14, a surface layer of the tailings dump is -
~ WO 01/16385 s PCT/ZA00/00155 ] ploughed using mechanical means, to a depth of the order of from 0,5 to 1,0 metres. In this way the surface layer is loosened and aerated. The compaction density is effectively reduced. At the same time dilute sulphuric acid is added to the surface layer to adjust the pH thereof to a value in the range of from 1,3 to 2,0 (step 16). The surface layer may be ploughed several times to ensure that it has the correct pH and moisture content and to ensure that such values are distributed substantially constantly throughout the surface layer.
Bacterial oxidation of the sulphide minerals in the surface layer is then allowed to take place for a controlled period the duration of which is dependent on a number of factors including the mineral type and climatic conditions such as the temperature and the rainfall.
For example with minerals such as chalcocite or bornite an oxidation period of the order of four weeks may be adequate. A longer period will be required for chalcopyrite. If the } ) temperature of the dump rises due to climatic conditions this is normally regarded as being advantageous for the temperature increase encourages bacterial activity.
The moisture content of the dump may require adjustment, for example by means of sprinklers (step 18), but this step depends on the climate and rainfall or drying of the dump by low humidity conditions.
It is apparent that an objective of the invention in this regard is to create favourable conditions for bacterial oxidation of copper minerals in the upper layer of the dump to take place (step 20).
After the upper layer has been oxidised to the required extent mechanical equipment is used to remove the oxidised material (step 22). Alternatively water guns or jets can remove the oxidised layer by sluicing or washing the maternal from the tailings dump. The reclaimed material is conveyed to agitated tanks where water 24, or an alternative suitable aqueous solution, possibly recycled from another part of the process, is added to form a slurry 26.
In the tanks copper dissolves into water forming an acid solution of copper sulphate and iron sulphate. In a separation step 28 the slurry is separated into solids and a solution by filtration or decantation techniques. The solids are washed in a step 30 and the liquid is added to the solution obtained by the separation step 28. The solids are then deposited on a new tailings dam (step 32).
The solution is subjected to a copper extraction step 34 using solvent extraction or ion exchange techniques.
Once the surface layer has been removed (step 22) in order to form the slurry the fresh upper surface layer of the tailings dump is treated in the described manner to provide aerated material with correct moisture and pH levels to establish favourable oxidation conditions. Sufficient oxidised material remains in the upper portion of the tailings pile to cause the pile to remain actively populated with bacteria.
It has been found that it is important to maintain the moisture content at about 18% although the content may vary from 16% to 20%. If the dump is too moist then air access is not possible. On the other hand if the dump is dry then bacterial action cannot take place effectively because migration of bacteria throughout the material is difficult.
Claims (15)
1. A method of recovering base metal from a tailings dump which includes the steps of: (a) aerating a surface layer of the dump; (b) adjusting the pH and the moisture content of the surface layer to provide conditions favourable for bacterial oxidation of sulphide minerals; (c) allowing bacterial oxidation to take place for a controlled period, (d) after the controlled period removing the oxidised surface layer and adding water thereto to form a slurry; 16 (e) separating the slurry into solids and a solution; and f) recovering base metal from the solution.
: 2. A method according to claim 1 wherein the surface layer is aerated by agitating or mechanically loosening the surface layer.
3. A method according tc claim 2 wherein the surface layer is aerated by ploughing the surface layer to a depth of between 0,5 to 1,0 metres.
4. A method according to any one of claims 1 to 3 wherein the pH is adjusted to a level in the range of from 1,3 to 2,0.
S. A method according to any one of claims 1 to 4 wherein the pH is adjusted by adding sulphuric acid to the surface layer.
6. A method according to any one of claims 1 to 5 wherein the moisture content of the surface layer is adjusted to a value in the range of from 16% to 20%.
7. A method according to claim 6 wherein the moisture content is adjusted to a value of the order of 18%.
8. A method according to any one of claims 1 to 7 wherein the said controlled period, in step (c), is at least four weeks.
9. A method according to any one of claims 1 to 8 wherein the oxidised surface layer is removed by at least one of the following: by mechanical means, and by the use 2 of water jets. | BN oo oo 3
10. A method according to any one of claims 1 to 9 wherein the slurry is directed to at least one tank in which agitation of the slurry takes place. ]
11. A method according to any one of claims 1 to 10 wherein base metal in sulphate form in solution is separated from the slurry.
12. A method according to any one of claims 1 to 11 wherein step (f) is carried out using solvent extraction or ion exchange techniques.
13. A method according to any one of claims 1 to 12 used for the recovery of copper from a tailings dump.
) | WO 01/16385 9 PCT/ZA00/00155
14. A method according to claim 13 wherein the tailings result from the grinding of Co copper ores followed by a flotation process.
15. A copper recovery process wherein copper ore is ground and then subjected to a flotation process which results in tailings which are transferred to a tailings pile, and wherein the tailings pile is subjected to the following: a surface layer of the pile is loosened and aerated, the pH of the surface layer is adjusted to a value in the range of from 1,3 to 2,0, the moisture content of the pile is adjusted to lie in a range of from 16% to 20%, and at least sulphide minerals in the surface layer are bacterially oxidised for a controlled period, whereafter the surface layer is removed, mixed with water to form a slurry which is conveyed to at least one agitation tank and, in the tank, the slurry is separated into solids and a solution from which copper is extracted using solvent extraction or ion exchange techniques. }
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA200201534A ZA200201534B (en) | 1999-09-01 | 2002-02-25 | Base metal recovery from a tailings dump by bacterial oxidation. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA994274 | 1999-09-01 | ||
| ZA200201534A ZA200201534B (en) | 1999-09-01 | 2002-02-25 | Base metal recovery from a tailings dump by bacterial oxidation. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| ZA200201534B true ZA200201534B (en) | 2002-10-30 |
Family
ID=27738033
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| ZA200201534A ZA200201534B (en) | 1999-09-01 | 2002-02-25 | Base metal recovery from a tailings dump by bacterial oxidation. |
Country Status (1)
| Country | Link |
|---|---|
| ZA (1) | ZA200201534B (en) |
-
2002
- 2002-02-25 ZA ZA200201534A patent/ZA200201534B/en unknown
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