Patent Grant
7051881
The present invention relates to the use of mixtures of thiocarbamates and mercaptobenzothiazoles as collectors for ores, in particular sulfidic ores.
The separation of minerals is achieved by a number of different processes, for example electrostatic or magnetic separation. However, in order to separate finely divided ores, the flotation process is the only economically justifiable method. The other processes are either only applicable to certain minerals or are restricted to special mineral combinations. Flotation utilizes the differing chemical properties of the surface of various minerals and can be carried out using a multiplicity of differing chemicals.
In the flotation process, the various minerals can be separated by adding chemicals which control the wettability of the individual minerals in the flotation pulp.
These chemicals can be roughly divided into a few categories, that is to say collectors, frothers, depressants, activators and modifiers.
Collectors are reagents which principally ensure that the mineral of value becomes hydrophobic. They are surface-active organic substances which are adsorbed to the surface of the mineral. Collectors contain a polar functional group which, because of its hydrophilicity, is bound to the mineral surface, and a nonpolar group which, owing to its hydrophobicity, is attached to an air bubble. The hydrophobic part of the collector is usually a hydrocarbon radical. Collectors are classified either on the basis of their functional group or according to the type of mineral connected.
Important commercially available collectors are xanthates, dithiophosphates and thionocarbamates (Schubert: Aufbereitung fester mineralischer Rohstoffe [Processing of solid mineral raw materials], volume II, 1977, pp. 296 ff). However, in some cases (for example when complex mixed ores are present), the recovery and selectivity achievable using these standard collectors is completely unsatisfactory, so that special collector types are required.
Thionocarbamates are selective and highly active collectors for many sulfide minerals, particularly for copper minerals and zinc blende. The main field of application is the flotation of copper ores in which the minerals of value present are especially copper glance (chalcosine Cu2S), indigo copper (covelline CuS), copper pyrites (chalcopyrite CuFeS2), peacock ore (bornite Cu5FeS4) and tetrahedrite (Cu12Sb4S13). A high selectivity of thionocarbamate is of importance, especially in the case of ores where the copper minerals are accompanied by greater contents of iron sulfide minerals (pyrites, marcasite, pyrrhotite, arsenopyrite).
U.S. Pat. No. 4,699,711 discloses a method for froth flotation of sulfide minerals, in particular copper-bearing sulfide minerals, and a corresponding collector. This collector, in a preferred embodiment, comprises short-chain alkyl-substituted thionocarbamates.
Mercaptobenzothiazole is, in the neutral to acidic range, a highly active all round collector for all sulfide minerals of Ag, Cu, Pb, Zn, Bi, Sb, As, Ni, Co, Mo and Fe, and of elemental metals such as Cu, Bi, Ag, Au and PGM (platinum group metals). In many cases the strongest xanthates (K amylxanthate, K hexylxanthate) exceed its activity, which does not apply at low pHs (<4) at which xanthates lose their activity. Mercaptobenzothiazole can be used either alone or in combination with other sulfhydryl collectors such as xanthates, aromatic and aliphatic dithiophosphates, thiocarbamates, xanthogenic esters etc. Mercaptobenzothiazole reinforces the activity and selectivity of the other collectors, the choice of which is determined by the mineral to be flotated and the character of the ore.
Thionocarbamates and mercaptobenzothiazoles are described in Schubert: Aufbereitung fester mineralischer Rohstoffe [Processing of solid mineral raw materials], volume II, 1977, pp. 300 ff.
O-Isopropyl N-ethylthionocarbamate and 2-mercaptobenzothiazole are described in R. Woods et al., Minerals Engineering, Vol. 13, No. 4, pp. 345–356 as collectors for copper minerals. However, the document does not mention any mixtures of these substances as suitable collectors.
EP-A-0 298 392 discloses a flotation method and a collector for sulfidic minerals. The collector consists of a primary or secondary amine which bears alkyl or alkenyl substituents having 8 to 22 carbon atoms, and also a sulfur compound. The sulfur compounds mentioned are, inter alia, mercaptobenzothiazoles and thionocarbamates, but not mixtures thereof.
It was an object of the present invention to find an improved flotation reagent for sulfidic ores, in particular for copper ore, in which case the reagent is to be suitable in particular for those ores which are associated with further minerals of value. The flotation reagent is, furthermore, to be effective in lower amounts than the flotation reagents of the prior art.
Surprisingly, it has now been found that thionocarbamates in combination with mercaptobenzothiazoles improve the flotation of sulfidic ores, in particular the flotation of copper ore which is associated with molybdenum and/or gold.
The invention thus relates to a flotation reagent comprising compounds of the formula (1)
and (2)
where R1 and R2 independently of one another are alkyl groups having 1 to 18 carbon atoms, and R4 and R4 independently of one another are hydrogen or C1–C6-alkyl, and M is hydrogen or an alkali metal, in a weight ratio of (1):(2)=95:5 to 75:25.
The invention further relates to the use of the inventive flotation reagent for the flotation of sulfidic ores. The sulfidic ores are preferably copper-bearing ores.
R1 and R2 can be straight-chain or branched radicals. They are preferably C1–C6-alkyl, in particular C1–C3-alkyl. The compound of the formula (1) is, in a preferred embodiment, O-isopropyl N-ethylthionocarbamate (IPETC).
R3 and R4 can be at any of the free aromatic positions. They are preferably C1–C3-alkyl, in particular H. M is preferably Na.
The mixing ratio of the compounds of the formulae 1 and 2 is preferably between 93:7 and 80:20, in particular between 92:8 and 87:13, by weight.
In a further preferred embodiment of the invention, the inventive flotation reagent comprises up to 50% by weight, based on the weight of the flotation reagent, of diethylene glycol or mono- or diethanolamine.
The inventive flotation reagent is preferably essentially free from alkyl- or alkenyl-substituted amines in which the alkyl or alkenyl groups do not contain hydroxyl groups.
Using the inventive flotation reagent, improved results for selectivity and yield can be achieved compared with standard collectors in the flotation of non-Fe-metal sulfides.
All metal sulfides (apart from Fe) can be flotated, with particular mention being made of Cu, Mo, Pb, Zn and Ni. Particularly good results may be observed in the processing of Cu, Zn and Mo. The inventive flotation reagent is usable in a wide pH range (2 to 12) and is added to the aqueous pulp at a concentration between preferably 0.01 and 1.0 kg/metric ton of pulp.
By means of the inventive flotation reagent, especially in the case of complex Cu-bearing mixed ores, a significant improvement in selectivity and recoveries is achieved.
Preparation of the Collector Mixture
The components are mixed at 50 to 80° C. in a stirred tank until a homogeneous solution is present.
Applications studies: flotation of chalcopyrite
| Number | Date | Country | Kind |
|---|---|---|---|
| 100 55 126 | Nov 2000 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP01/12628 | 10/31/2001 | WO | 00 | 4/30/2003 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO02/38277 | 5/16/2002 | WO | A |
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| 5929408 | Gutierrez et al. | Jul 1999 | A |
| Number | Date | Country |
|---|---|---|
| 1 190 864 | Jan 1970 | DE |
| 0 298 392 | Jan 1989 | EP |
| WO 9423841 | Oct 1994 | WO |
| WO 9813142 | Apr 1998 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20040099836 A1 | May 2004 | US |
