Stable Aqueous Composition Of Neutral Collectors And Their Use In Mineral Beneficiation Processes

Abstract

The instant invention relates to a composition in form of a stable aqueous emulsion comprising a) 1-50 wt.-% of at least one water insoluble thionocarbamate collector selected from the group consisting of dialkyl thionocarbamates, alkyl alkoxycarbonyl thionocarbamates and alkyl allyl thionocarbamates, b) 1-50 wt.-% of one or a mixture of surface active agents of the general formula

##STR00001## wherein R.sup.1 is a saturated or unsaturated, branched or linear C.sub.3 to C.sub.30 aliphatic or aromatic hydrocarbon group, R.sup.2 and R.sup.3 are independently from each other hydrogen or a C.sub.1 to C.sub.4 alkyl group, R.sup.4 is hydrogen or CH.sub.2COOX where X is hydrogen or sodium salt or potassium salt or ammonium salt, and n and m are independently from each other 0 to 50, c) 0.1-20 wt.-% of a mixture of at least one alcohol and at least one ether and/or ester, e) 1-90 wt.-% of water.

Claims

1. A composition in form of a stable aqueous emulsion comprising a) 1-50 wt.-% of at least one water insoluble thionocarbamate collector selected from the group consisting of dialkyl thionocarbamates, alkyl alkoxycarbonyl thionocarbamates and alkyl allyl thionocarbamates, b) 1-50 wt.-% of one or a mixture of surface active agents of the general formula ##STR00005## wherein R.sup.1 is a saturated or unsaturated, branched or linear C.sub.3 to C.sub.30 aliphatic or aromatic hydrocarbon group, R.sup.2 and R.sup.3 are independently from each other hydrogen or a C.sub.1 to C.sub.4 alkyl group, R.sup.4 is hydrogen or CH.sub.2COOX, where X is hydrogen or sodium salt or potassium salt or ammonium salt, and n and m are independently from each other 0 to 50, c) 0.1-20 wt.-% of a mixture of at least one alcohol and at least one ether and/or ester, and e) 1-90 wt.-% of water.

2. The composition of claim 1 wherein the water insoluble thionocarbamate collector is O-isopropyl-N-ethyl-thionocarbamate.

3. The composition of claim 1, wherein the surface active agent is described by the general formula ##STR00006## wherein R.sup.1 is a saturated or unsaturated, branched or linear C.sub.3 to C.sub.18 aliphatic or aromatic hydrocarbon group R.sup.2 and R.sup.3 are independently from each other hydrogen or C.sub.1 to C.sub.4 alkyl group R.sup.4 is hydrogen and n and m are independently from each other 0 to 50.

4. The composition as claimed in claim 1, wherein the alcohol is selected from the group consisting of monohydric alcohols and diols.

5. The composition as claimed in claim 1, wherein the alcohol comprises a hydrocarbon radical having from 8 to 14 carbon atoms.

6. The composition as claimed in claim 1, wherein the alcohol has a solubility in water of less than 50 g/liter at at 20 C. determined according to the OECD guideline 105.

7. The composition as claimed in claim 1, wherein the alcohol is 2-ethylhexanol and/or 2-ethylhexane-(1,3)-diol.

8. The composition as claimed in claim 1, wherein the ether corresponds to the formula
R.sup.5OR.sup.6 wherein R.sup.5 is a linear or branched alkyl or alkenyl group having 2 to 30 carbon atoms and R.sup.6 is a linear or branched alkyl or alkenyl group having 1 to 30 carbon atoms.

9. The composition as claimed in claim 8, wherein the ether is cyclic, the ring is formed by R.sup.5 and R.sup.6 and the ring size is from 6 to 30 carbon atoms.

10. The composition as claimed in claim 8, wherein R.sup.5 is an alkyl or alkenyl group having 4 to 22 carbon atoms.

11. The composition as claimed in claim 8, wherein R.sup.6 is an alkyl or alkenyl group having 2 to 22 carbon atoms.

12. The composition as claimed in claim 1, wherein the esters are derived from monobasic or polybasic carboxylic acids having 2 to 30 carbon atoms in the acid radical and monohydric or polyhydric alcohols having 1 to 30 carbon atoms in the alcohol radical.

13. The composition as claimed in claim 12, wherein the acid radical is an alkyl or alkenyl group having 4 to 22 carbon atoms.

14. The composition as claimed in claim 12, wherein the alcohol radical is an alkyl or alkenyl group having 2 to 22 carbon atoms.

15. The composition as claimed in claim 1, wherein the ethers and/or esters are selected from the group consisting of dihexyl ether, dioctyl ether, di-(2-ethylhexyl) ether, oleic acid eicosyl ester, 2-ethylhexyl stearate, 2-ethylhexylic acid butyrate, octanoic acid ethyl ester, hexanoic acid ethyl ester, 2-ethylhexylic acid butyl ester, 2-ethylhexyl butyrate and 2-ethylhexylic acid 2-ethylhexyl ester, adipic acid di(2-ethylhexyl ester), 2-ethylhexane-(1,3)-diol mono-n-butyrate, and 2-ethylhexane-(1,3)-diol di-n-butyrate.

16. The composition as claimed in claim 1, wherein the mixture of at least one alcohol and at least one ether and/or ester corresponds to the composition TABLE-US-00006 Concentration range Component (% by wt.) Di-2-ethylhexyl ether 10-25 2-Ethylhexylic acid 2-ethylhexyl ester 10-25 C.sub.16-Lactones 4-20 2-Ethylhexyl butyrate 3-10 2-Ethylhexane-(1,3)-diol mono-n-butyrate 5-15 2-Ethylhexanol 4-10 C.sub.4 to C.sub.6 acetates 2-10 2-Ethylhexane-(1,3)-diol 2-5 Ethers and esters > C.sub.20 0-20

17. The composition as claimed in claim 1, wherein component c) is a product obtained from distillation residues of the 2-ethyl-1-hexanol production process

18. The composition as claimed in claim 1, wherein further comprising an additional water soluble anionic collector (component d) in an amount of 1 to 50 wt. %, wherein the additional water soluble anionic collector is selected from the group consisting of diisoamyl dithiophosphate, diethyl dithiophosphate, diisopropyl dithiophosphate, diisobutyl dithiophosphate, disecbutyl dithiophosphate, and mercaptobenzothiazolate.

19. The composition as claimed in claim 1, wherein the median droplet size of the discontinuous phase is from 100 nm to 100 m.

20. A process for manufacturing a stable aqueous emulsion comprising the steps of mixing a thionocarbamate (component a), selected from the group consisting of dialkyl thionocarbamates, alkyl alkoxycarbonyl thionocarbamates and alkyl allyl thionocarbamates, with a surface active agent (component b) of the general formula ##STR00007## wherein R.sup.1 is a saturated or unsaturated, branched or linear C.sub.3 to C.sub.30 aliphatic or aromatic hydrocarbon group, R.sup.2 and R.sup.3 are independently from each other hydrogen or a C.sub.1 to C.sub.4 alkyl group, R.sup.4 is hydrogen or CH.sub.2COOX, where X is hydrogen or sodium salt or potassium salt or ammonium salt, and n and m are independently from each other 0 to 50, and a mixture of at least one alcohol and at least one ether and/or ester (component c) and optionally a water soluble, anionic collector (component d) to yield a homogeneous mixture, and adding the homogenous mixture to water under high mechanical shear generated by a rotor-stator homogenizer to form the stable aqueous emulsion.

21. The process according to claim 20, further comprising the step, wherein the stable aqueous emulsion is homogenized under a pressure of atmospheric pressure to up to 1500 bar in a high-pressure homogenizer.

22. A process for beneficiation of a metal sulfide mineral or ore, the process comprising the steps of bringing the mineral or ore in contact with an aqueous collector composition comprising a stable aqueous emulsion, wherein the stable aqueous emulsion comprises a) 1-50 wt.-% of at least one water insoluble thionocarbamate collector selected from the group consisting of dialkyl thionocarbamates, alkyl alkoxycarbonyl thionocarbamates and alkyl allyl thionocarbamates, b) 1-50 wt.-% of one or a mixture of surface active agents of the general formula ##STR00008## wherein R.sup.1 is a saturated or unsaturated, branched or linear C.sub.3 to C.sub.30 aliphatic or aromatic hydrocarbon group, R.sup.2 and R.sup.3 are independently from each other hydrogen or a C.sub.1 to C.sub.4 alkyl group, R.sup.4 is hydrogen or CH.sub.2COOX, where X is hydrogen or sodium salt or potassium salt or ammonium salt, and n and m are independently from each other 0 to 50, c) 0.1-20 wt.-% of a mixture of at least one alcohol and at least one ether and/or ester, and e) 1-90 wt.-% of water, to form a mineral pulp, and subsequently frothing the mineral pulp.

23. The process as claimed in claim 22, wherein the metal is selected from the group consisting of copper, cobalt, lead, zinc, nickel, molybdenum, gold, silver and platinum group metals.

24. The process according to claim 22, wherein the amount of the aqueous collector composition added is an amount between 0.5 g and 1000 g per ton of ore.

25.-27. (canceled)

Description

EXAMPLES

[0059] General procedure for preparation of emulsions: water insoluble thionocarbamate collector, emulsifier, mixture of alcohols and esters and/or ethers and optionally a water soluble, anionic collector are mixed under mechanical stirring at room temperature. The homogeneous mixture is slowly poured into the water and homogenized under high mechanical shear using an Ultra Turrax T25-IKA equipped with dispersing tool consisting of S25N shaft and 25G generator, 6500 rpm around 1 minute and after completed addition further 10 min at 9500 rpm.

[0060] The average droplet size in the emulsions was determined by using a light-scattering particle size analyzer, e.g. the Malvern Mastersizer 2000 To measure the droplets size distribution, 1-1.5 ml of emulsion was introduced in the measure compartment than contains about 1000 ml of water.

[0061] Composition (wt.-%) and droplet size (D.sub.50) of the emulsions

TABLE-US-00002 1 2 3 4 5 6 7 (comp.) Thiono- 10 10 10 15 10 10 10 carbamate (%) Emulsifier (%) 4 4 4 4 4 4 4 Mixture 1 5 3 5 3 3 of alcohol- ester-ether (%) Anionic 5 3 collector 1 (%) Anionic 5 collector 2 (%) Water (%) 85 81 83 76 78 75 86 D.sub.50 (nm) 200 500 245 800 265 255 250

[0062] Emulsions 1 to 6 are examples according to this invention. Emulsion 7 is according to WO 9725149

[0063] The water insoluble thionocarbamate present in emulsions 1 to 7 was 0-isopropyl-N-ethyl-thionocarbamate.

[0064] The emulsifier present in emulsions 1,2,3,5,6 and 7 was a propoxylated (20)-ethoxylated (25) butanol derivative.

[0065] The emulsifier present in emulsion 4 was a isotridecyl polyoxyethylene (7EO) acetic acid.

[0066] The mixture of alcohols, ethers and esters present in the emulsions 1 to 6 corresponds to the following composition:

TABLE-US-00003 Concentration range Component (% by wt) Di-2-ethylhexyl ether 15 2-Ethylhexylic acid 2-ethylhexyl ester 12 C.sub.16-Lactones 8 2-Ethylhexyl butyrate 5.5 2-Ethylhexane-(1,3)-diol mono-n-butyrate 10 2-Ethylhexanol 5 C.sub.4 to C.sub.6 acetates 3 2-Ethylhexane-(1,3)-diol 2.5 Ethers and esters > C.sub.20 2

[0067] The water soluble, anionic collector 1 present in the emulsion 5 and 6 was a 50 wt.-% aqueous solution of the sodium salt of mercaptobenzothiazolate.

[0068] The water soluble, anionic collector 2 present in the emulsion 6 was a 35 wt.-% aqueous solution of the sodium salt of diisoamyl dithiophosphate.

[0069] The emulsions are stable and did not show separation at room temperature when shelved for a period of 3 months and thereafter.

[0070] Flotation Test Results:

[0071] Test Procedure

[0072] A series of flotation tests were conducted using a sulfide copper ore received from a Chilean copper mine. The ore had a copper content from 0.90-1.0% and a silica content from 43-45%. The received ore was first ground in a stainless steel rod mill until the desired particle size distribution, which was 20%>212 micron, was obtained. This was determined to occur after 35 minutes of milling when the laboratory grinding mill was filled with 1200 g of ore, 600 ml water and 10 stainless steel rods. The mass of the rods was 9210 g. On completion of the grinding stage, the milled slurry was transferred to a 2.5 liter capacity flotation cell, where the percentage solids was adjusted to approximately 35% by adding sufficient tap water until the desired pulp level was attained. Next, the impeller speed was set to 700 rpm and slurry pH adjusted to 10.0 using CaO powder. This pH was maintained throughout the entire test. The flotation procedure followed and the flotation results for both are shown respectively in Tables 1 and 2.

TABLE-US-00004 TABLE 1 Flotation procedure Reagent addition Time Sample Collec- Froth- (min) name Action tor er CaO Transfer milled slurry to flotation cell Raise slurry level to target by addi- tion of water 0-2 Set slurry pH to As is needed target (10.0) and for pH 10 condition for 2 minutes 2-4 Add collector 2 g/t or Add if (aqueous emulsion) 4 g/t necessary to and condition maintain pH 10 for 2 minutes 4-5 Add frother and 30 g/t Add if condition for necessary to 1 minute maintain pH 10 5-12 Concen- Open air at 7 Add if trate l/min and float necessary to concentrate maintain pH 10 12 Close air; end of test

TABLE-US-00005 TABLE 2 Results of the flotation tests Dosage Thiono- Cu Cu Flotation carbamate Recov- Grade Test Collector (g per ton ore) ery (%) (%) 1 Emulsion 1 2 85.77 6.25 2 Emulsion 2 2 86.18 5.82 3 Emulsion 3 2 87.13 6.47 4 Emulsion 4 2 85.10 6.43 5 Emulsion 5 2 86.89 5.02 6 Emulsion 6 2 86.94 6.71 7 Emulsion 3 4 88.59 5.68 8 Emulsion 7 2 84.58 6.94 (comparison) 9 O-isopropyl-N-ethyl- 2 82.24 6.15 (comparison) thionocarbamate (100%) 10 O-isopropyl-N-ethyl- 4 85.12 6.33 (comparison) thionocarbamate (100%)

[0073] The results from the flotation tests show that the collector compositions according to this invention (emulsions 1 to 6) show excellent flotation efficiency and in particular, improved copper recovery in comparison with the emulsion 7, which only contains thionocarbamate, emulsifier and water as described in WO 9725149. Moreover, the emulsions 1 to 6 according to this invention show improved flotation efficiency than pure thionocarbamate collector.

[0074] The Cu grade obtained with the inventive emulsions is slightly lower than what was obtained with the emulsion 7 in the laboratory experiments. This difference in Cu grade is considered negligible because industrial flotation plants typically put the rougher concentrate through two, three or even four cleaning steps. In this way, the Cu grade of the final concentrate is typically increased to >20%. Furthermore, in the unlikely event that this small concentrate grade reduction is transferred to a plant scale (even considering two or three cleaning steps was done), a 1.0-1.5% increase in Cu recovery is still much more beneficial for economic reasons.

[0075] References to % mean wt.-% if not otherwise indicated.