NEW FROTHERS FOR MINERALS RECOVERY

Abstract

##STR00001##

The present invention pertains to a composition comprising at least one compound of formula (I) and to the use of said composition for recovering value minerals from ore and other feedstocks by flotation (formula (I)).

Claims

1. A composition comprising at least one compound of formula (I): ##STR00027## wherein: A represents a C1-C8 alkanediyl group that may be linear, branched or cyclic, B which can be the same or different at each occurrence, represents a C1-C8 alkanediyl group that may be linear, branched or cyclic, R represents H or a C1-C8 alkyl group that may be linear or branched, and n is an integer≥0 and ≤100.

2. The composition according to claim 1, wherein A is selected from the list consisting of —CH.sub.2—, —CH.sub.2—CH.sub.2—, —CH.sub.2—CH.sub.2—CH.sub.2—, —CH.sub.2—CH.sub.2—CH.sub.2—CH.sub.2—, —CH.sub.2—CH.sub.2—CH.sub.2—CH.sub.2—CH.sub.2—, and —CH(CH.sub.3)—.

3. The composition according to claim 2, wherein A is selected from the list consisting of —CH.sub.2—, —CH.sub.2—CH.sub.2—, —CH.sub.2—CH.sub.2—CH.sub.2—, —CH.sub.2—CH.sub.2—CH.sub.2—CH.sub.2— and —CH.sub.2—CH.sub.2—CH.sub.2—CH.sub.2—CH.sub.2—.

4. The composition according to claim 1, wherein B is selected from the list consisting of —CH.sub.2—CH.sub.2—, —CH.sub.2—CH(CH.sub.3)—, —CH(CH.sub.3)—CH.sub.2—, and —CH.sub.2—CH.sub.2—CH.sub.2—CH.sub.2—.

5. The composition according to claim 1, wherein R is H.

6. The composition according to claim 1, wherein R is selected from the list consisting of methyl, ethyl, propyl, isopropyl, sec-butyl, t-butyl, isobutyl and n-butyl.

7. The composition according to claim 1 comprising at least one compound selected from the list consisting of: ##STR00028##

8. The composition according to claim 1 comprising at least one compound selected from the list consisting of: ##STR00029##

9. The composition according to claim 1 comprising at least two compounds of formula (I).

10. The composition according to claim 1, further comprising at least one compound selected from the group consisting of frothers, collectors, water, compatibilizing agents, defoamers, dispersants, pH regulators, rheology regulators, surface active agents, activators, depressants, lubricants, anti-scalants and anti-corrosion agents.

11. The composition according to claim 10, wherein the compound is chosen from collectors and/or frothers.

12. A flotation process for recovering value minerals from ore and other feedstocks comprising adding to said ore and other feedstocks the composition as defined in claim 1.

13. The flotation process according to claim 12, wherein value minerals are sulfide minerals, non-sulfide minerals or native metals.

14. The flotation process according to claim 12, wherein value minerals are energy minerals.

15. (canceled)

16. The flotation process according to claim 12, wherein the composition further comprises at least one compound selected from the group consisting of frothers, collectors, water, compatibilizing agents, defoamers, dispersants, pH regulators, rheology regulators, surface active agents, activators, depressants, lubricants, anti-scalants and anti-corrosion agents.

17. The flotation process according to claim 16, wherein the composition further comprises frothers and/or collectors.

18. The flotation process according to claim 12, wherein the composition comprises at least one compound selected from the list consisting of: ##STR00030##

19. The flotation process according to claim 18, wherein the composition further comprises at least one compound selected from the group consisting of frothers, collectors, water, compatibilizing agents, defoamers, dispersants, pH regulators, rheology regulators, surface active agents, activators, depressants, lubricants, anti-scalants and anti-corrosion agents.

20. The flotation process according to claim 12, wherein the composition comprises at least one compound selected from the list consisting of: ##STR00031##

21. The flotation process according to claim 20, wherein the composition further comprises at least one compound selected from the group consisting of frothers, collectors, water, compatibilizing agents, defoamers, dispersants, pH regulators, rheology regulators, surface active agents, activators, depressants, lubricants, anti-scalants and anti-corrosion agents.

Description

EXAMPLES

[0096] Preparation of “Cleavable” Frothers

[0097] Synthesis of 4-Methylpentan-2-Yl 2-Hydroxyacetate (Frother 1)

##STR00018##

[0098] In a 500-mL round-bottom flask were added successively glycolic acid (13.8 g, 180 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (37.6 g, 360 mmol, 2 equiv), and toluene (230 mL) followed by sulfuric acid (96%) (1 mL, 18 mmol, 0.1 equiv). The resulting solution was heated under reflux and water was removed azeotropically using a Dean-Stark apparatus. After 3 h water had finished to distill and the reaction mixture was allowed to cool to room temperature. The resulting solution was washed with a saturated aqueous solution of NaHCO.sub.3 (twice) followed by a saturated aqueous solution of NaCl. The organic phase was dried over anhydrous magnesium sulfate and the volatiles (toluene and excess MIBC) were removed in vacuo. The crude product was purified by flash chromatography on silica gel to yield a first fraction of desired MIBC glycolate as a colorless liquid (15 g, 52% yield).

[0099] Alternative Synthesis of 4-Methylpentan-2-Yl 2-Hydroxyacetate (Frother 1)

##STR00019##

[0100] In a 250-mL round-bottom flask were added successively glycolic acid (30.4 g, 396 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (200 mL, 1.54 mol, 4 equiv), and sulfuric acid (96%) (1.1 mL, 20 mmol, 0.05 equiv). The resulting solution was heated at 130° C. for 6 h. The reaction mixture was then allowed to cool to room temperature and calcium carbonate (4.5 g) was added and the resulting suspension was stirred overnight. The white solid in suspension was then filtered and excess MIBC was removed in vacuo. The remaining crude product was purified by distillation to give MIBC glycolate as a colorless liquid (36 g, 57% yield).

[0101] Synthesis of Ethyl 2-(2-Hydroxyethoxy)Acetate

##STR00020##

[0102] As described in J. Photosci. 2000, 7, 143-148.

[0103] Synthesis of 4-Methylpentan-2-Yl 2-(2-Hydroxyethoxy)Acetate (Frother 2)

##STR00021##

[0104] In a 100-mL round-bottom flask were added successively ethyl 2-(2-(2-hydroxyethoxy)ethoxy)acetate (20 g, 132 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (52.1 g, 565 mmol, 4.3 equiv), and sulfuric acid (96%) (0.7 mL, 12.6 mmol, 0.1 equiv). The resulting solution was heated at 50° C. for 24 h. The reaction mixture was then allowed to cool to room temperature and calcium carbonate (15 g) was added and the resulting suspension was stirred overnight.

[0105] The white solid in suspension was then filtered and excess MIBC was removed in vacuo. [Care should be taken at this step since remaining traces of acidity or overheating will lead to product cyclization and liberation of MIBC.] The remaining crude product (7.8 g) was purified by flash chromatography on silica gel to give the desired product as a colorless liquid (6.2 g, 23% yield).

[0106] Synthesis of ethyl 2-(2-(2-hydroxyethoxy)ethoxy)acetate

##STR00022##

[0107] As described in Langmuir 2013, 29, 13111-13120.

[0108] Synthesis of 4-Methylpentan-2-Yl 2-(2-(2-Hydroxyethoxy)Ethoxy)Acetate (Frother 3)

##STR00023##

[0109] In a 250-mL round-bottom flask were added successively ethyl 2-(2-(2-hydroxyethoxy)ethoxy)acetate (30.3 g, 155 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (125.1 g, 156 mL, 1.2 mol, 8 equiv), and sulfuric acid (96%) (0.4 mL, 7.2 mmol, 0.05 equiv). The resulting solution was heated at 90° C. for 24 h. The reaction mixture was then allowed to cool to room temperature and calcium carbonate (5 g) was added and the resulting suspension was stirred overnight.

[0110] The white solid in suspension was then filtered and excess MIBC was removed in vacuo. The remaining crude product (32.2 g) was purified by flash chromatography on silica gel to give the desired product as a colorless liquid (25.4 g, 66% yield).

[0111] Synthesis of Ethyl 2-(2-(2-(2-Hydroxyethoxy)Ethoxy)Ethoxy)Acetate

##STR00024##

[0112] As described in Langmuir 2013, 29, 13111-13120.

[0113] Synthesis of 4-Methylpentan-2-Yl 2-(2-(2-(2-Hydroxyethoxy)Ethoxy)Ethoxy)Acetate (Frother 4)

##STR00025##

[0114] In a 250-mL round-bottom flask were added successively ethyl 2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)acetate (15 g, 63.5 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (26 g, 156 mL, 254 mmol, 4 equiv), toluene (150 mL), and sulfuric acid (96%) (0.38 mL, 6.8 mmol, 0.1 equiv). The resulting solution was heated under reflux and ethanol was removed azeotropically using a Dean-Stark apparatus. After 10 h the reaction mixture was allowed to cool to room temperature. Calcium carbonate (4 g) was added and the resulting suspension was stirred overnight. The white solid in suspension was then filtered and excess MIBC was removed in vacuo. The remaining crude product (22.3 g) was purified by flash chromatography on silica gel to give the desired product as a colorless liquid (7.6 g, 35% yield).

[0115] Synthesis of 4-Methylpentan-2-Yl 4-Hydroxybutanoate (Frother 5)

##STR00026##

[0116] In a 250-mL round-bottom flask were added successively 7-butyrolactone (GBL) (20 g, 230 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (100 g, 979 mol, 4 equiv), and sulfuric acid (96%) (0.5 g, 4.9 mmol, 0.02 equiv). The resulting solution was stirred at room temperature for 14 h time after which the equilibrium was reached (GBL/ester=63:37 by .sup.1H NMR). Calcium carbonate (3 g) was then added and the resulting suspension was stirred for 1 h. The white solid in suspension was then filtered and the filtrate was diluted with AcOEt (200 mL). The organic phase was washed with a Na.sub.2CO.sub.3 solution (1% in water, 100 mL), water (2×100 mL), and finally by a saturated NaCl solution (100 mL).

[0117] The organic phase was then dried over MgSO.sub.4, filtered and the resulting oil was purified by flash chromatography on silica gel to give the desired product as a colorless oil (13 g, 30% yield).

[0118] Flash Point Determination

[0119] The flash point of Frother 1 was determined using ASTM method D3828-87, method B, finite flash point method, also known as Setaflash closed cup method. Approximately 2 mL of the sample was placed in the cup and tested at 22° C., 35° C., 50° C., 70° C., 80° C., 85° C. and 87° C. The lowest temperature at which the combustion of the headspace is observed is defined as the flash point.

[0120] With a flash point of 87° C. Frother 1 is far less flammable than MIBC with a flash point of 41° C. This is highly advantageous for safety reasons either during storage and transport or during utilisation of this type of frothers.

[0121] Hydrolysis of “Cleavable” Frother In a 100 mL flask were added DI water (50 g), Ca(OH).sub.2 for adjusting the pH to 12, and “cleavable” Frother (20 μL). The resulting solution was stirred at room temperature for 24 h time after which the complete hydrolysis was reached (checked by LC-MS when the ester peak disappeared).

[0122] The resulting solution was used in the flotation test to evaluate the “cleavable” frothers flotation performance after hydrolysis.

[0123] Flotation Test

[0124] Before flotation tests in a Denver cell, a sample of 1 Kg Cu—Mo ore crushed to 2 mm and 0.6 g Ca(OH).sub.2 were milled in a laboratory stainless ball mill in the presence of 675 ml of water to achieve a grind of 80% passing 212 m. The pH of the resulting slurry was 9.8. The milled slurry was transferred to flotation cell with a capacity of 2.7 L and diluted to 32% solids content. The impeller speed was set at 1000 r/min and the slurry was agitated. Reagent addition strategy and flotation procedures were as follows. the collector was added into the flotation pulp, and the pulp was homogenized for 1 min; then, frother was added, and the pulp was homogenized for another 45 s. Airflow was turned on and the froth was scraped every 15 seconds for a total time of seven minutes to collect a Cu concentrate. The air flow rate supplied to the flotation cell was maintained at a flow rate of 3.25 L/min in all test. The pulp level was kept at the same level by addition of water.

[0125] The After tests, concentrates and tails were filtered, dried, weighed and analyzed for Cu content.

TABLE-US-00001 TABLE 1 Assays for Cu—Mo ore used in the flotation tests. Ore head Cu wt. Fe wt. Mo Gangue wt. assay % % ppm % Cu—Mo Ore 0.45 4.62 62 79.04

[0126] Determination of water recovery (water rec.%), was performed using the equation below:

[00001]$\mathrm{Water}\mathrm{rec}.\%=\frac{C\left(g\right)-C\mathrm{dried}\left(g\right)\times 100}{W\left(g\right)}$

[0127] With:

[0128] C=concentrate collected in function of time (water+solids);

[0129] C dried (g)=solids after concentrate drying;

[0130] W=total mass of water added in the cell.

[0131] Copper recovery (Cu rec. wt. %), Copper concentrate grade (Cu grade wt. %) were determined by analyzing the Cu content of ore, concentrates and tailings.

[0132] Coarse particles recovery % was determined by passing collected concentrates on 212 μm sieve.

[0133] Results

[0134] Flotation tests were performed using isopropylethylthionocarbamate (IPETC) as collector.

[0135] Blend of glycol ether are well known in the industry as strong frother and methyl isobutyl carbinol (MIBC) is well known as weak frother. Comparative examples were carried out using AEROFROTH® 68 (AF68-Blended Glycol Ethers) or AEROFROTH® 70 (AF70-MIBC) available from Solvay as “strong” or “weak” frothers respectively.

[0136] A first flotation test was performed at pH 9.5, which is a relatively low pH, which was chosen to simulate pH conditions of a rougher stage.

TABLE-US-00002 TABLE 2 Results of flotation test* before hydrolysis of the “cleavable” frother Water Rec. Cu Rec. Cu Grade Coarse*** Frother % % % total particles Rec. % AF68 12 85 8.7 6.8 Blended Glycol Ethers AF70 9 80 9.3 4.3 MIBC Frother 1 13 86 8.4 7.0 Frother 2 15 84 8.1 n.d. Frother 3 15 85 8.2 7.2 Frother 4 15 87 7.4 5.9 Frother 5 15 87 8.0 5.5 Blend** 16 84 8.2 6.4 *Flotation at pH 9.5 during 7 minutes. **Blend consisting of a solution comprising 6 ppm of Frother 1, 4 ppm of Frother 2, 6 ppm of Frother 3 and 5 ppm of Frother 4. ***particles size >212 μm.

[0137] Results of table 2 reveal that surprisingly Frothers 1 to 5 are strong frothers allowing higher water recovery than MIBC and more surprinsigly than blended glycol ethers. Even more surprisingly, the blend of Frothers 1 to 4 shows similar performance.

[0138] Moreover, Cu recovery and Cu grade are similar for flotation conducted respectively with Frother 1, Frother 2, Frother 3, Frother 4, Frother 5 and with a blend of “cleavable” frothers and for flotation conducted with blended glycol ethers.

[0139] Finally, Frothers 1, 3, 4 and 5 are strong frothers allowing higher coarse particles recovery than MIBC and more surprinsigly even higher coarse particles recovery than blended glycol ethers in the case of Frothers 1 and 3. The blend of Frothers 1 to 4 allows higher coarse particles recovery than MIBC.

[0140] As said, hydrolysis of Frothers 1 to 5, and of the blend of Frothers 1 to 4 was conducted at pH 12 by stirring their solution in water at 23° C. during 24 hours.

[0141] A second flotation test was then performed at pH 9.5 using the resulting hydrolyzed frothers or blend of frothers.

TABLE-US-00003 TABLE 3 Results of flotation test* after hydrolysis of the “cleavable” frothers Water Rec. Cu Rec. Cu Grade Frother % % % total AF68 12 85 8.7 Blended Glycol Ethers AF70 9 80 9.3 MIBC Frother 1 11 82 8.6 Frother 3 8 72 9.1 Frother 4 10 83 9.2 Frother 5 9 79 8.6 *Flotation at pH 9.5 during 7 minutes.

[0142] It is clear from the results compiled in table 3 that Frothers 1, 3, 4 and 5 which behaved like blended glycol ethers before hydrolysis behave more like MIBC after hydrolysis.

[0143] Whitout being bound to any theory it is assumed that the ester function of Frothers 1, 3, 4 and 5 was hydrolyzed thus giving hydrolysis products and MIBC and that surprisingly the mixture of them behaves like MIBC.

[0144] The inventors have shown that a frother composition according to the invention which initially behaves as a strong frother and which is hydrolyzed to give hydrolysis products and MIBC, adopts after hydrolysis the frothing behavior of MIBC.

[0145] The inventors have shown that frothers and compositions of frothers according to the invention can surprisingly behave as strong frother at a given pH with some performances exceeding those of well known strong frothers (e.g. blended glycol ethers) while behaving like less strong or even weak frother after or during a stage at higher pH.

[0146] Moreover the inventors have shown that these frothers and compositions, at least because of a higher flash point, are advantageous in term of safety to store, transport or handle versus other frothers such as MIBC.