LEACHING OF PRECIOUS AND CHALCOPHILE METALS

Abstract

A process for recovery of one or more target metals, selected from precious metals and chalcophile metals as respectively herein defined, from materials containing precious and/or chalcophile metal/s, said process including: (i) leaching the metal containing material with an aqueous solution containing: a metal liberator comprising an amino acid; and a metal retainer comprising one or more of ammonia, ammonium salts, carboxylic acids, carboxylic acid salts, dicarboxylic acids, dicarboxylic acid salts, hydroxy-carboxylic acids, hydroxy-carboxylic acid salts, ethylene diamine tetra-acetic acid (EDTA) and EDTA salts, to produce a leachate containing the target metal/s; and (ii) extracting the metal from the leachate.

Claims

1. A process for recovery of one or more target metals, selected from precious metals and chalcophile metals as respectively herein defined, from materials containing precious and/or chalcophile metals, the process including: leaching the material containing metals with an aqueous leaching solution containing: a metal liberator comprising an amino acid; and a metal retainer comprising one or more of ammonia, ammonium salts, carboxylic acids, carboxylic acid salts, dicarboxylic acids, dicarboxylic acid salts, hydroxy-carboxylic acids, hydroxy-carboxylic acid salts, ethylene diamine tetra-acetic acid (EDTA) and EDTA salts, to produce a leachate containing the one or more target metals; and (ii) extracting the one or more target metals from the leachate, wherein the one or more target metals are selected from gold, silver, palladium, platinum, copper, nickel, cobalt and zinc; and wherein the metal retainer is present in solution at a concentration of at least 0.001 M.

2. The process of claim 1, wherein the amino acid comprises one or more of Glycine, Histidine, Valine, Alanine, Phenylalanine, Cysteine, Aspartic Acid, Glutamic Acid, Lysine, Methionine, Serine, Threonine, and Tyrosine.

3. The process of claim 2, wherein the amino acid comprises glycine or glutamic acid.

4. The process of claim 1, wherein the amino acid concentration in solution ranges from 0.01 to 250 grams per litre.

5. The process of claim 1, wherein the aqueous leaching solution is substantially free of intentional additions of thiourea and/or transition metal salts.

6. The process of claim 1, wherein the metal retainer comprises ammonia or an ammonium salt.

7. The process of claim 6, wherein the ammonium salt is selected from ammonium sulfate, ammonium halide, ammonium carbonate, ammonium nitrate, ammonium oxalate and ammonium acetate.

8. The process of claim 1, wherein the molar ratio between the one or more target metals in solution and the metal retainer is at least 1:2.

9. The process of claim 1, wherein the leaching is conducted in the presence of an oxidant selected from air (gaseous and dissolved states) and oxygen (gaseous and dissolved states).

10. The process of claim 1, wherein the leaching is conducted in the presence of a small amount of a catalyst.

11. The process of claim 1, wherein the leaching is conducted under alkaline conditions.

12. The process of claim 1, wherein the leaching is conducted under acidic conditions.

13. The process of claim 1, wherein the material containing the precious metal and/or chalcophile metal is selected from an ore, an ore concentrate, a waste material, a mining or metallurgical process intermediate or a metal-contaminated soil.

14. The process of claim 1, wherein the one or more target metals are non-precious metals.

15. The process of claim 14, wherein the one or more target metals are selected from nickel, cobalt and copper.

16. The process of claim 15, wherein the one or more target metals are selected from nickel and cobalt.

17. The process of claim 13, wherein the material containing metals is a nickel and/or cobalt ore.

18. The process of claim 14, wherein the one or more target metals is copper.

19. The process of claim 13, wherein the material containing metals is e-waste.

20. The process of claim 1, wherein the aqueous leaching solution includes a dissolved oxygen concentration of 0.1-100 milligrams per litre.

21. The process of claim 1, wherein the mass ratio of metal liberator: metal retainer is at least 2:1.

22. A target metal recovered from the process of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Notwithstanding any other forms which may fall within the scope of the apparatus and method as set forth in the Summary, specific embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

[0080] FIG. 1 is a graph showing nickel recovery (%) versus time (hours) in solutions at pH 10, 40% solids at room temperature, containing as lixiviants: [0081] GlyAmm: 46.3 g/L glycine, 63 g/L (0.5M ammonium sulfate) (diamonds); [0082] Gly: 46.3 g/L glycine (triangles): [0083] Amm: 63 g/L (0.5M ammonium sulfate) (squares).

[0084] FIG. 2 is a graph showing cobalt recovery (%) versus time (hours) in solutions at pH 10, 40% solids at room temperature, containing as lixiviants: [0085] GlyAmm: 46.3 g/L glycine, 63 g/L (0.5M ammonium sulfate) (diamonds); [0086] Gly: 46.3 g/L glycine (triangles): [0087] Amm: 63 g/L (0.5M ammonium sulfate) (squares).

[0088] FIG. 3 is a graph showing copper extraction (%) from chalcopyrite versus time (hours) using amino acid solutions either in the absence of or in the presence of 0.3M of different additives. The amino acid solutions are glycine (crosses), glutamic acid (open circles), glycine and ammonia (closed circles), glutamic acid and ammonia (squares), glycine and acetate (diamonds) and glycine and citrate (triangles).

[0089] FIG. 4 is a graph showing copper extraction (%) versus time (hours) using glycine solutions either in the absence of (squares) or in the presence of (circles) ammonia.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Examples

[0090] Non-limiting Examples of a process for the recovery of one or more elements, selected from precious metals and chalcophile metals, are described below. The following abbreviations are used for lixiviants: GlyAmm is used for the system Glycine-Ammonium, Gly refers to Glycine, Amm refers to ammonium. The pressure and temperature of all Examples were 1 atmosphere and room temperature (20 deg C), respectively.

Example 1

[0091] Cyclone overflow of a nickel ore containing 0.67% Ni was leached with a solution containing 46.3 g/L glycine and 63 g/L (0.5M ammonium sulfate) (GlyAmm) at pH 10 and 40% solids at room temperature. Nickel recovery versus time was compared with that using two other leachants comprising 46.3 g/L glycine (Gly) and 63 g/L (0.5M ammonium sulfate) (Amm), respectively, under the same conditions. The results are presented in FIG. 1. It can be seen that nickel recovery is significantly higher when leached with the GlyAmm solution (diamonds) than when leached with the Gly solution (triangles) or the Amm solution (squares). Moreover, the nickel recovery when leached with the GlyAmm solution is more than the sum of the recoveries using the Gly and the Amm solutions, indicating the synergistic effect of the GlyAmm solution.

Example 2

[0092] Cyclone overflow of nickel-cobalt ore concentrate containing 0.15% Co was leached with a solution containing 46.3 g/L glycine and 63 g/L (0.5M ammonium sulfate) (GlyAmm) at pH 10 and 40% solids at room temperature. Cobalt recovery versus time was compared with that using two other leachants comprising 46.3 g/L glycine (Gly) and 63 g/L (0.5M ammonium sulfate) (Amm), respectively, under the same conditions. The results are presented in FIG. 2. Similarly, for nickel recovery in Example 1, it can be seen that cobalt recovery is also significantly higher when leached with the GlyAmm solution (diamonds) than when leached with the Gly solution (triangles) or the Amm solution (squares). Moreover, the cobalt recovery when leached with the GlyAmm solution is more than the sum of the recoveries using the Gly and the Amm solutions, indicating the synergistic effect of the GlyAmm solution.

Example 3

[0093] Pulverised chalcopyrite concentrate was leached with two leaching solutions: a Gly solution containing 0.5 M glycine and a GlyAmm solution containing 0.5 M glycine and 1 M ammonia in a bottle roller. In both cases, leaching was conducted at room temperature, at pH of 10 and at a bottle roller speed of 100 rpm. The results are presented in Table 1. It can be seen that the recovery of the precious metals gold and silver was significantly higher (up to a factor of 5 for gold) in the GlyAmm system. Copper recovery was also much higher when leached with GlyAmm: 85% as compared with only 50% when leached with glycine alone.

TABLE-US-00001 TABLE 1 Au Ag As Cu Ni Zn Al Ca ug/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L Gly (0.5M 5 0.017 0.5 460 BDL 15.5 2 6 glycine) GlyAmm 27 0.041 0.9 803 BDL 21.5 1.5 22 (0.5 glycine + 1M ammonia) Rec % Gly 50.0 GlyAmm 85.5 BDL = below the detection limit

Example 4

[0094] Chalcopyrite ore containing 22.1% Cu was leached with various amino acid-based solutions under the following conditions: 10 g/L amino acids, 1% solid content, particle size: 100%-45 m, pH 10.5, and at room temperature. The results are shown in FIG. 3, where copper extraction (%) is plotted against leach time (hours). The amino acid solutions comprise glycine or glutamic acid either alone or in the presence of 0.3 M different respective additives. The amino acid solutions are glycine (crosses), glutamic acid (open circles), glycine and ammonia (closed circles), glutamic acid and ammonia (squares), glycine and acetate (diamonds) and glycine and citrate (triangles).

[0095] The results show that leaching with either glycine or glutamic acid is enhanced in the presence of metal retainers such as ammonia, acetate ions or citrate ions. Generally, glycine-based solutions provide greater recoveries than glutamic acid-based solutions for any given leach time. Of the three metal retainers illustrated in FIG. 3, ammonia offers the greatest improvement in copper solubility, with the combination of glycine and ammonia providing the highest recovery of copper (90% recovery after a 48 hour leach).

Example 5

[0096] A mixed hydroxide precipitate (MHPan intermediate product produced during hydrometallurgical processing of nickel laterite ore), containing 30% Ni and 2.5% Co, was leached using respective glycine solutions with and without ammonia. In each case, the solution conditions were: 40 g/L glycine, 1% solid content, pH 10, and at room temperature and a leach time of 4 hours. The GlyAmm solution additionally contained 0.3M ammonia.

[0097] The results are set out in Table 2 below:

TABLE-US-00002 TABLE 2 Glycine Glycine-ammonia Ni % 98.8 100 Co % 75.3 98.6

[0098] While a slightly higher recovery of nickel was achieved when ammonia is present in the leaching solution, there was a significantly higher (>20%) recovery of cobalt using the GlyAmm solution.

Example 6

[0099] A mixture of copper and nickel (sulfate) salts was dissolved at room temperature in alkaline solutions (pH 10.5) containing amino acids with and without additional metal retainers. Each solution contained 1M amino acid and, where appropriate, 1M metal retainer. The results are set out below in Table 3.

TABLE-US-00003 TABLE 3 Gly- Glu- Glycine Glycine + Glycine + Glycine + cine tamic ammonia Gluconic citrate EDTA Cu g/L 4.5 5.6 25.2 26.2 25.3 29.5 Ni g/L 8.5 7.5 27.1 28.0 27.3 28.5

[0100] The results indicate that, under the conditions of this particular sample, relatively low recoveries of copper and nickel were observed when the sample was treated with solutions containing glutamic acid or glycine per se. Recoveries were significantly improved when metal retainers were respectively added to the amino acid solutions. In most cases, the nickel concentration was higher than for copper in each solution. Similar recoveries were observed when ammonia or citrate ions were the metal retainers. Slightly higher recoveries were observed when gluconic acid was the metal retainer. The highest recovery was obtained using the combination of glycine and EDTA.

Example 7

[0101] A copper oxide ore sample containing 66% malachite, 16.7% quartz and 3.35% hematite was leached in 20 g/L glycine in the absence and presence of 0.3M ammonia at pH and room temperature. The results are shown in FIG. 4, which is a plot of copper recovery (%) versus leach time (hours). Squares represent copper recovery in the absence of ammonia and circles represent copper recovery in the presence of ammonia. In the presence of ammonia, copper recovery reached 100% after 6 hours. However, in the absence of ammonia, the maximum recovery was only about 90%.

Example 8

[0102] A sample comprising metal oxide alkaline battery waste containing 43% Zn, 51% Mn and 0.5% Cu was leached in a solution containing 20 g/L glycine in the absence and presence (respectively) of 0.4M ammonia at pH 10.5 and room temperature for 24 hours. The sample was also leached in a solution containing 20 g/L glutamic acid and 0.4M ammonia. The results are set out in Table 4.

TABLE-US-00004 TABLE 4 Glycine Glycine-ammonia Glutamic-ammonia Zn % 32 85.2 81.3 Cu % 70.2 85 80.7 Mn % 0.1 2.1 0.5

[0103] The results show very good selectivity for zinc and copper over manganese. Further, there is a significant improvement in recovery of each of zinc, copper when the waste material is leached with a combination of glycine and ammonia, as compared to leaching with glycine alone. Moreover, leaching with a combination of glycine and ammonia also enhances recovery of both metals as compared with leaching with glutamic acid and ammonia.

Example 9

[0104] Material comprising nickel sulphide as pentlandite and containing 17% Ni, 0.45% Co, and 0.15% Zn was leached with glycine-based solutions having 20 g/L amino acids (glycine), pH 10, and at room temperature. In the first leaching solution, a glycine (20 g/L)-ammonia (10 g/L NH.sub.3) mixture was used to leach the pentlandite. The pH was readjusted during the leaching to pH 10, if required, by further additions of ammonia. In the second leaching solution, glycine only solutions were used and sodium hydroxide (NaOH) was used to readjust pH, if required.

[0105] The results of leaching with the first and second solutions are presented in Tables 5 and 6, respectively.

TABLE-US-00005 TABLE 5 Ni Co Zn S Fe Mg Metals in (g) 4.46 0.122 0.041 2.729 2.172 3.90 Metals out 0.746 0.04 0.009 1.0943 1.4823 3.24 residue (g) Metals out 3.65 0.092 0.028 1.9520 0.457 0.27 soluition (g) Totla out (g) 4.40 0.128 0.037 3.0463 1.9393 3.51 Recovery, % 81.9 75.5 69.1 71.53 21.0 6.86 Recovery, % 83.0 71.95 75.10 64.1 23.6 7.6 solu/Res

TABLE-US-00006 TABLE 6 Ni Co Zn S Fe Mg Metals in (g) 4.458 0.122 0.041 2.729 2.172 3.902 Metals out 0.860 0.038 0.022 0.589 1.503 3.296 residue (g) Metals out 3.007 0.070 0.011 1.877 0.230 0.079 soluition (g) Totla out (g) 3.867 0.109 0.033 2.466 1.733 3.375 Recovery, % 67.4 57.8 27.1 68.8 10.6 2.0 Recovery, % 77.8 64.6 33.8 76.1 13.3 2.3 solu/Res

[0106] The results in Tables 5 and 6 demonstrate the significantly better recovery of nickel, cobalt and zinc using a leaching solution that contains ammonia in combination with glycine as compared with a leaching solution that simply contains NaOH for pH modification.

[0107] The same material was also leached with an acidic leaching solution that included glycine and citrate at a solution pH of 4. The solution contained 20 g/L glycine and 20 g/L citric acid. The results are set out below in Table 7.

TABLE-US-00007 TABLE 7 Ni Co Zn S Fe Mg Metals in (g) 4.46 0.122 0.041 2.729 2.172 3.90 Metals out 0.879 0.04 0.008 1.0777 1.1507 2.41 residue (g) Metals out 3.45 0.085 0.029 1.9820 0.857 0.47 soluition (g) Totla out (g) 4.33 0.122 0.037 3.0597 2.0077 2.88 Recovery, % 77.4 69.9 71.6 72.63 39.4 12.05 Recovery, % 79.7 69.40 79.18 64.8 42.7 16.3 solu/Res

[0108] The results in Table 7 indicate that relatively high recoveries of Ni, Co and Zn can also be achieved at acidic pH by leaching with a glycine and citrate solution instead of a glycine and ammonia solution. Acidic leaching may be desirable for certain types of ore materials as well as e-waste. However, it is noted that there is a loss of selectivity of the target metals over other elements in the material, in particular Fe and Mg, under these acidic conditions. It may therefore be necessary to include a neutralisation step after the leaching step, and subsequently precipitate the other elements from solution.

Example 10

[0109] The extraction of precious metals, including palladium and platinum, from a nickel concentrate using a leaching solution containing amino acid and ammonia, has been tested. Table 8 lists the metals content of the tested nickel concentrate containing the precious and PGM metals.

TABLE-US-00008 TABLE 8 Au, Ag, Pd, Pt, Ni, Fe, Ca, Mg, S, Mn, Co, Zn, Cu, Sample ppm ppm ppm ppm % % % % % % % % % Ni 0.51 1.5 1.08 0.3 6.1 33.5 0.33 4.04 6.04 0.09 0.12 0.012 0.30 conc.

[0110] Table 9 sets out the leach conditions and metals extracted (%) from the Ni-concentrate containing precious and PGMs (palladium and platinum) metals when leached using a solution containing 0.5 mol/L glycine and 1.1 mol/L ammonia at pH 10.2.

TABLE-US-00009 TABLE 9 Leach conditions and metals extraction Ni-Conc. Solid, % 10 Ammonia, mole 1.1 Glycine, mole 0.5 Residence time, hours 72 Ni Extraction, % 90.9 Co Extraction, % 85.5 Pd Extraction, % 44.5 Au Extraction, % 60.1 Pt Extraction, % 19.9 Ag Extraction, % 51.2

[0111] The results in Tables 8 and 9 indicate that high recoveries of Ni and Co, and reasonable to good recoveries of precious metals comprising Au, Ag, Pd and Pt, can be achieved at alkaline pH by leaching with a glycine and ammonia solution.

Example 11

[0112] The extraction of precious metals, including palladium and platinum, from an oxide sample containing gold and platinum group metals (PGMs) using a leaching solution containing amino acid and ammonia, has been tested. Table 10 lists the metals content of the tested oxide sample.

TABLE-US-00010 TABLE 10 Sample Au, ppm Pd, ppm Pt, ppm Oxide sample 0.05 2.53 0.38

[0113] In the glycine-ammonia system, it was found that increasing one or more of temperature, pH, glycine concentration and dissolved oxygen increases the quantity of precious metals (including palladium and platinum) extracted. The leaching solution contained 0.5 mol/L glycine and 1.1 mol/L ammonia at pH 10.2. The solids content, leach conditions and % metals extracted are listed in Table 11 below.

TABLE-US-00011 TABLE 11 Leach conditions and metals extraction Oxide sample Solid, % 12.5 Ammonia, mole 1.1 Glycine, mole 0.5 Residence time, hours 48 Pd Extraction, % 44.1 Au Extraction, % 52.1 Pt Extraction, % 17.9

[0114] The results in Tables 10 and 11 indicate that reasonable to good recoveries of precious metals comprising Au, Pd and Pt, can be achieved at alkaline pH by leaching with a glycine and ammonia solution.

[0115] Whilst a number of specific process embodiments have been described, it should be appreciated that the process may be embodied in many other forms.

[0116] In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word comprise and variations such as comprises or comprising are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the apparatus and method as disclosed herein.