A method for removing contaminants from contaminated acidic base metal solutions

Abstract

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Description

TITLE OF THE INVENTIONA method for removing contaminants from contaminated acidic base metal solutionsFIELD OF THE INVENTION

[0001] The present invention relates to acidic base metal solutions. More specifically, the present invention is concerned with a method for removal of contaminants from acidic base metal solutions.BACKGROUND OF THE INVENTION

[0002] The recovery of metals from ores, concentrates, and recycled or residual materials by hydrometallurgical extraction processes typically uses strong inorganic / organic acids or alkaline watery solutions to selectively dissolve and precipitate the metals. Recovery of base metals, such as copper, cobalt, nickel or zinc for example, by sulfuric acid typically generates solutions contaminated with arsenic, antimony and other species such as cadmium, bismuth or mercury for example. Methods for decontaminating these solutions below a target threshold, such as by adsorption of the contaminants on an adsorbant for example, have been presented.

[0003] There is still a need in the art for a method for removal of contaminants from acidic base metal solutions.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] In the appended drawings:

[0005] FIG. 1 is a flowchart of a method according to an embodiment of an aspect of the present disclosure; and

[0006] FIG. 2 is a flowchart of a method according to another embodiment of an aspect of the present disclosure.SUMMARY OF THE INVENTION

[0007] More specifically, in accordance with the present invention, there is provided a method for removal of contaminants from a contaminated acidic solution of a base metal, comprising adsorption of the contaminants over activated carbon, and separating a decontaminated acidic solution of the base metal from activated carbon loaded with the contaminants.

[0008] There is further provided a method for controlling contaminant contents in an acidic base metalsolution, comprising contacting the acidic base metal solution with activated carbon, and separating an acidic base metal solution with target contents of the contaminants from activated carbon loaded with corresponding contents of the contaminants.

[0009] There is further provided a method for controlling arsenic and antimony contents in an acidic sulfate solution of copper, comprising contacting the acidic sulfate solution of copper with activated carbon, and separating an acidic sulfate solution of copper with arsenic and antimony target contents from activated carbon loaded with corresponding contents of the arsenic and antimony.

[0010] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0011] The present invention is illustrated in further detail by the following non-limiting examples.

[0012] A method for treating an acidic base metal solution BMTI2SO4 contaminated with arsenic As and antimony Sb according to an embodiment of an aspect of the present disclosure is illustrated in FIG. 1 .

[0013] The base metal BMTI2SO4 solution is contacted with activated carbon, which loads with arsenic and antimony, and a treated BMTLSCU. i.e., a base metal solution with a corresponding reduced amount of arsenic and antimony, typically in a range between about 1 and about 5 gpL, is then separated from the loaded activated carbon by a first liquid-solid phase separation. The loaded activated carbon is then desorbed of the As and Sb contaminants by using a slurry of iron hydroxide Fe(OH)3, and a second liquid-solid phase separation yields purified activated carbon and an arsenic and antimony containing iron hydroxide Fe(OH)3.

[0014] In an embodiment of the present disclosure as illustrated in FIG. 2, the As / Sb-loaded activated carbon separated from the treated BM*H2SO4 by the first liquid-solid phase separation is desorbed of the As / Sb contaminants by using a sodium chloride NaCI 0.1 M solution, and the second liquid-solid phase separation yields purified activated carbon and an arsenic and antimony bearing sodium chloride NaCI solution; the arsenic and antimony bearing sodium chloride solution is treated by iron-based coprecipitation using anhydrous ferric chloride FeCh and calcium hydroxide Ca(OH)2 to yield a treated sodium chloride NaCI solution and an iron oxi-hydroxide contaminated with As and Sb FeO(OH) after a third liquid-solid phase separation.

[0015] The decontaminated acidic solution of the base metal may be separated from the loaded carbon using a sodium chloride solution, filtrating, and separating the contaminants from a resulting contaminated sodium chloride solution by one of: precipitation and adsorption using calcium, iron, sodium and magnesium hydroxides for example.

[0016] The purified activated carbon may be reused as activated carbon again.

[0017] The resulting As / Sb contaminated iron product may be stabilized via vitrification into an arsenic As and antimony Sb containing glass, using a glass forming system, as known in the art.

[0018] The activated carbon and its adsorbing parameters are selected according to the strength of the acidic base metal solution to be treated, the sulfuric acid H2SO4 concentration being in a range between about 150 and about 300 gpL; to its selectivity for the contaminants, such as As, Sb, as described hereinabove, and also Hg Bi, Pd and Cd for example, to be removed therefrom; and to the base metals BM of interest in the base metal solution, such as Cu, Ni and Co for example, to be recovered therefrom.

[0019] Tests were performed as discussed hereinabove in relation to FIG. 1 with a starting solution of 25 g / L of copper in sulfuric acid at 230 g / L H2SO4, contaminated with 35 ppm of arsenic and 18 ppm of antimony, at pH < 1. A 500 mL aliquot of the starting solution was contacted with 100 g of active carbon (Fisher G-6 Darco) by mild stirring in a one-liter beaker for one hour at ambiant temperature.

[0020] Carbon loaded with arsenic As and antimony Sb was separated from the mixture by filtration and a treated base metal sulfuric acid solution was recovered. The loaded carbon was stirred in a slurry of 100 g of iron hydroxide Fe(OH)3 in 300 mL of water to desorb its arsenic and antimony content. The analysis of the iron hydroxide after a 2 hours contact time with the loaded carbon at ambiant temperature indicated that the iron hydroxide retained the arsenic and antimony and that the carbon was unloaded thereof.

[0021] Removing arsenic and antimony from the loaded activated carbon using an iron hydroxide slurry is cost-effective and the product contaminated with the arsenic and antimony obtained may be stabilized into a glass capturing the contaminants via vitrification. Alternatively, the contaminants may be removed from the loaded carbon by alkaline leaching in a sodium hydroxide aqueous solution or acidic leaching in diluted sulfuric acid, yielding a contaminated solution from which the contaminants may be precipitated. Thus, the active carbon may be regenerated.

[0022] Tests were performed using thus regenerated carbon with a second 500 mL aliquot of the starting, contaminated, solution, yielding similar results as those obtained with the first aliquot of the starting solution in terms of contaminants retention on the carbon, the regenerated carbon charging with the contaminants while the sulfuric acid, the resulting decontaminated solution comprising the copper contents of the starting solution: analysis of the decontaminated solution resulting from the adsorption step showed that the arsenic content was reduced to 4 ppm and the antimony content was reduced to 0.5 ppm from the corresponding contents in the starting solution, while the concentration of copper was 25 g / L in 20 % acid, unchanged from that in the starting solution.

[0023] Other experiments were conducted with a starting base metal solution more concentrated in bothcopper and contaminants (40 g / L of copper 20 % H2SO4, 7 g / L of arsenic and 180 ppm of antimony), in view of a target contaminant threshold in the decontaminated base metal solution.

[0024] For the adsorption step, a 1 L aliquot of the starting solution was contacted with 100 g of the activated carbon (PAC-600) by mild stirring in a 2 L beaker for two hours at room temperature. After the liquid solid phase separation, the loaded carbon was washed with about 200 mL of distilled water and dried at 60 °C overnight. The solution resulting from the adsorption test contained 5.2 g / L As, 39 g / L Cu and 35 ppm Sb. The treatment was repeated on this resulting solution, yielding a decontaminated solution having concentration of As of 3.8 g / L and a concentration of Sb down to 18 ppm, with minimal impact on the Cu concentration.

[0025] Desorption of the loaded activated carbon was performed using a solution of 0.1 M NaCI at 40 °C during 7 hours for about 100 g of activated carbon, yielding regenerated carbon and a saline solution containing 500 mg / L As, 450 mg / L Cu and 15 mg / L Sb.

[0026] For the precipitation step, anhydrous ferric chloride FeCIs was added to the solution (Fe to As molar ratio typically in a range between 2 and 5) and solubilized. Calcium hydroxide Ca(OH)2 was added to the solution to reach a pH between 1 and 1 .5 and the aqueous solution was filtrated. After the filtration, the pH was raised to 6 to precipitate the contaminants with the iron oxyhydroxide. The contaminant loaded precipitate obtained may be stabilized via vitrification using a glass forming system, into a glass capturing the contaminants.

[0027] The selectivity and efficiency achieved in the experiments described hereinabove are unexpected at the highly acidic pH range, below or near 0, well below the point of zero charge of activated carbon, at which the experiments were conducted (230 g / L H2SO4, i.e 20% H2SO4). Furthermore, arsenic being present almost entirely in the form of neutral species for both oxidation states H3AsO3(aq) and H3AsO4(aq) in such pH range, an inhibition of the adsorption efficiency of the activated carbon was expected due to arsenic adsorbsion by the activated carbon through weak Van der Waals forces.

[0028] There is thus disclosed a method for removal of contaminants, such as As and Sb for example, from acidic solutions of base metals such as Cu for example, at pH below or near 0. Other base metals may be present in the base metal solution to be decontaminated, such as Co and Ni, for example; and other contaminants, such as Hg, Bi, Pb or Cd for example, if present, may also be removed therefrom if present.

[0029] The present method allows selectively removing contaminants, and recovering metals of interest and sulfuric acid while preserving the contents of the metals of interest and the sulfuric acid.

[0030] The method provides for decontamination of acidic base metal solutions, with minimal impact on their chemical compositions.

[0031] The presently disclosed method for removing contaminants from strong acidic solutions of base metals by adsorption of contaminants present therein on an adsorbant preserves the composition of valuable solutions of the base metals thereof. The method may be applied to a range of base metals, such as Cu, Co and Ni, and contaminants, such as As, Sb, Hg Bi, Pd and Cd.

[0032] The scope of the claims should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims

Claims1. A method for removal of contaminants from a contaminated acidic solution of a base metal, comprising adsorption of the contaminants over activated carbon, and separating a decontaminated acidic solution of the base metal from activated carbon loaded with the contaminants.

2. The method as in claim 1 , wherein a pH of the contaminated acidic solution of the base metal is below a point of zero charge of the activated carbon.

3. The method as in claim 1 , wherein the contaminated acidic solution of the base metal comprises copper, arsenic, antimony, sulfuric acid in a range between 150 and 300 g / L; the method comprising putting the contaminated acidic solution of the base metal with the activated carbon.

4. The method as in claim 1 , wherein the contaminated acidic solution of the base metal comprises copper, arsenic in a range between 6 g / L and 12 g / L, antimony in a range between 100 mg / L and 500 mg / L, sulfuric acid in a range between 150 and 300 g / L; the method comprising putting the contaminated acidic solution of the base metal with the activated carbon, the decontaminated acidic solution of the base metal having an arsenic content less than 5 g / L and an antimony content less than 50 ppm.

5. The method as in claim 1 , wherein the contaminated acidic solution of the base metal comprises copper, arsenic in a range between 6 g / L and 12 g / L, antimony in a range between 100 mg / L and 500 mg / L, sulfuric acid in a range between 150 and 300 g / L; the method comprising putting the contaminated acidic solution of the base metal in contactwith the activated carbon, the decontaminated acidic solution of the base metal having an arsenic content 3.2 g / L and an antimony content of 18 ppm.

6. The method as in claim 1 , comprising separating the decontaminated acidic solution of the base metal from the loaded carbon by phase separation, and recovering the contaminants from the loaded carbon, yielding regenerated carbon.

7. The method as in claim 1 , comprising separating the decontaminated acidic solution of the base metal from the loaded carbon by phase separation, and recovering the contaminants from the loaded carbon using ferric hydroxide, yielding regenerated carbon.

8. The method as in claim 1 , comprising separating the decontaminated acidic solution of the base metal from the loaded carbon by phase separation, recovering the contaminants from the loaded carbon by stirring a slurry of ferric hydroxide with the loaded carbon, and filtering, yielding regenerated carbon and ferric iron loaded with the contaminants.

9. The method as in claim 1 , comprising separating the decontaminated acidic solutionof the base metal from the loaded carbon by phase separation, recovering the contaminants from the loaded carbon using ferric hydroxide, yielding regenerated carbon and iron oxide loaded with the contaminants.

10. The method as in claim 1 , further comprising separating the decontaminated acidic solution of the base metal from the loaded carbon, and recovering the contaminants from the loaded carbon using a sodium chloride solution.1 1 . The method as in claim 1 , further comprising separating the decontaminated acidic solution of the base metal from the loaded carbon using a sodium chloride solution of a concentration in a range between 0.05 M and 0.5 M, and filtrating.

12. The method as in claim 1 , further comprising separating the decontaminated acidic solution of the base metal from the loaded carbon using a sodium chloride solution of a concentration in a range between 0.05 M and 0.5 M, filtrating, and separating the contaminants from a resulting contaminated sodium chloride solution by one of: precipitation and adsorption using one of calcium, iron, sodium and magnesium hydroxides.

13. The method as in claim 1 , further comprising separating the decontaminated acidic solution of the base metal from the loaded carbon using a sodium chloride solution of a concentration in a range between 0.05 M and 0.5 M, filtrating, and separating the contaminants from a resulting contaminated sodium chloride solution by calcium and iron hydroxides.

14. The method of claim 1 , wherein the base metal is at least one of : Cu, Co and Ni; and the contaminants are at least one of: As, Sb, Hg Bi, Pd and Cd.

15. A method for controlling contaminant contents in an acidic base metal solution, comprising contacting the acidic base metal solution with activated carbon, and separating an acidic base metal solution with target contents of the contaminants from activated carbon loaded with corresponding contents of the contaminants.

16. The method of claim 15, further comprising regenerating the loaded carbon.

17. The method of claim 15, wherein the base metal is at least one of : Cu, Co and Ni; and the contaminants are at least one of: As, Sb, Hg Bi, Pd and Cd.

18. A method for controlling arsenic and antimony contents in an acidic sulfate solution of copper, comprising contacting the acidic sulfate solution of copper with activated carbon, and separating an acidic sulfate solution of copper with arsenic and antimony target contents from activated carbon loaded with corresponding contents of the arsenic and antimony.

19. The method of claim 18, further comprising regenerating the loaded carbon using ferric hydroxide to retain the arsenic and antimony contents thereof.

20. The method of claim 18, further comprising regenerating the loaded carbon using a sodium chloride aqueous solution to retain the arsenic and antimony contents thereof.