METHOD FOR RECYCLING VALUABLE METALS FROM SPENT BATTERIES

Abstract

A process has been developed in order to recover and recycle the metals present in spent batteries, including alkaline spent batteries alone or mixed with other types of spent batteries. This method shows a good potential in terms of metals recoveries efficiencies and economic feasibility. Firstly, the spent batteries are crushed (optionally after having been frozen in the case of spent batteries of mixed types). Then, the undesirable parts (plastics, steel cases, papers, etc.) are removed by screening. The collected powder, containing the metals, is mixed with a solution of sulfuric acid in the presence of a reducing agent. The solid/liquid separation is carried out by filtration and the leachate is purified in order to selectively recover the metals. The purification steps consist of: a) recovering Zn by solvent extraction followed by an electrowinning process; b) simultaneously recovering Mn and Cd by solvent extraction process; c) selectively recovering Cd from the mixture solution of Cd and Mn by electrowinning process; d) precipitating Mn from a pure solution of MnSO.sub.4 in a carbonate form; e) removing the impurities present in the effluent by solvent extraction in order to obtain a pure NiSO.sub.4 solution; f) precipitating Ni from a NiSO.sub.4 solution in a carbonate form.

Claims

1. A process for recovering valuable metals from spent batteries comprising the steps of: a) crushing the spent batteries; b) separating debris as a coarse fraction and a fine fraction; c) leaching metals present in the fine fraction with strong inorganic acid and a reducing agent to produce an aqueous leachate; d) extracting Zn from the leachate by electrowinning to obtain a metallic deposit of Zn and a Zn-depleted aqueous solution; and e) extracting Mn from the Zn-depleted aqueous solution of d) by precipitation at pH of about 8-9 to obtain precipitated Mn and a Zn- and Mn-depleted aqueous solution.

2. The process of claim 1, wherein in the leaching step c), the strong inorganic acid is selected from the group consisting of: sulfuric acid (H.sub.2SO.sub.4), hydrochloric acid (HCl) and nitric acid (HNO.sub.3).

3. The process of claim 1, wherein the reducing agent in step c) is sodium meta bisulfite or gaseous SO.sub.2, which reduces Mn(IV) to Mn(II).

4. The process of claim 1, wherein the electrowinning in step d) is carried out at about pH 2.

5. The process of claim 1, further comprising a step: d-i) eliminating residual Zn by precipitation as ZnS using NaOH and Na.sub.2S to obtain a rich MnSO.sub.4 solution.

6. The process of claim 5, wherein elimination of residual Zn in step d-i) is carried out by selective precipitation at pH of about 4.5.

7. The process of claim 5, further comprising eliminating impurities remaining following step d-i), by using an organic phase composed of CYANEX 272 at pH of about 2.5, at a temperature of about 40 C. to about 60 C.

8. The process of claim 1, wherein the recovery of Mn as MnCO.sub.3 in step e) is carried out at pH of about 8-9.

9. The process of claim 1, wherein the spent batteries are alkaline batteries, and said step d) is carried out at a temperature of about 20 C.

10. The process of claim 1, wherein the spent batteries belong to a mixture of different types of spent batteries, and said step d) is carried out at a temperature of about 50 C.

11. The process of claim 10, wherein the batteries are selected from the group consisting of: alkaline (Zn/MnO.sub.2); Zn-carbon; NiCd; NiMH; Li ion; Li M; and mixtures thereof.

12. The process of claim 10, wherein the crushing step a) is carried out at low temperature at least under 20 C.

13. The process of claim 10, further comprising step d-ii) extracting Zn from the leachate by aqueous solvent extraction.

14. The process of claim 13, wherein the extraction of Zn in step d-ii) is carried out using an organic phase comprising CYANEX 272 at pH of about 2.5, at a temperature of about 40 C. to about 60 C.

15. The process of claim 14, wherein the Zn is stripped from the organic phase by the addition of H.sub.2SO.sub.4 at a ratio organic:aqueous phases of 2:1 (v/v).

16. The process of claim 10, wherein step e) further comprises extracting Mn from the Zn-depleted aqueous solution of step d) by aqueous solvent extraction.

17. The process of claim 10, further comprising a step: d-iii) extracting Cd from the Zn-depleted aqueous solution of d) by organic solvent extraction and electrodeposition to obtain a Zn-, Cd- and Mn-depleted solution.

18. The process of claim 10, wherein the extractions of Cd and Mn in steps d-iii) and e) are carried out simultaneously using an organic phase composed of DEHPA at pH of about 2.5.

19. The process of claim 10, further comprising steps: f) eliminating impurities from the Zn-, Cd- and Mn-depleted aqueous solution at pH about 5-6 to obtain a purified solution of NiSO.sub.4; and g) precipitating Ni from the NiSO.sub.4 solution.

20. A process for recovering metals from alkaline spent batteries comprising the steps of: a) crushing to obtain a coarse fraction and a fine fraction rich in Zn and Mn; b) carrying out leaching on the fine particles in presence of sulfuric acid and a reducing agent to reduce Mn(IV) to Mn(II); c) selectively recovering Zn by electrowinning; d) eliminating residual Zn by precipitation as ZnS using NaOH and Na.sub.2S to obtain a rich MnSO.sub.4 solution; and e) precipitating the Mn in carbonate form from the MnSO.sub.4-rich solution.

21. A process for recovering valuable metals from a mixture of spent batteries comprising the steps of: a) crushing the spent batteries at a temperature at least as low as 20 C.; b) separating debris as a coarse fraction and a fine fraction by passing the debris through a screen or a sieve; c) leaching metals present in the fine fraction with a strong inorganic acid and a reducing agent to produce an aqueous leachate; d) extracting Zn from the leachate by solvent extraction and electrodeposition to obtain a metallic deposit of Zn and a Zn-depleted aqueous solution; e) extracting Cd from the Zn-depleted aqueous solution by solvent extraction and electrodeposition; f) extracting Mn from the Zn-depleted aqueous solution of d) by organic solvent extraction and precipitation to obtain a Zn-, Cd- and Mn-depleted aqueous solution; g) eliminating impurities from the Zn-, Cd- and Mn-depleted aqueous solution by organic solvent extraction to obtain a purified solution of NiSO.sub.4; and h) precipitating Ni from the NiSO.sub.4 solution.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0022] FIG. 1 shows a simplified schematic flow diagram of the mechanical pre-treatment of a mixture of spent batteries developed to obtain the fine powder that contains the valuable metals.

[0023] FIG. 2 shows the composition of elements in a mixture of spent batteries.

[0024] FIG. 3 illustrates a simplified schematic flow diagram of a recycling process of valuable metals (Zn, Mn, Cd and Ni) from a mixture of spent batteries.

[0025] FIG. 4 illustrates a simplified schematic flow diagram of the leaching process used for the simultaneous solubilisation of valuable metals (Zn, Mn, Cd and Ni) from a mixture of spent batteries.

[0026] FIGS. 5-7 show a detailed flow diagram of the hydrometallurgical steps used for the recovery of each valuable metal according to FIG. 3.

[0027] FIG. 5 shows the zinc recuperation process from the leachate.

[0028] FIG. 6 shows the cadmium recuperation process from Zn-free aqueous solution.

[0029] FIG. 7 shows the manganese recovery process from a mixture of battery waste.

[0030] FIG. 8 illustrates a schematic diagram of the simplified metal recovery process applied to alkaline spent batteries.

ABBREVIATIONS AND DEFINITIONS

Abbreviations

[0031] As used herein, the abbreviation S/L ratio means solid/liquid ratio.

[0032] As used herein, the abbreviation O/A ratio means organic to aqueous ratio.

Definitions

[0033] The terms about and around as used herein refer to a margin of +or 10% of the number indicated. For the sake of precision, the terms about or around when used in conjunction with, for example: 90% means 90% +/9% i.e. from 81% to 99%. More precisely, the terms about or around, when used in connection a pH unit, means +or 0.5 unit.

[0034] As used herein the singular forms a, and, and the include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a cell includes a plurality of such cells and reference to the culture includes reference to one or more cultures and equivalents thereof known to those skilled in the art, and so forth. All technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs unless clearly indicated otherwise.

[0035] As used in this specification and claim(s), the words comprising (and any form of comprising, such as comprise and comprises), having (and any form of having, such as have and has), including (and any form of including, such as includes and include) or containing (and any form of containing, such as contains and contain) are inclusive or open-ended and do not exclude additional, un-recited elements or method steps.

[0036] The term scrubbing means a purification step of the organic phase in which the undesired elements are removed.

[0037] The term stripping means a step transferring a metal of interest from the organic phase to the aqueous phase by addition of a diluted or concentrated acid or basic solution.

[0038] The term purified is used herein to indicate that the compound is enriched, and the absolute level of enrichment or purity is not critical. Those skilled in the art can readily determine appropriate levels of purity according to the use to the original concentration of the compound in the crude material prior to the process.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

Alkaline or Mixed Spent Batteries

[0039] In accordance with a particular aspect, there is provided a process for recovering valuable metals from spent batteries comprising the steps of: crushing the spent batteries; separating debris as a coarse fraction and a fine fraction; leaching metals present in the fine fraction with strong inorganic acid and a reducing agent to produce an aqueous leachate; extracting Zn from the leachate by electrowinning to obtain a metallic deposit of Zn and a Zn-depleted aqueous solution; extracting Mn from the Zn-depleted aqueous solution of d) by precipitation at pH of about 8-9 to obtain precipitated Mn and a Zn- and Mn-depleted aqueous solution.

[0040] Particularly, the separating step b), is carried out by passing debris through a screen or a sieve. More particularly, the leaching step c) is carried out at ambient temperature. Most particularly, the strong inorganic acid, in the leaching step c), is chosen from: sulfuric acid (H.sub.2SO.sub.4), hydrochloric acid (HCl) and nitric acid (HNO.sub.3); and, in particular the strong inorganic acid is chosen from: a used acid or a recycled acid.

[0041] In accordance with a particular aspect, the reducing agent in step c) is sodium meta bisulfite or gaseous SO.sub.2, which reduces Mn(IV) to Mn(II).

[0042] In accordance with a particular aspect, the electrowinning in step d) is carried out at about pH 2 with any suitable electrode known in the art, and more particularly with a stainless steel cathode and a Ti/IrO.sub.2 anode. In particular, the extraction of Zn in step d) is kept at a temperature of about 20 C. to about 60 C., more particularly at about 50 C. for mixed batteries and about 20 C. for alkaline batteries.

[0043] In accordance with a particular aspect, the process as defined hereinabove further comprises step of: d-i) eliminating residual Zn by precipitation as ZnS using NaOH and Na.sub.2S to obtain a rich MnSO.sub.4 solution. Particularly, the elimination of residual Zn is carried out by selective precipitation at pH of about 4.5. More particularly, the elimination of impurities remaining following step d-i), is carried out by using an organic phase composed of CYANEX 272 at pH of about 2.5. More particularly, step d-i) is carried out at a temperature of about 40 to about 60 C.

[0044] In accordance with a particular aspect, the recovery of Mn as MnCO.sub.3 in step e) is carried out at pH of about 8 to about 9.

[0045] In accordance with a particular aspect of the process as defined hereinabove, the spent batteries are alkaline batteries or a mixture of different types of spent batteries.

Mixed Spent Batteries

[0046] In accordance with a particular aspect, the spent batteries belong to a mixture of different types of spent batteries, particularly selected from: alkaline (Zn/MnO.sub.2); Zn-carbon; NiCd; NiMH; Li ion; Li M; and mixtures thereof.

[0047] In accordance with a particular embodiment of the process when the spent batteries are of mixed types, the crushing step a) is carried out at low temperature, particularly at least under 20 C. More particularly, the low temperature is achieved by freezing the spent batteries using liquid nitrogen before the crushing step a).

[0048] In accordance with a particular embodiment of the process when the spent batteries are of mixed types, the extraction of Zn in step d) is carried out at a temperature of about 50 C. for mixed batteries. In accordance with a particular embodiment of the process when the spent batteries are of mixed types further comprises step d-ii) of extracting Zn from the leachate by aqueous solvent extraction. Particularly, the extraction of Zn in step d-ii) is carried out using an organic phase comprising CYANEX 272 at pH of about 2.5 and more particularly at a temperature of about 40 C. to about 60 C. More particularly, the Zn is stripped from the organic phase by the addition of H.sub.2SO.sub.4 at a ratio organic:aqueous phases (O:A) of about 2:1 (v/v).

[0049] In accordance with a particular embodiment of the process when the spent batteries are of mixed types, step e) further comprises extracting Mn from the Zn-depleted aqueous solution of step d) by aqueous solvent extraction. Particularly, the extraction of Mn in step e) is carried using Na.sub.2CO.sub.3 as the neutralizing agent at pH of about 8-9.

[0050] Particularly, the process further comprises a step of: d-iii) extracting Cd from the Zn-depleted aqueous solution of d) by organic solvent extraction and electrodeposition to obtain a Zn-, and Cd- and Mn-depleted solution. Particularly, the extractions of Cd and Mn in steps d-iii) and e) are carried out simultaneously using an organic phase composed of DEHPA at pH of about 2.5. More particularly, the Cd- and/or Mn-rich organic phase is scrubbed at a ratio organic:aqueous phases (O:A) of about 20:1 (v/v) at a pH of about 2.3. Still, more particularly, the Cd and/or Mn is stripped from the scrubbed organic phase by the addition of H.sub.2SO.sub.4 at a ratio O:A of 4:1 (v/v). Most particularly, the extraction of Cd in step d-iii or step e) is carried out at a temperature of about 40 to 60 C., even most particularly, at about 50 C.

[0051] In accordance with a particular embodiment of the process when the spent batteries are of mixed types, the extraction of Cd in step d-iii) is carried out by electrowinning at pH of about 2.

[0052] In accordance with a particular embodiment of the process when the spent batteries are of mixed types, further comprises steps: f) eliminating impurities from the Zn-, Cd- and Mn-depleted aqueous solution at pH about 5-6 to obtain a purified solution of NiSO.sub.4; and g) precipitating Ni from the NiSO.sub.4 solution. Particularly, the Ni precipitation in step g) is carried using Na.sub.2CO.sub.3 as a neutralizing agent at pH of about 7-10.

Alkaline Spent Batteries

[0053] In accordance with an alternative embodiment, there is provided a method for recovering metals from alkaline spent batteries comprising the steps of: a) crushing to obtain a coarse fraction and a fine fraction rich in Zn and Mn; b) carrying out leaching on the fine particles in presence of sulfuric acid and a reducing agent to reduce Mn(IV) to Mn(II); c) selectively recovering Zn by electrowinning; d) eliminating residual Zn by precipitation as ZnS using NaOH and Na.sub.2S to obtain a rich MnSO.sub.4 solution; and e) precipitating the Mn in carbonate form from the MnSO.sub.4-rich solution.

[0054] In accordance with a particular embodiment of the process when the spent batteries are alkaline, the electrowinning in step c) is carried out at pH of about 2, with any suitable electrode known in the art, more particularly with a stainless-steel cathode and a Ti/IrO.sub.2 anode. In accordance with a particular embodiment of the process when the spent batteries are alkaline batteries, the extraction of Zn in step d) is carried out at a temperature of about 20 C. More particularly, the elimination of the residual Zn as ZnS in step d) is carried at pH of about 4.5. Still, more particularly, the recovery of Mn as MnCO.sub.3 in step e) is carried out at pH of about 8-9.

Figures Explanations

[0055] The present invention concerns a chemical process used for the recovery of metals (Zn, Mn, Cd and Ni) from unsorted spent batteries. The different types of residual batteries such as alkaline, ZnC, NiCd, NiMH, Li-ion and LiM batteries may be mixed together according to the proportion of each type of batteries collected for the recycling. The main metals composition comprises Zn, Mn, Ni, Cd and Co, etc. The present method can reduce the costs of the process because it does not require expensive sorting steps, and also reduces the disposal of toxic metals in landfill sites.

[0056] In a particular aspect, the fine particles are removed from the spent batteries by mechanical treatment (FIG. 1.) under an inert atmosphere. First, liquid nitrogen is used to cool down the battery cast at a temperature estimated to be around 80 C. This method allows a secure crushing step of spent batteries even if they are not fully discharged. By cooling down the spent batteries, the risks of violent reactions are diminished or avoided, especially when isolating the metallic powder of the LiM and NiMH batteries. The mechanical treatment also includes a screening step used to remove the coarse particles. These undesirable coarse particles (iron scraps, paper and plastic) present in the sample are removed by screening the fine particles through two different sieves (about 1 mm and about 2 mm sieves). The mixture of fine particles is then dried at about 60 C. and grinded to a powder. As a result, the average fine particles size of the resulting powder is estimated at around 200 m to 250 m, particularly about 214 m.

[0057] According to an aspect of the present invention, the fine particles (powder) are then submitted to a chemical leaching step. These fine particles are mixed with a solution of inorganic acid (H.sub.2SO.sub.4) which is a very effective oxidizing agent that can release two protons. A stoichiometry value of sodium metabisulfite (a reducing agent) is added to the leaching solution to improve the dissolution of MnO.sub.2. After the dissolution step, the solid phase is separated from the liquid phase by filtration. As shown in FIG. 2, analysis of the elements present in the effluent emerging from the leaching process is conducted by ICP-AES. This effluent contains 33.7% of S (37.1 g), 26.0% of Mn (28.6 g), 18.9% of Zn (20.8 g), 3.27% of Cd (3.60 g), 9.08% of Na (10.0 g), 4.12% of Ni (4.50 g), 0.64% of Fe (0.70 g), 0.27% of Co (0.30 g) and 0.38% of the others.

[0058] According to another aspect of the invention several solvent extraction, electrowinning and precipitation steps have been developed to selectively recover the valuable metals (Zn, Mn, Cd and Ni).

[0059] The separation method comprises the steps of: [0060] a) Adjusting the pH of a leaching solution. A solvent extraction is then applied to transfer

[0061] Zn from the leachate to an organic phase. Then, Zn is stripped by a diluted H.sub.2SO.sub.4 solution. Finally, Zn is electrodeposited in a metallic form with a purity of 99%. [0062] b) Simultaneously recovering Mn and Cd by solvent extraction at pH about 2.5. The Cd and Mn present in the organic phase are then stripped by a diluted H.sub.2SO.sub.4 solution in order to obtain a solution rich in Mn.sup.2+ and Cd.sup.2+ in acidic sulfate solution. [0063] c) Selectively electrodepositing Cd from the acidic sulfate solution containing Cd.sup.2+ and Mn.sup.2+. Finally, the Cd.sup.2+ is recovered by electrodeposition in a metallic form with a purity of 97% while Mn still remains in the sulfate solution. [0064] d) Precipitating Mn from the acidic sulfate solution containing Mn from step b) with Na.sub.2CO.sub.3 at pH 8-9. MnCO.sub.3 is obtained as a final product with a purity of 94-97%. [0065] e) Simultaneously removing the impurities such as Co, Cd and Zn from the Zn-, Mn- and Cd-depleted leachate by solvent extraction at pH about 5.5 and leaving the Ni in the sulfate solution (Zn-, Mn-, Cd-depleted leachate). [0066] f) Precipitating Ni from NiSO.sub.4 solution from step e) with Na.sub.2CO.sub.3 at pH 7-10. A final product of NiCO.sub.3 is obtained, particularly with a purity of about 95-97%.

[0067] FIG. 1 illustrates the mechanical treatment steps in a particular embodiment of the present invention. The mechanical treatment process includes: 1) a freezing step of the spent batteries using liquid nitrogen; 2) a crushing step of the spent batteries; 3) a screening step using two sieves (1 mm and 2 mm sieves) in order to remove the coarse particles; 4) a drying step at 60 C.; 5) a grinding step to reduce the particles' size (i.e. fine particles into a powder).

[0068] FIG. 2 reveals the compositions of leachate obtained from the leaching process.

[0069] FIG. 3 reveals the total chemical leaching and metals recoveries processes used after the mechanical treatment.

[0070] FIG. 4 illustrates the dissolution of the solids and the salts in the presence of sulfuric acid and sodium metabisulfite, introduced as a reducing agent to improve the solubilization of the valuable metals (Zn, Mn, Cd and Ni). The solid is separated from liquid by filtration. The leachate obtained contains the valuable metals such as Mn, Zn, Cd and Ni and other metals such as Co and Fe.

[0071] The individual separation steps are described in greater details in the following sections with references to FIGS. 5 to 7.

[0072] As FIG. 5 shows that the leaching solution is subjected to a pH adjustment to about 2.5 by the use of a neutralizing agent (i.e. sodium hydroxide), before being sent to the solvent extraction step where Zn is selectively extracted from the solution and transferred to the organic phase.

[0073] A solvent extraction step is used to recover selectively Zn by controlling an equilibrium pH. At least one organic extraction steps may be necessary to completely extract Zn from the aqueous solution. During the extraction step, a NaOH solution is added to control the equilibrium pH. The iron is inevitably co-extracted with Zn in the organic phase because it is extracted at a lower equilibrium pH compared to Zn. After solvent-aqueous separation, the organic solvent containing Zn and Fe is subjected to a stripping step by using a solution of H.sub.2SO.sub.4. The first stripping step is conducted to recover almost all Zn from the solvent (organic phase) and the second stripping step, carried out with concentrated acid, is necessary in order to remove the residual Fe from the organic solvent in order to allow the recycling of the solvent in the solvent-aqueous separation process. The loss of solvent is estimated at 50 ppm for each solvent-aqueous separation step. The ZnSO.sub.4 solution obtained from the first stripping process is then treated by electrodeposition in order to recover the Zn under metallic form, particularly with a purity up to 99%.

[0074] The aqueous solution which is depleted of zinc is then transferred to the second solvent extraction step in order to simultaneously extract Cd and Mn.

[0075] An acidic solvent extraction step is applied to the Zn-depleted aqueous solution in order to simultaneously extract Cd and Mn. As presented in FIG. 6, a solution of NaOH is used to adjust the pH of the Zn-depleted aqueous solution to about 2.5. At least one organic extraction steps may be necessary to completely extract Cd and Mn from the Zn-depleted aqueous solution. The equilibrium pH of 2.5 is controlled by the addition of a solution of NaOH during the extraction step. However, a small amount of Co and Ni are co-extracted even if the pH is carefully controlled. The organic solvent is then separated from the aqueous phase. A scrubbing step may then be performed to remove the impurities of Co and Ni from the organic solution rich in Cd and Mn.

[0076] The scrubbing solution is initially prepared by diluting the analytical reagents grade of

[0077] MnSO.sub.4 and CdSO.sub.4 with distilled water. Then, small amounts of this scrubbing solution are intensively mixed with the organic solvent during 10 minutes. The impurities including Ni and Co are mostly eliminated from the organic solvent. The organic solvent rich in Cd and Mn is then stripped by the addition of a solution of H.sub.2SO.sub.4 in a single step.

[0078] The solution containing CdSO.sub.4 and MnSO.sub.4 is then sent to the electrowinning step. The Cd is selectively recovered by electrowinning in its metallic form while the Mn still remains in solution. The deposit of Cd obtained is then washed with distilled water to remove the soluble Mn.

[0079] The Cd-depleted effluent is then sent to the precipitation step. Mn is precipitated in its carbonate form (MnCO.sub.3). Sodium and sulfur are the main impurities present in the precipitate of MnCO.sub.3. After washing the precipitate three times with distilled water (10% solid/liquid ratio), these impurities are almost completely removed.

[0080] After the two solvent-aqueous extraction steps, the aqueous solution is depleted of Zn, Cd and Mn. This solution (Zn-, Cd- and Mn-depleted aqueous solution) is then transferred to the third solvent extraction step as shown in FIG. 7. The Zn-, Cd- and Mn-depleted aqueous solution mainly contains Ni and some impurities (Co, Zn and Cd). In order to remove these impurities, the pH of the solution is adjusted to about 5.5. The impurities are selectively extracted from the Zn-, Cd- and Mn-depleted aqueous solution and transferred to the organic solvent at pH about 5.5 in a single extraction step. The impurities present in the organic phase are then stripped by the addition of sulfuric acid and recycled back to the extraction stage. The organic solvent can then be recycled into the solvent-aqueous extraction step.

[0081] The aqueous solution depleted of the impurities mainly contains Ni. The Ni is then recovered as NiCO.sub.3 by precipitation with Na.sub.2CO.sub.3. The sodium and sulfur are the main impurities present in the NiCO.sub.3 precipitate as well as for the precipitate of MnCO.sub.3. Two washing steps using distilled water with a solid/liquid ratio of 10% (w/w) are sufficient to obtain a precipitate of NiCO.sub.3 in high purity (about 95-97% purity).

[0082] FIG. 8 illustrates the particular process developed for the recycling of Zn and Mn from alkaline spent batteries. The alkaline spent batteries are firstly crushed and screened in order to remove the coarse particles. The fine particles are further grinded in order to homogenize the sample and to reduce the particles size, particularly into a powder. These fine particles contain zinc oxide, unreacted metallic zinc, manganese oxide and carbon powder. The metals present in the fine particles are then leached in sulfuric acid in the presence of a reducing agent to improve the dissolution of Mn(IV). The solid (residual cake) is then separated by filtration. Then, Zn is selectively recovered from the aqueous solution containing Mn and Zn at pH 2 by electrowinning. A deposit of metallic zinc with a high purity is obtained after this step. The pH of the leaching solution obtained after electrowinning step is then adjusted by the addition of a solution of NaOH at pH 4.5 following by the addition of Na.sub.2S to precipitate the residual zinc present in the aqueous solution. During this precipitation step, a small amount of Mn co-precipitate with Zn. This ZnS precipitate that contains some Mn impurities can be recycled back to the leaching step.

[0083] The Zn-depleted aqueous solution (MnSO.sub.4 solution) is then transferred to a second precipitation step. The pH of the Zn-depleted aqueous solution is adjusted to about 7 by the addition of a solution of NaOH followed by Na.sub.2CO.sub.3 in order to precipitate the Mn. Almost all Mn is precipitated at pH between 8 and 9 in the carbonate form. A precipitate of MnCO.sub.3 with a high purity (about 98%) is obtained after this step. The inorganic components in this particular embodiment have been analyzed by inductive coupled plasma atomic emission spectroscopy (ICP-AES).

[0084] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present invention, and are not intended to limit the scope of what the inventors regard as their invention nor are they intended to represent that the experiments below are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, molecular weight is average molecular weight, temperature is in degrees Centigrade, and pressure is at or near atmospheric.

EXAMPLES

Example 1

Recovery of Metals from a Mixture of Spent Batteries

Recovery of Zinc

[0085] Refer to FIG. 1, the collected spent batteries were frozen using nitrogen liquid and were then crushed in order to remove steel castings. The fine particles were screened through a 1-2 mm aperture sieves, dried at 60 C. and then grinded. The fine particles obtained huge amounts of Zn, Mn, Cd and Ni. The leaching step was carried out by mixing 109 g of the fine particles with 49 g of sodium metabisulfite and 1 L of a solution of H.sub.2SO.sub.4 (1.34 M) as shown in FIG. 4. The leaching process was conducted during 45 minutes at ambient temperature. The solid cake was then separated from the liquid by filtration. According to our experiments, 1 L of the leaching solution was composed of Mn (28.6 g), Zn (20.8 g), Cd (3.6 g), Ni (4.5 g), Fe (0.7 g) and Co (0.3 g) and the pH of the solution was equal to 1.

[0086] From FIG. 5, the pH of the leachate was then adjusted at 2.5 by the addition of a solution of NaOH (10 M), which was suitable for the selective extraction of Zn from the leachate by an organic solvent. The organic solvent consisted of 30 vol. % of CYAN EX 272, 2 vol. % of

[0087] TBP (tri-butyl phosphate) and 68 vol. % of kerosene. Two stages of organic solvent extraction with an O/A ratio of 2/1 (v/v) were required to completely extract the Zn from the aqueous solution. The temperature of the extraction step was kept at 50 C. After organic and aqueous phase separation, the residual metals present in the aqueous phase were analyzed by ICP-AES. The mass balance was used to calculate the amount of Zn present in the organic phase, which was equal to 20.7 g. Iron was co-extracted with zinc into the organic phase. The Zn was selectively stripped from the organic phase by the addition of a solution of H.sub.2SO.sub.4 (0.4 M) at an O/A ratio of 2/1 (v/v). Most of the zinc present in the organic phase was stripped in a single step. The residual Fe present in the organic phase was then stripped by the addition of a more concentrated solution of H.sub.2SO.sub.4 (1 M) with an O/A ratio of 2/1 (v/v). The stripped solution obtained from the second stripping step was recycled to the next cycle. The extraction and the stripping retention times were fixed to 10 minutes for all the steps.

[0088] The stripping effluent obtained from the first stripping step contained 9.6 g/L of ZnSO.sub.4. This solution was then sent to an electrowinning compartment. The zinc was then electrodeposited at pH 2 by using stainless steel as cathode and Ti/IrO.sub.2 as anode. After two hours of electrowinning at a current density fixed at 360 A/m.sup.2, 86% of the Zn was deposited on the cathode. Approximately 16.4 g of a metallic deposit of Zn (99% purity) was obtained as a final product. The amount of the impurities such as Cd or Fe which could be present in the metallic deposit of zinc was measured. To obtain these values, the deposited cathode was washed in 5% HNO.sub.3 then the metals compositions in this aqueous solution were measured by ICP-AES.

Recovery of Cadmium

[0089] The Zn-depleted aqueous solution from [0075] mainly contained metals such as Mn (27.7 g), Cd (3.5 g), Ni (4.4 g), Zn (0.1 g) and Co (0.3 g). In accordance with FIG. 6, the pH of this solution was adjusted to 2.9 before being mixed with the organic solvent. The organic solvent consisted of 30 vol. % of D2EHPA; 5 vol. % of TBP and 65 vol. % of kerosene. Two extraction steps were required to completely extract Cd from the solution and the O/A ratio was fixed at 2/1 (v/v). The temperature was maintained at 50 C. for all of the experiments and the equilibrium pH of 2.2 was obtained by the addition of a solution of NaOH. Cd and Mn were co-extracted and transferred to the organic phase. Using mass balance calculation, approximately 25.8 g of Mn, 2.7 g of Cd, 0.9 g of Ni, 0.1 g of Zn and 0.1 g of Co were transferred to the organic phase. After the separation of the organic phase from the aqueous phase, a scrubbing method was used to eliminate the main impurities such as Ni and Co from the organic phase. The scrubbing solution which was concentrated in Mn and Cd allowed the removal of Co and Ni from the organic phase by replacing the impurities molecules present in organic phase by Mn and Cd with pH control. The initial scrubbing solution contained 32 g/L of Mn and 7.4 g/L of Cd. The scrubbing O/A ratio was equal to 20/1 (v/v) and its initial pH was fixed at 2.3. The organic solvent collected after the scrubbing step mainly contained Mn and Cd. Approximately 200 mL of scrubbed solution, collected after the first scrubbing stage, was recycled to the extraction step. The Cd and Mn present in the organic solvent were then stripped by the addition of a solution of H.sub.2SO.sub.4 (1.2 M) with the O/A of 4/1 (v/v). After the stripping step, the aqueous solution collected contained Mn (23.8 g), Cd (2.3 g), Ni (0.02 g), Co (0.01 g) and Zn (0.1 g). The reaction time of the extraction steps including the scrubbing step and the stripping step were fixed at 10 minutes for all the tests. The stripped solution was then transferred to the electrolysis compartments. Here, the Cd was selectively electrodeposited from the aqueous solution while the other metals (Mn and traces of Ni, Co, Zn) still remained in the aqueous solution. Stainless steel and Ti/IrO.sub.2 were used as the cathode and the anode, respectively. The selective electrowinning of Cd was conducted at pH 2 during 240 minutes with a current density fixed at 360 A/m.sup.2. The Cd recuperation efficiency by electrowinning was equal to 100% with a loss of manganese estimated at 2.9%. The Cd metallic powder obtained was then washed using distilled water with a solid/liquid ratio (S/L ratio) fixed at 10% in order to eliminate the dissolved manganese. The Cd powder obtained was digested by AQUA REGIA (HNO.sub.3: HCl=3:1) in order to determine the impurities. Finally, 2.36 g of metallic Cd with a purity of 97% was obtained.

Recovery of Manganese

[0090] After the electrowinning of Cd, the pure aqueous solution of MnSO.sub.4 was further transferred to the precipitation step as revealed in FIG. 6. This effluent contained 23.8 g of Mn. The pH of the solution was adjusted to 7 by the addition of a NaOH solution followed by the addition of 53 g of Na.sub.2CO.sub.3. The Mn present in the pure MnSO.sub.4 aqueous solution was almost all (over 90%) precipitated at pH 8-9. Filtration was used to separate MnCO.sub.3 precipitate from the liquid (supernatant). The precipitate of MnCO.sub.3 was washed three times by distilled water with a S/L ratio fixed at 10%. A precipitate of MnCO.sub.3 with a 97% purity (23.8 g as Mn) was obtained as a final product.

Recovery of Nickel

[0091] The Zn-, Cd- and Mn-depleted aqueous solution obtained from the D2EHPA extraction step contained Mn (1.89 g), Cd (0.79 g), Ni (3.45 g) and Co (0.21 g). This aqueous solution (raffinate) depleted of Zn, Cd and Mn was then transferred to the third solvent extraction step as shown in FIG. 7. The organic solvent consisted of 10 vol. % of CYAN EX 272, 2 vol. % of TBP and 88 vol. % of kerosene. The pH of the raffinate was initially adjusted to 5.5. The O/A ratio of 0.5/1 (v/v) was applied to selectively extract the impurities (Co, Cd and Mn residues) with an equilibrium pH equal to 5.7 The organic phase was then separated from the aqueous phase. The organic solvent was then stripped with a solution of H.sub.2SO.sub.4 (0.4 M) with O/A ratio of 2/1 (v/v). The temperature and the reaction time were fixed at 50 C. and 10 minutes, respectively.

[0092] The washed organic solvents in all solvent extraction steps in this example were reused in the next treatment cycle and the acid solutions emerging from the electrodeposition were returned to the stripping step.

[0093] By removing the impurities from the Zn-, Mn- and Cd-depleted aqueous solution using solvent extraction, the aqueous solution rich in Ni (2.4 g as Ni) obtained was transferred to the precipitation compartment. 13 g of Na.sub.2CO.sub.3 were added to precipitate the Ni at pH 7-10. The precipitate of NiCO.sub.3 was then washed two times by distilled water. A S/L ratio fixed at 10% was applied in the washing step and a precipitate of NiCO.sub.3 (2.4 g as Ni) with a purity of 97% was obtained as a final product.

Example 2

Recovery of Metals from a Synthetic Solution Representative of a Mixture of Spent Batteries

[0094] This example related to the recovery of valuable metals (Cd, Mn and Ni) from a synthetic solution is different from Example 1 where the recovery of cadmium, manganese and nickel was conducted with a real leaching solution emerging from the application of the leaching process to a mixture of spent batteries. The composition of the synthetic solution presented herein was slightly different from those obtained from the leaching of valuable metals from a mixture of spent batteries to simulate the behavior of the recovery process with variation of the initial composition of spent batteries (alkaline, alkaline, Zn-Carbon, NiCd, NiMH, Li-ion and LiM batteries).

Recovery of Zinc

[0095] According to Example 1, 1 L of the leaching solution was composed of Mn (26.1 g), Zn (18.5 g), Cd (3.7 g), Ni (3.2 g), Fe (0.5 g) and Co (0.3 g) and the pH of the solution was equal to 1.

[0096] From FIG. 5, the pH of the leachate was then adjusted at 2.5 by the addition of a solution of NaOH (10 M), which was suitable for the selective extraction of Zn from the leachate by an organic solvent. The organic solvent consisted of 20 vol. % of CYAN EX 272, 2 vol. % of TBP and 78 vol. % of kerosene. Two stages of organic solvent extraction with an O/A ratio of 2/1 (v/v) were required to completely extract the Zn from the aqueous solution. The temperature of the extraction step was kept at 50 C. After organic and aqueous phase separation, the residual metals present in the aqueous phase were analyzed by ICP-AES. The mass balance was used to calculate the amount of Zn present in the organic phase, which was equal to 18.3 g. Iron was co-extracted with zinc into the organic phase. The Zn was selectively stripped from the organic phase by the addition of a solution of H.sub.2SO.sub.4 (0.4 M) at an O/A ratio of 2/1 (v/v). Most of the zinc present in the organic phase was stripped in a single step. The residual Fe present in the organic phase was then stripped by the addition of a more concentrated solution of H.sub.2SO.sub.4 (1 M) with an O/A ratio of 2/1 (v/v). The stripped solution obtained from the second stripping step was recycled to the next cycle. The extraction and the stripping retention times were fixed to 10 minutes for all the steps.

[0097] The stripping effluent obtained from the first stripping step contained 9.2 g/L of ZnSO.sub.4.

[0098] This solution was then sent to an electrowinning compartment. The zinc was then electrodeposited at pH 2 by using stainless steel as cathode and Ti/IrO.sub.2 as anode. After two hours of electrowinning at a current density fixed at 360 A/m.sup.2, 92% of the Zn was deposited on the cathode. Approximately 16.8 g of a metallic deposit of Zn (99% purity) was obtained as a final product. The amount of the impurities such as Cd or Fe which could be present in the metallic deposit of zinc was measured. To obtain these values, the deposited cathode was washed in 5% HNO.sub.3 then the metals compositions in this aqueous solution were measured by ICP-AES.

Recovery of Cadmium

[0099] The Zn-depleted synthetic aqueous solution from [0084] mainly contained metals such as Mn (26.1 g), Cd (3.7 g), Ni (3.2 g), Zn (0.2 g) and Co (0.3 g). This solution was prepared according to the metals composition in the raffinate solution from Zn-CYANEX272 solvent extraction at pH 2.5. In accordance with FIG. 6, the pH of this solution was adjusted to 2.9 before being mixed with the organic solvent. The organic solvent consisted of 30 vol. % of D2EHPA; 5 vol. % of TBP and 65 vol. % of kerosene. Two extraction steps were required to completely extract Cd from the solution and the O/A ratio was fixed at 2/1 (v/v). The temperature was maintained at 50 C. for all of the experiments and the equilibrium pH of 2.9 was controlled by the addition of a solution of NaOH. Cd and Mn were co-extracted and transferred to the organic phase. Using mass balance calculation, approximately 25.8 g of Mn, 3.5 g of Cd, 0.7 g of Ni, 0.2 g of Zn and 0.1 g of Co were transferred to the organic phase. After the separation of organic phase from the aqueous phase, a scrubbing method was used to eliminate the main impurities such as Ni and Co from the organic phase. The scrubbing solution which was concentrated in Mn and Cd allowed the removal of Co and Ni from the organic phase by replacing the impurities molecules present in organic phase by Mn and Cd with pH control. The initial scrubbing solution contained 19.8 g/L of Mn and 12.5 g/L of Cd. The scrubbing O/A ratio was equal to 20/1 (v/v) and its initial pH was fixed at 2.3. The organic solvent collected after the scrubbing step mainly contained Mn and Cd. Approximately 200 mL of scrubbed solution, collected after the first scrubbing stage, was recycled to the extraction step. The Cd and Mn present in the organic solvent were then stripped by the addition of a solution of H.sub.2SO.sub.4 (1.2 M) with the O/A of 4/1 (v/v). After the stripping step, the aqueous solution collected contained Mn (24.2 g), Cd (4.4 g), Ni (0.05 g), Co (0.03 g) and Zn (0.04 g). The reaction time of the extraction steps including the scrubbing step and the stripping step were fixed at 10 minutes for all the tests. The synthetic solution was prepared according to the metal composition in the stripped solution (stripped solution from CdMn-D2EHPA solvent extraction step) then transferred to the electrolysis compartments. Here, the Cd was selectively electrodeposited from the aqueous solution while the other metals (Mn and traces of Ni, Co, Zn) still remained in the aqueous solution. Stainless steel and Ti/IrO.sub.2 were used as the cathode and the anode, respectively. The selective electrowinning of Cd was conducted at pH 2 during 90 minutes with a current density fixed at 360 A/m.sup.2. The Cd recuperation efficiency by electrowinning was equal to 98% with a loss of manganese estimated at 3.7%. The Cd metallic powder obtained was then washed using distilled water with a solid/liquid ratio (S/L ratio) fixed at 10% in order to eliminate the dissolved manganese. The Cd powder obtained was digested by AQUA REGIA (HNO.sub.3: HCl=3:1) in order to determine the impurities. Finally, 4.3 g of metallic Cd with a purity of 97% was obtained.

Recovery of Manganese

[0100] After the electrowinning of Cd, the pure aqueous solution of MnSO.sub.4 was further transferred to the precipitation step as revealed in FIG. 6. This effluent contained 23.3 g of Mn. The pH of the solution was adjusted to 7 by the addition of a NaOH solution followed by the addition of 53 g of Na.sub.2CO.sub.3. The Mn present in the pure MnSO.sub.4 aqueous solution was almost all (aver 90%) precipitated at pH 8-9. Filtration was used to separate MnCO.sub.3 precipitate from the liquid (supernatant). The precipitate of MnCO.sub.3 was washed three times by distilled water with a S/L ratio fixed at 10%. A precipitate of MnCO.sub.3 with a 94% purity (23.1 g as Mn) was obtained as a final product.

Recovery of Nickel

[0101] The Zn-, Cd- and Mn-depleted aqueous solution obtained from the D2EHPA extraction step [0086] contained Mn (0.3 g), Cd (0.2 g), Ni (2.5 g) and Co (0.2 g). This aqueous solution (raffinate) depleted of Zn, Cd and Mn was then transferred to the third solvent extraction step as shown in FIG. 7. The organic solvent consisted of 10 vol. % of CYAN EX 272, 2 vol. % of TBP and 88 vol. % of kerosene. The pH of the raffinate was initially adjusted to 5.5. The O/A ratio of 0.5/1 (v/v) was applied to selectively extract the impurities (Co, Cd and Mn residues) with an equilibrium pH equal to 5.7. The organic phase was then separated from the aqueous phase. The organic solvent was then stripped with a solution of H.sub.2SO.sub.4 (0.4 M) with O/A ratio of 2/1 (v/v). The temperature and the reaction time were fixed at 50 C. and 10 minutes, respectively.

[0102] The washed organic solvents in all solvent extraction steps in this example were reused in the next treatment cycle and the acid solutions emerging from the electrodeposition were returned to the stripping step.

[0103] By removing the impurities from the Zn-, Mn- and Cd-depleted aqueous solution using solvent extraction, the aqueous solution rich in Ni (2.3 g as Ni) obtained was transferred to the precipitation compartment. 13 g of Na.sub.2CO.sub.3 were added to precipitate the Ni at pH 7-10. The precipitate of NiCO.sub.3 was then washed two times by distilled water. A S/L ratio fixed at 10% was applied in the washing step and a precipitate of NiCO.sub.3 (2.3 g as Ni) with a purity of 95% was obtained as a final product.

Example 3

Recovery of Zinc and Manganese from Alkaline Spent Batteries

[0104] The process developed for the recycling of valuable metals from mixed spent batteries can be adapted for the recovery of Zn and Mn from alkaline spent batteries which are considered as the majority of commercial battery products. The recycling process used for alkaline spent batteries consists of: a) crushing and grinding; b) screening to obtain the fine particles; c) acid extracting; d) selectively recovering Zn by electrowinning; e) removing residual Zn by precipitation using NaOH and Na.sub.2S; e) solid-liquid separation; g) recovering Mn by precipitation in a carbonate form using Na.sub.2CO.sub.3.

[0105] The present example is adapted to treat spent alkaline batteries. The recycling of Zn and Mn from alkaline spent batteries process comprises the steps of: [0106] Crushing and grinding the alkaline spent batteries. [0107] Screening to retain the coarse particles and grinding the fine particles to obtain a fine powder. [0108] Acid extraction with H.sub.2SO.sub.4 and addition of a stoichiometry amount of a reducing agent to reduce Mn(IV) to Mn(II) and to improve the solubilization of Mn. [0109] Solid-liquid separation by filtration. [0110] Treating the leachate (ZnSO.sub.4 and MnSO.sub.4 solution) by electrowinning. During this step, Zn is selectively electrodeposited with a purity of 98%. [0111] Treating the Zn that is still present in the solution by precipitation with NaOH and Na.sub.2S at pH 4.5. In this step, some amount of Mn is co-precipitated with Zn. This precipitate is recycled back to the leaching step. [0112] Precipitation of the Mn from the sulfate solution with Na.sub.2CO.sub.3 at pH 8-9. A precipitate of MnCO.sub.3 (purity of 98%) is obtained as a final product.

[0113] The alkaline spent batteries recycling process in this example is revealed in FIG. 8. Crushing, screening and grinding methods are applied in order to obtain a fine alkaline batteries powder. Approximately 109 g of homogenized powder was mixed with 1 L of a solution of H.sub.2SO.sub.4 (1.34 M) during 45 minutes at ambient temperature.

[0114] At the beginning of the leaching step, 49 g of sodium metabisulfite (Na.sub.2S.sub.2O.sub.5) were added to the leaching solution to reduce Mn(IV) to Mn(II). After the solid-liquid separation, the leaching solution mainly contained of 23.1 g of Mn, 17.3 g of Zn and 0.23 g of Fe. The Zn was selectively electrodeposited from the leachate at pH 2 using stainless steel as cathode and Ti/IrO.sub.2 as anode. The current density was fixed at 270 A/m.sup.2. Three steps of electrowinning were conducted in order to recover the quantity maximum of metallic zinc without any pH control. The reaction time of each electrowinning step was equal to 90 minutes. Only a small quantity of Fe was co-deposited with Zn, so it was negligible in this example. If Fe is present in high concentration, it can be eliminated by precipitation at pH 4 in the presence of an oxidizing agent H.sub.2O.sub.2 to oxidize Fe(II) to Fe(III) and improve the precipitation of iron as ferric hydroxide (Fe(OH).sub.3). The deposit of Zn was then washed with distilled water to eliminate the soluble manganese. The cathode was washed with 5% HNO.sub.3 in order to determine the impurities present in the deposit of metallic zinc. Approximately 13.8 g of metallic zinc with a purity of 98% was obtained as a final product. Manganese was supposed to be oxidized to MnO.sub.2 at the anode. The quantity of manganese recuperated was estimated at 4.3 g and this deposit could be reused as the primary source.

[0115] The effluent emerging from the electrowinning (Zn-depleted solution) mainly contained Zn (3.5 g), Mn (18.8 g) and Fe (0.23 g). The Zn remaining in the leachate was removed by precipitation in order to obtain a pure MnSO.sub.4 solution. A solution of NaOH was used to adjust the pH to 4 followed by the addition of 15.7 g of Na.sub.2S. With this precipitation step, 99% of Zn was precipitated at pH 4.5 from 1 L of the leachate emerging from the electrowinning. The Mn co-precipitated with Zn during this precipitation step and 17% of Mn was lost. Then, Mn was recovered as the carbonate form by precipitation using Na.sub.2CO.sub.3. The precipitation step consisted of the adjustment of the pH to 7 by addition of a solution of NaOH followed by the addition of 32.7 g of Na.sub.2CO.sub.3. Mn was precipitated at pH between 8 and 9. A precipitate of MnCO.sub.3 was then washed three times with distilled water (10% S/L ratio). After the washing steps, only 0.4% of the Mn initially present in the precipitate was lost and a precipitate of MnCO.sub.3 (15.7 g as Mn) with a purity of 98% was obtained as a final product.

[0116] While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features herein before set forth, and as follows in the scope of the appended claims.

[0117] All patents, patent applications and publications mentioned in this specification are herein incorporated by reference to the same extent as if each independent patent, patent application or publication was specifically and individually indicated to be incorporated by reference.

REFERENCES

[0118] RIS international Ltd., 2007. Canadian Consumer Battery Baseline Study. Available at the following address: www.docstoc.com/docs/79783916/Canadian-Consumer-Battery-Baseline-Study-Final-Report. Consulted on 27 Jul. 2015. [0119] Call2Recycle, 2012. Quebec takes environmental preservation to next level with battery recycling. Available at the following address: www.call2recycle.ca/quebec-takes-environmental-preservation-to-next-level-with-battery-recycling/. Consulted on 26 Jul. 2015.