Method for separating cobalt and lithium from waste liquid

Abstract

The invention provides a method for separating cobalt and lithium from waste liquid, which comprises the following steps: mixing mechanically activated target serpentine powder with waste liquid containing cobalt ions and lithium ions, and sequentially carrying out stirring treatment and solid-liquid separation treatment to obtain a lithium-containing solution and a cobalt-containing solid. Compared with the existing process for separating cobalt and lithium through chemical precipitation, the method provided by the invention can be used for separating cobalt and lithium solutions with lower concentration, the selective separation coefficient is higher, the specific adsorption removal rate of cobalt can reach 98% at most, and the loss rate of lithium is lower than 1%; and meanwhile, waste liquid and waste gas pollution cannot be generated in the cobalt-lithium separation process, and introduction of other impurity ions is avoided.

Description

Technical Field

[0001] The invention relates to the field of environmental technology, and in particular to a method for separating cobalt and lithium from waste liquid. Background Art

[0002] The separation of lithium and cobalt in waste liquid often adopts the chemical cobalt precipitation method, that is, adding sodium hydroxide or potassium hydroxide solution as a precipitant to the cobalt-lithium waste liquid containing lithium ions and cobalt ions, controlling the pH of the cobalt-lithium salt solution at 9-10, so that the cobalt ions are converted into cobalt hydroxide precipitation and transported to the salt device for separation of cobalt hydroxide and lithium ion salt solution, thereby achieving cobalt-lithium separation. However, the traditional chemical cobalt precipitation separation process requires a large amount of alkali consumption, and a large amount of waste alkali and waste materials are generated after the separation is completed, which has the problems of waste of resources, low recovery rate and great environmental pollution. In addition, the chemical cobalt precipitation method cannot achieve efficient separation of low-concentration cobalt-lithium solutions (such as: cobalt and lithium concentrations are less than 200 mg / L). Therefore, it is urgent to develop a new green and efficient cobalt-lithium separation method. Summary of the invention

[0003] The present invention provides a method for separating cobalt and lithium from waste liquid. The method has a simple process flow, does not involve the introduction of other impurity ions, avoids the generation of a large amount of waste liquid and harmful gases during the separation process, and can achieve efficient separation of low-concentration cobalt and lithium solutions.

[0004] In detail, the present invention provides a method for separating cobalt and lithium from waste liquid, comprising the following steps:

[0005] The mechanically activated target serpentine powder is mixed with waste liquid including cobalt ions and lithium ions, and stirring treatment and solid-liquid separation treatment are carried out in sequence to obtain a lithium-containing solution and a cobalt-containing solid.

[0006] In an optional embodiment, the target serpentine powder is obtained by mechanical activation of serpentine.

[0007] In an optional embodiment, the mechanical activation comprises the following process:

[0008] A mixed system including serpentine powder and ball milling media balls is prepared, and the mixed system is dry-milled.

[0009] In an optional embodiment, the rotation speed of the dry grinding process is 300-500 rpm.

[0010] In an optional embodiment, the dry grinding treatment time is 0.5 to 3 hours.

[0011] In an optional embodiment, the stirring treatment is carried out at a temperature of 20 to 70° C. and for a time of 90 to 120 minutes.

[0012] In an optional embodiment, the mass ratio of the added mass of the target serpentine powder to the mass of the cobalt ions in the waste liquid is 20-30.

[0013] In an optional embodiment, the pH value of the waste liquid is 6-8.

[0014] In an optional embodiment, in the waste liquid, the cobalt ions and / or the lithium ions are derived from the positive electrode materials of waste lithium-ion batteries.

[0015] In an alternative embodiment, the waste liquid is obtained by a method comprising the following process:

[0016] 1) Dismantling, discharging and crushing the waste lithium-ion batteries in turn to obtain the positive electrode sheets of the waste lithium-ion batteries;

[0017] 2) separating the positive electrode sheets of the waste lithium-ion batteries to obtain positive electrode materials;

[0018] 3) dissolving the positive electrode material in an acid solution to obtain the waste liquid comprising cobalt ions and lithium ions.

[0019] In an optional embodiment, the process of obtaining the lithium-containing solution and the cobalt-containing solid further comprises the following steps:

[0020] The cobalt-containing solid is immersed in an acidic solution, stirred and separated to obtain a cobaltate solution;

[0021] And / or, adding carbonate or passing carbon dioxide gas into the lithium-containing solution, filtering and washing to obtain lithium carbonate solid.

[0022] Compared with the existing chemical precipitation separation process of cobalt and lithium, the method provided by the present invention can be used for the concentration as low as 200 mg·L -1 The cobalt and lithium solutions can be separated with a high selective separation coefficient; at the same time, the cobalt and lithium separation process will not produce waste liquid and waste gas pollution and avoid the introduction of other impurity ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0024] Figure 1 The element analysis diagram and results of the serpentine in Example 1 after mechanical activation;

[0025] Figure 2 is a morphology diagram of the serpentine of Example 1 after mechanical activation;

[0026] Figure 3 The element analysis diagram and results of the serpentine in Example 1 after adsorption;

[0027] Figure 4 This is the morphology of the serpentine in Example 1 after adsorption. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0029] The present invention provides a method for separating cobalt and lithium from waste liquid, comprising the following steps:

[0030] The mechanically activated target serpentine powder is mixed with waste liquid including cobalt ions and lithium ions, and stirring treatment and solid-liquid separation treatment are carried out in sequence to obtain a lithium-containing solution and a cobalt-containing solid.

[0031] The above method provided by the present invention can achieve efficient separation of cobalt and lithium. The reason is that: serpentine (main chemical component Mg3Si2O5(OH)4) is a natural layered magnesium silicate mineral. The crystal structure of this material is rich in hydroxyl (-OH), but in the natural state, the activity is insufficient and the adsorption effect on cobalt ions is low. The present invention can destroy its crystal structure through mechanical activation, so that the hydroxyl is fully exposed to the surface of the powder particles. Through the bonding between the hydroxyl and the cobalt ions, efficient adsorption of cobalt ions can be achieved. Moreover, since the microscopic area on the surface of the target serpentine powder particles is an alkaline environment, even if the solution is neutral, the cobalt-lithium solution can be adsorbed on Co. 2+ In addition, due to the special crystal structure of the mechanically activated target serpentine powder, lithium cannot be adsorbed by the serpentine powder.

[0032] Exemplarily, the stirring process specifically includes: using a magnetic stirrer for stirring, and the stirring speed of the stirring process is 300 to 800 rpm.

[0033] In some embodiments, the solid-liquid separation can be performed by using a Buchner funnel.

[0034] In some embodiments, the target serpentine powder is obtained by mechanical activation of serpentine powder.

[0035] The mechanical activation includes, but is not limited to, using any one of a ceramic ball mill, a cone ball mill, a vibration mill, a drum mill or a planetary ball mill.

[0036] In some embodiments, the mechanical activation comprises the following process:

[0037] A mixed system including serpentine powder and ball milling media balls is prepared, and the mixed system is dry-milled.

[0038] In some embodiments, the dry grinding process is carried out at a rotation speed of 300 to 500 rpm. The ball mill is dry-milled at a rotation speed of 300 to 500 rpm, which can fully destroy the crystal structure of the serpentine powder in a short time, expose more hydroxyl groups on the surface of the powder particles, and help the serpentine powder to absorb Co 2+ Highly efficient and selective adsorption.

[0039] Exemplarily, serpentine powder and ball milling media balls are placed in a ball mill and dry-milled at any rotation speed of 320rpm, 330rpm, 340rpm, 350rpm, 360rpm, 370rpm, 380rpm, 390rpm, 400rpm, 410rpm, 42rpm, 430rpm, 440rpm, 450rpm, 460rpm, 470rpm, 480rpm, 490rpm, etc.

[0040] In some embodiments, the dry grinding treatment time is 0.5 to 3 hours. The dry grinding treatment time affects the crystal structure of the serpentine powder, and the dry grinding treatment time within the above embodiment can further ensure that lithium is not adsorbed. Exemplarily, the dry grinding treatment time is 0.7 hours, 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, 2 hours, 2.3 hours, 2.5 hours, 2.7 hours, etc.

[0041] It can be understood that the stirring treatment is performed to the extent that the cobalt content no longer changes. In some embodiments, the stirring treatment is performed at a temperature of 20 to 70° C. for 90 to 120 minutes.

[0042] In some embodiments, the mass ratio of the added mass of the target serpentine powder to the mass ratio of the cobalt ions in the waste liquid is 20 to 30. Among them, the mass ratio of the added mass of the serpentine powder to the mass ratio of the cobalt in the waste liquid is within the above range, which can more fully adsorb the cobalt ions and avoid the residual cobalt ions affecting the purity of the lithium salt solution.

[0043] Exemplarily, the mass ratio of the added mass of the target serpentine powder to the mass of the cobalt ions in the waste liquid is 21, 22, 23, 24, 25, 26, 27, 28, 29, etc.

[0044] In some embodiments, the mass ratio of the ball milling medium balls to the serpentine powder is 40 to 70:1.

[0045] Exemplarily, the ball milling medium balls are zirconium balls, ceramic balls, stainless steel balls, etc.

[0046] It can be understood that the method of the present invention has a wide range of applications and has a high separation efficiency for both high and low concentrations of cobalt-containing lithium waste liquids. In some embodiments, the concentration of cobalt ions in the waste liquid is 50 to 500 mg·L -1 ; and / or, the concentration of lithium ions is 50 to 5000 mg·L -1 .

[0047] Since the method of the present invention can separate cobalt and lithium without adding any alkali, in some embodiments, the pH value of the waste liquid is 6-8.

[0048] Exemplarily, the ratio of the mass of the target serpentine powder added to the mass of cobalt in the waste liquid is any value among 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, etc.

[0049] In some embodiments, the D50 of the serpentine powder is 5 microns.

[0050] In some embodiments, the cobalt ions and / or lithium ions in the waste liquid are derived from the positive electrode materials of waste lithium-ion batteries.

[0051] It can be understood that the scheme of the present invention can be used for the separation of cobalt and lithium in any waste liquid containing cobalt ions and lithium ions, for example, for the separation and recovery of metallic lithium (Li) and cobalt (Co) in waste lithium-ion batteries; the positive electrode material of the waste lithium-ion batteries includes one or more of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0052] Since the positive electrode material of the battery contains metal foil and a positive electrode material layer coated on the metal foil, and also contains some impurities such as diaphragms, in order to initially separate the positive electrode material from the metal foil, diaphragms and other impurities, pre-treatment is required. Taking lithium cobalt oxide batteries as an example, the waste liquid is obtained by a method including the following processes:

[0053] 1) Dismantling, discharging and crushing the waste lithium-ion batteries in turn to obtain the positive electrode sheets of the waste lithium-ion batteries;

[0054] 2) separating the positive electrode sheets of the waste lithium-ion batteries to obtain positive electrode materials;

[0055] 3) dissolving the positive electrode material in an acid solution to obtain the waste liquid comprising cobalt ions and lithium ions.

[0056] In one embodiment, the waste liquid is obtained by a method comprising the following steps:

[0057] a. Disassembly, discharge, and crushing: The waste lithium cobalt oxide battery is manually disassembled, immersed in an electrolyte aqueous solution, and then the battery shell is peeled off to separate the positive electrode sheet from the negative electrode sheet to obtain the positive electrode sheet of the waste lithium battery;

[0058] b. Separating the positive electrode material and the metal foil: soaking the positive electrode sheet in an organic solvent until the positive electrode material is separated from the current collector, then taking out the current collector and filtering to obtain the positive electrode material;

[0059] c. Preliminary separation: dissolving the positive electrode material with hydrochloric acid to obtain a mixed chloride salt solution of cobalt ions and lithium ions.

[0060] In the above step a, the waste battery can be fully discharged by soaking it in an electrolyte aqueous solution, and cracks can be generated at the contact point between the positive electrode sheet and the negative electrode sheet of the battery, so that the battery shell can be easily peeled off and the positive electrode sheet can be separated; the amount of the electrolyte aqueous solution and the time for soaking the waste lithium ion battery in the electrolyte aqueous solution are only required to make the waste battery fully discharged and cracks can be generated at the contact point between the positive electrode sheet and the negative electrode sheet of the battery. For example, the amount of the electrolyte aqueous solution is 1-20 times the weight of the waste lithium ion battery, and the time for soaking the waste lithium ion battery in the electrolyte aqueous solution is more than 1 hour, preferably 2-5 hours. In addition, the soaking temperature can be 10-40°C; the content of the electrolyte in the electrolyte aqueous solution is 10-50% by weight, and the electrolyte can be any electrolyte, preferably one or more of sodium chloride, sodium sulfate, sodium nitrate, potassium chloride, potassium sulfate and potassium nitrate. From the perspective of reducing costs, the electrolyte is more preferably sodium chloride.

[0061] The organic solvent in step b above can be one or more of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide and tetrahydrofuran; the amount of the organic solvent can be 5-20 times the weight of the positive electrode sheet, the soaking time can be 1-6 hours, and the temperature can be 60-100°C.

[0062] In some embodiments, after obtaining the lithium-containing solution and the cobalt-containing solid, the following process is further included:

[0063] The cobalt-containing solid is immersed in an acidic solution, stirred and separated to obtain a cobaltate solution;

[0064] And / or, adding carbonate or passing carbon dioxide gas into the lithium-containing solution, filtering and washing to obtain lithium carbonate solid.

[0065] The present invention is further described below in conjunction with specific embodiments:

[0066] Example 1

[0067] This embodiment provides a method for separating cobalt and lithium from waste liquid, wherein the method simulates waste liquid with a mixed salt solution of cobalt ions and lithium ions, and specifically comprises the following steps:

[0068] (1) placing serpentine powder and ball milling medium in a ball milling jar at a mass ratio of 50:1, sealing the ball milling jar and placing it in a planetary ball mill for ball milling at a speed of 400 rpm for 1 h to obtain the target serpentine powder;

[0069] (2) After the ball milling, 100 mg of mechanically activated serpentine was taken out and put into 100 mL of a mixed salt solution of cobalt ions and lithium ions (wherein the anions were chloride ions and nitrate ions, the concentrations of cobalt and lithium were both 50 mg / L, and the pH value of the mixed salt solution was 6-8). The mass ratio of serpentine added to the mass of cobalt in the solution was 20:1. A magnetic stirrer was used for stirring. The magnetic particle stirring speed was 300 rpm and the stirring time was 90 min.

[0070] Figure 1 The elemental analysis diagram of the target serpentine powder in this example is shown below. Figure 2 The target serpentine powder morphology of this example is shown; Figure 3 The elemental analysis diagram of the target serpentine powder after adsorption is shown in this example. Figure 4 The morphology of the target serpentine powder after adsorption is shown in Figure 2. Figure 1 and Figure 3 It can be seen that the target serpentine powder in this example can selectively adsorb cobalt ions.

[0071] Example 2

[0072] This embodiment provides a method for separating cobalt and lithium from waste liquid, which is basically the same as that of Embodiment 1, except that the rotation speed of the planetary ball mill is 300 rpm.

[0073] Example 3

[0074] This embodiment provides a method for separating cobalt and lithium from waste liquid, which is basically the same as that of Embodiment 1, except that the rotation speed of the planetary ball mill is 500 rpm.

[0075] Example 4

[0076] The embodiment provides a method for separating cobalt and lithium from waste liquid, which is basically the same as that of embodiment 1, except that the rotation speed of the planetary ball mill is 700 rpm.

[0077] Example 5

[0078] This embodiment provides a method for separating cobalt and lithium from waste liquid, which is basically the same as that of Embodiment 1, except that the ball milling time of the planetary ball mill is 0.5 h.

[0079] Example 6

[0080] This embodiment provides a method for separating cobalt and lithium from waste liquid. The method is basically the same as that in Embodiment 1, except that the ball milling time of the planetary ball mill is 3 hours.

[0081] Example 7

[0082] This embodiment provides a method for separating cobalt and lithium from waste liquid, which is basically the same as that of Embodiment 1, except that the ball milling time of the planetary ball mill is 4 hours.

[0083] Example 8

[0084] The embodiment provides a method for separating cobalt and lithium from waste liquid, which is basically the same as that of embodiment 1, except that the stirring time is 60 minutes.

[0085] Example 9

[0086] The embodiment provides a method for separating cobalt and lithium from waste liquid, which is basically the same as that of embodiment 1, except that the stirring time is 120 min.

[0087] Example 10

[0088] The embodiment provides a method for separating cobalt and lithium from waste liquid. The method is basically the same as that of embodiment 1, except that the ratio of the mass of the target serpentine powder added to the mass of cobalt in the waste liquid is 10.

[0089] Embodiment 11

[0090] The embodiment provides a method for separating cobalt and lithium from waste liquid, which is basically the same as that of embodiment 1, except that the ratio of the mass of the target serpentine powder added to the mass of cobalt in the waste liquid is 30.

[0091] Example 12

[0092] The embodiment provides a method for separating cobalt and lithium from waste liquid. The method is basically the same as that of embodiment 1, except that the cobalt concentration is 20 mg·L -1 .

[0093] Embodiment 13

[0094] The embodiment provides a method for separating cobalt and lithium from waste liquid. The method is basically the same as that of embodiment 1, except that the cobalt concentration is 500 mg·L -1 .

[0095] Comparative Example 1

[0096] This comparative example provides a method for separating cobalt and lithium from waste liquid, the method comprising the following steps: directly taking out 100 mg of serpentine powder, adding it into 100 mL of a mixed salt solution of cobalt ions and lithium ions consistent with Example 1, the mass ratio of the serpentine powder added to the mass ratio of cobalt in the solution is 20:1, using a magnetic stirrer for stirring, the magnetic particle stirring speed is 300 rpm, and the stirring time is 90 min.

[0097] Comparative Example 2

[0098] This comparative example provides a method for separating cobalt and lithium from waste liquid, and the method comprises the following steps: taking 100 mg of magnesium hydroxide powder of the same mass as that in Example 1 and putting it into 100 mL of a mixed salt solution of cobalt ions and lithium ions consistent with Example 1, the mass ratio of the added magnesium hydroxide powder to the mass of cobalt in the solution is 20:1, and stirring is performed using a magnetic stirrer, the magnetic particle stirring speed is 300 rpm, and the stirring time is 90 min.

[0099] Separation effect test

[0100] The cobalt content in the waste liquid before and after the separation treatment of the embodiment and the comparative example was tested using EPA 6010D-2018, and the lithium content in the waste liquid before and after the separation treatment of the embodiment and the comparative example was tested using GB / T17413.1-2010, and the cobalt / lithium removal rate was calculated respectively, wherein the removal rate of the element to be tested = (MV-CV) / (MV)×100%; wherein C is the content of the element to be tested in the waste liquid after stirring treatment (g / L), V is the volume of the waste liquid, and M is the content of the element to be tested in the waste liquid before stirring treatment (g / L). The results are shown in Table 1.

[0101] Table 1 Removal rate results

[0102] Group Cobalt removal rate / % Lithium removal rate / % Example 1 96.58 0 Example 2 90.25 0 Example 3 97.34 0 Example 4 97.34 0 Example 5 90.34 0 Example 6 97.41 0 Example 7 97.40 0 Example 8 98.01 0 Example 9 98.35 0 Example 10 75.24 0 Embodiment 11 98.67 0 Example 12 96.89 0 Embodiment 13 85.23 0 Comparative Example 1 2 0 Comparative Example 2 43.5 0

[0103] It can be seen from Table 1 that, compared with the comparative example, the method of the embodiment of the present invention can effectively separate cobalt and lithium in the waste liquid, and the method has a wider range of application and has a good separation effect for high and low concentrations of cobalt-lithium waste liquid.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for separating cobalt and lithium from waste liquid, characterized in that: The steps include: The mechanically activated target serpentine powder is mixed with waste liquid including cobalt ions and lithium ions, and stirring treatment and solid-liquid separation treatment are carried out in sequence to obtain a lithium-containing solution and a cobalt-containing solid.

2. The method according to claim 1, characterized in that The mechanical activation includes the following processes: A mixed system including serpentine powder and ball milling media balls is prepared, and the mixed system is dry-milled.

3. The method according to claim 2, characterized in that The rotation speed of the dry grinding process is 300-500 rpm.

4. The method according to claim 3, characterized in that The dry grinding treatment time is 0.5 to 3 hours.

5. The method according to any one of claims 1 to 4, characterized in that: The stirring treatment is performed at a temperature of 20 to 70° C. and for a time of 90 to 120 minutes.

6. The method according to any one of claims 1 to 5, characterized in that: The mass ratio of the added mass of the target serpentine powder to the mass of the cobalt ions in the waste liquid is 20-30.

7. The method according to any one of claims 1 to 6, characterized in that: The pH value of the waste liquid is 6-8.

8. The method according to any one of claims 1 to 7, characterized in that: In the waste liquid, the cobalt ions and / or the lithium ions are derived from the positive electrode materials of waste lithium-ion batteries.

9. The method according to claim 8, characterized in that The waste liquid is obtained by a method comprising the following steps: 1) Dismantling, discharging and crushing the waste lithium-ion batteries in turn to obtain the positive electrode sheets of the waste lithium-ion batteries; 2) separating the positive electrode sheets of the waste lithium-ion batteries to obtain positive electrode materials; 3) dissolving the positive electrode material in an acid solution to obtain the waste liquid comprising cobalt ions and lithium ions.

10. The method according to any one of claims 1 to 9, characterized in that: The process of obtaining the lithium-containing solution and the cobalt-containing solid further includes the following steps: The cobalt-containing solid is immersed in an acidic solution, stirred and separated to obtain a cobaltate solution; And / or, adding carbonate or passing carbon dioxide gas into the lithium-containing solution, filtering and washing to obtain lithium carbonate solid.

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