Impurity removal method for Fe and Al impurities in battery leachate

Abstract

The invention relates to an impurity removal method for Fe and Al impurities in a battery leachate, which comprises the following steps: carrying out first-stage impurity removal on the battery leachate containing Fe and Al impurities by adopting a first pH regulator, adding an organic curing agent at the same time, reacting, and separating to obtain first-stage filter residues and first-stage filtrate; and carrying out second-stage impurity removal on the first-stage filtrate by adopting a second pH regulator, and separating after reaction to obtain the battery leachate. The method disclosed by the invention has the advantages of low loss of valuable metals Ni and Co, high open circuit rate of impurities Fe and Al, high separation speed and the like, and is simple in process flow and suitable for production line operation.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to a method for removing Fe and Al impurities from battery leachate. Background Technology

[0002] Currently, the recycling of valuable metals from waste batteries often employs a hydrometallurgical process involving sulfuric acid leaching. However, the process of grinding the recycled battery black powder introduces Fe and Al impurity metal elements, and the introduction of Fe and Al is also unavoidable during the hydrometallurgical process, which increases the difficulty of separating valuable elements (Li, Ni, Co, Mn).

[0003] Existing technologies often employ pH adjustment to precipitate and remove Fe and Al impurities. However, this direct pH adjustment method frequently leads to difficulty in separating Co and Ni entrained in the precipitate, resulting in the loss of valuable Co and Ni elements and failing to efficiently open the path for Fe and Al impurities. Research has found that using phosphates as precipitants for Fe and Al impurities can reduce the loss of valuable elements during the removal process. However, this requires the addition of oxidants and alkali adjusters, incurring additional auxiliary material costs and lacking economic advantages. Furthermore, the traditional process for removing Fe and Al impurities forms Fe(OH)3 colloids, which are finely and uniformly dispersed, making solid-liquid separation of the slurry difficult. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for removing Fe and Al impurities from battery leachate to address the above problems. The method described in this invention has advantages such as low loss of valuable metals such as Ni and Co, high open circuit rate of Fe and Al impurities, and fast separation speed. Moreover, the process is simple and suitable for production line operation.

[0005] A method for removing Fe and Al impurities from battery leaching solution includes the following steps:

[0006] The battery leachate containing Fe and Al impurities was first removed by using a first pH adjuster, and an organic curing agent was added at the same time. After the reaction, the first filter residue and the first filtrate were separated.

[0007] The first-stage filtrate was purified by using a second pH adjuster, and the resulting battery leachate was obtained after the reaction.

[0008] In one embodiment, the organic curing agent satisfies at least one of the following conditions:

[0009] (1) The surface potential of the organic curing agent is -3.5mV to -2.5mV;

[0010] (2) The molecular structure of the organic curing agent includes at least one of carboxylic acid groups, amide groups, and sulfonic acid groups;

[0011] (3) The organic curing agent is selected from high molecular organic polymers.

[0012] In one embodiment, the organic curing agent is selected from at least one of chitosan, amino-modified gelatin, polyethyleneimine, polyethylene sulfonic acid, and polydimethyldiallyl ammonium chloride.

[0013] In one embodiment, during the first impurity removal step, the organic curing agent has a mass concentration of 5 ppm to 40 ppm in the battery leachate containing Fe and Al impurities.

[0014] In one embodiment, the first impurity removal step satisfies at least one of the following conditions:

[0015] (1) The first pH adjuster is selected from at least one of calcium carbonate, calcium oxide, sodium carbonate, and sodium hydroxide;

[0016] (2) The pH value of the battery leachate after adding the first pH adjuster is 2.5 to 4.0;

[0017] (3) The reaction time is 0.5 h to 3 h;

[0018] (4) Let stand for 0.1h to 2h before separation.

[0019] In one embodiment, the separation rate after the first stage of impurity removal reaction is 0.08 m³ / (m²·h) to 0.12 m³ / (m²·h).

[0020] In one embodiment, the first section of filter residue is acid-washed to obtain waste residue.

[0021] In one embodiment, the second impurity removal step satisfies at least one of the following conditions:

[0022] (1) The second pH adjuster is selected from at least one of calcium carbonate, calcium oxide, sodium carbonate, and sodium hydroxide;

[0023] (2) The pH of the first filtrate after adding the second pH adjuster is 3.0 to 6.0;

[0024] (3) The reaction time is 0.5h to 3h.

[0025] In one embodiment, in the second stage of impurity removal, a second stage of filter residue is obtained after separation. The second stage of filter residue is acid-dissolved using a third pH adjuster, and the resulting dissolved slurry is recycled into the first stage of impurity removal.

[0026] In one embodiment, the acid dissolution step satisfies at least one of the following conditions:

[0027] (1) The third pH adjuster is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid;

[0028] (2) The pH value is 0.5 to 3.5.

[0029] In the impurity removal method described in this invention, a first pH adjuster is used for the first stage of impurity removal, and an organic curing agent is added in combination. This selectively enhances the curing of Fe and Al in the battery leachate, and synergistically captures Fe(OH)3 and Al(OH)3 colloids to promote their growth and development, effectively accelerating the separation speed of the slurry, enhancing the chelation of Fe and Al into the waste residue, and optimizing the production line conditions. At the same time, a second pH adjuster is used for a deeper second stage of impurity removal on the first stage filtrate, further improving the removal effect of Fe and Al impurities in the battery leachate, thereby obtaining a battery leachate with extremely low Fe and Al content, and effectively reducing the loss of valuable elements caused by the precipitation of Fe and Al in the battery leachate.

[0030] Therefore, the method described in this invention has advantages such as low loss of valuable metals Ni and Co, high open circuit rate of impurities Fe and Al, and fast separation speed. In addition, the process is simple, the cost of auxiliary materials is controllable, and it is suitable for production line operation. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart of a method for removing Fe and Al impurities from battery leaching solution according to an embodiment of the present invention. Detailed Implementation

[0033] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. In this invention, when referring to numerical ranges, unless otherwise specified, such ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Furthermore, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0035] Through long-term and in-depth research, the applicant discovered that in order to reduce the entrainment loss of valuable Co and Ni elements during the removal of Fe and Al impurities by adjusting pH, a two-stage pH adjustment method is often used in chemical precipitation. For example, Fe is removed between pH 2.5 and 3.5, and Al is removed between pH 3.5 and 5.5. After the second stage of Al removal, the precipitate is back-dissolved into the first stage of Fe removal. This approach can significantly reduce the loss of organometallic materials caused by high pH removal. However, aluminum impurities in the system are difficult to open, leading to circulation within the system. Approximately 75% of the Al circulates between the first and second stages of removal. This results in additional consumption of acid and alkali additives, and the accumulation of Fe and Al impurities significantly reduces the filtration rate of the first stage of removal, deteriorating the production line conditions.

[0036] To overcome the above-mentioned technical problems, the present invention provides a method for removing Fe and Al impurities from battery leachate, combined with... Figure 1 As shown, the method includes the following steps:

[0037] Step 1: The battery leachate containing Fe and Al impurities is removed in the first stage using a first pH adjuster, while an organic curing agent is added. After the reaction, the first stage filter residue and the first stage filtrate are separated.

[0038] Step 2: Use a second pH adjuster to remove impurities from the first filtrate in the second stage, and then separate the resulting battery leachate after the reaction.

[0039] In step one of the impurity removal method of the present invention, a first pH adjuster is used for the first stage of impurity removal, and an organic curing agent is added in conjunction. The organic curing agent undergoes hydration and hydrolysis in the solution, as shown in Formulas 1 and 2, where OM represents the organic curing agent. Further, the charged organic monomers obtained from hydrolysis can selectively adsorb Fe and Al impurities in the battery leachate, as shown in Formulas 3 and 4, forming Fe and Al-containing complex precipitates, enhancing the chelation of Fe and Al and allowing them to enter the waste residue, thereby opening the circuit along with the waste residue, while avoiding the loss of valuable elements such as Co and Ni in the battery leachate.

[0040] nOM + 3nH₂O → 3nH + +nOM(OH)3 3- (Formula 1);

[0041] nHOM→nH + +nOM - (Formula 2);

[0042] Fe 3+ +Al 3+ +OM(OH)3 3- +3OM - →Al(OH)3OM+Fe·3OM↓(Formula 3;

[0043] Fe 3+ +Al 3+ +OM(OH)3 3- +3OM - →Fe(OH)3OM+Al·3OM↓(Formula 4)

[0044] On the one hand, the organic curing agent can adhere to the surface of the precipitated Fe(OH)3 and Al(OH)3 colloidal particles, reducing the distance between particles through the crosslinking effect, thereby promoting the growth and development of Fe(OH)3 and Al(OH)3 colloidal particles, achieving the effect of flocculation and sedimentation, which is beneficial to solid-liquid separation, thus effectively improving the separation speed and optimizing the production line conditions. On the other hand, unlike traditional flocculants, the organic curing agent used in this invention has a selective complexing and fixing effect on Fe and Al impurities. Even if the Fe and Al in the first stage filter residue are acid-washed, they will not be washed away, thereby significantly improving the open circuit rate of Fe and Al impurities in the waste residue under low pH conditions.

[0045] It should be noted that battery leachate containing Fe and Al impurities typically refers to a solution containing Fe and Al impurities obtained through the chemical leaching step in the wet recycling process of waste lithium batteries. "Impurity open circuit" means that the impurities in the battery leachate separate from the valuable metal elements and enter the waste residue, thus being removed as the waste residue is disposed of.

[0046] In one embodiment of the present invention, the surface potential of the organic curing agent is preferably -3.5mV to -2.5mV, which is more conducive to the selective fixation of trivalent Fe and Al impurity ions, thereby avoiding the loss of valuable metals such as Co and Ni in the battery leachate.

[0047] It should be noted that the surface potential of the organic curing agent is measured by preparing an aqueous solution of the organic curing agent at a concentration of 10 ppm to 40 ppm. The surface potential of the organic curing agent at a certain concentration includes, but is not limited to, any one of -3.5 mV, -3.2 mV, -3.0 mV, -2.7 mV, and -2.5 mV, or any range between two of them, more preferably -3.2 mV to -2.7 mV.

[0048] In one embodiment of the present invention, the molecular structure of the organic curing agent includes at least one of a carboxylic acid group, an amide group, and a sulfonic acid group, which is more conducive to the selective fixation of trivalent Fe and Al impurity ions.

[0049] Preferably, the organic curing agent is selected from high molecular weight organic polymers.

[0050] More preferably, the organic curing agent is selected from at least one of chitosan, amino-modified gelatin, polyethyleneimine, polyethylene sulfonic acid, and polydimethyldiallyl ammonium chloride.

[0051] It is understandable that when an organic curing agent is a combination of two or more substances, the surface potential of the organic curing agent represents the surface potential of the curing agent under the combination of two or more substances.

[0052] In one embodiment of the present invention, in the first impurity removal step, the mass concentration of the organic curing agent in the battery leaching solution containing Fe and Al impurities is preferably 5 ppm to 40 ppm. When the mass concentration of the organic curing agent is too low, the complexation and fixation effect is weak and the open circuit rate is not high; when the mass concentration of the organic curing agent is too high, the solution will become viscous and the subsequent filtration speed will be slow. Therefore, by adjusting the concentration of the organic curing agent in the battery leaching solution, it is beneficial to further optimize the complexation and fixation effect and improve the subsequent filtration speed.

[0053] It is understood that the mass concentration of the organic curing agent in the battery leachate containing Fe and Al impurities includes, but is not limited to, any one of 5 ppm, 10 ppm, 17 ppm, 20 ppm, 25 ppm, 40 ppm or a range between any two, more preferably 17 ppm to 25 ppm.

[0054] In one embodiment of the present invention, the first pH adjuster is selected from at least one of calcium carbonate, calcium oxide, sodium carbonate, and sodium hydroxide.

[0055] In one embodiment of the present invention, in the first impurity removal step, the pH value of the battery leachate to which the first pH adjuster is added is 2.5 to 4.0, including but not limited to any one of 2.5, 3.0, 3.5, 4.0 or any range between two, more preferably 2.8 to 3.3.

[0056] In one embodiment of the present invention, the reaction time for the first stage of impurity removal is 0.5h to 3h, including but not limited to any one of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h or any range between two, more preferably 1h to 1.5h.

[0057] In one embodiment of the present invention, after the first stage of impurity removal, the mixture is left to stand for 0.1 h to 2 h before separation, which is more conducive to improving the separation speed.

[0058] In one embodiment of the present invention, the separation rate after the first stage of impurity removal reaction is from 0.08 m³ / (m²·h) to 0.12 m³ / (m²·h), including but not limited to any one of 0.08 m³ / (m²·h), 0.09 m³ / (m²·h), 0.10 m³ / (m²·h), 0.11 m³ / (m²·h), 0.12 m³ / (m²·h) or a range between any two, more preferably from 0.09 m³ / (m²·h) to 0.11 m³ / (m²·h).

[0059] It should be noted that the present invention does not limit the separation process; methods such as filtration can be used for separation.

[0060] In one embodiment of the present invention, the first section of filter residue is acid-washed to obtain waste residue. Specifically, a dilute solution of sulfuric acid can be used to acid-wash the first section of filter residue.

[0061] In step two of the impurity removal method of the present invention, a second pH adjuster is used to perform a second stage of deep impurity removal on the first stage filtrate, which further improves the removal effect of Fe and Al impurities in the battery leachate, thereby obtaining a battery leachate with extremely low Fe and Al content.

[0062] In one embodiment of the present invention, the second pH adjuster is selected from at least one of calcium carbonate, calcium oxide, sodium carbonate, and sodium hydroxide. It is understood that the first pH adjuster and the second pH adjuster may be the same or different, and the present invention does not impose any limitation on this.

[0063] In one embodiment of the present invention, in the second impurity removal step, the pH value of the first filtrate to which the second pH adjuster is added is 3.0 to 6.0, including but not limited to any one of 3.0, 3.5, 4.0, 4.5, 5.0, 5.3, 5.5, 6.0 or any range between two, more preferably 4.5 to 5.3.

[0064] In one embodiment of the present invention, the reaction time for the second stage of impurity removal is 0.5h to 3h, including but not limited to any one of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h or any range between two, more preferably 0.5h to 1.5h.

[0065] In one embodiment of the present invention, combined with Figure 1 As shown, in the second stage of impurity removal, a second stage of filter residue is obtained after separation. The second stage of filter residue is acid-dissolved using a third pH adjuster. The resulting dissolved slurry is then recycled into the first stage of impurity removal, which enables the recovery and utilization of entrained valuable elements and further reduces the loss of valuable elements.

[0066] In one embodiment of the present invention, the third pH adjuster is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid.

[0067] In one embodiment of the present invention, the pH value of the second stage of impurity removal is 0.5 to 3.5, including but not limited to any one of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.2, 3.5 or a range between any two, more preferably 2.0 to 3.2.

[0068] The following specific embodiments will further illustrate the method for removing Fe and Al impurities from the battery leaching solution. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0069] Example 1

[0070] The battery leachate containing Fe and Al impurities had Fe and Al concentrations of 3.08 g / L and 6.47 g / L, respectively. Calcium carbonate was added to adjust the pH of the slurry to 2.85. 12 ppm of polyethyleneimine and 6 ppm of amino-modified gelatin were added. Under this combination, the surface potential of the curing agent mixture was approximately -3.3 mV. After reacting for 60 min, the mixture was allowed to stand for 30 min and then filtered to obtain the first filter residue and the first filtrate.

[0071] The first filter residue was acid-washed with dilute sulfuric acid to obtain waste residue.

[0072] Sodium carbonate was added to the first filtrate to further adjust the pH to 4.02. After reacting for 60 minutes, the mixture was filtered to obtain battery leachate and second filter residue. The second filter residue was acid-dissolved by adjusting the pH to 2.10 with sulfuric acid and then circulated into a first-stage impurity removal section for further impurity removal.

[0073] Example 2

[0074] The battery leachate containing Fe and Al impurities had Fe and Al concentrations of 3.08 g / L and 6.47 g / L, respectively. Sodium carbonate was added to adjust the pH of the slurry to 2.90. 6 ppm of chitosan and 12 ppm of polyethyleneimine were added. The surface potential of the curing agent mixture under this combination was approximately -2.7 mV. After reacting for 30 min, the mixture was allowed to stand for 60 min and then filtered to obtain the first filter residue and the first filtrate.

[0075] The first filter residue was acid-washed with dilute sulfuric acid to obtain waste residue.

[0076] Sodium hydroxide was added to the first filtrate to further adjust the pH to 4.10. After reacting for 30 minutes, the mixture was filtered to obtain battery leachate and second filter residue. The second filter residue was acid-dissolved by adjusting the pH to 1.80 with hydrochloric acid and then circulated into a first-stage impurity removal section for further impurity removal.

[0077] Example 3

[0078] The battery leachate containing Fe and Al impurities had Fe and Al concentrations of 3.22 g / L and 6.19 g / L, respectively. Calcium oxide was added to adjust the pH of the slurry to 3.10. 10 ppm of amino-modified gelatin and 6 ppm of polydimethyldiallylammonium chloride were added. The surface potential of the curing agent mixture under this combination was approximately -3.1 mV. After reacting for 120 min, the mixture was allowed to stand for 60 min and then filtered to obtain the first filter residue and the first filtrate.

[0079] The first filter residue was acid-washed with dilute sulfuric acid to obtain waste residue.

[0080] Calcium carbonate was added to the first filtrate to adjust the pH to 5.00. After reacting for 90 minutes, the mixture was filtered to obtain battery leachate and second filter residue. The second filter residue was acid-dissolved by adjusting the pH to 1.40 with sulfuric acid and then circulated into a first-stage impurity removal section for further impurity removal.

[0081] Example 4

[0082] The battery leachate containing Fe and Al impurities had Fe and Al concentrations of 3.22 g / L and 6.19 g / L, respectively. Sodium hydroxide was added to adjust the pH of the slurry to 3.20. 15 ppm of chitosan and 15 ppm of polydimethyldiallylammonium chloride were added. The surface potential of the curing agent mixture under this combination was approximately -2.6 mV. After reacting for 90 min, the mixture was allowed to stand for 90 min and then filtered to obtain the first filter residue and the first filtrate.

[0083] The first filter residue was acid-washed with dilute sulfuric acid to obtain waste residue.

[0084] Calcium carbonate was added to the first filtrate to adjust the pH to 4.50. After reacting for 70 minutes, the mixture was filtered to obtain battery leachate and second filter residue. The second filter residue was acid-dissolved by adjusting the pH to 1.20 with nitric acid and then circulated into a first-stage impurity removal section for further impurity removal.

[0085] Comparative Example 1

[0086] The battery leachate containing Fe and Al impurities had Fe and Al concentrations of 3.08 g / L and 6.47 g / L, respectively. Calcium carbonate was added to adjust the pH of the slurry to 2.85. No organic curing agent was added. The mixture was reacted directly for 60 min, then allowed to stand for 30 min before filtration to obtain the first filter residue and the first filtrate.

[0087] The first filter residue was acid-washed with dilute sulfuric acid to obtain waste residue.

[0088] Sodium carbonate was added to the first filtrate to further adjust the pH to 4.02. After reacting for 60 minutes, the mixture was filtered to obtain battery leachate and second filter residue. The second filter residue was acid-dissolved by adjusting the pH to 2.10 with sulfuric acid and then circulated into a first-stage impurity removal section for further impurity removal.

[0089] Comparative Example 2

[0090] The battery leachate containing Fe and Al impurities had Fe and Al concentrations of 3.22 g / L and 6.19 g / L, respectively. Calcium oxide was added to adjust the pH of the slurry to 3.10. No organic curing agent was added. The mixture was reacted directly for 120 min, then allowed to stand for 60 min before filtration to obtain the first filter residue and the first filtrate.

[0091] The first filter residue was acid-washed with dilute sulfuric acid to obtain waste residue.

[0092] Calcium carbonate was added to the first filtrate to adjust the pH to 5.00. After reacting for 90 minutes, the mixture was filtered to obtain battery leachate and second filter residue. The second filter residue was acid-dissolved by adjusting the pH to 1.40 with sulfuric acid and then circulated into a first-stage impurity removal section for further impurity removal.

[0093] Comparative Example 3

[0094] The battery leachate containing Fe and Al impurities had Fe and Al concentrations of 3.08 g / L and 6.47 g / L, respectively. Sodium carbonate was added to adjust the pH of the slurry to 4.04. No organic curing agent was added. The mixture was reacted directly for 60 minutes, then allowed to stand for 30 minutes before filtration to obtain the first filter residue and the battery leachate. The first filter residue was acid-washed with dilute sulfuric acid to obtain waste residue.

[0095] Comparative Example 4

[0096] The battery leachate containing Fe and Al impurities had Fe and Al concentrations of 3.08 g / L and 6.47 g / L, respectively. Sodium carbonate was added to adjust the pH of the slurry to 4.00, and 20 ppm of polyvinyl sulfonic acid (with a surface potential of approximately -3.4 mV) was added. After reacting for 60 min, the mixture was allowed to stand for 30 min and then filtered to obtain the first filter residue and the battery leachate. The first filter residue was then acid-washed with dilute sulfuric acid to obtain waste residue.

[0097] The Fe and Al contents of the first filtrate and battery leachate, the Fe, Al, Co, and Ni contents and water content of the waste residue, and the filtration rate of the first stage of impurity removal were measured in all examples and comparative examples. The results are shown in Table 1.

[0098] Table 1

[0099]

[0100] According to the test data of the embodiments in Table 1, by adding a curing agent, the open circuit content of Fe and Al impurities in the waste residue is increased, which is beneficial to reduce the consumption of auxiliary materials for impurities in the two-stage circulation process; the Co and Ni content and moisture content in the waste residue are reduced; in addition, the addition of organic curing agent causes the Fe(OH)3 and Al(OH)3 colloidal particles to grow larger, which promotes a significant increase in filtration speed.

[0101] Compared to Comparative Example 1, Example 1, by adding a curing agent, increased the open-circuit content of Al impurities in the waste residue, reduced the loss of Co and Ni in the waste residue, and decreased the moisture content of the waste residue, thereby increasing the filtration speed of the first stage of impurity removal and obtaining qualified waste residue (Co+Ni<0.7%). Similarly, Example 2 also showed a promoting effect compared to Comparative Example 2.

[0102] Furthermore, Comparative Example 3 shows that even with a single-stage alkali adjustment and impurity removal process, the battery leachate still contains high levels of Fe and Al, with Fe and Al contents of 0.38 g / L and 1.42 g / L, respectively. The waste residue also contains 3.27% Co and 8.06% Ni, indicating incomplete impurity removal and significant metal loss. Comparative Example 4 shows that with the addition of an organic curing agent during the single-stage alkali adjustment and impurity removal process, the battery leachate contains Fe and Al contents of 0.23 g / L and 0.93 g / L, respectively, and the waste residue contains 2.94% Co and 6.83% Ni, respectively.

[0103] Therefore, the impurity removal method provided by the present invention, by setting up a two-cycle impurity removal process and using an organic curing agent, can significantly reduce the entrainment loss of metal in the waste residue, increase the open circuit amount of Fe and Al in the waste residue, obtain qualified waste residue, and obtain battery leachate with extremely low Fe and Al content for subsequent processes. In addition, it can also significantly improve the filtration speed in the first stage of impurity removal process.

[0104] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for removing Fe and Al impurities from battery leachate, characterized in that, The method includes the following steps: The battery leachate containing Fe and Al impurities was first removed by using a first pH adjuster, and an organic curing agent was added at the same time. After the reaction, the first filter residue and the first filtrate were separated. The first-stage filtrate was purified by using a second pH adjuster, and the resulting battery leachate was obtained after the reaction.

2. The method for removing Fe and Al impurities from battery leachate according to claim 1, characterized in that, The organic curing agent satisfies at least one of the following conditions: (1) The surface potential of the organic curing agent is -3.5mV to -2.5mV; (2) The molecular structure of the organic curing agent includes at least one of carboxylic acid groups, amide groups, and sulfonic acid groups; (3) The organic curing agent is selected from high molecular organic polymers.

3. The method for removing Fe and Al impurities from battery leachate according to claim 1 or 2, characterized in that, The organic curing agent is selected from at least one of chitosan, amino-modified gelatin, polyethyleneimine, polyethylene sulfonic acid, and polydimethyldiallyl ammonium chloride.

4. The method for removing Fe and Al impurities from battery leachate according to claim 1, characterized in that, In the first impurity removal step, the organic curing agent has a mass concentration of 5 ppm to 40 ppm in the battery leachate containing Fe and Al impurities.

5. The method for removing Fe and Al impurities from battery leachate according to claim 1, characterized in that, The first impurity removal step satisfies at least one of the following conditions: (1) The first pH adjuster is selected from at least one of calcium carbonate, calcium oxide, sodium carbonate, and sodium hydroxide; (2) The pH value of the battery leachate after adding the first pH adjuster is 2.5 to 4.0; (3) The reaction time is 0.5 h to 3 h; (4) Let stand for 0.1h to 2h before separation.

6. The method for removing Fe and Al impurities from battery leachate according to claim 1, characterized in that, After the first stage of impurity removal reaction, the separation rate is 0.08 m³ / (m²·h) to 0.12 m³ / (m²·h).

7. The method for removing Fe and Al impurities from battery leachate according to claim 1, characterized in that, The first section of filter residue is acid-washed to obtain waste residue.

8. The method for removing Fe and Al impurities from battery leachate according to claim 1, characterized in that, The second impurity removal step must satisfy at least one of the following conditions: (1) The second pH adjuster is selected from at least one of calcium carbonate, calcium oxide, sodium carbonate, and sodium hydroxide; (2) The pH of the first filtrate after adding the second pH adjuster is 3.0 to 6.0; (3) The reaction time is 0.5h to 3h.

9. The method for removing Fe and Al impurities from battery leachate according to claim 1, characterized in that, In the second stage of impurity removal, a second stage of filter residue is obtained after separation. The second stage of filter residue is acid-dissolved using a third pH adjuster, and the resulting dissolved slurry is recycled back into the first stage of impurity removal.

10. The method for removing Fe and Al impurities from battery leachate according to claim 9, characterized in that, The acid dissolution step must satisfy at least one of the following conditions: (1) The third pH adjuster is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid; (2) The pH value is 0.5 to 3.5.

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