A method for recovering lithium from waste medical lithium carbonate

Abstract

The application discloses a method for recovering lithium from waste medical lithium carbonate, and belongs to the technical field of waste medical lithium carbonate recovery. The method comprises the steps of pretreatment, leaching, pre-impurity removal, specific adsorption, lithium precipitation and desorption. + A stable coordination bond is formed, and the introduced sulfonic acid group strongly repels impurity ions through Coulomb repulsion; finally, battery-grade lithium carbonate is obtained through reverse desorption, lithium precipitation, washing and drying. The method for recovering lithium from waste medical lithium carbonate provided by the application has high selectivity and strong anti-interference ability, is suitable for the characteristics of complex impurities in medical lithium carbonate, and has high industrial feasibility.

Description

Technical Field

[0001] This invention relates to the field of waste medical lithium carbonate recycling technology, specifically to a method for recovering lithium from waste medical lithium carbonate. Background Technology

[0002] With the increasing demand for diagnosis and treatment of mental illnesses, the use of medical lithium carbonate, a core drug for treating bipolar disorder, continues to rise, leading to a growing amount of waste medical lithium carbonate (including expired drugs and production waste). Lithium carbonate is an important strategic resource with strong demand in fields such as power batteries and energy storage equipment. However, natural lithium ore reserves are limited and mining costs are high. Therefore, recovering lithium resources from waste medical lithium carbonate can achieve resource recycling, alleviate the supply and demand imbalance of lithium resources, and reduce environmental pollution caused by the indiscriminate disposal of waste drugs, possessing significant economic value and environmental significance.

[0003] In addition to lithium, medical-grade lithium carbonate also contains calcium residue from the production process. 2+ Mg 2+ Fe 3+ Na + K + Impurities include ions such as starch and cellulose, as well as organic impurities such as excipients and trace amounts of biological metabolites. While research on lithium recovery from waste medical lithium carbonate has explored the use of functional materials to assist in lithium separation, existing materials generally suffer from insufficient compatibility. Traditional adsorbent materials (such as natural zeolite and unmodified manganese oxide) are not suitable for Li... + Its specific recognition ability is weak, and it easily adsorbs a large number of impurity ions in waste liquid with high magnesium-to-lithium ratio, which cannot meet the requirements for deep removal of complex impurities in medical lithium carbonate waste.

[0004] Therefore, there is an urgent need to develop a lithium recovery method that combines high selectivity, strong anti-interference ability, and adaptability to the characteristics of medical waste. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for recovering lithium from waste medical lithium carbonate, comprising the following steps:

[0006] S1: The waste medical lithium carbonate raw material is first coarsely crushed, medium crushed and ball-milled, and then roasted in stages;

[0007] S2: After calcination, ball mill again, ultrasonically clean with ethanol solution, add composite leaching agent for leaching, filter to remove insoluble residue, and obtain leachate;

[0008] S3: Add NaOH solution to the leachate, adjust the pH of the leachate, stir and filter to obtain the first filtrate;

[0009] S4: Add saturated Na2CO3 solution and activated carbon to the first filtrate, stir, and then filter to obtain the second filtrate;

[0010] S5: The modified adsorbent is filled into the fixed bed, and the second filtrate is pumped into the fixed bed. After adsorption for 2-3 hours, the second filtrate is discharged.

[0011] S6: The eluent is reverse-flowed into the fixed bed, saturated Na2CO3 solution is added, stirred, washed with deionized water, centrifuged and dried to obtain battery-grade lithium carbonate;

[0012] The modified adsorbent was obtained by introducing imine diacetic acid groups and sulfonic acid groups onto the surface of λ-MnO2.

[0013] In this case, most of the easily treatable impurities are first removed through physicochemical methods, and then iminodiacetic acid and aminosulfonic acid are simultaneously grafted onto the λ-MnO2 surface via covalent bonds to form a modified adsorbent. The grafted iminodiacetic acid group (-N(CH2COOH)2) has a central N atom that can form an N / O tripentate coordination site with the two carboxyl O atoms, and its electron cloud is distributed in the Li... + Ion potential matching, can be used with Li + Ions form stable N→Li + O→Li + Coordinate key, to realize L + Specific adsorption; simultaneously, the grafted sulfonic acid group (-SO3H) completely ionizes in aqueous solution to generate a strongly negatively charged sulfonate ion (R-SO3). ─ A dense negatively charged layer is formed on the surface of the modified adsorbent. According to Coulomb's law, for positively charged Mg... 2+ Ca 2+ The divalent ions generate Coulomb repulsion, directly blocking their approach to the adsorption site, while simultaneously inhibiting Na... + K + When monovalent heteroions form effective repulsion, Li can ultimately achieve + High selective adsorption and low adsorption rate of impurity ions result in high-purity Li after desorption. + Solution.

[0014] Preferably, the step-by-step roasting in S1 involves first pre-roasting at 250-270℃ for 30-40 minutes, followed by main roasting at 500-520℃ for 50-60 minutes; the particle size of the lithium carbonate raw material after coarse crushing, medium crushing, and ball milling is ≤150μm.

[0015] In this case, pre-roasting at 250-270℃ utilizes the low-temperature thermal effect to remove residual moisture and organic excipients from waste medical lithium carbonate, avoiding carbonization and agglomeration of organic matter at high temperatures; main roasting at 500-520℃ destroys the crystal structure of lithium carbonate through moderate high temperature, reduces its crystallinity, and transforms it into an activated state that is easily soluble in acid, while avoiding lithium volatilization or material sintering and agglomeration caused by high temperature.

[0016] Preferably, the particle size of the lithium carbonate raw material after ball milling in S2 is ≤75μm; the volume fraction of the ethanol solution is 8-10%, the ultrasonic cleaning power is 150-200W, and the cleaning time is 20-25min.

[0017] Preferably, the composite leachate in S2 is a sulfuric acid-phosphoric acid composite leachate, wherein the concentration of sulfuric acid is 1.8-2.2 mol / L and the concentration of phosphoric acid is 1.5-2.0 mol / L.

[0018] In this case, sulfuric acid, as the main leaching agent, undergoes a metathesis reaction with lithium carbonate, transforming Li... + It is converted into a soluble lithium salt, achieving efficient dissolution; phosphoric acid can combine with Ca through complexation. 2+ Mg 2+ It forms a stable complex, reducing its dissolution in the leachate; at the same time, the moderate viscosity of phosphoric acid can alleviate CO2 bubble boiling and stabilize the leaching system.

[0019] Preferably, the leaching conditions in S2 are 50-55°C, a stirring rate of 500-600 r / min, and ultrasonic assisted leaching at 20-25 kHz, with a leaching time of 35-45 min.

[0020] Preferably, the mass fraction of NaOH in S3 is 8-10%, the pH of the leachate is 8.2-8.5, the stirring temperature is 50-60℃, and the stirring time is 30-40 min.

[0021] Preferably, in step S4, the Ca in the first filtrate is measured. 2+ The amount of saturated Na2CO3 solution added is based on the Ca content in the first filtrate. 2+ The activated carbon is added at 1.1-1.3 times the concentration; the stirring temperature is 50-55℃ and the time is 40-50 min; the solid-liquid ratio of the activated carbon to the first filtrate is 1:(125-200) g / mL; the adsorption temperature is 40-50℃ and the time is 30-50 min.

[0022] Preferably, the preparation of the modified adsorbent in step S5 includes the following steps:

[0023] T1: At room temperature, add MnSO4 solution dropwise to KMnO4 solution at a rate of 2-5 mL / min, stir at 250-300 r / min for 30-60 min, adjust the pH to 2.0-4.0 with 0.05-0.1 mol / L H2SO4 solution, continue stirring for 30-50 min to form a precipitate, filter and wash until the pH is 7-8, dry at 55-60℃ for 30-60 min to obtain λ-MnO2 powder;

[0024] T2: Add deionized water to the reaction vessel, then add iminodiacetic acid and aminosulfonic acid in sequence, and stir at 200-250 r / min until completely dissolved to form a uniform modified solution;

[0025] T3: Add pure λ-MnO2 powder to the above modified solution, stir at 250-300 r / min for 30-60 min, place in a constant temperature water bath at 60℃, keep warm and stir for 1.5-1.6 h, filter after the reaction is complete, wash with deionized water until the pH of the filtrate is 7, and vacuum dry at 60-65℃ for 8-10 h to obtain the modified adsorbent.

[0026] Preferably, the eluent in S6 is a mixed solution of 0.5-0.6 mol / L hydrochloric acid and 0.1-0.15 mol / L sodium fluoride solution, with a volume ratio of 2:1.

[0027] Preferably, the concentration of the MnSO4 solution is 0.4-0.6 mol / L; the concentration of the KMnO4 solution is 0.08-0.12 mol / L; the volume ratio of the MnSO4 solution to the KMnO4 solution is (3-3.3):2; and the mass-volume ratio of the deionized water, iminodiacetic acid, aminosulfonic acid, and λ-MnO2 is (200-300) mL: (2-3) g: (1-1.5) g: (4-6) g.

[0028] Beneficial technical effects:

[0029] This application first removes most of the easily treatable impurities through physicochemical methods, and then simultaneously grafts iminodiacetic acid and aminosulfonic acid onto the surface of λ-MnO2 via covalent bonds to form a modified adsorbent; wherein the grafted iminodiacetic acid group (-N(CH2COOH)2) has a central N atom that can form an N / O tripentate coordination site with the two carboxyl O atoms, and the electron cloud is distributed in Li + Ion potential matching, can be used with Li + Ions form stable N→Li + O→Li + Coordination bonds enable specific adsorption of Li⁺; simultaneously, the grafted sulfonic acid group (-SO₃H) completely ionizes in aqueous solution to generate a strongly negatively charged sulfonate ion (R-SO₃). ─A dense negatively charged layer is formed on the surface of the modified adsorbent. According to Coulomb's law, for positively charged Mg... 2+ Ca 2+ The divalent ions generate Coulomb repulsion, directly blocking their approach to the adsorption site, while simultaneously inhibiting Na... + K + When monovalent heteroions form effective repulsion, Li can ultimately achieve + With high selective adsorption and low adsorption rate of impurity ions, a high-purity Li⁺ solution can be obtained after desorption, which is perfectly suited to the technical requirements of medical lithium carbonate recovery. Attached Figure Description

[0030] Figure 1 A flowchart illustrating a method for recovering lithium from waste medical lithium carbonate provided in this application. Specific implementation methods

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0032] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0033] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application. The invention will be further described below with reference to embodiments, but is not limited thereto.

[0034] Example 1

[0035] like Figure 1 As shown, this embodiment provides a method for recovering lithium from waste medical lithium carbonate, including the following steps:

[0036] S1: Take 1 kg of waste medical lithium carbonate raw material, and successively crush it into coarse, medium and ball mill until the particle size of the lithium carbonate raw material is ≤150μm; pre-calcine at 260℃ for 35 min, main calcine at 510℃ for 55 min, and air-cool it for later use.

[0037] S2: After calcination, the lithium carbonate raw material is ball-milled twice until the particle size is ≤75μm. It is added to 500mL of 8vol.% ethanol solution and ultrasonically cleaned at 180W for 22min. Then, 800mL of sulfuric acid-phosphoric acid composite leaching agent is added, in which the concentration of sulfuric acid is 2.2mol / L and the concentration of phosphoric acid is 2.0mol / L. The mixture is stirred at 52℃ and 550r / min and ultrasonically assisted leaching at 22kHz for 40min. The mixture is then filtered through a 1μm fine filter to obtain the leachate.

[0038] S3: Add 9 wt.% NaOH solution to the leachate, adjust the pH of the leachate to 8.3, stir at 55℃ for 35 min, and filter to obtain the first filtrate;

[0039] S4: Determine the Ca content in the first filtrate. 2+ Content, according to Ca 2+ Add saturated Na2CO3 solution at 1.15 times the concentration to the first filtrate, stir at 52℃ for 45 min; add activated carbon at a solid-liquid ratio of 1:160 g / mL, adsorb at 45℃ for 40 min, and then filter through a 0.2 μm fine filter to obtain the second filtrate.

[0040] S5: Modified adsorbent fills the fixed bed; the second filtrate is pumped into the fixed bed at a flow rate of 2.5 BV / h, adsorbed at 48℃ for 2.5 h, and then the waste liquid is discharged.

[0041] S6: A resolving agent (0.55 mol / L hydrochloric acid + 0.12 mol / L sodium fluoride, with a volume ratio of hydrochloric acid to sodium fluoride of 2:1) is introduced into the fixed bed in reverse at a flow rate of 1.2 BV / h. The eluent is eluted for 28 min, and the eluent is collected. A saturated Na2CO3 solution is added to the eluent, and the mixture is stirred at 92℃ and 450 r / min for 1.2 h. The mixture is then allowed to stand for 2.5 h. The mixture is washed three times with water at 50℃ and dried under vacuum at 115℃ for 4.5 h to obtain battery-grade lithium carbonate.

[0042] Preparation of modified adsorbents:

[0043] T1: At room temperature, 0.5 mol / L MnSO4 solution was added dropwise to 0.1 mol / L KMnO4 solution at a volume ratio of 3:2 at a rate of 3 mL / min. The mixture was stirred at 280 r / min for 45 min, and the pH was adjusted to 3.0 with 0.1 mol / L H2SO4 solution. The mixture was stirred for another 30 min to form a precipitate. The precipitate was filtered and washed until the pH reached 7. The precipitate was then dried at 58℃ for 45 min to obtain λ-MnO2.

[0044] T2: Add 200mL of deionized water to a beaker, add 3g of aminophosphonic acid and 1.4g of iminodiacetic acid, stir at 220r / min to dissolve, and obtain the modified solution;

[0045] T3: Add 6g of λ-MnO2 powder to the modified solution, stir at 250r / min for 60min, then place in a constant temperature water bath at 60℃ and stir for 1.5h. After the reaction is complete, filter, wash with deionized water until the pH of the filtrate is 7, and vacuum dry at 62℃ for 9h to obtain the modified adsorbent.

[0046] Test results: Lithium recovery rate 98.0%, product purity 99.93%.

[0047] Example 2

[0048] like Figure 1 As shown, this embodiment provides a method for recovering lithium from waste medical lithium carbonate, including the following steps:

[0049] S1: Take 1 kg of waste medical lithium carbonate raw material, and successively crush it into coarse, medium and ball mill until the particle size of the lithium carbonate raw material is ≤150μm; pre-calcine at 270℃ for 30 min, main calcine at 520℃ for 50 min, and air-cool it for later use.

[0050] S2: After calcination, the lithium carbonate raw material is ball-milled twice until the particle size is ≤75μm. It is added to 500mL of 10vol. ethanol solution and ultrasonically cleaned at 180W for 22min. Then, 800mL of sulfuric acid-phosphoric acid composite leaching agent is added, in which the concentration of sulfuric acid is 2.0mol / L and the concentration of phosphoric acid is 1.6mol / L. The mixture is stirred at 52℃ and 550r / min and ultrasonically assisted leaching at 22kHz for 40min. The mixture is then filtered through a 1μm fine filter to obtain the leachate.

[0051] S3: Add 9 wt. NaOH solution to the leachate, adjust the pH of the leachate to 8.3, stir at 55℃ for 35 min, and filter to obtain the first filtrate;

[0052] S4: Determine the Ca content in the first filtrate. 2+ Content, according to Ca 2+ Add saturated Na2CO3 solution at 1.1 times the concentration to the first filtrate, stir at 50℃ for 45 min; add activated carbon at a solid-liquid ratio of 1:125 g / mL, adsorb at 45℃ for 40 min, and then filter through a 0.2 μm fine filter to obtain the second filtrate.

[0053] S5: Modified adsorbent fills the fixed bed; the second filtrate is pumped into the fixed bed at a flow rate of 2.5 BV / h, adsorbed at 48℃ for 2.5 h, and then the waste liquid is discharged.

[0054] S6: A resolving agent (0.55 mol / L hydrochloric acid + 0.12 mol / L sodium fluoride, with a volume ratio of hydrochloric acid to sodium fluoride of 2:1) is introduced into the fixed bed in reverse at a flow rate of 1.2 BV / h. The eluent is eluted for 28 min, and the eluent is collected. A saturated Na2CO3 solution is added to the eluent, and the mixture is stirred at 92℃ and 450 r / min for 1.2 h. The mixture is then allowed to stand for 2.5 h. The mixture is washed three times with water at 50℃ and dried under vacuum at 115℃ for 4.5 h to obtain battery-grade lithium carbonate.

[0055] Preparation of modified adsorbents:

[0056] T1: At room temperature, 0.6 mol / L MnSO4 solution was added dropwise to 0.12 mol / L KMnO4 solution at a volume ratio of 3.1:2 at a rate of 4 mL / min. The mixture was stirred at 280 r / min for 45 min, and the pH was adjusted to 3.0 with 0.1 mol / L H2SO4 solution. The mixture was stirred for another 30 min to form a precipitate. The precipitate was filtered and washed until the pH reached 7. The precipitate was then dried at 58℃ for 45 min to obtain λ-MnO2.

[0057] T2: Add 200mL of deionized water to a beaker, add 3g of aminophosphonic acid and 1.5g of iminodiacetic acid, stir at 220r / min to dissolve, and obtain the modified solution;

[0058] T3: Add 5g of λ-MnO2 powder to the modified solution, stir at 250r / min for 60min, then place in a 60℃ constant temperature water bath and stir for 1.5h. After the reaction is complete, filter, wash with deionized water until the pH of the filtrate is 7, and vacuum dry at 62℃ for 9h to obtain the modified adsorbent.

[0059] Test results: Lithium recovery rate 97.8%, product purity 99.9%.

[0060] Example 3

[0061] like Figure 1 As shown, this embodiment provides a method for recovering lithium from waste medical lithium carbonate, including the following steps:

[0062] S1: Take 1 kg of waste medical lithium carbonate raw material, and successively crush it into coarse, medium and ball mill until the particle size of the lithium carbonate raw material is ≤150μm; pre-calcine at 260℃ for 35 min, main calcine at 510℃ for 55 min, and air-cool it for later use.

[0063] S2: After calcination, the lithium carbonate raw material is ball-milled twice until the particle size is ≤75μm. It is added to 500mL of 8vol.% ethanol solution and ultrasonically cleaned at 180W for 22min. Then, 800mL of sulfuric acid-phosphoric acid composite leaching agent is added, in which the concentration of sulfuric acid is 2.2mol / L and the concentration of phosphoric acid is 1.8mol / L. The mixture is stirred at 52℃ and 550r / min and ultrasonically assisted leaching at 22kHz for 40min. The mixture is then filtered through a 1μm fine filter to obtain the leachate.

[0064] S3: Add 10wt. NaOH solution to the leachate, adjust the pH of the leachate to 8.3, stir at 55℃ for 35min, and filter to obtain the first filtrate;

[0065] S4: Determine the Ca content in the first filtrate. 2+ Content, according to Ca 2+ Add 1.2 times the concentration of saturated Na2CO3 solution and stir at 52℃ for 45 min; add activated carbon at a solid-liquid ratio of 1:200 g / mL, adsorb at 45℃ for 40 min, and then filter through a 0.2 μm fine filter to obtain the second filtrate.

[0066] S5: Modified adsorbent fills the fixed bed; the second filtrate is pumped into the fixed bed at a flow rate of 2.5 BV / h, adsorbed at 48℃ for 2.5 h, and then the waste liquid is discharged.

[0067] S6: A resolving agent (0.6 mol / L hydrochloric acid + 0.15 mol / L sodium fluoride, with a volume ratio of hydrochloric acid to sodium fluoride of 2:1) is introduced into the fixed bed in reverse at a flow rate of 1.2 BV / h. The eluent is eluted for 28 min, and the eluent is collected. A saturated Na2CO3 solution is added to the eluent, and the mixture is stirred at 92℃ and 450 r / min for 1.2 h. The mixture is then allowed to stand for 2.5 h. The mixture is washed three times with water at 50℃ and dried under vacuum at 115℃ for 4.5 h to obtain battery-grade lithium carbonate.

[0068] Preparation of modified adsorbents:

[0069] T1: At room temperature, 0.4 mol / L MnSO4 solution was added dropwise to 0.1 mol / L KMnO4 solution at a volume ratio of 3.2:2 at a rate of 3 mL / min. The mixture was stirred at 280 r / min for 45 min, and the pH was adjusted to 3.0 with 0.1 mol / L H2SO4 solution. The mixture was stirred for another 30 min to form a precipitate. The precipitate was filtered and washed until the pH reached 7. The precipitate was then dried at 58℃ for 45 min to obtain λ-MnO2.

[0070] T2: Add 200mL of deionized water to a beaker, add 2.5g of aminophosphonic acid and 1.2g of iminodiacetic acid, stir at 220r / min to dissolve, and obtain the modified solution;

[0071] T3: Add 5g of λ-MnO2 powder to the modified solution, stir at 250r / min for 60min, then place in a 60℃ constant temperature water bath and stir for 1.5h. After the reaction is complete, filter, wash with deionized water until the pH of the filtrate is 7, and vacuum dry at 62℃ for 9h to obtain the modified adsorbent.

[0072] Test results: Lithium recovery rate 97.7%, product purity 99.91%.

[0073] Example 4

[0074] like Figure 1 As shown, this embodiment provides a method for recovering lithium from waste medical lithium carbonate, including the following steps:

[0075] S1: Take 1 kg of waste medical lithium carbonate raw material, and successively crush it into coarse, medium and ball mill until the particle size of the lithium carbonate raw material is ≤150μm; pre-calcine at 260℃ for 35 min, main calcine at 520℃ for 55 min, and air cool it for later use.

[0076] S2: After calcination, the lithium carbonate raw material is ball-milled twice until the particle size is ≤75μm. It is added to 500mL of 10vol.% ethanol solution and ultrasonically cleaned at 180W for 22min. Then, 800mL of sulfuric acid-phosphoric acid composite leaching agent is added, in which the concentration of sulfuric acid is 2.0mol / L and the concentration of phosphoric acid is 1.5mol / L. The mixture is stirred at 52℃ and 550r / min and ultrasonically assisted leaching at 22kHz for 40min. The mixture is then filtered through a 1μm fine filter to obtain the leachate.

[0077] S3: Add 9wt. NaOH solution to the leachate, adjust the pH of the leachate to 8.3, stir at 55℃ for 35 min, and filter to obtain the first filtrate;

[0078] S4: Determine the Ca content in the first filtrate. 2+ Content, according to Ca 2+ Add saturated Na2CO3 solution at 1.1 times the concentration to the first filtrate, stir at 52℃ for 45 min; add activated carbon at a solid-liquid ratio of 1:180 g / mL, adsorb at 45℃ for 40 min, and then filter through a 0.2 μm fine filter to obtain the second filtrate.

[0079] S5: Modified adsorbent fills the fixed bed; the second filtrate is pumped into the fixed bed at a flow rate of 2.5 BV / h, adsorbed at 48℃ for 2.5 h, and then the waste liquid is discharged.

[0080] S6: A resolving agent (0.5 mol / L hydrochloric acid + 0.1 mol / L sodium fluoride, with a volume ratio of hydrochloric acid to sodium fluoride of 2:1) is introduced into the fixed bed in reverse at a flow rate of 1.2 BV / h. The eluent is eluted for 28 min, and the eluent is collected. A saturated Na2CO3 solution is added to the eluent, and the mixture is stirred at 92℃ and 450 r / min for 1.2 h, and then allowed to stand for aging for 2.5 h. The mixture is washed three times with water at 50℃ and then vacuum dried at 115℃ for 4.5 h to obtain battery-grade lithium carbonate.

[0081] Preparation of modified adsorbents:

[0082] T1: At room temperature, 0.4 mol / L MnSO4 solution was added dropwise to 0.1 mol / L KMnO4 solution at a volume ratio of 3:2 at a rate of 3 mL / min. The mixture was stirred at 280 r / min for 45 min, and the pH was adjusted to 3.0 with 0.1 mol / L H2SO4 solution. The mixture was stirred for another 30 min to form a precipitate. The precipitate was filtered and washed until the pH reached 7. The precipitate was then dried at 58℃ for 45 min to obtain λ-MnO2.

[0083] T2: Add 200mL of deionized water to a beaker, add 2.2g of aminophosphonic acid and 1.5g of iminodiacetic acid, stir at 220r / min to dissolve, and obtain the modified solution;

[0084] T3: Add 4g of λ-MnO2 powder to the modified solution, stir at 250r / min for 60min, then place in a constant temperature water bath at 60℃ and stir for 1.55h. After the reaction is complete, filter, wash with deionized water until the pH of the filtrate is 7, and vacuum dry at 62℃ for 9h to obtain the modified adsorbent.

[0085] Test results: Lithium recovery rate 97.3%, product purity 99.9%.

[0086] Example 5

[0087] like Figure 1 As shown, this embodiment provides a method for recovering lithium from waste medical lithium carbonate, including the following steps:

[0088] S1: Take 1 kg of waste medical lithium carbonate raw material, and successively crush it into coarse, medium and ball mill until the particle size of the lithium carbonate raw material is ≤150μm; pre-calcine at 250℃ for 40 min, main calcine at 500℃ for 60 min, and air-cool it for later use.

[0089] S2: After calcination, the lithium carbonate raw material is ball-milled twice until the particle size is ≤75μm. It is added to 500mL of 9vol. ethanol solution and ultrasonically cleaned at 180W for 22min. Then, 800mL of sulfuric acid-phosphoric acid composite leaching agent is added, with the concentration of sulfuric acid and phosphoric acid being 1.8mol / L. The mixture is stirred at 52℃ and 550r / min and ultrasonically assisted leaching at 22kHz for 40min. The mixture is then filtered through a 1μm fine filter to obtain the leachate.

[0090] S3: Add 9 wt. NaOH solution to the leachate, adjust the pH of the leachate to 8.3, stir at 55℃ for 35 min, and filter to obtain the first filtrate;

[0091] S4: Determine the Ca content in the first filtrate. 2+ Content, according to Ca 2+ Add saturated Na2CO3 solution at 1.1 times the concentration to the first filtrate, stir at 52℃ for 45 min; add activated carbon at a solid-liquid ratio of 1:190 g / mL, adsorb at 45℃ for 40 min, and then filter through a 0.2 μm fine filter to obtain the second filtrate.

[0092] S5: Modified adsorbent fills the fixed bed; the second filtrate is pumped into the fixed bed at a flow rate of 2.5 BV / h, adsorbed at 48℃ for 2.5 h, and then the waste liquid is discharged.

[0093] S6: A resolving agent (0.55 mol / L hydrochloric acid + 0.12 mol / L sodium fluoride, with a volume ratio of hydrochloric acid to sodium fluoride of 2:1) is introduced into the fixed bed in reverse at a flow rate of 1.2 BV / h. The eluent is eluted for 28 min, and the eluent is collected. A saturated Na2CO3 solution is added to the eluent, and the mixture is stirred at 92℃ and 450 r / min for 1.2 h. The mixture is then allowed to stand for 2.5 h. The mixture is washed three times with water at 50℃ and dried under vacuum at 115℃ for 4.5 h to obtain battery-grade lithium carbonate.

[0094] Preparation of modified adsorbents:

[0095] T1: At room temperature, 0.6 mol / L MnSO4 solution was added dropwise to 0.12 mol / L KMnO4 solution at a volume ratio of 3.1:2 at a rate of 3 mL / min. The mixture was stirred at 280 r / min for 45 min, and the pH was adjusted to 3.0 with 0.1 mol / L H2SO4 solution. The mixture was stirred for another 30 min to form a precipitate. The precipitate was filtered and washed until the pH reached 7. The precipitate was then dried at 58℃ for 45 min to obtain λ-MnO2. T2: 200 mL of deionized water was added to a beaker, along with 2 g of aminophosphonic acid and 1 g of iminodiacetic acid. The mixture was stirred at 220 r / min to dissolve the precipitate and obtain the modified solution.

[0096] T3: Add 5g of λ-MnO2 powder to the modified solution, stir at 250r / min for 60min, then place in a 60℃ constant temperature water bath and stir for 1.55h. After the reaction is complete, filter, wash with deionized water until the pH of the filtrate is 7, and vacuum dry at 62℃ for 9h to obtain the modified adsorbent.

[0097] Test results: Lithium recovery rate 97.6%, product purity 99.91%.

[0098] Example 6

[0099] like Figure 1 As shown, this embodiment provides a method for recovering lithium from waste medical lithium carbonate, including the following steps:

[0100] S1: Take 1 kg of waste medical lithium carbonate raw material, and successively crush it into coarse, medium and ball mill until the particle size of the lithium carbonate raw material is ≤150μm; pre-calcine at 260℃ for 35 min, main calcine at 500℃ for 60 min, and air-cool it for later use.

[0101] S2: After calcination, the lithium carbonate raw material is ball-milled twice until the particle size is ≤75μm. It is added to 500mL of 8vol. ethanol solution and ultrasonically cleaned at 180W for 22min. Then, 800mL of sulfuric acid-phosphoric acid composite leaching agent is added, in which the concentration of sulfuric acid is 2.2mol / L and the concentration of phosphoric acid is 2.0mol / L. The mixture is stirred at 52℃ and 550r / min and ultrasonically assisted leaching at 22kHz for 40min. The mixture is then filtered through a 1μm fine filter to obtain the leachate.

[0102] S3: Add 9 wt. NaOH solution to the leachate, adjust the pH of the leachate to 8.3, stir at 55℃ for 35 min, and filter to obtain the first filtrate;

[0103] S4: Determine the Ca content in the first filtrate. 2+ Content, according to Ca 2+ Add saturated Na2CO3 solution at 1.15 times the concentration to the first filtrate, stir at 52℃ for 45 min; add activated carbon at a solid-liquid ratio of 1:180 g / mL, adsorb at 45℃ for 40 min, and then filter through a 0.2 μm fine filter to obtain the second filtrate.

[0104] S5: Modified adsorbent fills the fixed bed; the second filtrate is pumped into the fixed bed at a flow rate of 2.5 BV / h, adsorbed at 48℃ for 2.5 h, and then the waste liquid is discharged.

[0105] S6: A resolving agent (0.5 mol / L hydrochloric acid + 0.12 mol / L sodium fluoride, with a volume ratio of hydrochloric acid to sodium fluoride of 2:1) is introduced into the fixed bed in reverse at a flow rate of 1.2 BV / h. The eluent is eluted for 28 min, and the eluent is collected. A saturated Na2CO3 solution is added to the eluent, and the mixture is stirred at 92℃ and 450 r / min for 1.2 h, and then allowed to stand for aging for 2.5 h. The mixture is washed three times with water at 50℃ and then vacuum dried at 115℃ for 4.5 h to obtain battery-grade lithium carbonate.

[0106] Preparation of modified adsorbents:

[0107] T1: At room temperature, 0.5 mol / L MnSO4 solution was added dropwise to 0.1 mol / L KMnO4 solution at 3 mL / min, stirred at 280 r / min for 45 min, the pH was adjusted to 3.0 with 0.1 mol / L H2SO4 solution, and stirring was continued for 30 min to form a precipitate. The precipitate was filtered and washed until the pH was 7, and dried at 58℃ for 45 min to obtain λ-MnO2.

[0108] T2: Add 200mL of deionized water to a beaker, add 2.7g of aminophosphonic acid and 1.5g of iminodiacetic acid, stir at 220r / min to dissolve, and obtain the modified solution;

[0109] T3: Add 6g of λ-MnO2 powder to the modified solution, stir at 250r / min for 60min, then place in a constant temperature water bath at 60℃ and stir for 1.55h. After the reaction is complete, filter, wash with deionized water until the pH of the filtrate is 7, and vacuum dry at 62℃ for 9h to obtain the modified adsorbent.

[0110] Test results: Lithium recovery rate 97.4%, product purity 99.92%.

[0111] Comparative Example 1

[0112] This comparative example provides a method for recovering lithium from waste medical lithium carbonate. The difference between this method and Example 1 is that unmodified λ-MnO2 is used, while other process parameters and operating steps are the same as in Example 1.

[0113] Test results: Lithium recovery rate 82.3%, product purity 98.5%.

[0114] Comparative Example 2

[0115] This comparative example provides a method for recovering lithium from waste medical lithium carbonate. The difference from Example 1 is that the composite leaching agent is replaced with a 2.0 mol / L single sulfuric acid solution, while other process parameters and operating steps are the same as in Example 1.

[0116] Test results: Lithium recovery rate 90.5%, product purity 99.2%.

[0117] Comparative Example 3

[0118] This comparative example provides a method for recovering lithium from waste medical lithium carbonate. The difference from Example 1 is that the leachate in S2 is directly pumped into a fixed bed for adsorption, omitting the precipitation process using NaOH solution in S3 and the calcium removal process using Na2CO3 and activated carbon adsorption in S4. Other process parameters and operating steps are the same as in Example 1.

[0119] Test results: Lithium recovery rate 88.7%, product purity 99.0%.

[0120] The present invention provides a method for recovering lithium from waste medical lithium carbonate in Examples 1-6. First, most easily processed impurities are removed using physicochemical methods. Then, iminodiacetic acid and aminosulfonic acid are simultaneously grafted onto the surface of λ-MnO2 via covalent bonds to form a modified adsorbent. The grafted iminodiacetic acid group (-N(CH2COOH)2) has a central N atom that forms an N / O tripentate coordination site with the two carboxyl O atoms. The electron cloud is distributed in the Li... + Ion potential matching allows for the formation of stable N→Li groups with Li⁺ ions. + O→Li + Coordinate bond, realizing Li + Specific adsorption; simultaneously, the grafted sulfonic acid group (-SO3H) completely ionizes in aqueous solution to generate a strongly negatively charged sulfonate ion (R-SO3). ─ A dense negatively charged layer is formed on the surface of the modified adsorbent. According to Coulomb's law, for positively charged Mg... 2+ Ca 2+ The divalent ions generate Coulomb repulsion, directly blocking their approach to the adsorption site, while simultaneously inhibiting Na... + K + When monovalent heteroions form effective repulsion, Li can ultimately achieve + High selective adsorption and low adsorption rate of impurity ions allow for the extraction of high-purity Li after desorption. + The solution is perfectly suited to the technical requirements of medical lithium carbonate recovery.

[0121] Comparative Example 1, due to the use of unmodified λ-MnO2, lacks the specific coordination sites of the imine diacetic acid group and the Coulomb repulsion of the sulfonic acid group, thus affecting the Li + The selective adsorption of phosphoric acid is weak, and it easily adsorbs a large number of impurity ions, resulting in a significant decrease in lithium recovery rate and product purity. Comparative Example 2, by using a single sulfuric acid instead of the sulfuric acid-phosphoric acid composite leaching agent, lost the ability of phosphoric acid to leach Ca... 2+ Mg 2+The complexation effect increases the concentration of impurity ions in the leachate, leading to increased pressure in subsequent adsorption and purification, thus affecting the recovery efficiency. Comparative Example 3 omitted the NaOH precipitation in S3 and the Na2CO3 calcium removal and activated carbon adsorption steps in S4, failing to remove some impurity ions and organic pollutants beforehand. This not only allowed a large number of impurity ions to enter the adsorption process, occupying adsorption sites and reducing Li... + Adsorption efficiency may also be affected by organic impurities contaminating the surface of the adsorbent, further weakening its selectivity and ultimately leading to a decrease in lithium recovery rate and product purity.

[0122] It should be understood that the above are only some embodiments of the present invention. It should be pointed out that for those skilled in the art, other modifications and improvements can be made without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for recovering lithium from waste medical lithium carbonate, characterized in that, Includes the following steps: S1: The waste medical lithium carbonate raw material is first coarsely crushed, medium crushed and ball milled, and then roasted in stages; S2: After calcination, ball mill again, ultrasonically clean with ethanol solution, add composite leaching agent for leaching, filter to remove insoluble residue, and obtain leachate; S3: Add NaOH solution to the leachate, adjust the pH of the leachate, stir and filter to obtain the first filtrate; S4: Add saturated Na2CO3 solution and activated carbon to the first filtrate, stir, and then filter to obtain the second filtrate; S5: The modified adsorbent is filled into the fixed bed, and the second filtrate is pumped into the fixed bed. After adsorption for 2-3 hours, the second filtrate is discharged. S6: The eluent is reverse-flowed into the fixed bed, saturated Na2CO3 solution is added, stirred, washed with deionized water, centrifuged and dried to obtain battery-grade lithium carbonate; The modified adsorbent is obtained by introducing imine diacetic acid groups and sulfonic acid groups onto the surface of λ-MnO2.

2. The method for recovering lithium from waste medical lithium carbonate according to claim 1, characterized in that, The stepwise roasting in S1 involves first pre-roasting at 250-270℃ for 30-40 minutes, followed by main roasting at 500-520℃ for 50-60 minutes; the particle size of the lithium carbonate raw material after coarse crushing, medium crushing, and ball milling is ≤150μm.

3. The method for recovering lithium from waste medical lithium carbonate according to claim 1, characterized in that, The particle size of the lithium carbonate raw material after ball milling in S2 is ≤75μm; the volume fraction of the ethanol solution is 8-10%, the ultrasonic cleaning power is 150-200W, and the cleaning time is 20-25min.

4. The method for recovering lithium from waste medical lithium carbonate according to claim 1, characterized in that, The composite leachate in S2 is a sulfuric acid-phosphoric acid composite leachate, wherein the concentration of sulfuric acid is 1.8-2.2 mol / L and the concentration of phosphoric acid is 1.5-2.0 mol / L.

5. A method for recovering lithium from waste medical lithium carbonate according to claim 1, characterized in that, The leaching conditions in S2 are: 50-55℃, stirring rate of 500-600r / min, with simultaneous application of 20-25kHz ultrasonic-assisted leaching, and leaching time of 35-45min.

6. The method for recovering lithium from waste medical lithium carbonate according to claim 1, characterized in that, The mass fraction of NaOH solution in S3 is 8-10%, and the pH of the leachate is 8.2-8.5; the stirring temperature is 50-60℃, and the stirring time is 30-40 min.

7. A method for recovering lithium from waste medical lithium carbonate according to claim 1, characterized in that, In step S4, the Ca in the first filtrate is measured. 2+ The amount of saturated Na2CO3 solution added is based on the Ca content in the first filtrate. 2+ The activated carbon is added at 1.1-1.3 times the concentration; the stirring temperature is 50-55℃ and the time is 40-50 min; the solid-liquid ratio of the activated carbon to the first filtrate is 1:(125-200) g / mL; the adsorption temperature is 40-50℃ and the time is 30-50 min.

8. A method for recovering lithium from waste medical lithium carbonate according to claim 1, characterized in that, The preparation of the modified adsorbent in S5 includes the following steps: T1: At room temperature, add MnSO4 solution dropwise to KMnO4 solution at a rate of 2-5 mL / min, stir at 250-300 r / min for 30-60 min, adjust the pH to 2.0-4.0 with 0.05-0.1 mol / L H2SO4 solution, continue stirring for 30-50 min to form a precipitate, filter and wash until the pH is 7-8, dry at 55-60℃ for 30-60 min to obtain λ-MnO2 powder; T2: Add deionized water to the reaction vessel, then add iminodiacetic acid and aminosulfonic acid in sequence, and stir at 200-250 r / min until completely dissolved to form a modified solution; T3: Add λ-MnO2 powder to the above modified solution, stir at 250-300 r / min for 30-60 min, place in a constant temperature water bath at 60℃, keep warm and stir for 1.5-1.6 h, filter after the reaction is complete, wash with deionized water until the pH of the filtrate is 7, and vacuum dry at 60-65℃ for 8-10 h to obtain the modified adsorbent.

9. A method for recovering lithium from waste medical lithium carbonate according to claim 1, characterized in that, The eluent in S6 is a mixed solution of 0.5-0.6 mol / L hydrochloric acid and 0.1-0.15 mol / L sodium fluoride solution, with a volume ratio of 2:

1.

10. A method for recovering lithium from waste medical lithium carbonate according to claim 8, characterized in that, The concentration of the MnSO4 solution is 0.4-0.6 mol / L; the concentration of the KMnO4 solution is 0.08-0.12 mol / L; the volume ratio of the MnSO4 solution to the KMnO4 solution is (3-3.3):2; the mass-volume ratio of the deionized water, iminodiacetic acid, aminosulfonic acid and λ-MnO2 is (200-300) mL: (2-3) g: (1-1.5) g: (4-6) g.

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