A method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead and barium in lithium carbonate

Abstract

This invention relates to the field of high-purity material analysis technology, and discloses a method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium in lithium carbonate. The steps are as follows: dissolving a lithium carbonate sample in nitric acid to obtain an acidified sample solution; adjusting the acidified sample solution to an alkaline pH range of 9.5-10.5 using an ammonia-ammonium acetate alkaline buffer solution; passing the alkaline solution through a solid-phase extraction column filled with iminodiacetic acid-type chelating resin, where copper, cadmium, nickel, cobalt, zinc, lead, and barium ions are selectively adsorbed onto the resin; and eluting the adsorbed heavy metal ions with acid to achieve separation and enrichment. This invention effectively overcomes the inhibition and interference of the lithium carbonate matrix on the detection of trace heavy metals, and in particular significantly improves the adsorption and recovery rate of elements such as barium. It achieves efficient separation and enrichment of multiple heavy metals in complex matrices, providing a reliable pretreatment solution for high-sensitivity and high-accuracy quality control analysis of lithium carbonate products.

Description

Technical Field

[0001] This invention relates to the field of high-purity material analysis technology, and in particular to a method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead and barium in lithium carbonate. Background Technology

[0002] Lithium carbonate, especially battery-grade lithium carbonate, is a key precursor for cathode materials in lithium-ion batteries. The content of trace heavy metal impurities directly affects the battery's electrochemical performance, safety, and lifespan. Therefore, there are extremely strict limits on the content of harmful elements such as Cu, Cd, Ni, Co, Zn, Pb, and Ba in lithium carbonate. Pharmacopoes of various countries also set strict limits on the content of trace heavy metal impurities in pharmaceutical-grade lithium carbonate.

[0003] Currently, when using sensitive instruments such as inductively coupled plasma mass spectrometry (ICP-MS) to determine lithium carbonate solutions, the following main challenges are faced: (1) Severe matrix effect: High concentrations of lithium (Li) matrix in the sample can inhibit the ionization efficiency of trace heavy metal ions to be measured, resulting in significant signal suppression or interference, affecting quantitative accuracy. (2) Salt deposition: High total dissolved solids (TDS) can easily cause blockage of the sampling cone and retrieval cone of ICP-MS, affecting instrument stability and lifespan. (3) Interference from simultaneous determination of multiple elements: Complex matrices may cause polyatomic ion interference or background increase, especially for elements with certain mass numbers. (4) Low recovery rate of elements such as barium: When using conventional solid-phase extraction column purification methods with acidic or neutral media, the adsorbent material does not adsorb barium, resulting in loss during pretreatment.

[0004] In existing technologies, direct dilution is often used to reduce the matrix concentration, but this simultaneously reduces the sensitivity of the analyte, bringing it close to or below the detection limit. Other separation methods include co-precipitation and solvent extraction, but these are cumbersome, time-consuming, and difficult to achieve simultaneous and efficient recovery of multiple elements with significantly different properties.

[0005] Therefore, developing a pretreatment method that can efficiently and selectively remove lithium carbonate matrix and simultaneously and effectively adsorb and enrich various trace heavy metals (especially barium) is crucial for improving the accuracy, precision, and applicability of impurity analysis in lithium carbonate. Summary of the Invention

[0006] Purpose of the invention: To address the problems existing in the prior art, this invention provides a method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium in lithium carbonate. Through a clever "acid dissolution-alkalization-selective adsorption" process, it effectively eliminates interference from the lithium matrix while ensuring a high recovery rate of the target heavy metal elements. The method is simple, efficient, and reliable.

[0007] Technical solution: In a first aspect, the present invention provides a method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium from lithium carbonate, comprising the following steps: S1. Dissolution: Dissolve the lithium carbonate sample with acid to obtain an acidified sample solution; This step converts the lithium carbonate sample into an ionic state and ensures that heavy metal elements exist in the form of free cations. S2. Alkalization: Adjust the pH of the acidified sample solution to 9.5-10.5 using an alkaline buffer solution; In this step, the acidified sample solution is adjusted to pH 9.5-10.5 to enable the iminodiacetic acid type resin to more efficiently chelate and adsorb various divalent metal ions (especially barium ions Ba). 2+ ); S3. Adsorption separation: The alkalized solution obtained in step S2 is passed through a solid-phase extraction column packed with iminodiacetic acid-type chelating resin, so that heavy metal ions such as copper, cadmium, nickel, cobalt, zinc, lead, and barium ions in the alkalized solution are adsorbed onto the resin. In this step, under the set pH conditions, Cu 2+ Cd 2+ Ni 2+ Co 2+ Zn 2+ Pb 2+ Ba 2+ It is specifically chelated and adsorbed by the resin, while a large amount of Li + NH4 + NO3 － The matrix and impurity ions flow out with the solution, thereby achieving the separation of the target impurity elements from the main matrix; S4. Elution: Elute the heavy metal ions adsorbed on the resin with acid solution, collect the eluent, and complete the separation and enrichment. In this step, the acidic environment disrupts the chelation between metal ions and resin, quantitatively eluting the adsorbed heavy metal ions and collecting a small volume of pure eluent with low matrix and high enrichment factor.

[0008] Further, in S1, the specific steps of dissolution are as follows: weigh the lithium carbonate sample, wet it with water, and then add acid until the sample is completely dissolved. Here, slight heating or standing can be used to completely dissolve the sample.

[0009] Furthermore, the acid is nitric acid, and the amount of nitric acid added is 0.5-2 mL. The amount of nitric acid used is related to the weight of lithium carbonate weighed out, and the purpose is to ensure that the lithium carbonate is completely dissolved.

[0010] Further, in S2, the alkaline buffer solution is an ammonia-ammonium acetate mixture; wherein the volume ratio of ammonia to ammonium acetate solution is 1:1, and the amount of ammonia-ammonium acetate mixture added is 1.3-20 mL. Ammonium acetate provides a stable buffer environment, preventing excessively high local pH from causing certain metal ions (such as lead and cadmium) to precipitate as hydroxides.

[0011] Preferably, in step S2, the acidified sample solution is adjusted to pH=10.

[0012] At pH 10, iminodiacetic acid type resins efficiently chelate and adsorb various divalent metal ions (especially barium ions Ba). 2+ (The optimal conditions)

[0013] Furthermore, in step S3, prior to the adsorption separation step, an activation step is included, wherein the activation is performed by rinsing with an acid solution, ultrapure water, and an alkaline buffer solution in sequence.

[0014] Furthermore, in S4, the acid solution is a nitric acid solution with a volume fraction of 2%-10%.

[0015] Preferably, in step S4, the acid solution is a nitric acid solution with a volume fraction of 5%-10%.

[0016] In a second aspect, the present invention provides a method for determining the content of copper, cadmium, nickel, cobalt, zinc, lead and barium in lithium carbonate, comprising: separating and enriching a lithium carbonate sample using the method described in any one of the above methods, collecting the eluent; and then using atomic spectroscopy or mass spectrometry to quantitatively analyze the heavy metal elements in the eluent.

[0017] Furthermore, the atomic spectroscopy or mass spectrometry detection technology is specifically any one of inductively coupled plasma mass spectrometry (ICP-MS), graphite furnace atomic absorption spectrometry (GF-AAS), or inductively coupled plasma optical emission spectrometry (ICP-OES).

[0018] Thirdly, the present invention provides an application of the method described in any of the above in the purity detection, product quality control, or trace impurity element analysis of high-purity lithium carbonate products such as pharmaceutical-grade lithium carbonate and battery-grade lithium carbonate.

[0019] Beneficial Effects: The method of this invention effectively overcomes the inhibition and interference of the lithium carbonate matrix on the detection of trace heavy metals through specific pH control, and in particular significantly improves the adsorption and recovery rate of elements such as barium. It achieves efficient separation and enrichment of multiple heavy metals in complex matrices, providing a reliable pretreatment solution for high-sensitivity and high-accuracy quality control analysis of lithium carbonate products. Compared with existing technologies, the specific beneficial effects are as follows: 1. Highly efficient matrix elimination: The specific adsorption column can selectively retain target heavy metals and almost completely remove high-concentration lithium matrix, fundamentally solving the problems of matrix inhibition, cone blockage and background interference in instrument analysis such as ICP-MS.

[0020] 2. High recovery of multiple elements simultaneously: By precisely controlling the "acid dissolution (stabilizing ions) - alkalization (optimizing adsorption conditions)" process, seven elements with different properties, Cu, Cd, Ni, Co, Zn, Pb and Ba, can all obtain high and stable recovery rates (usually up to 80%-97%) under the same conditions. The recovery rate of barium, which is relatively low in traditional methods, has been particularly optimized.

[0021] 3. Significant enrichment effect: Trace impurities in the sample are adsorbed from a large volume of sample solution and eluted with a small volume of acid, achieving pre-enrichment of impurity elements and effectively reducing the detection limit of the method.

[0022] 4. High method versatility: The pretreatment process is standardized, and the purified sample solution has strong compatibility. It is not only suitable for high-end ICP-MS, but also for various detection equipment such as GF-AAS and ICP-OES, which improves the versatility of the method.

[0023] 5. Simple and efficient operation: Compared with complex separation methods such as coprecipitation, solid phase extraction columns are simple and fast to operate, easy to achieve batch processing, consume less reagents, and are environmentally friendly. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the embodiments.

[0025] The reagents and instruments used in this invention are as follows: Lithium carbonate sample (battery grade); Nitric acid, ammonia, and ammonium acetate (analytical grade); Iminodiacetic acid type resin solid phase extraction column (0.5g packing material, 1mL column volume); Inductively coupled plasma mass spectrometry (ICP-MS).

[0026] Implementation method 1: This embodiment provides a method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium from lithium carbonate, as detailed below: 1. Separation and enrichment steps: (1) Dissolution: Accurately weigh 0.2 g (accurate to 0.0001 g) of lithium carbonate sample into a 50 mL polytetrafluoroethylene beaker. Add 1 mL of ultrapure water to wet the sample, and then slowly add 0.5 mL of concentrated nitric acid. Gently shake until the sample is completely dissolved and no bubbles are generated.

[0027] (2) Alkalization: Add 4.2 mL of (1+1) ammonia-ammonium acetate mixture (made by mixing 20 mL of ammonia and 20 mL of 3 mol / L ammonium acetate solution fresh for use) to the above solution, then bring the volume to 50.0 mL with ultrapure water and mix thoroughly. The pH of the solution at this time is about 10.

[0028] (3) Purification and elution: a. Column activation: The extraction column was rinsed sequentially with 10 mL of 5% nitric acid, 10 mL of ultrapure water, and 5 mL of 1 mol / L ammonium acetate-ammonia solution (pH=10) at a flow rate of approximately 3 mL / min.

[0029] b. Sample loading and adsorption: Accurately transfer 20.0 mL of the alkalized sample solution and pass it through the activated extraction column at a flow rate of approximately 3 mL / min.

[0030] c. Eluting to remove impurities: Elute the column with 5 mL of 1 mol / L ammonium acetate-ammonia solution (pH=10), discarding all eluent to remove residual lithium matrix.

[0031] d. Elution and enrichment: Elute with 10.0 mL of 5% nitric acid solution at a flow rate of about 2 mL / min to remove all seven adsorbed heavy metals, and collect the eluent in a clean injection tube.

[0032] 2. Testing: (1) The collected eluent was analyzed directly by ICP-MS. Rh or In was used as an online internal standard, and the standard curve method was used for detection.

[0033] (2) Calculate the content of each heavy metal element in the sample.

[0034] 3. Method Validation: The method was validated using a spiked recovery experiment. A certain amount of mixed standard solution was added to a lithium carbonate sample with known low background, and the sample was processed and analyzed according to the above steps. The results showed that the recoveries of the seven elements were between 80% and 97%, and the relative standard deviation (RSD) was less than 5%, indicating that the method is accurate and reliable. The experimental data are shown in Table 1.

[0035] Implementation Method 2: This embodiment is largely the same as Embodiment 1, except that the alkalization step in this embodiment is as follows: 1.3 mL of a (1+1) ammonia-ammonium acetate mixture (made by mixing 20 mL of ammonia and 20 mL of 3 mol / L ammonium acetate solution fresh for use) is added to the above solution, and then the volume is adjusted to 50.0 mL with ultrapure water and thoroughly mixed. At this point, the pH of the solution is approximately 9.5.

[0036] Apart from the above, this implementation method is exactly the same as implementation method 1, and will not be described again here.

[0037] The recovery was verified using a spiked recovery experiment. A certain amount of mixed standard solution was added to a lithium carbonate sample with known low background, and the sample was processed and analyzed according to the above steps. The results showed that the recoveries of the seven elements were between 80% and 95%, and the relative standard deviation (RSD) was less than 5%, indicating that the method is accurate and reliable. The experimental data are shown in Table 2:

[0038] Implementation Method 3: This embodiment is largely the same as Embodiment 1, except that the alkalization step in this embodiment is as follows: 20 mL of a (1+1) ammonia-ammonium acetate mixture (made by mixing 20 mL of ammonia and 20 mL of 3 mol / L ammonium acetate solution fresh for use) is added to the above solution, and then the volume is adjusted to 50.0 mL with ultrapure water and thoroughly mixed. At this point, the pH of the solution is approximately 10.5.

[0039] Apart from the above, this implementation method is exactly the same as implementation method 1, and will not be described again here.

[0040] The method was validated using a spiked recovery experiment. A certain amount of mixed standard solution was added to a lithium carbonate sample with known low background, and the sample was processed and analyzed according to the above steps. The results showed that the recoveries of the seven elements were between 80% and 93%, and the relative standard deviation (RSD) was less than 5%, indicating that the method is accurate and reliable. The experimental data are shown in Table 3.

[0041] Comparative Example 1: As a comparative example, a recovery experiment was conducted on a 0.2 g (accurate to 0.0001 g) lithium carbonate sample. The sample was dissolved in 0.5 mL of nitric acid and diluted to 50 mL. After shaking, the sample was directly analyzed by ICP-MS to calculate the recovery rate. The results showed that: (1) the lithium matrix signal was extremely strong, while the signals of elements such as Cu, Cd, Ni, Co, Zn, Pb, and Ba were suppressed, and the measured values ​​were significantly lower; (2) after analyzing multiple samples, white deposits were visible blocking the cone pores of the sampling cone. The experimental data are shown in Table 4.

[0042] After processing using the method of this invention, the lithium content in the eluent is extremely low, the signal of the target element is stable, the recovery rate is ideal, and the key components of the instrument are protected. Comparative Example 2:

[0043] As a comparative example, a recovery experiment was conducted on a 0.2 g (accurate to 0.0001 g) lithium carbonate sample. The sample was dissolved in 0.5 mL of nitric acid, and then diluted to 50 mL (pH 4-7) with 1 mol / L ammonium acetate solution. After shaking, the sample was purified by an exchange column and analyzed by ICP-MS to calculate the recovery rate. The results showed that: (1) the recovery rates of Cu, Cd, Ni, Co, Zn, and Pb were ≥70%, and no sediment was found in the sampling cone after continuous analysis of multiple samples; (2) the recovery rate of Ba was ≤10%, and the measured value was significantly lower than expected. The experimental data are shown in Table 5.

[0044] After processing using the method of this invention, the recovery rates of Cu, Cd, Ni, Co, Zn, Pb, and Ba are all ≥80%.

[0045] Meanwhile, the method of this invention has been successfully applied to the quality inspection of high-purity lithium carbonate products provided by multiple companies. Verification has shown that this method can stably and accurately determine impurity elements such as Cu, Cd, Ni, Co, Zn, Pb, and Ba at levels as low as 0.01 mg / kg, fully meeting the impurity control requirements of current battery material industry standards.

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium from lithium carbonate, characterized in that, Includes the following steps: S1. Dissolution: Dissolve the lithium carbonate sample with acid to obtain an acidified sample solution; S2. Alkalization: Adjust the pH of the acidified sample solution to 9.5-10.5 using an alkaline buffer solution; S3. Adsorption separation: The alkalized solution obtained in step S2 is passed through a solid-phase extraction column packed with iminodiacetic acid-type chelating resin, so that heavy metal ions such as copper, cadmium, nickel, cobalt, zinc, lead, and barium ions in the alkalized solution are adsorbed onto the resin. S4. Elution: Elute the heavy metal ions adsorbed on the resin with acid, collect the eluent, and complete the separation and enrichment.

2. The method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium from lithium carbonate according to claim 1, characterized in that: In S1, the specific steps of dissolution are as follows: weigh the lithium carbonate sample, add water to wet it, and then add acid until the sample is completely dissolved.

3. The method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium from lithium carbonate according to claim 2, characterized in that: The acid is nitric acid, and the amount of nitric acid added is 0.5-2 mL.

4. The method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium from lithium carbonate according to claim 1, characterized in that: In S2, the alkaline buffer solution is a mixture of ammonia and ammonium acetate; wherein the volume ratio of ammonia to ammonium acetate solution is 1:1, and the amount of ammonia-ammonium acetate mixture added is 1.3-20 mL.

5. The method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium from lithium carbonate according to claim 1, characterized in that: In step S2, the acidified sample solution is adjusted to pH = 10.

6. The method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium from lithium carbonate according to claim 1, characterized in that: In step S3, prior to the adsorption separation step, there is also a step of activating the solid-phase extraction column, wherein the activation is performed by rinsing with an acid solution, ultrapure water and an alkaline buffer solution in sequence.

7. The method for simultaneously separating and enriching copper, cadmium, nickel, cobalt, zinc, lead, and barium from lithium carbonate according to claim 1, characterized in that: In S4, the acid solution is a nitric acid solution with a volume fraction of 5%-10%.

8. A method for determining the content of copper, cadmium, nickel, cobalt, zinc, lead, and barium in lithium carbonate, characterized in that, include: The lithium carbonate sample is separated and enriched using the method described in any one of claims 1-7, and the eluent is collected. Then, atomic spectroscopy or mass spectrometry was used to quantitatively analyze the heavy metal elements in the eluent.

9. The method for determining the content of copper, cadmium, nickel, cobalt, zinc, lead, and barium in lithium carbonate according to claim 8, characterized in that: The atomic spectroscopy or mass spectrometry detection technology specifically refers to any one of inductively coupled plasma mass spectrometry, graphite furnace atomic absorption spectrometry, or inductively coupled plasma emission spectrometry.

10. The application of the method as described in any one of claims 1-7 or any one of claims 8-9 in the purity detection, product quality control, or trace impurity element analysis of high-purity lithium carbonate products such as pharmaceutical-grade lithium carbonate and battery-grade lithium carbonate.

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