JP2020091275A - Lithium evaluation method - Google Patents

Abstract

To provide a technique that can correctly and accurately evaluate lithium contained in a sample even when a coexistence element is included, without being affected by various problems specific to a relative analysis method using an equipment analyzer.SOLUTION: A lithium evaluation method is characterized by calculating a content of lithium by separating the lithium contained in a sample in a form of a lithium compound and measuring a weight of the lithium compound.SELECTED DRAWING: Figure 1

Description

The present invention relates to a lithium evaluation method.

Lithium, which is one of the rare metals, is used in ceramics, heat-resistant glass, optical glass, and other ceramic materials, as well as various batteries for small electronic devices, automobiles, and in-house power generation, as well as drugs for depression. It is widely used as medical and pharmaceutical products, heat and pressure resistant grease, flux for continuous casting of steel and polymerization catalyst for synthetic rubber, and most of lithium is in the form of lithium compounds such as lithium carbonate. It is used. Lithium carbonate is used as a positive electrode material and an electrolyte of a lithium ion battery (LIB), and the demand thereof has been rapidly increasing in recent years. Lithium hydroxide is also mainly used as a positive electrode material for lithium-ion batteries and is also used in automobile grease. In addition, lithium bromide is used as a refrigerant absorbing material for large-scale air-conditioning absorption refrigerators in buildings and factories, and lithium chloride is used as an air-conditioning dehumidifying agent and welding flux. Metallic lithium is a raw material for butyllithium for primary battery negative electrode foil materials and synthetic rubber catalysts.In addition to the form of compounds and metals, lithium ore is directly used as a melting point depressant in the ceramics field. Has been.

As described above, since lithium has a wide range of industrial uses and is in great demand, it has been studied how to accurately evaluate the lithium content of intermediates and final products obtained in the manufacturing process of each field.・Development has been carried out.

As a method for evaluating the lithium content, an ion chromatography method has been proposed in Patent Document 1 and Patent Document 2. Further, the ICP method is proposed in Patent Document 3.

JP-A-11-287793 JP, 2010-25791, A JP, 2010-78381, A

These evaluation methods were relative analysis methods that required an instrumental analysis device and required standard substances and standard solutions that served as the scale of analysis. For this reason, there is a problem that the accuracy of analysis of lithium decreases due to the instrumental analysis device, such as a relative error of 1 to 3% depending on the stability of the plasma in the inductively coupled plasma (ICP) emission spectroscopic analysis device. It was Further, these relative analysis methods have a problem that the analysis accuracy of lithium is lowered due to the influence of ionization interference and optical interference received from other coexisting elements.

On the other hand, there is an absolute analysis method which is an evaluation method for measuring the absolute amount of the evaluation element. In this method, since it is not necessary to compare the standard substance and the sample with the instrument analyzer, it is possible to prevent the decrease in the analysis accuracy due to the instrument analyzer as described above. Further, in this method, since the absolute amount of the evaluation element is measured, it is possible to prevent a decrease in analysis accuracy due to the influence of other coexisting elements. For this reason, the absolute analysis method has an advantage over the relative analysis method in that high-precision analysis is possible.

However, with an alkali metal such as lithium, there is a problem that it is very difficult to apply the gravimetric method or the titration method, which allows highly accurate analysis, due to its nature.

The present invention has been made in view of the above problems, and by using the gravimetric method, which is an absolute analysis method, for lithium contained in a sample, it is affected by various problems peculiar to a relative analysis method by an instrumental analyzer. It is another object of the present invention to provide a technique that enables accurate and highly accurate evaluation even when a coexisting element is contained.

As a result of research, the present inventor has separated lithium from coexisting elements such as nickel, cobalt, manganese, and aluminum contained in a sample by utilizing ion exchange operation, precipitation operation, and electrolysis operation, and further in the process of operation. By decomposing and removing the produced by-products such as ammonium sulfate, it has been found that the weight of lithium can be finally weighed in the form of a lithium compound including lithium sulfate.

In a first aspect of the present invention, a lithium evaluation method is provided, in which lithium contained in a sample is separated in the form of a lithium compound and the weight of the lithium compound is weighed to determine the lithium content. To do.

According to this aspect, the lithium contained in the sample can be accurately and highly accurately evaluated even when the coexisting element is contained, without being affected by various problems peculiar to the relative analysis method by the instrumental analyzer.

A second aspect of the present invention is, in the lithium evaluation method of the first aspect, a sample dissolving step of dissolving the weighed sample with an acid to obtain a solution, and then controlling the acid concentration of the solution. The dissolved solution whose acid concentration is controlled is passed through an ion-exchange resin column to obtain an effluent, and then an ion exchange step of controlling the acid concentration of the effluent, and the effluent whose acid concentration is controlled are treated with white smoke. After that, electrolysis is performed by adding an alkali to obtain an electrolysis residual liquid, the electrolysis residual liquid is fixed in volume, and a part of the electrolysis residual liquid is dispensed into a container, followed by heating and high heat with the container. Provided is a lithium evaluation method characterized by comprising a lithium compound production step of decomposing and removing a byproduct by performing to obtain a lithium compound, and an analysis step of weighing the lithium compound together with the container and quantifying lithium. To do.

In this way, the lithium contained in the sample can be evaluated accurately and with high accuracy without being affected by the problems peculiar to the relative analysis method by the instrumental analyzer, even when the coexisting element is contained.

A third aspect of the present invention is the lithium evaluation method of the second aspect, wherein the pH of the effluent whose acid concentration is controlled is adjusted with an acid and/or an alkali between the ion exchange step and the electrolysis step. , A method for evaluating lithium, comprising a precipitation step of producing a precipitate of a metal hydroxide by boiling, and filtering the precipitate to obtain a filtrate, wherein the filtrate is treated with white smoke in the electrolysis step. I will provide a.

By doing so, even when the sample contains aluminum or the like, lithium contained in the sample can be evaluated accurately and highly accurately.

A fourth aspect of the present invention provides the lithium evaluation method according to the first or second aspect, wherein the lithium compound is lithium sulfate.

From the viewpoint of hygroscopicity and complexity of the production process, lithium sulfate is preferable as the lithium compound to be weighed.

A fifth aspect of the present invention provides the lithium evaluation method according to the second aspect, wherein the acid is hydrochloric acid and the ion exchange resin column is an anion exchange resin column. ..

By doing so, coexisting elements such as cobalt, manganese, iron, and zinc can be adsorbed on the column in the form of a chloro complex and separated from lithium as the element to be analyzed.

A sixth aspect of the present invention provides the lithium evaluation method according to the second aspect, wherein the container is a quartz stoppered Erlenmeyer flask.

By doing so, it is possible to make it difficult for the droplets to scatter out of the container in the lithium compound producing step. Then, in the lithium analysis step, it is possible to prevent the lithium compound from absorbing moisture in the atmosphere and becoming a hydrate.

A seventh aspect of the present invention provides the lithium evaluation method of the second or third aspect, wherein the alkali in the lithium evaluation method is aqueous ammonia.

By using aqueous ammonia, it is possible to prevent impurities other than the coexisting elements derived from the sample from being newly mixed as impurities.

An eighth aspect of the present invention is the lithium evaluation method according to any one of the first to seventh aspects, wherein the sample contains at least one of nickel, cobalt, manganese, and aluminum. provide.

Even when the above coexisting element is contained, the lithium contained in the sample can be evaluated accurately and highly accurately.

A ninth aspect of the present invention provides the lithium evaluation method according to the second aspect, wherein the by-product is ammonium sulfate.

This makes it possible to prevent impurities other than the coexisting element derived from the sample from being newly mixed as impurities.

A tenth aspect of the present invention is the lithium evaluation method of the second aspect, wherein the lithium loss in the ion exchange step and the electrolysis step is determined by atomic absorption method, flameless atomic absorption method, ICP method, ICP-MS. The present invention provides a lithium evaluation method, which is characterized by using at least one of an ion chromatography method and an ion chromatography method.

In this way, the amount of lithium loss in the ion exchange process and the electrolysis process can be reflected, so that the lithium contained in the sample can be evaluated accurately and highly accurately.

An eleventh aspect of the present invention is the lithium evaluation method of the third aspect, wherein the lithium loss in the ion exchange step, the precipitation step and the electrolysis step is determined by atomic absorption method, flameless atomic absorption method, ICP method. , ICP-MS method, and ion chromatograph method are used to provide a lithium evaluation method.

By doing so, the loss of lithium in the ion exchange step, the precipitation step, and the electrolysis step can be reflected, so that the lithium contained in the sample can be evaluated accurately and highly accurately.

A twelfth aspect of the present invention is, in the lithium evaluation method according to any one of the first to eleventh aspects, after calculating the lithium content, the lithium compound is used as one or more of an ICP method and an ICP-MS method. Provided is a method for evaluating lithium, which is characterized by performing a qualitative analysis using.

In this way, it can be confirmed that the coexisting element does not remain in the lithium compound obtained in the lithium analysis step, so that the lithium contained in the sample can be evaluated accurately and highly accurately.

A thirteenth aspect of the present invention provides the lithium evaluation method according to any one of the first to twelfth aspects, characterized in that the lithium compound is morphologically analyzed using an X-ray diffraction method. To do.

By doing so, it is possible to confirm that the obtained lithium compound is neither hydrated by moisture absorption nor carbonated by carbon dioxide in the atmosphere. Therefore, the lithium contained in the sample can be accurately evaluated with high accuracy.

According to the present invention, by using the gravimetric method, which is an absolute analysis method, for the lithium contained in the sample, it is not affected by the problems peculiar to the relative analysis method by the instrumental analyzer, and even when the coexisting element is contained. Can be evaluated accurately and with high accuracy.

FIG. 1 is a flowchart for explaining a lithium evaluation method according to one aspect of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unreasonably limit the content of the present invention described in the claims, and can be modified without departing from the gist of the present invention. In addition, not all of the configurations described in the present embodiment are essential as solving means of the present invention.

The lithium evaluation method according to one embodiment of the present invention is based on a gravimetric method in which the weight of lithium contained in a sample is directly weighed, and evaluates lithium by an absolute analysis method.

Here, as a lithium evaluation method that has been performed since the past, the atomic absorption method, the flame light method, and the ICP method and the ion chromatography method are typical examples.

For example, as an ion chromatographic method, a sample is heated and decomposed with a mixed acid of hydrochloric acid, nitric acid, and water, then hydrogen peroxide water is added and boiled, and then a measurement solution in which rubidium is added as an internal standard element is used as an ion chromatographic method. (Patent Document 1), a separation column filled with a cation exchange resin, and an ion chromatograph equipped with an anion-exchange suppressor are used to heat a sample with nitric acid and hydrogen peroxide solution. There is a method of measuring at least one of potassium, ammonium and amine compounds as an internal standard element in a measurement solution obtained by decomposition (Patent Document 2). Further, as an ICP method, when a sample solution obtained by thermally decomposing a sample with nitric acid and hydrogen peroxide solution is measured with an inductively coupled plasma (ICP) emission spectroscopic analyzer, the plasma excitation temperature is set to 4900 K or higher and measured. In addition, the internal standard method is applied to, and when the analysis target element contains at least two kinds of lithium, nickel, cobalt, manganese, and aluminum, gallium is used as the internal standard element for lithium, aluminum, and manganese. There is a method (Patent Document 3) in which copper is used for nickel, cobalt and cobalt.

However, in the atomic absorption method, the flame light method, and the ICP method, the analysis accuracy is usually a relative error of 1 to 3% mainly due to the flame flame or the stability of the plasma, and a higher accuracy analysis is required. In the case of carrying out, it is necessary to take appropriate measures against ionization interference and optical interference received from other coexisting elements. In the ion chromatograph method, sample weighing operation, thermal decomposition operation, constant volume operation to adjust the volume of the solubilized sample to a fixed amount, sample solution, and dilution to dilute the standard solution for calibration curve to a fixed rate There has been a problem that the accuracy of lithium analysis is markedly reduced by continuously performing a series of pretreatment operations such as an operation.

By the way, the internal standard method is a standard solution of a calibration curve method, and both a measurement solution in which a sample is pretreated, in the measurement with an analyzer, an element exhibiting a physical behavior similar to the element to be analyzed, This is a method to correct the measured value of the analysis target element by adding a fixed amount as an internal standard element and monitoring the effect on the internal standard element (originally, the sample does not contain the internal standard element). .. And, originally, in the measurement by the analyzer, it is a method for correcting the physical interference that the element to be analyzed receives in the measurement, such as the decrease of the introduction efficiency of the measurement solution due to the influence of the matrix component.

However, in any of the above evaluation methods, the internal standard element may be added/mixed immediately after the sample is weighed, not at the measurement stage in the analyzer, and then the pretreatment operation may be performed. However, like the isotope dilution method (method of adding a certain amount of concentrated stable isotope of the element to be analyzed to the sample and correcting the measured value according to its behavior), which is adopted as the standard value determination method for standard substances, It is impossible for the element to be analyzed and the internal standard element to show exactly the same chemical and physical properties, and the difference in various properties between them is, for example, due to the complicated pretreatment operation. Strict attention is required because there is a risk that it will appear as a significant analytical error and will have an adverse effect.

Each of the above evaluation methods is a relative analysis method that requires an instrumental analyzer, and requires a standard substance and a standard solution that serve as a measuring scale for analysis.The only relative analysis method is the isotope dilution method. , It is a method to determine the standard value of the standard substance. On the other hand, from a long time ago, the standard value of a standard substance has been determined by a gravimetric method in which the weight of the element to be analyzed itself is directly weighed, or an analytical value based on the addition volume of a reagent that quantitatively reacts with the element to be analyzed. An absolute analysis method that does not require an instrumental analysis device has been adopted because it is a method based on stoichiometry, such as a volumetric method for obtaining However, even at present, it is said that it is very difficult to apply the gravimetric method or the titration method, which enables highly accurate analysis, to alkali metals such as lithium due to their properties.

For example, in the gravimetric method, lithium is analyzed and evaluated by measuring the weight of lithium contained in the sample. For that purpose, it is necessary to separate lithium and other coexisting elements. Further, in the highly accurate analysis, it is confirmed that the separated lithium does not contain an element other than lithium (also referred to as “coexisting element” in the present application) as an impurity, and the separated coexisting element does not contain lithium. Will be needed. The presence of these impurities and the like hinders accurate measurement of the lithium weight and significantly reduces the lithium analysis accuracy.

The coexisting elements include elements having various properties such as nickel, cobalt, manganese, and aluminum. For this reason, it was difficult to separate the lithium and the coexisting element so that impurities and the like were not included. In addition, when the alkali metal element is contained as an impurity, it is particularly difficult to separate it from lithium, so that there is a problem that the accuracy of analysis of lithium is significantly reduced. For this reason, there is a problem in that reagents containing an alkali metal element such as sodium hydroxide cannot be used during the separation of lithium for highly accurate analysis.

MEANS TO SOLVE THE PROBLEM In order to solve the above-mentioned subject, this inventor uses ion exchange operation, precipitation operation, and electrolysis operation as a means to separate lithium from a sample, and from nickel, cobalt, manganese, aluminum, etc. which are coexisting elements. , Focused on the ability to separate lithium. Further, in the lithium compound production step and the lithium analysis step, byproducts such as ammonium sulfate produced in the course of the operation are gently decomposed and removed, and finally, a lithium compound including lithium sulfate is finally removed. In the form, it was found that lithium can be evaluated accurately and highly accurately, and the present invention has been completed.

In the present application, “analysis” usually refers to “quantitative analysis”, and when “qualitative analysis” is performed, that fact is described each time. In addition, "quantitative analysis" is an analysis method for correctly determining the content of the analysis target component in the sample, and "qualitative analysis" is what the sample is and what component it is composed of. Or an analysis method for obtaining qualitative information such as how much the component to be analyzed is contained (also referred to as semi-quantitative). Generally, "qualitative analysis" reveals unknown ingredients and their rough contents, and then "quantitative analysis" is conducted on the components to be analyzed. If known, a “quantitative analysis” can be performed immediately.

The outline of the lithium evaluation method according to one aspect of the present invention will be described below.

[1. Overview of lithium evaluation method]
First, an outline of a lithium evaluation method will be described with reference to the drawings. FIG. 1 is a flowchart for explaining a lithium evaluation method according to one aspect of the present invention. As shown in FIG. 1, the lithium evaluation method according to one aspect of the present invention includes a sample dissolution step S1, an ion exchange step S2, a precipitation step S3, an electrolysis step S4, a lithium compound production step S5, and a lithium analysis step S6. It

[1-1. Sample dissolution step S1]
In the sample dissolving step S1, the sample is heated and decomposed with hydrochloric acid for the subsequent steps including the ion exchange step S2 described later, and hydrochloric acid is further added to control the acid concentration. In the ion exchange step S2 described below, it is preferable to dissolve the sample with hydrochloric acid in order to separate the coexisting element from lithium by adsorbing the chloro complex on the anion exchange resin column. Although the chloro complex produced varies depending on the acid concentration, the acid concentration is preferably 8 M or more and 12 M or less, and more preferably 9 M or more and 11 M or less. By controlling the acid concentration in this range, the adsorption capacity of the chloro complex of cobalt and manganese on the resin column can be optimized, so that these coexisting elements and lithium can be separated in the ion exchange step S2. it can. If the acid concentration is less than 8M, the cobalt chloro complex is not sufficiently adsorbed on the resin column, and lithium and coexisting elements cannot be separated.

[1-2. Ion exchange step S2]
In the ion exchange step S2, an anion exchange resin column is used, and coexisting elements such as cobalt, manganese, iron, and zinc are adsorbed on the column in the form of a chloro complex (complex anion), and lithium as an element to be analyzed is removed from the column. Drain. This makes it possible to separate lithium and coexisting elements. By the way, when a cation exchange resin column is used, lithium is adsorbed to the column, but with a simple liquid such as hydrochloric acid, coexisting elements such as nickel, cobalt, manganese, and aluminum are also contained in the column. It is difficult to completely separate lithium because it is adsorbed and remains on. However, also in the anion-exchange resin column, nickel, aluminum, and the like do not form a chloro complex (complex anion) in addition to lithium, so they flow out from the column together with lithium.

[1-3. Precipitation step S3]
In the precipitation step S3, coexisting elements such as aluminum that could not be separated from lithium in the ion exchange step S2 are separated in the form of metal hydroxide. Ammonia water is preferable as the alkali for controlling the precipitation pH. By using aqueous ammonia, it is possible to prevent alkali metal elements such as sodium and potassium from being mixed as impurities, and lithium can be accurately and highly accurately evaluated in a lithium analysis step S6 described later. Further, by using aluminum hydroxide as the coexisting element such as aluminum, the coexisting element can be separated from lithium. Furthermore, by using ammonium sulfate as a by-product generated in the electrolysis step S4 described later, ammonium sulfate can be removed as gaseous ammonia, gaseous sulfur dioxide, nitrogen gas, and water vapor in the lithium compound production step S5 described later. .. For this reason, it is possible to prevent a by-product described below from remaining as a solid in the lithium compound production step S5, so that lithium can be evaluated accurately and highly accurately in the lithium analysis step S6.

Alkali other than aqueous ammonia, such as aqueous sodium hydroxide solution, cannot be used as an alkali for controlling the precipitation pH because sodium and potassium, which are the same alkali metal elements as lithium, are mixed as impurities. Therefore, also in the precipitation step S3, nickel and the like, which do not precipitate as a metal hydroxide, remain in the filtrate together with lithium by forming the ammonia water and the ammine complex. If aluminum or the like is not contained in the sample, this precipitation step S3 can be omitted.

[1-4. Electrolysis step S4]
In the electrolysis step S4, coexisting elements such as nickel that could not be separated from lithium in the ion exchange step S2 and the precipitation step S3 are deposited and separated in the form of metal on the platinum cathode. At the stage after this electrolysis step S4, lithium can be separated from all coexisting elements. In the electrolysis step S4, ammonia water is added to the effluent obtained in the ion exchange step S2 to make it alkaline, and constant current electrolysis is performed as described later. The reason for using the ammonia water and the effect thereof are the same as those described in the outline of the precipitation step S3, and therefore will be omitted. In the electrolysis step S4, since sulfuric acid is used for the pretreatment of the sample and the electrolytic solution is ammoniacal, ammonium sulfate remains as a by-product together with lithium in the electrolytic residual solution.

[1-5. Lithium compound production step S5]
In the lithium compound producing step S5, ammonium sulfate, which is a by-product, is decomposed and removed by various operations such as heat concentration, evaporation to dryness, and intense heat, and only a lithium compound is produced. As described above, ammonium sulfate can be removed as gaseous ammonia, gaseous sulfur dioxide, nitrogen gas, and water vapor in this step. Therefore, it is possible to prevent the by-product from remaining as a solid, so that lithium can be accurately and highly accurately evaluated in a lithium analysis step S6 described later. However, in each of these operations, especially when evaporating to dryness or high heat, when the amount of by-product ammonium sulfate increases, the droplets easily disperse, and when the droplets go out of the container, the lithium contained in the droplets is lost. And cause a large error. By performing this step using a quartz stoppered Erlenmeyer flask, it is possible to make it difficult for the droplets to disperse outside the container during evaporation to dryness or strong heat, and to prevent loss of lithium contained in the droplets. Can be prevented. Therefore, lithium can be evaluated accurately and highly accurately.

[1-6. Lithium analysis step S6]
In the lithium analysis step S6, the produced lithium compound is allowed to cool and then weighed by an electronic balance. However, since lithium compounds have strong hygroscopicity depending on the type, they tend to absorb moisture in the air and become anhydrous salts to hydrates. Here, by performing the decomposition and removal of the by-product in the lithium compound production step S5 using the quartz stoppered Erlenmeyer flask, the lithium analysis step can be performed in a state of being shielded from the atmosphere. Therefore, it is possible to prevent a weight change due to hygroscopicity, and to evaluate lithium accurately and highly accurately. Note that after obtaining the weight of the lithium compound, the lithium compound is dissolved in water, and ICP qualitative analysis and ICP-MS qualitative analysis are performed using the aqueous solution, whereby the coexisting element does not remain in the lithium compound. You can check. Thereby, the lithium contained in the sample can be evaluated accurately and highly accurately.

Further, as will be described later, the lithium lost in the ion exchange step S2, the precipitation step S3, and the electrolysis step S4 is treated by one of atomic absorption method, flameless atomic absorption method, ICP method, ICP-MS method, and ion chromatography method. It is possible to analyze using the above. Then, the lithium content can be calculated by reflecting the lithium loss in each step in the measurement result of the lithium analysis step S6. Therefore, lithium can be evaluated accurately and highly accurately.

As described above, the present invention has been made based on the above findings obtained as research results, and has the above effects.

[2. Lithium evaluation method]
<One Embodiment of the Present Invention>
Hereinafter, a lithium evaluation method according to an embodiment of the present invention will be described.

In the present embodiment, the sample indicates at least one of nickel, cobalt, manganese, and aluminum, and the case of evaluating lithium in the sample is taken as an example.

The lithium evaluation method of the present embodiment includes a sample dissolution step S1, an ion exchange step S2, a precipitation step S3, an electrolysis step S4, a lithium compound production step S5, and a lithium analysis step S6. The details of each step will be described below.

[2-1. Sample dissolution step S1]
In the sample dissolving step S1, first, about 0.5 to 2 g of a sample to be analyzed is weighed by an electronic balance, and then water and hydrochloric acid are added and dissolved to obtain a solution. In addition, for heating and cooling in the beaker, the watch glass is used as a lid as necessary including the subsequent steps.

By the way, when performing the gravimetric method, in the course of analysis, elements other than the coexisting elements derived from the sample are newly mixed as impurities, which not only increases unnecessary separation operation, but also makes separation difficult and makes the analysis itself impossible. There is a fear. Therefore, the dissolution of the sample does not have a large adverse effect on the subsequent steps including the ion exchange step S2, and therefore it is preferable to treat the sample so that it becomes a simple liquid such as an inorganic acid. It is preferable to avoid the treatment by alkali melting such as.

In the ion exchange step S2 of the next step, in order to adsorb and separate as many kinds of coexisting elements contained in the sample as possible, the liquid property of the solution is hydrochloric acid rather than nitric acid or sulfuric acid. Is preferred. The acid concentration of hydrochloric acid may vary depending on the types of coexisting elements to be separated. For example, for cobalt and manganese, hydrochloric acid is 10 mol (hereinafter also simply referred to as “M”), for iron, hydrochloric acid is 8M, and zinc is 8M. If so, it is preferable to use hydrochloric acid 2M.

[2-2. Ion exchange step S2]
In the ion exchange step S2, as described above, an anion exchange resin column, which is an ion exchange resin having an amino group introduced as a functional group and capable of exchanging anions such as chloride ion and sulfate ion, is used. To do. As the anion exchange resin to be packed in the column, other than Dowex: Dowex (registered trademark) series manufactured by The Dow Chemical Company, Amberlite: Amberlite (registered trademark) series manufactured by Organo Co., etc. are put on the market. It is possible to use a strongly basic one or a weakly basic one which is widely spread. For example, in the case of a strongly basic one, a type I Dowex-1x8 (100 having a trimethylammonium group is used. -200 mesh) and the like.

As the anion exchange resin column, for example, a column based on JIS-M-8129 (a method for determining cobalt in ore) can be used. A glass column tube with a cock (inner diameter: approx. 25 mm, chromatographic length: approx. 350 mm) is loosely packed with absorbent cotton (glass cotton or Teflon cotton) loosened in water to a thickness of 5-10 mm The anion exchange resin (strongly basic, Cl ⁻ type) swollen with is made into a slurry and poured. After the resin has settled, water-loospered absorbent cotton is loosely packed to a thickness of 5-10 mm. Further, the packing method of the absorbent cotton and the opening degree of the cock are adjusted, and the flow rate of the effluent is controlled to be about 3 to 5 mL (SV=1 to 2) per minute.

Here, while BV (Bed Volume) is a unit indicating how many times the resin volume is passed, SV (Space Velocity) is a unit per hour. , A unit indicating how many times the resin volume is passed.

The anion exchange resin is regenerated to OH ⁻ form with aqueous ammonia (7+100) as shown in formula (I), and then Cl 2 is added with hydrochloric acid (1+100) as shown in formula (II). ^It is preferable to use it after exchanging the mold. Here, "1+100" means hydrochloric acid 1+water 100 by volume in the case of hydrochloric acid. Further, in the following formulas (I) and (II), A represents a matrix of the ion exchange resin.
A-N.Cl + NH ₄ OH → A-N-OH + NH ₄ Cl (I)
A-N · OH + HCl → A-N · Cl + H 2 O (II)

By performing the above operation, it is possible to prevent a decrease in the adsorption capacity that may occur due to the deterioration of the anion exchange resin due to continuous use. Regeneration is performed in the order of hydrochloric acid (1+100)→water→ammonia water (7+100)→water→hydrochloric acid (1+100) in the order of a liquid amount corresponding to the amount of anion exchange resin used, that is, 360 mL each in the above example Pass through the column.

Before passing the solution obtained in the sample dissolving step S1 through the column, the prepared hydrochloric acid having the same acid concentration as that of the solution is passed through the column so that the entire column is filled with the prepared hydrochloric acid. Further, after passing the solution through the column, lithium is completely discharged from the column by using at least twice the resin volume of the prepared hydrochloric acid. The obtained effluent is once subjected to heat concentration and evaporation to dryness for a later step, and then the produced salt is dissolved again by heating with water and hydrochloric acid to control the concentration of the predetermined hydrochloric acid. If the concentration of hydrochloric acid is too low, the salts produced by evaporation to dryness become undissolved, which hinders accurate measurement of the weight of lithium and significantly reduces the accuracy of lithium analysis. The concentration of hydrochloric acid is not particularly limited as long as it can dissolve salts, but the higher the concentration of hydrochloric acid, the more the amount of ammonia water used in the precipitation step, and it takes time to remove hydrochloric acid in the pretreatment of the electrolysis step. The cost and time required for lithium analysis increases. From the viewpoints of analysis accuracy, cost and time, the hydrochloric acid concentration is preferably 1 M or more and 2 M or less.

The coexisting element adsorbed on the column can be eluted from the column by using a prepared hydrochloric acid suitable for each element, or by using an eluent in which 1 g of ascorbic acid is dissolved in 1 L of hydrochloric acid (1+9). In addition, the coexisting elements contained in the obtained recovery liquid are used together with lithium lost in the ion exchange operation (remaining in the column), atomic absorption method, flameless atomic absorption method, ICP method, ICP-MS method, ion chromatography method. It is possible to analyze using at least one of the above.

As the next step of the ion exchange step S2, when the sample contains aluminum or the like, the precipitation step S3 is omitted. When the sample does not contain aluminum or the like, the precipitation step S3 is omitted and the process proceeds to the electrolysis step S4.

[2-3. Precipitation step S3]
In the precipitation step S3, when the sample contains aluminum or the like, water is added to the effluent whose acid concentration is controlled in the ion exchange step S2 to adjust the liquid volume, and then hydrochloric acid (1+1) and/or ammonia water is used. The precipitation pH is controlled to a predetermined value, and the coexisting element is precipitated and separated in the form of a metal hydroxide. The precipitation pH is preferably 5 or more and 10 or less, more preferably 6 or more and 9 or less. By controlling the precipitation pH within these ranges, aluminum can be precipitated as aluminum hydroxide and lithium and coexisting elements can be separated. As described above, as the alkali for controlling the precipitation pH, ammonia water is used, which does not newly mix as an impurity other than the coexisting element derived from the sample. In order to reduce the amount of ammonium sulfate produced in the subsequent lithium compound producing step S5, it is particularly preferable to reduce the amount of ammonia water added as carefully as possible by carefully controlling the precipitation pH. An ammonium salt such as ammonium chloride can be added together as a pH buffer, but in this case as well, be careful not to increase the addition amount too much. Further, from the viewpoint of separation from coexisting elements, it is particularly preferable to heat the effluent at a low temperature and boil to precipitate the precipitate before separating and collecting the precipitate of the metal hydroxide. By boiling, the rate of formation of the precipitate is increased, and the precipitation particles can be coarsened while suppressing the adsorption of other components by the precipitation, so that the separation of lithium and coexisting elements can be promoted. In addition, the washing efficiency of the precipitate can be improved. The precipitation separation can be carried out by a known means such as suction filtration in addition to ordinary natural filtration. Examples of the filter paper used for filtration include ordinary quantitative filter papers (5 types A defined in JIS P 3801, It is preferable to use 5 type B, 5 type C), cellulose acetate filter paper, hydrophilic PTFE filter paper, or the like. In addition, the separated precipitate may be washed with pure water or diluted ammonia water 5 to 6 times.

The coexisting element precipitated in the form of a metal hydroxide is dissolved by, for example, warm hydrochloric acid (1+1), and is absorbed together with lithium lost in the precipitation operation (remains in the precipitation) by atomic absorption method, flameless atomic absorption method, ICP method, It is possible to analyze using at least one of the ICP-MS method and the ion chromatograph method.

[2-4. Electrolysis step S4]
In the electrolysis step S4, sulfuric acid (1+1) is added to the effluent having the acid concentration controlled in the ion exchange step S2 or the filtrate obtained in the precipitation step S3 to heat and concentrate it to generate white smoke. The liquid volume is adjusted with sulfuric acid (1+1) and water, and ammonia water is added to make it alkaline, and constant current electrolysis is performed. A commercially available electrolysis device can be used for electrolysis, and for example, an electrolysis analysis device AES-2D manufactured by Yanaco Technical Science Co., Ltd., an electrolysis analysis device ANA-2-2 manufactured by Tokyo Koden Co., Ltd., or the like can be used. You can As the electrode, a spiral platinum anode and a cylindrical platinum cathode described in JIS-H-1101 (copper ingot analysis method) can be used. After boiling in nitric acid (1+1), water, It is washed with ethanol and dried at 105°C for 30 minutes or more before use. In addition to the electrolytic beaker (200 mL tall beaker may be used), two semi-circular watch glasses are used, and the electrolysis conditions are set such that the current is 0.3 to 0.7 A and the time is 10 to 30 hours. Further, by the above heating concentration, hydrochloric acid in the effluent or the filtrate can be removed by evaporation. As a result, chlorine can be prevented from remaining as an impurity, so that lithium can be accurately and accurately evaluated in the lithium analysis step S6. Since sulfuric acid is a non-volatile acid and has a boiling point of 337° C., which is higher than the boiling point of hydrochloric acid of 110° C., it is possible to confirm that hydrochloric acid does not exist in the effluent or the filtrate due to generation of white smoke of sulfuric acid. In the present application, the operations of adding sulfuric acid, concentrating by heating and generating white smoke are also referred to as white smoke treatment.

The coexisting element deposited on the platinum cathode is analyzed by, for example, an electrolytic gravimetric method in which the dry weight of the platinum cathode before the electrolysis operation (before the coexisting element deposition) is subtracted from the platinum cathode dry weight after the electrolysis operation (after the coexisting element deposition). However, in addition to that, only the coexisting elements were thermally decomposed with nitric acid (1+1) from the platinum cathode after the electrolysis operation (after the coexisting element was deposited), and the lithium lost in the electrolysis operation (remaining on the platinum cathode side). At the same time, it is possible to analyze using at least one of atomic absorption method, flameless atomic absorption method, ICP method, ICP-MS method, and ion chromatography method.

[2-5. Lithium compound production step S5]
In the lithium compound production step S5, the electrolysis residual liquid obtained in the electrolysis step S4 is heated and concentrated, and once fixed to a predetermined liquid volume, an appropriate amount is aliquoted and transferred to an ignition container. By performing this operation, it is possible to reduce the amount of ammonium sulfate coexisting and to make it difficult for the droplets to scatter out of the container during evaporation to dryness or strong heat, as described above. It is particularly preferable to the case. Further, a quartz stoppered Erlenmeyer flask is used as the above-mentioned container for high heat. As a result, since the container mouth is narrowed, it is possible to make it difficult for the droplets to scatter out of the container during evaporation to dryness or high heat. Therefore, it is particularly preferable to use a platinum plate, a quartz plate, a magnetic plate, or the like. .. It should be noted that ammonium sulfate starts to gradually decompose from about 120° C., and releases ammonia at 357° C. to melt. During evaporation to dryness, the treatment is carried out within the range of 100 to 320° C. while adjusting the heating temperature so that the concentrated liquid does not bump. In the case of intense heat, if you treat it at a high temperature suddenly, the droplets will be easily scattered, so it is better to raise the temperature as gently as possible. Use an electric muffle furnace to change the temperature rise pattern from room temperature to 350°C (10 minutes). It is particularly preferable to carry out ignition under the conditions of →400°C (20 minutes) →450°C (10 minutes) and the temperature rising time to each set temperature is 10 minutes. Upon ignition, ammonium sulfate is removed from the ignition vessel as gaseous ammonia, gaseous sulfur dioxide, nitrogen gas, and water vapor.

[2-6. Lithium analysis step S6]
In the lithium analysis step S6, the lithium compound obtained in the lithium compound generation step S5 is allowed to cool in a desiccator, and then the weight of each ignition container is weighed by an electronic balance. After the ignition is completed, the lithium compound is promptly stored in a desiccator in a desiccator so that the lithium compound does not become a hydrate by absorbing moisture in the air, and allowed to cool to room temperature. When a quartz co-stoppered Erlenmeyer flask is used for the ignition container, it is particularly preferable to using a platinum dish, a quartz dish, a magnetic dish, or the like, because it can be sealed and shut off from the atmosphere. In addition, in weighing, the types of lithium compounds include lithium sulfate, lithium chloride, lithium carbonate, lithium bromide, etc., but lithium chloride has the highest hygroscopicity and forms lithium carbonate and lithium bromide. It is particularly preferable to use lithium sulfate because it requires a complicated process.

By converting the weight of the obtained lithium compound into the equivalent weight of lithium and reflecting the sample amount in the sample dissolution step S1, the constant volume and the aliquot in the lithium compound production step S5, and the lithium loss in each step, The content can be calculated. Note that after obtaining the weight of the lithium compound, the lithium compound is dissolved in water, and ICP qualitative analysis and ICP-MS qualitative analysis are performed using the aqueous solution, whereby the coexisting element does not remain in the lithium compound. You can check. Furthermore, in the above qualitative analysis, in the unlikely event that residual amounts of coexisting elements that may affect the quantitative value of lithium are confirmed, the atomic absorption method, flameless atomic absorption method, ICP method, ICP-MS are successively followed. It is possible to analyze using at least one of the ion chromatography and the ion chromatograph method, and subtract from the lithium quantitative value. Thereby, the lithium contained in the sample can be evaluated accurately and highly accurately. In addition, a part of the obtained lithium compound is collected, or a sample for confirming the compound morphology is prepared separately from the sample for parallel analysis, which will be described later, and the sample is analyzed by X-ray diffraction (XRD) method. Morphological analysis is possible. From this, it can be confirmed that the obtained lithium compound is not hydrated by moisture absorption or carbonated by carbon dioxide in the atmosphere. Since the effects of hydration and carbonation can be eliminated, lithium contained in the sample can be evaluated accurately and with high accuracy.

<Details of analysis method according to this embodiment>
Details of the analysis method according to the present embodiment will be described below.

According to the process shown in FIG. 1, the lithium contained in Samples X and Y (both are metal composite oxides) was evaluated. Table 1 shows the composition of the matrix elements in the samples X and Y, which were separately analyzed by the inductively coupled plasma (ICP) emission spectroscopy analyzer. The sample X contains nickel, cobalt, and aluminum, and the sample Y contains nickel, cobalt, and manganese as main components, and coexists with lithium which is an element to be analyzed.

In addition, the amount of lithium loss in each step, a qualitative analysis of the lithium compound (lithium sulfate) after weighing, each comparative example (analysis of lithium by a conventional method using an acid decomposition solution), and ICP The method was used. Each sample was introduced into an inductively coupled plasma (ICP) emission spectroscopy analyzer (ICP-OES "Agilent 730-ES" manufactured by Agilent Technologies, Inc.), and lithium and coexisting elements were measured under the measurement conditions shown in Table 2. And, qualitative analysis was performed. The measurement wavelength of each element was 610.365 nm for lithium, 222.295 nm for nickel, 235.341 nm for cobalt, 396.152 nm for aluminum, and 279.827 nm for manganese, and yttrium selected as an internal standard element was 371. It was set to 0.030 nm. Regarding the liquid properties of the measurement solution, the hydrochloric acid was 1.2 M, the yttrium concentration was 10 mg/L, and the calibration curve concentrations were 0, 1, 5, 10, and 50 mg/L.

Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

<Example 1>
In the present example, the lithium contained in the sample X was processed and evaluated in parallel with three samples by the process shown in FIG.

First, 2 g of the sample X was weighed in a 200 mL beaker, 10 mL of pure water and 20 mL of hydrochloric acid were added, and then heat decomposed. After allowing the solution to cool, 30 mL of hydrochloric acid was added to control the acid concentration to 10 M hydrochloric acid, and the flow rate of the effluent was about 3 to 5 mL (SV=1 to 2) per minute on the anion exchange resin column. I passed it through. As the anion exchange resin column, a column based on JIS-M-8129 (a method for determining cobalt in ore) described above was used, and as the resin, Dowex-1x8 (100-200 mesh) was used. The effluent was received in a 500 mL beaker, and further 360 mL of prepared hydrochloric acid (hydrochloric acid 10M) was passed through the column while subdivided to wash, and lithium was completely discharged from the column.

Coexisting elements such as cobalt and manganese adsorbed on the column were eluted from the column by using hydrochloric acid (1+9) as an eluent and passing 360 mL through the column while subdividing. Then, the obtained recovered solution was transferred to a 500 mL volumetric flask, 14 mL of hydrochloric acid and 50 mL of an yttrium solution (100 mg/L) as an internal standard solution were added, and the volume was adjusted to 500 mL with water. The coexisting element contained in the recovered liquid was analyzed by the ICP method while appropriately performing the dilution operation together with lithium lost (remaining in the column) by the ion exchange operation.

The effluent was concentrated by heating, transferred to a 200 mL tall beaker, and continuously heated to evaporate to dryness. Then, 20 mL of pure water and 2 mL of hydrochloric acid 12M were added to dissolve the produced salt, and the acid concentration of the effluent was dissolved. Was controlled again to about 1M hydrochloric acid. Further, pure water was added to the effluent to adjust the liquid volume to about 100 mL, and then the pH was adjusted to around 7 with hydrochloric acid (1+1) and ammonia water containing 28% by mass of ammonia to form a metal hydroxide precipitate. Let The formed precipitate was heated at 120° C. until it was boiled and held for 15 minutes or more to be heat-aged. Then, it isolate|separated by natural filtration using filter paper (5A, 125 mm), and also wash|cleaned 5 to 6 times with warm ammonia water (1+100). The filtrate was collected in a 200 mL tall beaker.

Coexisting elements such as aluminum contained in the precipitate were dissolved in 50 mL of warm hydrochloric acid (1+1), and the recovered solution was transferred to a 500 mL volumetric flask, and 50 mL of an internal standard solution of yttrium solution (100 mg/L) was added. Then, the volume was adjusted to 500 mL with water. The coexisting elements contained in the recovered liquid were analyzed by the ICP method while appropriately performing the dilution operation together with the lithium lost in the precipitation operation (remaining in the precipitation).

To the obtained filtrate, 10 mL of sulfuric acid (1+1) was added, heated and concentrated to generate white smoke, then allowed to cool, 10 mL of sulfuric acid (1+1) was added again, and pure water was added to 100 mL. It was adjusted. Further, after adding 50 mL of ammonia water containing 28% by mass of ammonia to make it alkaline, in addition to the above-described electrolytic analyzer ANA-2-2 manufactured by Tokyo Koden Co., Ltd., JIS-H-1101. Using the platinum electrode and beakers described in (Copper metal analysis method), the current was set to 0.3 A (current density: about ² mA/dm ² ), and the time was set to 15 hours to carry out electrolysis. ..

Coexisting elements such as nickel deposited on the platinum cathode surface were decomposed by heating using 100 mL of nitric acid (1+1), and the obtained recovery solution was transferred to a 500 mL volumetric flask, 50 mL of hydrochloric acid, and an yttrium solution as an internal standard solution. 50 mL of (100 mg/L) was added, and the volume was adjusted to 500 mL with water. The coexisting elements contained in this recovered liquid were analyzed by the ICP method while appropriately performing the dilution operation together with lithium lost by the electrolysis operation (remaining on the platinum cathode side).

The electrolysis residual liquid after taking out the platinum electrode was concentrated by heating, transferred to a 100 mL total volume flask, and made up to 100 mL with pure water. From the electrolysis residual liquid, 50 mL was taken with a 50 mL hole pipette, transferred to a 200 mL quartz stoppered Erlenmeyer flask made of Cosmos Bead Co., Ltd., and weighed, and heated at 100 to 320° C. using a hot plate. While adjusting, heat concentration and evaporation to dryness were performed. The obtained salt is placed in an electric muffle furnace together with the flask, and the temperature is raised from room temperature→350° C. (10 minutes)→400° C. (20 minutes)→450° C. (10 minutes) and the temperature rise time to each set temperature is 10 It was ignited in a heating pattern of minutes.

The flask was taken out from the electric muffle furnace, cooled to such an extent that it was not burned even if it was touched by hand, then immediately stoppered and stored in a desiccator, and the obtained lithium sulfate was allowed to cool to room temperature. After that, the flask was taken out from the desiccator, the weight (post-operation flask weight) was weighed with an electronic balance, and the original flask weight (pre-operation flask weight) was subtracted to obtain the weight of lithium sulfate. In addition, since 50 mL was collected from 100 mL of the electrolytic residual liquid, the weight of the obtained lithium sulfate was doubled to obtain the weight equivalent to the original amount of the sample, and then a coefficient of 0.1263 (lithium sulfate Li ₂ SO ₄ 1 mol The mass in terms of lithium was calculated by multiplying the mass of 13.882/the molar mass of lithium sulfate by 109.945).

After obtaining the weight of lithium sulfate, the lithium sulfate was dissolved in water, the resulting aqueous solution was transferred to a 100 mL total volume flask, and the volume was adjusted to 100 mL with water. Using this aqueous solution, ICP qualitative analysis was performed to confirm the presence or absence of residual coexisting elements in lithium sulfate.

After adding the lithium loss in each step of the ion exchange step, the precipitation step, and the electrolysis step to the obtained lithium equivalent weight, and subtracting the blank sample content described below to obtain the total lithium weight, the formula (III) Finally, the quantitative value of lithium was calculated as shown in.
Lithium quantitative value [%]=(total lithium weight [g]/sample amount [g])×100 (III)

In this example, apart from the samples 1 to 3, lithium added samples 4 to 5 were prepared as samples for evaluating the lithium recovery rate. Specifically, after the sample is weighed in the sample dissolving step, 0.2661 g of lithium carbonate is added so that the lithium amount becomes 0.05 g, and thereafter, the same steps as those of the samples 1 to 3 are performed according to the step shown in FIG. Processed. The lithium recovery rate (also referred to as “recovery rate”) was calculated as shown in formula (IV).
Lithium recovery rate [%]
={(Additional sample lithium weight [g]-Sample average lithium weight [g])
/Lithium addition amount [g]}×100 (IV)

In addition, in this example, in addition to the samples 1 to 3, blank samples 6 to 7 for blank test were prepared. Specifically, in the sample dissolving step, the same processes as those for the samples 1 to 3 were performed according to the process shown in FIG. 1 except that the sample was not weighed.

Further, in this example, a morphological confirmation sample 8 was prepared as a sample for confirming the compound form, in addition to the samples 1 to 3. Specifically, according to the process shown in FIG. 1, the same treatments as those for the samples 1 to 3 are performed, and the obtained lithium compound is analyzed by an X-ray diffraction (XRD) analyzer (“X'PertPRO” manufactured by Spectris Co., Ltd.). Was used for morphological analysis. In the X-ray diffraction analyzer, CuKα ray was used as a radiation source for the sample collected in the sample holder, the measurement speed was 2°/min, the tube voltage was 45 kV, the tube current was 40 mA, and the measurement range was 2θ= The measurement was performed under the condition of 10 to 80°. Then, the compound form was identified by collating the standard diffraction pattern of the compound with the diffraction pattern of the sample using a PDF (Powder Diffraction File) database in ICDD (International Center for Diffraction Data).

Table 3 shows the lithium quantitative value, the lithium recovery rate, and the form of the lithium compound in this example.

<Example 2>
In Example 2, the sample to be analyzed was Sample Y, and the same procedure as in Example 1 was performed except that the precipitation step was omitted, and the lithium quantitative value and the lithium recovery rate were calculated.

Table 3 shows the lithium quantitative value, the lithium recovery rate, and the form of the lithium compound in Example 2.

<Comparative Example 1>
In Comparative Example 1, the sample to be analyzed is sample X, and after the thermal decomposition in the sample dissolution step, the obtained acid decomposition solution is transferred to a 500 mL total volume flask, 30 mL of hydrochloric acid, and an yttrium solution (100 mg as an internal standard solution). /L) was added to 50 mL, and the volume was adjusted to 500 mL with pure water. Lithium and coexisting elements in this acid decomposition solution were analyzed by the ICP method while appropriately performing a dilution operation.

Table 3 shows the lithium quantitative value and the lithium recovery rate in Comparative Example 1.

<Comparative example 2>
In Comparative Example 2, the same operation as in Comparative Example 1 was performed except that the sample to be analyzed was Sample Y.

Table 3 shows the lithium quantitative value and the lithium recovery rate in Comparative Example 2.

<Evaluation result>
As shown in Table 3, according to Examples 1 and 2, the three lithium quantitative values of Samples 1 to 3 were found to be the same in the calculation with three significant figures. It was also found that the lithium recovery rates of the lithium-added samples 4 to 5 were all 99.9% or more. Further, in the morphological confirmation sample 8, it was confirmed that the obtained lithium compound was composed only of lithium sulfate (Li ₂ SO ₄ ), and other forms of compounds such as hydrates and carbonates were detected. There wasn't. From this result, if the present invention is used, by separating the lithium contained in the sample in the form of a lithium compound such as lithium sulfate, even if a coexisting element is contained, the lithium recovery rate is very good. Therefore, it was confirmed that lithium can be collected and lithium can be evaluated accurately and highly accurately. After weighing the weight of lithium sulfate, an ICP qualitative analysis was performed on lithium sulfate in order to confirm the presence or absence of coexisting elements, but no coexisting element was detected. Furthermore, the content of coexisting elements was analyzed by the ICP method together with the amount of lithium loss in each step. The quantitative values of nickel, cobalt, aluminum, and manganese were almost the same as the composition of the matrix elements shown in Table 1. It was The results show that cooperating elements such as nickel, cobalt, aluminum and manganese can be evaluated along with lithium when operated according to the present invention. Further, from this result, it was confirmed that if the present invention was used, it was possible to reflect the amount of lithium loss in each step, and lithium could be evaluated accurately and highly accurately.

On the other hand, according to Comparative Examples 1 and 2, the lithium quantitative values of the samples 1 to 3 did not match in the calculation with three significant figures. The lithium recovery rates of the lithium-added samples 4 to 5 were all less than 99.9%. As described above, this is considered to be influenced by various problems peculiar to the relative analysis method by the instrumental analyzer, such as plasma stability during ICP measurement. From the above, it was confirmed that the ICP method cannot perform accurate and highly accurate evaluation comparable to the gravimetric method which is an absolute analysis method.

Although each embodiment and each example of the present invention have been described in detail as above, it is understood by those skilled in the art that many modifications are possible without materially departing from the novel matters and effects of the present invention. , It will be easy to understand. Therefore, such modifications are all included in the scope of the present invention.

For example, a term described in the specification or the drawings at least once together with a different term having a broader meaning or the same meaning can be replaced with the different term in any place in the specification or the drawing. The configuration and operation of the lithium evaluation method are not limited to those described in the embodiments and examples of the present invention, and various modifications can be made.

S1 sample dissolution step, S2 ion exchange step, S3 precipitation step, S4 electrolysis step, S5 lithium compound production step, S6 lithium analysis step

By converting the weight of the obtained lithium compound into the equivalent weight of lithium and reflecting the sample amount in the sample dissolution step S1, the constant volume and the aliquot in the lithium compound production step S5, and the lithium loss in each step, The content can be calculated. Note that after obtaining the weight of the lithium compound, the lithium compound is dissolved in water, and ICP qualitative analysis and ICP-MS qualitative analysis are performed using the aqueous solution, whereby the coexisting element does not remain in the lithium compound. You can check. Furthermore, in the above qualitative analysis, in the unlikely event that residual amounts of coexisting elements that may affect the quantitative value of lithium are confirmed, the atomic absorption method, flameless atomic absorption method, ICP method, ICP-MS are successively followed. It is possible to analyze using at least one of the ion chromatography and the ion chromatograph method, and subtract from the lithium quantitative value. Thereby, the lithium contained in the sample can be evaluated accurately and highly accurately. In addition, a part of the obtained lithium compound is collected, or a sample for confirming the compound morphology is prepared separately from the sample for parallel analysis, which will be described later, and the sample is analyzed by X-ray diffraction (XRD) method. Morphological analysis is possible. From this, it can be confirmed that the obtained lithium compound is not hydrated by moisture absorption or carbonated by carbon dioxide in the atmosphere. Since the effects of hydration and carbonation can be eliminated, lithium contained in the sample can be evaluated accurately and with high accuracy. That is, for example, in the present invention, it is particularly preferable that the form of the lithium compound finally obtained through all the analysis steps is lithium sulfate as described above. However, if the obtained lithium compound contains other forms such as hydrates and carbonates, if the total weight of the lithium compound is converted to lithium equivalent weight as lithium sulfate, it will coexist in the lithium compound. As in the case where there is residual element, it will affect the quantitative value of lithium. Therefore, the obtained lithium compound is subjected to morphological analysis using the X-ray diffraction (XRD) method, and the result is reflected (in this example, it is proved that the lithium compound is a single compound of lithium sulfate). Thereby, the reliability of the lithium quantitative value can be further improved.

Claims (13)

A lithium evaluation method, wherein lithium contained in a sample is separated in the form of a lithium compound, and the weight of the lithium compound is weighed to determine the lithium content. Dissolving the weighed sample with an acid to obtain a solution, and then a sample dissolving step of controlling the acid concentration of the solution,
An ion exchange step of controlling the acid concentration of the effluent after the solution having an acid concentration controlled is flown through an ion exchange resin column to obtain an effluent,
After treating the effluent with controlled acid concentration with white smoke, electrolyzing with alkali to obtain an electrolysis residual liquid, and
Lithium compound producing step of decomposing and removing the by-product by constant volume of the electrolytic residual liquid and fractionating a part of the electrolytic residual liquid in a container, and then heating and igniting the entire container to obtain a lithium compound When,
The lithium compound is weighed together with the container, an analysis step of quantifying lithium,
The method for evaluating lithium according to claim 1, further comprising: Between the ion exchange step and the electrolysis step, the pH of the effluent whose acid concentration is controlled is adjusted with an acid and/or an alkali, and the mixture is boiled to form a precipitate of metal hydroxide, and the precipitate is formed. Having a precipitation step of obtaining a filtrate by filtration,
The method for evaluating lithium according to claim 2, wherein the filtrate is treated with white smoke in the electrolyzing step. The lithium evaluation method according to claim 1, wherein the lithium compound is lithium sulfate. The lithium evaluation method according to claim 2, wherein the acid is hydrochloric acid and the ion exchange resin column is an anion exchange resin column. The lithium evaluation method according to claim 2, wherein the container is a quartz stoppered Erlenmeyer flask. The lithium evaluation method according to claim 2 or 3, wherein the alkali in the lithium evaluation method is aqueous ammonia. The lithium evaluation method according to claim 1, wherein the sample contains at least one of nickel, cobalt, manganese, and aluminum. The lithium evaluation method according to claim 2, wherein the by-product is ammonium sulfate. The lithium loss in the ion exchange step and the electrolysis step is determined by using at least one of atomic absorption method, flameless atomic absorption method, ICP method, ICP-MS method, and ion chromatography method. The lithium evaluation method according to claim 2. Obtaining the lithium loss in the ion exchange step, the precipitation step, and the electrolysis step by using at least one of atomic absorption method, flameless atomic absorption method, ICP method, ICP-MS method, and ion chromatography method. The lithium evaluation method according to claim 3, wherein After calculating the lithium content, the lithium compound is qualitatively analyzed using at least one of ICP method and ICP-MS method, and the lithium according to claim 1. Evaluation methods. The lithium evaluation method according to any one of claims 1 to 12, wherein the lithium compound is subjected to morphological analysis using an X-ray diffraction method.

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