Recovery method for metal impurities

Abstract

To recover metal impurities in an organic solvent in a high yield.SOLUTION: A recovery method for metal impurities intended to recover metal impurities in an organic solvent includes: capturing metal impurities in a sample solution on an adsorbent by passing the organic solvent as the sample solution into the adsorbent; and eluting metal impurities captured on the adsorbent in an eluent and recovering the metal impurities by passing the eluent into the adsorbent by upward flow. The step of passing the eluent includes passing the eluent at a linear speed of 35 m / h or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for recovering metal impurities. [Background technology]

[0002] Highly purified organic solvents are used in the manufacturing process of electronic devices such as semiconductors. Metal impurities contained in organic solvents, even in trace amounts, can have a significant effect on the characteristics of the device, so their concentration must be strictly controlled. For this reason, there is a demand for highly accurate analysis of trace amounts of metal impurities in organic solvents. In particular, there is a demand for highly accurate analysis even when the metal impurity concentration in an organic solvent is so low that it is below the detection limit of analytical equipment such as an inductively coupled plasma mass spectrometry (ICP-MS).

[0003] As a method for analyzing such low-concentration metal impurities, a method is known in which a sample liquid sampled in a bottle is heated and concentrated to increase the concentration of metal impurities in the sample liquid, and then the metal impurities in the concentrated sample liquid are analyzed (see, for example, Patent Documents 1 and 2). However, in this method, there is a limit to the concentration rate by heating, and a large amount of sample liquid needs to be sampled in order to obtain sufficient sensitivity. In addition, since the heat concentration of the sample liquid is performed in an open environment, the risk of contamination increases. In response to this, Patent Document 3 describes a method for concentrating metal impurities in a sample liquid, in which the sample liquid is passed through an ion exchanger such as a monolithic organic porous ion exchanger, and the metal impurities are captured and concentrated by the ion exchanger. This concentration method is preferably used in the field of ultrapure water production because of its high concentration efficiency and low risk of contamination in the concentration process, and it is considered that this method can also be applied to organic solvents. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-141721 A [Patent Document 2] JP 2002-5799 A [Patent Document 3] International Publication No. 2019 / 221186 Summary of the Invention [Problem to be solved by the invention]

[0005] When an organic solvent is passed through an ion exchanger, particularly a monolithic organic porous ion exchanger, the water contained in the ion exchanger is gradually replaced by the organic solvent, but it is known that when the water is mixed with the organic solvent, the dissolved gas in the organic solvent is generated as bubbles. That is, since the solubility of the gas in water is lower than that of the gas in the organic solvent, the solubility of the gas in the organic solvent decreases compared to before mixing, and the gas originally dissolved in the organic solvent is generated as bubbles. Therefore, it is known that, as a measure against such bubbles, it is preferable to pass the organic solvent through the ion exchanger in an upward flow. However, in the application of the concentration method using an ion exchanger to an organic solvent, other suitable conditions, particularly conditions for recovering metal impurities with a high recovery rate, have not been fully examined.

[0006] Therefore, an object of the present invention is to recover metal impurities in an organic solvent with a high recovery rate. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the method for recovering metal impurities of the present invention is a method for recovering metal impurities in an organic solvent, and includes the steps of passing an organic solvent as a sample liquid through an adsorbent and capturing the metal impurities in the sample liquid in the adsorbent, and passing an eluent through the adsorbent in an upward flow manner and eluting the metal impurities captured by the adsorbent into the eluent and recovering them, wherein the step of passing the eluent includes passing the eluent at a linear velocity of 35 m / h or more. Effect of the Invention

[0008] As described above, according to the present invention, metal impurities in an organic solvent can be recovered at a high recovery rate. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of an impurity recovery device according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic configuration diagram of an impurity recovery device according to a second embodiment of the present invention. [Diagram 3] 1 is a graph showing the calculation results of lithium recovery rates in Examples 1 and 2 and Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Configurations common to the following embodiments will be denoted by the same reference numerals in the drawings, and duplicated descriptions will be omitted as appropriate.

[0011] (First embodiment) 1 is a schematic diagram of an impurity recovery device according to a first embodiment of the present invention. Note that the configuration of the impurity recovery device shown in the figure is merely an example, and it goes without saying that it can be modified as necessary, for example, by adding valves or measuring instruments.

[0012] The impurity recovery device 10 collects metal impurities from the organic solvent flowing through the raw solution supply line L1. The organic solvent to be collected is not particularly limited, but examples thereof include various organic solvents such as alcohols (isopropyl alcohol, methanol, ethanol, etc.), ketones (cyclohexanone, methyl isobutyl ketone, acetone, methyl ethyl ketone, etc.), alkenes (2,4-diphenyl-4-methyl-1-pentene, 2-phenyl-1-propene, etc.), esters (propylene glycol monomethyl ether acetate, isopropyl acetate, etc.), aromatics, and amines (N-methylpyrrolidone, etc.), as well as mixtures thereof.

[0013] The impurity recovery device 10 has a sampling line L11 and an impurity collection kit 11 provided on the sampling line L11. The sampling line L11 is connected to the raw solution supply line (solvent supply line) L1 via an on-off valve V1, and the impurity collection kit 11 has a concentration column 12 and an integrating flow meter 13. The sampling line L11 functions as a sample liquid passing means for extracting a part of the organic solvent flowing through the raw solution supply line L1 as a sample liquid and passing the extracted sample liquid through the concentration column 12. The concentration column 12 captures and concentrates metal impurities in the sample liquid thus extracted, and is composed of a resin container and an ion exchanger (adsorbent) filled in the container. The concentration column 12 has an inlet and an outlet for the sample liquid at the bottom and top of the container, respectively, and therefore the sample liquid is passed through the concentration column 12 in an upward flow. The integrating flow meter 13 has a function of measuring the total amount of sample liquid passing through the concentration column 12. Instead of the integrating flow meter 13, a combination of an instantaneous flow meter and a calculation device that integrates the measured value may be used.

[0014] Examples of the ion exchanger packed in the concentration column 12 include ion exchange resins, ion adsorption membranes (porous membranes having ion exchange ability), and monolithic organic porous ion exchangers. Among these, the monolithic organic porous ion exchanger is preferably used. The monolithic organic porous ion exchanger is a monolithic organic porous body, that is, a porous body having a large number of communicating holes between the skeletons formed by organic polymers, in which ion exchange groups are introduced into the skeleton of the porous body that serves as a flow path for the reaction solution. The monolithic organic porous ion exchanger allows liquid to pass at a high spatial velocity compared to general granular ion exchange resins, and the required time can be significantly reduced. In addition, the captured metal impurities are easily eluted into the eluent for quantitative analysis, and the amount of eluent used can be reduced, so the amount of sample liquid passed can also be reduced. Furthermore, the eluent recovered after passing through the monolithic organic porous ion exchanger is in an acid-added state, so that the eluted metal impurities do not adhere to a recovery container such as a bottle, and therefore it is excellent in storage (keeping). In this respect, the monolithic organic porous ion exchanger is also advantageous. As the monolithic organic porous ion exchanger, at least one of a monolithic organic porous cation exchanger and a monolithic organic porous anion exchanger can be used depending on the type of metal element to be captured. Specific examples of the monolithic organic porous ion exchanger will be described later.

[0015] The impurity recovery device 10 also has a fluid supply line L12 and a supply source of a replacement fluid and an eluent (both not shown). The fluid supply line L12 is connected to the sampling line L11 (specifically, the upstream side of the impurity collection kit 11) via an on-off valve V2, and the supply sources of the replacement fluid and the eluent are connected to the upstream side of the fluid supply line L12 in a switchable manner. Therefore, the fluid supply line L12, together with the sampling line L11, functions as a replacement fluid supply means for supplying a replacement fluid to the concentration column 12, and also functions as an eluent passing means for supplying and passing the eluent. In addition, since the fluid supply line L12 is connected to the sampling line L11 at the inlet side of the concentration column 12, the replacement fluid and the eluent are passed through the concentration column 12 in an upward flow manner, similar to the sample liquid.

[0016] Here, a method for recovering metal impurities in an organic solvent using the above-mentioned impurity recovery apparatus 10 and a method for analyzing the thus recovered metal impurities will be described. Note that the metal impurities referred to here include not only those in the form of ions or particles, but also those present in the form of compounds or complexes.

[0017] First, an organic solvent is passed through the concentration column 12 as a sample liquid. Specifically, the on-off valve V1 of the sampling line L11 is opened, and a part of the organic solvent flowing through the raw liquid supply line L1 is passed through the concentration column 12 as a sample liquid. In this way, metal impurities in the sample liquid are captured and concentrated by the ion exchanger in the concentration column 12. The passing speed at this time is not particularly limited, but is preferably 2000 h in space velocity (SV). -1 It is preferable that the temperature is less than 1000h. -1 It is more preferable that the temperature is less than 200 h. -1 It is particularly preferable that the linear velocity (LV) is 1000 m / h or less, and more preferably 500 m / h or less. The liquid passing time (concentration time) at this time depends on the type of ion exchanger packed in the concentration column 12 and the above-mentioned liquid passing speed, but is not particularly limited as long as the metal impurities to be analyzed are concentrated to a degree that allows them to be quantified with sufficient accuracy. In order to calculate the content of the metal impurities in the sample liquid from the results of the quantitative analysis described later, the total liquid passing amount of the sample liquid to the concentration column 12 is required, and at this time, the total liquid passing amount is measured by the integrating flow meter 13. After that, when a predetermined liquid passing time has elapsed, the opening and closing valve V1 is closed to stop passing the sample liquid to the concentration column 12.

[0018] Next, a replacement process is performed to flow a replacement fluid into the concentration column 12. Specifically, the on-off valve V2 of the fluid supply line L12 is opened, and the connection source of the fluid supply line L12 is switched to the replacement fluid supply source. In this way, the replacement fluid is supplied from the replacement fluid line L12 through the sampling line L11 to the concentration column 12, and the sample liquid remaining in the concentration column 12, particularly in the ion exchanger, is replaced with the replacement fluid. This makes it possible to prevent the eluent (aqueous solution containing an acid) used in the elution process described later from coming into contact with an organic solvent, thereby ensuring safety.

[0019] As the replacement fluid, at least one of water and gas is used. The water used here is preferably as pure as possible, that is, the water with the metal impurity concentration reduced as much as possible is preferable. Specifically, the metal impurity concentration is preferably reduced to less than 10 ng / L, more preferably less than 1 ng / L, and particularly preferably less than 0.1 ng / L. The gas used here is preferably a high-purity gas with a purity of 99.9% or more, more preferably 99.99% or more. The type of high-purity gas is not particularly limited, and for example, an inert gas (nitrogen, argon, helium, etc.) or oxygen can be used. Note that air can also be used as the high-purity gas if the metal impurities are sufficiently removed.

[0020] During the passage of the sample liquid, the amount of metal impurities captured by the ion exchanger gradually decreases along the direction of the passage of the liquid. Therefore, it is preferable that the direction of the replacement fluid is the same as the direction of the passage of the sample liquid. This allows the metal impurities captured by the ion exchanger to be recaptured downstream even after they are desorbed, and prevents them from being discharged from the concentration column 12. When water is used as the replacement fluid, its flow rate is not particularly limited, but is preferably at least 20,000 h SV. -1 It is preferable that the temperature is 100 to 4000 h or less. -1It is more preferable that the LV is 1000 m / h or less, and more preferably 1 to 80 m / h. The time for which the replacement fluid is passed depends on the type and flow rate of the ion exchanger packed in the concentration column 12, but is not particularly limited as long as the sample liquid remaining in the ion exchanger can be replaced with the replacement fluid.

[0021] When the inside of the concentration column 12 has been sufficiently replaced with the replacement fluid, the supply of the replacement fluid to the concentration column 12 is stopped to terminate the replacement process. Then, the connection source of the fluid supply line L12 is switched from the replacement fluid supply source to the elution fluid supply source, and an elution process is performed in which the elution fluid is passed through the concentration column 12. In this way, the elution fluid is supplied from the fluid supply line L12 through the sampling line L11 to the concentration column 12, and the metal impurities captured by the ion exchanger in the concentration column 12 are eluted into the elution fluid and collected in a collection container installed downstream of the sampling line L11.

[0022] The eluent used here is an aqueous solution containing an acid. The acid contained in the eluent may be either an inorganic acid or an organic acid, and examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid. Among these, nitric acid, sulfuric acid, and hydrochloric acid are preferred because they facilitate the elution of ionic metal impurities and can be prepared with high purity. The acid concentration in the eluent is not particularly limited, but is preferably 0.1 to 3.0N. In addition, the eluent is preferably one in which the concentration of each metal impurity is 100ng / L or less, more specifically, nitric acid or hydrochloric acid in which the concentration of each metal impurity is 100ng / L or less is more preferred, and nitric acid or hydrochloric acid in which the concentration of each metal impurity is 10ng / L or less is particularly preferred.

[0023] The amount of the eluent passing through is not particularly limited as long as the concentration of metal impurities in the recovered eluent is higher than the detection limit of an analyzer described later, but as described later, it is preferable that it is as small as possible. Therefore, in order to efficiently elute metal impurities with such a small amount of passing through, it is preferable that the passing speed of the eluent is as low as possible. This is because, by analogy with the regeneration treatment of a general ion exchanger, for example, in a cation exchanger, it is considered that the exchange between the metal ions adsorbed on the cation exchanger and the hydrogen ions in the acid solution is promoted by increasing the contact efficiency with the acid solution. However, in the elution treatment such as that of this embodiment, as shown in the examples described later, it is preferable that the passing speed of the eluent is as high as possible, specifically, 35 m / h or more in LV. This makes it possible to recover the metal impurities captured by the ion exchanger with a higher recovery rate. The amount of eluent passed through (recovery amount), like the total amount of sample liquid passed through the concentration column 12, is required to calculate the content of metal impurities in the sample liquid, and is therefore measured by an integrating flow meter 13 during the elution process or measured using a recovery container with a measuring function.

[0024] Thereafter, the metal impurities in the collected eluent are quantified, and the metal impurity concentration in the sample liquid is calculated from the obtained metal concentration. For example, an inductively coupled plasma mass spectrometer (ICP-MS), an inductively coupled plasma atomic emission spectrometer (ICP-AES), an atomic absorption spectrometer, an ion chromatograph, or the like can be used to quantify the metal impurities. There is no particular limitation on the type of metal impurity element to be analyzed here, and for example, at least one of Li, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Sr, Mo, Ag, Cd, In, Sn, Sb, Ba, W, Au, Pt, and Pb can be analyzed. The metal impurity concentration in the sample liquid can be calculated as a value obtained by dividing the obtained metal concentration by the concentration factor of the eluent (a value obtained by dividing the total amount of the sample liquid passed by the amount of the eluent recovered). The quantitative analysis described above may be performed on-site where the impurity recovery device 10 is installed, or may be performed at a location away from the site.

[0025] According to the above-mentioned calculation method, even if the metal impurity concentration in the organic solvent is so low as to be below the detection limit of the analysis device, the metal impurity concentration in the organic solvent can be obtained by increasing the concentration ratio of the eluent until the metal impurity concentration in the eluent is equal to or higher than the detection limit. Therefore, it is preferable that the concentration ratio of the eluent is as high as possible, and therefore, if the total amount of sample liquid passing is the same, it is preferable that the amount of eluent recovered is as small as possible. In other words, if the metal impurities can be recovered with a smaller amount of eluent, it is possible to measure (evaluate) even lower concentrations of metal impurities in the organic solvent without increasing the total amount of sample liquid passing. From this viewpoint, it is preferable that the direction of passage of the eluent to the concentration column 12 is opposite to the direction of passage of the sample liquid. In other words, as described above, the amount of metal impurities captured in the ion exchanger gradually decreases along the direction of passage of the sample liquid, but by passing the eluent in the opposite direction, it is possible to recover such metal impurities with a smaller amount of eluent.

[0026] The impurity collection kit 11 (or at least the concentration column 12) may be removably attached to the sampling line L11. Therefore, after stopping the passage of the sample liquid to the concentration column 12, the impurity collection kit 11 (or at least the concentration column 12) may be removed from the sampling line L11, and the above-mentioned replacement process and elution process may be performed, for example, at a location other than the site where the impurity recovery device 10 is installed. For this purpose, the impurity collection kit 11 may be provided with a sealing means for sealing the inside so that contamination or leakage does not occur when the impurity collection kit 11 is removed from the sampling line L11. In addition, at this time, the replacement process and the elution process may be performed at the same location or at different locations. That is, the replacement process and the elution process may both be performed at a location other than the site where the impurity recovery device 10 is installed, or the replacement process may be performed at a location other than the site where the impurity recovery device 10 is installed, and the elution process may be performed at a location still other than the site where the impurity recovery device 10 is installed.

[0027] Here, two types of monolithic organic porous ion exchangers will be described as specific examples of the monolithic organic porous ion exchanger that is preferably used as the adsorbent packed in the concentration column 12. One is described in paragraphs

[0019] to

[10] of JP-A-2010-234357.

[0028] The first monolithic organic porous ion exchanger is described in paragraphs

[0052] to

[0061] of the same publication, and the other is the second monolithic organic porous ion exchanger described in paragraphs

[0052] to

[0061] of the same publication. Hereinafter, the monolithic organic porous ion exchanger will be simply referred to as a "monolith ion exchanger", and the monolithic organic porous material will also be simply referred to as a "monolith". In addition, the monolithic organic porous intermediate, which is an intermediate (precursor) in the production of a monolith, will also be simply referred to as a "monolith intermediate".

[0028] The first monolith ion exchanger is obtained by introducing ion exchange groups into a monolith, and has a continuous macropore structure in which bubble-like macropores overlap each other, and these overlapping parts form openings (mesopores) with an average diameter of 30 to 300 μm, preferably 30 to 200 μm, and particularly preferably 35 to 150 μm, in a water-wet state.

[0029] The method for producing the first monolith ion exchanger is composed of the following four steps, as described in paragraphs

[0029] to

[0051] of JP 2010-234357 A. (1) First, a mixture of an oil-soluble monomer not containing an ion exchange group, a surfactant, and water is stirred to prepare a water-in-oil emulsion. Then, the water-in-oil emulsion is polymerized to obtain a first monolith intermediate having a continuous macropore structure with a total pore volume of 5 to 16 ml / g. (2) A mixture is prepared that includes a vinyl monomer, a crosslinking agent having at least two vinyl groups in one molecule, an organic solvent that dissolves the vinyl monomer and the crosslinking agent but does not dissolve the polymer produced by polymerization of the vinyl monomer, and a polymerization initiator. (3) This mixture is left to stand and polymerized in the presence of the first monolith intermediate obtained in (1) above to obtain a first monolith having a thicker skeleton than the first monolith intermediate. (4) Thereafter, an ion exchange group is introduced into the first monolith thus obtained to produce a first monolith ion exchanger.

[0030] On the other hand, the second monolith ion exchanger is a bicontinuous structure consisting of a three-dimensionally continuous skeleton having a thickness of 1 to 60 μm and three-dimensionally continuous pores having a diameter of 10 to 100 μm between the skeletons, the skeleton being made of an aromatic vinyl polymer containing 0.3 to 5.0 mol % of crosslinked structural units among all structural units having ion exchange groups introduced therein. The second monolith ion exchanger has a total pore volume of 0.5 to 5 ml / g, an ion exchange capacity per volume in a water-wet state of 0.3 to 5 mg equivalent / ml, and ion exchange groups are uniformly distributed in the porous ion exchanger.

[0031] The second monolith ion exchanger is manufactured through the following four steps as described in paragraphs

[0062] to

[0083] of JP 2010-234357 A. First, a mixture of an oil-soluble monomer not containing an ion exchange group, a surfactant, and water is stirred to prepare a water-in-oil emulsion. Then, the water-in-oil emulsion is polymerized to obtain a second monolith intermediate having a continuous macropore structure with a total pore volume of more than 16 ml / g and less than 30 ml / g. (2) A mixture is prepared consisting of an aromatic vinyl monomer, a crosslinker having at least two or more vinyl groups in one molecule and 0.3 to 5 mol % relative to the total oil-soluble monomer, an organic solvent that dissolves the aromatic vinyl monomer and the crosslinker but does not dissolve the polymer produced by polymerization of the aromatic vinyl monomer, and a polymerization initiator. (3) This mixture is left to stand and polymerized in the presence of the second monolith intermediate obtained in (1) above to obtain a second monolith having a bicontinuous structure. (4) Thereafter, ion exchange groups are introduced into the second monolith thus obtained to produce a second monolith ion exchanger.

[0032] Second embodiment 2 is a schematic diagram of an impurity recovery device according to a second embodiment of the present invention. This embodiment differs from the first embodiment in that it is provided with a configuration for reducing the amount of organic solvent discarded in the recovery of metal impurities. The following description will focus on such differences.

[0033] In the first embodiment, the sample liquid passed through the concentration column 12 is directly discharged to the outside through the sampling line L11 and discarded, but from the viewpoint of reducing the amount of waste, it may be returned to the raw liquid supply line L1 without being discharged to the outside. To achieve this, the impurity recovery device 10 of this embodiment has a return line L13, a liquid delivery pump 14, and a purification member 15.

[0034] The return line L13 is provided to connect the downstream side of the impurity collection kit 11 and the raw solution supply line L11 in the sampling line L11, and to return the sample liquid passed through the concentration column 12 to the raw solution supply line L1. The return line L13 is connected to the sampling line L11 via the on-off valve V4 on the upstream side of the on-off valve V3 provided in the sampling line L11. The liquid delivery pump 14 has a function of pressurizing the sample liquid returned to the raw solution supply line L11. Note that a check valve may be provided instead of or in addition to the liquid delivery pump 14. The purification member 15 has a function of removing impurities (such as fine particles) other than metal impurities contained in the sample liquid. The purification member 15 is not particularly limited as long as it is used for purifying an organic solvent, and for example, an ion exchanger (such as an ion exchange resin or a monolithic organic porous ion exchanger) or a filtration membrane (such as a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane)) can be used alone or in combination.

[0035] With this configuration, in this embodiment, when the sample liquid starts to pass through the concentration column 12, the on-off valve V3 of the sampling line L11 is closed and the on-off valve V4 of the return line L13 is opened at the same time. As a result, the sample liquid passed through the concentration column 12 is returned to the raw solution supply line L1 through the return line L13 without being discharged to the outside. After the sample liquid passes through the concentration column 12, the on-off valve V3 of the sampling line L11 is opened and the on-off valve V4 of the return line L13 is closed, and the replacement process and elution process are performed in the same procedure as in the first embodiment.

[0036] (Example) Next, the effects of the present invention will be described with reference to specific examples.

[0037] Example 1 In this example, a test device simulating the impurity recovery device shown in FIG. 1 was used to recover and analyze metal impurities in an organic solvent, and the recovery rate of each metal element was calculated.

[0038] Specifically, an organic solvent was passed through the concentration column as a sample solution, and the metal elements contained in the sample solution were captured and concentrated by the ion exchanger in the concentration column. A cylindrical container with a diameter of 10 mm and a monolithic organic porous cation exchanger with a length of 50 mm was used as the concentration column. As the sample solution, isopropyl alcohol (IPA) adjusted to have the concentrations of each of the metal elements Li, Na, Mg, K, Ca, Mn, Fe, Co, Ni, Cu, Sr, Cd, In, Ba, and Pb of 100 ng / L was used, and 522 mL of it was passed through at an LV of 10 m / h.

[0039] Next, 50 mL of ultrapure water was passed through the concentration column as a replacement fluid at an LV of 75 m / h, and then high-purity nitrogen gas was supplied at a flow rate of 4 L / min to replace the sample liquid remaining in the concentration column with the replacement fluid. Then, an eluent was passed through the concentration column, and the metal elements in the sample liquid captured in the concentration column were eluted into the eluent and recovered. 2N nitric acid was used as the eluent, and 200 mL of it was passed through at an LV of 44 m / h. Then, the content of each metal element (amount of each metal) in the recovered eluent was measured using ICP-MS, and the value obtained by dividing the metal concentration by the concentration factor of the eluent (522 mL / 200 mL = 2.6 times in this embodiment) was calculated as the metal concentration in the sample liquid. Then, the metal concentration in the sample liquid was measured separately, and the recovery rate, which is the ratio (percentage) of the above-mentioned calculated value to the measured value, was calculated.

[0040] Example 2 The measurement was carried out under substantially the same conditions as in Example 1, except that 150 mL of the eluent was passed through at an LV of 37 m / h.

[0041] Comparative Example 1 The measurement was carried out under the same conditions as in Example 1, except that 150 mL of the eluent was passed through at an LV of 31 m / h.

[0042] Comparative Example 2 The measurement was carried out under the same conditions as in Example 1, except that 150 mL of the eluent was passed through at an LV of 20 m / h.

[0043] Comparative Example 3 The measurement was carried out under the same conditions as in Example 1, except that 150 mL of the eluent was passed through at an LV of 5 m / h.

[0044] Table 1 shows the calculation results of the recovery rates in Examples 1 and 2 and Comparative Examples 1 to 3. Table 1 shows only the calculation results for Li (lithium), Na (sodium), and K (potassium), which showed a large change in recovery rate with respect to the change in LV of the eluent among the above-mentioned metal elements. For reference, Table 1 also shows the LV of the eluent.

[0045] [Table 1]

[0046] From the results of Table 1, it was confirmed that in Examples 1 and 2, the recovery rates of all metal elements were in the range of 100±20%, and good results were obtained, whereas in Comparative Examples 1 to 3, the recovery rates decreased as the LV of the eluent decreased. In other words, from the viewpoint of the recovery rate, it is preferable that the LV of the eluent is as high as possible. On the other hand, when looking at each type of metal element, the recovery rate of lithium shows the most rapid change with respect to the change in the LV of the eluent. FIG. 3 shows a graph in which the calculation results of the recovery rate of lithium are plotted against the LV of the eluent. The dashed lines in the graph are auxiliary lines to make the change in the recovery rate easier to see.

[0047] From the results in Figure 3, it was confirmed that even in the case of lithium, where the recovery rate varies greatly depending on the LV of the eluent, a high recovery rate of 80% or more can be achieved by passing the eluent at a LV of 35 m / h or more. [Explanation of symbols]

[0048] 10 Impurity recovery device 11 Impurity Collection Kit 12 Concentration column 13 Integral flow meter 14 Liquid delivery pump 15 Refining Materials L1 Raw solution supply line L11 Sampling Line L12 Fluid supply line L13 Return Line V1~V4 Opening and closing valves

Claims

1. A method for recovering metal impurities in an organic solvent, comprising the steps of: passing the organic solvent as a sample liquid through an adsorbent and capturing the metal impurities in the sample liquid on the adsorbent; and passing an eluent through the adsorbent in an upward flow manner to elute the metal impurities captured by the adsorbent into the eluent and recover the metal impurities. The method for recovering metal impurities, wherein the step of passing the eluent comprises passing the eluent at a linear velocity of 35 m / h or more.

2. 2. The method for recovering metal impurities according to claim 1, further comprising a step of flowing at least one of water and gas as a replacement fluid through the adsorbent after the sample liquid has been passed through the adsorbent, thereby replacing the sample liquid remaining in the adsorbent with the replacement fluid.

3. 3. The method for recovering metal impurities according to claim 1, wherein the step of passing the sample liquid comprises taking out a part of the organic solvent flowing through a solvent supply line as the sample liquid and passing the sample liquid through the adsorbent.

4. 4. The method for recovering metal impurities according to claim 3, wherein the step of passing the sample liquid includes passing the sample liquid that has been passed through the adsorbent through a purification member to purify it, and returning the purified sample liquid to the solvent supply line.

5. 3. The method for recovering metal impurities according to claim 1, wherein the adsorbent is a monolithic organic porous ion exchanger.

6. 3. The method for recovering metal impurities according to claim 1, wherein the metal impurities include at least one of lithium, sodium, and potassium.

7. 3. The method for recovering metal impurities according to claim 1, wherein the organic solvent is an alcohol.

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