Lithium-containing solution production method

Abstract

Provided is a lithium-containing solution production method with which the production cost for producing lithium can be reduced by reducing the amount of solutions subsequent to an adsorption step, increasing the lithium content in a lithium-containing solution, and reducing the amount of solutions used in steps subsequent to a manganese oxidation step.　The lithium-containing solution production method involves executing an adsorption step, an elution step, and a manganese oxidation step in the stated order. In the adsorption step, a prescribed anion exchange resin is used together with a lithium adsorbent. With this aspect, it is possible to promote an adsorption reaction since the amount of hydrogen ions generated in the adsorption step can be reduced by the action of the anion exchange resin. Therefore, the amount of solutions subsequent to the adsorption step can be reduced, the lithium content of the lithium-containing solution is increased, and the amount of solutions used in steps subsequent to the manganese oxidation step is reduced. As a result, the production cost for producing lithium can be reduced.

Description

Method for producing a lithium-containing solution

[0001] The present invention relates to a method for producing a lithium-containing solution. More specifically, the present invention increases the lithium content rate in the solution after the elution step by increasing the adsorption efficiency in the adsorption step, and suppresses the amount of the solution used in the step after the elution step, thereby suppressing the production cost for lithium production. The present invention relates to a method for producing a lithium-containing solution that can be used.

[0002] Lithium manganate (LiMn ２ O ４ 、Li １．３３ Mn １．６７ O ４ 、Li １．６ Mn １．６ O ４ etc.) having a spinel structure is obtained by contacting a mineral acid such as hydrochloric acid. Λ-MnO ２ (HMnO ２ O ４ 、H １．３３ Mn １．６７ O ４ 、H １．６ Mn １．６ O ４ etc.) is known to selectively adsorb lithium. This Λ-MnO ２ is one of the adsorbents attracting attention in the DLE (Direct Lithium Extraction) technology. When this Λ-MnO ２ is used for lithium recovery, Λ-MnO ２ does not adsorb impurities, so there is an advantage that the amount of the neutralizing agent used in lithium recovery can be significantly reduced. Therefore, commercial use of this method is expected. A method for producing a lithium-containing solution using this Λ-MnO ２ is disclosed in Patent Document 1.

[0003] The method for producing a lithium-containing solution of Patent Document 1 includes an adsorption step, an elution step, and a manganese oxidation step. As the acid-containing solution used in the elution step, an acid is added to the total amount of the elution solution obtained in the elution step to adjust the hydrogen ion concentration of the acid-containing solution, thereby suppressing the amount of the elution solution used in the step after the elution step.

[0004] International Publication No. 2022 / 210847

[0005] Lithium adsorbent obtained from lithium manganate (e.g., H １．６ Mn １．６ O ４ The reaction between lithium and lithium chloride is shown in Equation 1. This reaction is reversible; the reaction proceeds to the right when the pH is high and to the left when the pH is low. That is, when a lithium adsorbent obtained from lithium manganate is brought into contact with brine containing lithium ions at a high pH, ​​the lithium adsorbent adsorbs lithium to become lithium manganate (adsorption step), and when it is brought into contact with the acid again, the lithium ions elute into the aqueous solution and return to the lithium adsorbent (elution step). Equation 1 shows the reaction with lithium chloride, but a similar chemical reaction occurs with other types of lithium salts such as lithium sulfate.

[0006] [Math 1] 1.6 LiCl + H １．６ Mn １．６ O ４ ⇔1.6HCl+Li １．６ Mn １．６ O ４

[0007] However, when lithium is adsorbed using a lithium adsorbent obtained from lithium manganate, an acid corresponding to the amount of adsorbed lithium is generated simultaneously with the adsorption of lithium, and the pH of the solution in the adsorption process decreases. The chemical reaction of lithium adsorption presents a problem in that as the pH decreases, the reaction shown in equation 1 becomes less likely to proceed to the right, and when the pH drops to a certain value, the adsorption reaction stops occurring.

[0008] To address the above issues, adopting a method that involves adding a liquid alkali neutralizing agent, such as an aqueous sodium hydroxide solution, during lithium adsorption presents the problem of increased liquid volume after the adsorption process. Furthermore, lithium adsorbents are sometimes used as particulate matter with a binder. This binder can degrade due to strong alkalis such as sodium hydroxide, reducing its binding ability and potentially causing the particulate matter to disintegrate.

[0009] In view of the above circumstances, the present invention aims to provide a method for producing a lithium-containing solution that can reduce the manufacturing cost for lithium production by suppressing the amount of solution after the adsorption step, increasing the lithium content in the lithium-containing solution obtained through the adsorption step, elution step, and manganese oxidation step, and suppressing the amount of solution used in the step after the manganese oxidation step.

[0010] The first invention provides a method for producing a lithium-containing solution, comprising: an adsorption step of contacting a lithium adsorbent obtained from lithium manganate with a low-concentration lithium-containing solution to obtain lithium manganate after adsorption; an elution step of contacting the adsorbed lithium manganate with an acid-containing solution to obtain an eluent; and a manganese oxidation step of adding an oxidizing agent and a pH adjusting agent to the eluent to oxidize manganese and obtain a lithium-containing solution with suppressed manganese concentration, all of which are performed in this order, wherein in the adsorption step, at least one of the following is used: an anion exchange resin having a hydroxyl group bonded to a nitrogen atom, or an anion exchange resin having an amino group with a site unbonded to hydrogen. The second invention provides a method for producing a lithium-containing solution, characterized in that, in the first invention, the weight ratio of the anion exchange resin to the lithium adsorbent is 0.5 or more and 2.5 or less. The third invention provides a method for producing a lithium-containing solution, characterized in that, in the first invention, the lithium adsorbent constitutes particulate matter, and the particulate matter contains a binder. The method for producing a lithium-containing solution of the fourth invention is characterized in that, in the first invention, a regeneration step is provided after the elution step to restore the function of the anion exchange resin, and the anion exchange resin that has undergone the regeneration step is used in the adsorption step.

[0011] According to the first invention, by using a predetermined anion exchange resin together with a lithium adsorbent in the adsorption process, the amount of hydrogen ions generated in the adsorption process can be reduced by the action of the anion exchange resin in eluting hydroxide ions. Therefore, the pH in the adsorption process can be kept high without using an additional alkali neutralizing agent, and the adsorption reaction can be promoted. As a result, the amount of solution after the adsorption process can be suppressed, the lithium content in the lithium-containing solution obtained through the adsorption process, elution process, and manganese oxidation process can be increased, and the amount of solution used in the process after the manganese oxidation process can be suppressed. This can reduce the manufacturing cost for lithium production. According to the second invention, by having a weight ratio of the anion exchange resin to the lithium adsorbent of 0.5 to 2.5, the amount of anion exchange resin can be suppressed while maintaining a high pH in the adsorption process. According to the third invention, even if the lithium adsorbent constitutes particulate matter and the particulate matter contains a binder, since the anion exchange resin is used together with the lithium adsorbent in the adsorption process, the degradation of the binder can be suppressed, and the lifespan of the particulate matter can be extended. According to the fourth invention, a regeneration step is provided after the elution step in which the functional groups of the anion exchange resin are returned to the hydroxyl group form, and the anion exchange resin that has undergone the regeneration step is used in the adsorption step, thereby suppressing the increase in costs caused by the use of the anion exchange resin.

[0012] This is a flow chart of the method for producing a lithium-containing solution according to the first embodiment of the present invention. This is a flow chart of the method for producing a lithium-containing solution according to the second embodiment of the present invention. This is a graph showing the relationship between mixing and stirring time and pH. This is a graph showing the relationship between mixing and stirring time and lithium adsorption amount.

[0013] Next, embodiments of the present invention will be described based on the drawings. However, the embodiments shown below are illustrative of a method for producing a lithium-containing solution to embody the technical concept of the present invention, and the present invention does not limit the method for producing a lithium-containing solution to the following.

[0014] The present invention provides a method for producing a lithium-containing solution, comprising the following steps in order: an adsorption step in which a low-concentration lithium-containing solution is brought into contact with a lithium adsorbent obtained from lithium manganate to obtain lithium manganate after adsorption; an elution step in which the lithium manganate after adsorption is brought into contact with an acid-containing solution to obtain an eluent; and a manganese oxidation step in which an oxidizing agent and a pH adjusting agent are added to the eluent to oxidize the manganese and obtain a lithium-containing solution with suppressed manganese concentration. In the adsorption step, an anion exchange resin is used together with the lithium adsorbent.

[0015] In the adsorption process, by using an anion exchange resin together with the lithium adsorbent, the amount of hydrogen ions generated during the adsorption process can be reduced by the action of the anion exchange resin. This allows the pH in the adsorption process to remain high without the use of additional alkaline neutralizing agents, thereby promoting the adsorption reaction. Consequently, the amount of solution after the adsorption process can be reduced, increasing the lithium content in the lithium-containing solution obtained through the adsorption, elution, and manganese oxidation processes, and reducing the amount of solution used in the processes after the manganese oxidation process. This reduces the manufacturing cost for lithium production.

[0016] Furthermore, it is preferable that the weight ratio of the anion exchange resin to the lithium adsorbent is 0.5 to 2.5. This configuration makes it possible to maintain a high pH during the adsorption process while suppressing the amount of anion exchange resin used.

[0017] Furthermore, it is preferable that the lithium adsorbent constitutes particulate matter, and that this particulate matter contains a binder. Even when the lithium adsorbent constitutes particulate matter and that particulate matter contains a binder, since an anion exchange resin is used together with the lithium adsorbent in the adsorption process, the degradation of the binder can be suppressed, and the lifespan of the particulate matter can be extended.

[0018] Furthermore, it is preferable that a regeneration step is provided after the elution step to restore the function of the anion exchange resin, and that the anion exchange resin that has undergone the regeneration step is used in the adsorption step. This configuration makes it possible to suppress the increase in costs caused by the use of the anion exchange resin.

[0019] (First Embodiment) (Pre-adsorption Step) In the adsorption step, a lithium adsorbent is brought into contact with a low-concentration lithium-containing solution to obtain lithium manganate after adsorption. The method for obtaining the lithium adsorbent used in this adsorption step will be described below. Figure 1 shows a flow chart of the method for producing the lithium-containing solution according to the first embodiment of the present invention, but the explanation of the "pre-adsorption step" is located at the top of Figure 1, H １．６ Mn １．６ O ４ This is the stage where it can be obtained.

[0020] Lithium manganese oxide becomes a lithium adsorbent when subjected to acid treatment, as shown in Equation 2. １．６ Mn １．６ O ４ Although expressed as such, lithium manganate is not limited to this. For example, Li １．３３ Mn １．６７ O ４ It is also possible to use Li １．６ Mn １．６ O ４ In that case, the lithium adsorbent is H １．６ Mn １．６ O ４ However, lithium manganese, for example, Li １．３３ Mn １．６７ O ４ In that case, the lithium adsorbent is H １．３３ Mn １．６７ O ４ This is the result. Furthermore, while HCl was used as the acid for the acid treatment, it is not limited to this. For example, sulfuric acid, nitric acid, etc., can also be used.

[0021] The shape of lithium manganese is determined considering the adsorption of lithium during the adsorption process. For example, lithium manganese can be in various forms, such as powder, granulated powder, or columnar form sprayed onto column fibers. When acid treatment is performed, for example, as a lithium adsorbent, H １．６ Mn １．６ O ４ This is obtained. The shape of the lithium adsorbent is the same as the shape of lithium manganese oxide before the acid treatment.

[0022] [Math 2] Li １．６ Mn １．６ O ４ +1.6HCl → H １．６ Mn １．６ O ４ +1.6 LiCl

[0023] (Adsorption Step) Figure 1 shows a flow chart of a method for producing a lithium-containing solution according to the first embodiment of the present invention. In the adsorption step, a low-concentration lithium-containing solution is brought into contact with a lithium adsorbent, and post-adsorption lithium manganate is obtained by the ion exchange reaction between H and Li shown in Equation 3. In this specification, the lithium manganate obtained in the adsorption step may be referred to as post-adsorption lithium manganate.

[0024] [Math 3] H １．６ Mn １．６ O ４ +1.6LiCl → Li １．６ Mn １．６ O ４ +1.6HCl

[0025] Low-concentration lithium-containing solutions include, for example, seawater or brine from salt lakes. For instance, seawater contains an average of 0.17 ppm of lithium. However, these low-concentration lithium-containing solutions also contain dissolved elements such as sodium, magnesium, or calcium in addition to lithium. The lithium-containing solution manufacturing method of the present invention makes it possible to selectively recover lithium from low-concentration lithium-containing solutions containing these dissolved elements. Note that a low-concentration lithium-containing solution means that the amount of lithium per unit volume is smaller compared to the lithium-containing solutions described later.

[0026] In the adsorption process, the method of contact between the low-concentration lithium-containing solution and the adsorbent differs depending on the form of the adsorbent. For example, if the adsorbent is in powder form, one method is to add a predetermined amount of the adsorbent to the low-concentration lithium-containing solution and stir it for a predetermined time, causing contact between the solution and the adsorbent, and allowing lithium to be adsorbed onto the adsorbent. If the adsorbent is in particulate form, one method is to enclose the particulate adsorbent in a liquid passage container and pass the low-concentration lithium-containing solution through it, causing contact between the solution and the adsorbent, and allowing lithium to be adsorbed onto the adsorbent. If the adsorbent is sprayed onto the fibers of a column, one method is to pass the low-concentration lithium-containing solution through the column, causing contact between the solution and the adsorbent, and allowing lithium to be adsorbed onto the adsorbent. When passing the low-concentration lithium-containing solution, repeated passage may be performed to ensure sufficient contact with the adsorbent.

[0027] In the adsorption process of this embodiment, an anion exchange resin is used together with a lithium adsorbent. Anion exchange resin is a type of synthetic resin that has a structure in its molecular structure that ionizes as an ion exchange group, and that ion exchange group has the properties of anions. However, if the neutralization salt of a strong acid and a weak base is an anion exchange resin, the substance that releases the strong acid from it is also generally considered an anion exchange resin. Anion exchange resins are classified into weakly basic anion exchange resins that have primary to tertiary amino groups as functional groups and strongly basic anion exchange resins that have quaternary ammonium groups as functional groups, but either type of anion exchange resin is acceptable. In the case of a weakly basic anion exchange resin, of the four electron pairs around the nitrogen atom, in equation 4, one electron pair is used for R and the two H atoms, i.e., a total of three electron pairs, and the remaining one is a lone pair. In equation 5, two electron pairs are used for R2, one electron pair is used for H, and the remaining one is a lone pair. In equation 6, three electron pairs are used in R3, and the remaining one is a lone pair. A hydrogen ion is adsorbed (coordinate bonded) to this lone pair. In other words, a weakly basic anion exchange resin is an anion exchange resin that has an amino group with an unbonded site to hydrogen. In the case of a primary amino group, the reaction equation is shown in equation 4; in the case of a secondary amino group, in equation 5; and in the case of a tertiary amino group, in equation 6. By coordinating the hydrogen ion to the amino group, the amount of hydrogen ions in the solution during the adsorption process can be reduced. Note that the right-hand side of equations 4 to 6 is expressed as a hydrogen ion and a chloride ion ion bonded ionically, but it can also be rephrased as a reaction to remove hydrochloric acid, a strong acid, from an aqueous solution. Furthermore, in the case of a strongly basic anion exchange resin, i.e., an anion exchange resin with a quaternary ammonium group, in equation 7, a negatively charged hydroxyl group OH is bonded to a positively charged nitrogen atom N by electrostatic attraction, and the hydroxyl group OH is water-soluble. The reaction equation represented by equation 7 dissolves the hydroxide ions bonded to the quaternary ammonium group in the solution, and by reacting these dissolved hydroxide ions with hydrogen ions to form water, the amount of hydrogen ions in the solution during the adsorption process can be reduced. Although hydrochloric acid is listed as the acid in each reaction equation, it is not limited to this. For example, other acids such as sulfuric acid will produce similar reactions.Furthermore, R in each reaction equation represents a carbon skeleton formed by the bonding of carbon atoms to each other, to which hydrogen, nitrogen, oxygen, etc., are bonded. Also, R, R2, R3, and R4 each consist of one or more atomic groups, but the multiple atomic groups do not need to have the same composition. Bonding with the nitrogen atom occurs between the carbon atoms belonging to the atomic group and the nitrogen atom in question. Typically, in R-N (equation 4), one carbon atom is bonded to the nitrogen atom; in R2-N (equation 5), two carbon atoms are bonded to the nitrogen atom; in R3-N (equation 6), three carbon atoms are bonded to the nitrogen atom; and in R4-N (equation 7), four carbon atoms are bonded to the nitrogen atom. When the atomic group is large, it is possible for distant carbon atoms belonging to the same atomic group R4 (or R2, R3) to be bonded to the nitrogen atom N. When the atomic group is small, it is more common for one carbon atom from each of the multiple atomic groups belonging to R4 (or R2, R3) to be bonded to the nitrogen atom N.

[0028] [Number 4] R-NH ２ +HCl → R-NH ２ HCl

[0029] [Number 5] R ２ -NH + HCl → R ２ - NH・HCl

[0030] [Number 6] R ３ -N + HCl → R ３ - N·HCl

[0031] [Number 7] R ４ -NOH+HCl→R ４ -NCl+H ２ O

[0032] In the adsorption process, by using an anion exchange resin together with the lithium adsorbent, the amount of hydrogen ions generated during the adsorption process can be reduced by the action of the anion exchange resin. This allows the pH in the adsorption process to remain high without the use of additional alkaline neutralizing agents, thereby promoting the adsorption reaction. Consequently, the amount of solution after the adsorption process can be reduced, increasing the lithium content in the lithium-containing solution obtained through the adsorption, elution, and manganese oxidation processes, and reducing the amount of solution used in the processes after the manganese oxidation process. This reduces the manufacturing cost for lithium production.

[0033] The method of using anion exchange resin may vary depending on the form of the lithium adsorbent or the method of contact with the low-concentration lithium-containing solution. For example, if the lithium adsorbent is in powder form, a predetermined amount of the adsorbent and a predetermined amount of anion exchange resin are added to a beaker or similar container holding a low-concentration lithium-containing solution, and the mixture is stirred for a predetermined time. This causes the low-concentration lithium-containing solution and the lithium adsorbent to come into contact, and lithium is adsorbed onto the lithium adsorbent.

[0034] If the lithium adsorbent is in the form of particulate matter, the particulate matter containing the lithium adsorbent and an anion exchange resin are sealed in a liquid-passing container, and a low-concentration lithium-containing solution is passed through it, causing the low-concentration lithium-containing solution to come into contact with the lithium adsorbent, and lithium is adsorbed onto the lithium adsorbent.

[0035] If a lithium adsorbent is sprayed onto the column fibers, an anion exchange resin is sealed within the column, and a low-concentration lithium-containing solution passes through the column, bringing the low-concentration lithium-containing solution into contact with the lithium adsorbent, causing lithium to be adsorbed onto the lithium adsorbent.

[0036] The above describes contact methods that are likely to be adopted in relation to the shape of the lithium adsorbent, but the combination of lithium adsorbent shape and contact method is not limited to the above combinations. For example, a method may be adopted in which particulate matter containing lithium adsorbent is immersed in a low-concentration lithium-containing solution and stirred.

[0037] Furthermore, in any form or contact method of the lithium adsorbent, the weight ratio of the anion exchange resin to the lithium adsorbent is preferably 0.5 to 2.5. That is, it is preferable that the value obtained by dividing the "weight of the anion exchange resin" by the "weight of the lithium adsorbent" is between 0.5 and 2.5.

[0038] By setting the weight ratio of the anion exchange resin to the lithium adsorbent to 0.5 to 2.5, it is possible to maintain a high pH during the adsorption process while suppressing the amount of anion exchange resin used.

[0039] After the adsorption process, the adsorbent becomes lithium manganate. Similarly, a low-concentration lithium-containing solution becomes a post-adsorption liquid after the lithium is adsorbed by the adsorbent. This post-adsorption liquid is discharged into the sea or lake from which the low-concentration lithium-containing solution was collected. Before discharge, the post-adsorption liquid is treated to a state suitable for discharge, such as through neutralization.

[0040] (Elumination process) In the elution process, the adsorbed lithium manganate is brought into contact with an acid-containing solution, and an eluent is obtained by the reaction shown in Equation 8. At this time, the adsorbed lithium manganate is Li ＋ and H ＋ Through this exchange reaction between cations, the lithium adsorbent is regenerated and reused in the adsorption process.

[0041] [Number 8] Li １．６ Mn １．６ O ４ +1.6HCl → H １．６ Mn １．６ O ４ +1.6 LiCl

[0042] In this embodiment, the acid-containing solution includes a solution of an acid alone, such as hydrochloric acid, and a solution obtained by adding acid to an elution solution obtained through an elution step. For example, in this embodiment, the elution step is divided into several stages. In the first stage, the acid-containing solution is a solution of an acid alone. In the second stage and beyond, the elution step is carried out using the elution solution obtained in the previous stage, with acid added to this elution solution. However, this is not limited to this. For example, in some cases, only a solution of an acid alone may be used as the acid-containing solution.

[0043] In the elution step of this embodiment, the hydrogen ion concentration of the acid-containing solution that is brought into contact with the adsorbed lithium manganate is preferably 0.1 mol / L or more and 4.0 mol / L or less. Furthermore, the hydrogen ion concentration is preferably 0.5 mol / L or more and 2.0 mol / L or less.

[0044] If the hydrogen ion concentration of the acid-containing solution is lower than 0.1 mol / L, the cation exchange reaction cannot proceed sufficiently, and the efficiency of this exchange reaction decreases. Furthermore, if the acid-containing solution is higher than 4.0 mol / L, the entire lithium manganate dissolves in the acid solution, making it impossible to reuse the adsorbed lithium manganate as a lithium adsorbent. While hydrochloric acid is preferred for the acid-containing solution, it is not limited to this. For example, sulfuric acid or acetic acid may also be used.

[0045] Depending on the form of lithium manganate, the method of contact between the adsorbed lithium manganate and the acid solution during the elution process differs. For example, if the lithium manganate is in powder form, one method is to add the powdered adsorbed lithium manganate to the acid solution and stir it to bring the adsorbed lithium manganate into contact with the acid solution. If the lithium manganate constitutes particulate matter or is sprayed onto the fibers of a column, one method is to place the particulate lithium manganate and the column inside a liquid passage container, and then pass the acid solution through the container to bring the adsorbed lithium manganate into contact with the acid solution.

[0046] Furthermore, if the adsorbed lithium manganate is in the form of a powder or particulate matter, in this embodiment, it is preferable to separate the adsorbed lithium manganate from the anion exchange resin in the elution step. This is because the lithium adsorbent after the elution step can be used again in the adsorption step. This separation can be performed, for example, by sieving.

[0047] (Manganese Oxidation Process) In the manganese oxidation process, divalent manganese is oxidized to tetravalent manganese by adding an oxidizing agent and a pH adjusting agent to the eluent obtained in the elution process, thereby obtaining a lithium-containing solution with a suppressed manganese concentration. Since tetravalent manganese is poorly soluble, it precipitates in the solution. This suppresses the concentration of manganese in the eluent. Furthermore, the precipitated manganese can be reused as a raw material for lithium adsorbents.

[0048] To oxidize divalent manganese to tetravalent manganese, an oxidizing agent and a pH adjuster are added to the eluent. When adding the oxidizing agent and pH adjuster, it is preferable to adjust the pH to a range of 3 to 7 and the oxidation-reduction potential to 600 mV to 1100 mV using a silver-silver chloride electrode. That is, the pH and oxidation-reduction potential are measured simultaneously, and the oxidizing agent and pH adjuster are added simultaneously or alternately so that they fall within the above range. Examples of oxidizing agents include sodium hypochlorite, sodium chlorite, ozone, and permanganate. However, the agent is not limited to these, and any agent that can adjust the oxidation-reduction potential is acceptable. Examples of pH adjusters include alkali neutralizing agents such as sodium hydroxide and slaked lime. However, the agent is not limited to these, and any agent that can adjust the pH is acceptable.

[0049] (Post-manganese oxidation step) In this embodiment, lithium exists in the form of lithium chloride (LiCl) in the lithium-containing solution obtained in the manganese oxidation step. By adding alkali to this solution or by superheating and concentrating it, lithium can be obtained in the form of, for example, lithium carbonate.

[0050] Furthermore, after adsorption, lithium manganate becomes a lithium adsorbent when exposed to an acid solution, and this lithium adsorbent is reused in the adsorption process.

[0051] (Second Embodiment) Figure 2 shows a flow chart of the method for producing a lithium-containing solution according to the second embodiment of the present invention. The difference between the first embodiment and the second embodiment is that, after the elution step, a regeneration step is provided in which the functional groups of the anion exchange resin separated from the adsorbed lithium manganate are returned to the hydroxyl group form. Other aspects are the same as in the first embodiment. Therefore, only the differences will be explained below, and other explanations will be omitted.

[0052] (Regeneration Process) Many of the anion exchange resins used in the regeneration process come into contact with an acid during the adsorption and elution processes, so they do not have the function of reducing hydrogen ions from the solution in the adsorption process, which is a function of the anion exchange resin. In this embodiment, in the elution process, a regeneration process is carried out to restore the function of the anion exchange resin separated from lithium manganate after adsorption, such as returning the functional group of the anion exchange resin to the hydroxyl form, and the anion exchange resin obtained through this regeneration process is used in the adsorption process.

[0053] As a method of restoring the function of reducing hydrogen ions from the solution in the adsorption process, such as returning the functional group of the anion exchange resin to the hydroxyl form, it is preferably carried out by passing the anion exchange resin separated in the elution process through an alkaline aqueous solution such as an aqueous sodium hydroxide solution, an aqueous ammonia solution, or an aqueous sodium carbonate solution. Chemical reaction formulas when an aqueous sodium hydroxide solution is used in the regeneration process are shown in Formulas 9 to 12.

[0054] [Formula 9] R-NH ２ + HCl + NaOH → R-NH ２ + NaCl + H ２ O

[0055] [Formula 10] R ２ -NH + HCl + NaOH → R ２ -NH + NaCl + H ２ O

[0056] [Formula 11] R ３ -N + HCl + NaOH → R ３ -N + NaCl + H ２ O

[0057] [Formula 12] R ４ -NCl + NaOH → R ４ -NOH + NaCl

[0058] After the elution process, a regeneration process for restoring the function of the anion exchange resin is provided, and by using the anion exchange resin that has undergone the regeneration process in the adsorption process, it is possible to suppress an increase in the cost due to the use of the anion exchange resin.

[0059] Incidentally, the regeneration process may be carried out in a state where an anion exchange resin and a lithium adsorbent are mixed. That is, since the lithium adsorbent has no ability to adsorb metal elements other than lithium, when the above alkaline aqueous solution does not contain lithium, in the regeneration process, the lithium adsorbent maintains its adsorption ability without adsorbing any metal elements, while the anion exchange resin is regenerated, and the lithium adsorbent can be used as it is in the next adsorption process. Similarly, even when the alkaline aqueous solution contains some lithium and the adsorption ability of the lithium adsorbent decreases, if the adsorption ability remains in the lithium adsorbent, it can be used in the next adsorption process. Incidentally, when the alkaline aqueous solution contains a significant amount of lithium (when saturation of the lithium adsorbent is a concern), the anion exchange resin and the lithium adsorbent need to be separated in the elution process. As a separation method, sieving or the like can be performed.

[0060] Hereinafter, specific examples of the method for producing a lithium-containing solution according to the present invention will be described, but the present invention is not limited to these examples.

[0061] <Example 1> (Adsorption step) 10 g of a powdery lithium adsorbent H １．６ Mn １．６ O ４ and 20 g of a weakly basic anion exchange resin (A830W: manufactured by Purolite Co., Ltd.) were mixed. In this case, the weight ratio of the anion exchange resin to the lithium adsorbent is 2. This mixture was added to a 1-L beaker containing 400 mL of salt lake brine adjusted to pH 8.5 and stirred and mixed for 60 minutes to carry out the adsorption step. The analytical values of the salt lake brine used in this adsorption step are shown in Table 1. Also, the pH was measured every 10 minutes from the start of stirring and mixing until 60 minutes. The results are shown in Table 2 and FIG. 3. Also, a predetermined amount of solution was sampled from the beaker every 10 minutes.

[0062] (Elution step) Lithium manganate after adsorption present in the solution whose pH was measured was brought into contact with an acid-containing solution. The acid-containing solution was only hydrochloric acid having a hydrogen ion concentration of 0.5 mol / L. The pH of the acid-containing solution at this time was 0.4. All the solutions flowing out of the column were mixed to form a uniform solution.

[0063] (Manganese Oxidation Process) The manganese oxidation process was carried out using the second eluent. An oxidizing agent and a pH adjuster were used during this process to obtain a lithium-containing solution. The amount of lithium contained in this lithium-containing solution is shown in Table 3 and Figure 4.

[0064] <Example 2> The difference between Example 1 and Example 2 is that the anion exchange resin used in the adsorption step is 10 g of a strongly basic anion exchange resin (DIAION SA10A: manufactured by Mitsubishi Chemical Corporation). All other parameters are the same as in Example 1. The pH was measured every 10 minutes from the start of stirring and mixing until 60 minutes had passed. The results are shown in Table 2 and Figure 3. The amount of lithium contained in the lithium-containing solution obtained after the manganese oxidation step is shown in Table 3 and Figure 4.

[0065] <Example 3> The difference between Example 1 and Example 3 is that the anion exchange resin used in the adsorption step is 20 g of a strongly basic anion exchange resin (DIAION SA10A: manufactured by Mitsubishi Chemical Corporation). All other parameters are the same as in Example 1. The pH was measured every 10 minutes from the start of stirring and mixing until 60 minutes had passed. The results are shown in Table 2 and Figure 3. The amount of lithium contained in the lithium-containing solution obtained after the manganese oxidation step is shown in Table 3 and Figure 4.

[0066] <Comparative Example 1> The difference between Example 1 and Comparative Example 1 is that an anion exchange resin was not used in the adsorption process. All other parameters were the same as in Example 1. pH was measured every 10 minutes from the start of stirring and mixing until 60 minutes had passed. The results are shown in Table 2 and Figure 3. The amount of lithium contained in the lithium-containing solution obtained after the manganese oxidation process is shown in Table 3 and Figure 4.

[0067]

[0068]

[0069]

[0070] As shown in Figure 3, there was almost no difference in pH between Example 1 and Example 3 at the beginning and end of the stirring and mixing process. In Example 2, the pH remained above 8.0 even after 60 minutes of stirring and mixing, indicating less pH decrease compared to the comparative example. Furthermore, as shown in Figure 4, after 60 minutes of stirring and mixing, all examples were able to adsorb more than 1.0 mmol / g (manganese-based adsorbent), whereas in the comparative example, adsorption was insufficient during the adsorption process, and only 0.8 mmol / g (manganese-based adsorbent) of lithium was obtained.

Claims

1. A method for producing a lithium-containing solution, characterized in that: an adsorption step of contacting a lithium adsorbent obtained from lithium manganate with a low-concentration lithium-containing solution to obtain lithium manganate after adsorption; an elution step of contacting the adsorbed lithium manganate with an acid-containing solution to obtain an eluent; and a manganese oxidation step of adding an oxidizing agent and a pH adjusting agent to the eluent to oxidize manganese and obtain a lithium-containing solution with suppressed manganese concentration, wherein in the adsorption step, at least one of the following is used together with the lithium adsorbent: an anion exchange resin having a hydroxyl group bonded to a nitrogen atom, or an anion exchange resin having an amino group with a site not bonded to hydrogen.

2. The method for producing a lithium-containing solution according to claim 1, characterized in that the weight ratio of the anion exchange resin to the lithium adsorbent is 0.5 or more and 2.5 or less.

3. The method for producing a lithium-containing solution according to claim 1, characterized in that the lithium adsorbent constitutes particulate matter, and the particulate matter contains a binder.

4. The method for producing a lithium-containing solution according to claim 1, characterized in that a regeneration step is provided after the elution step to restore the function of the anion exchange resin, and the anion exchange resin that has undergone the regeneration step is used in the adsorption step.

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