Method for producing precursor for lithium adsorbent after firing, and method for producing pellets for lithium adsorption

Abstract

Provided is a method for producing a precursor of a roasted lithium adsorbent containing a large amount of tetravalent manganese having a low solubility in water. This method for producing a precursor for a roasted lithium adsorbent comprises an oxidizing roasting step for oxidizing and roasting a precursor for a powdered lithium adsorbent containing manganese at 300-600 DEG C inclusive to obtain a precursor for a powdered roasted lithium adsorbent. Divalent manganese can be converted into tetravalent manganese by oxidizing and roasting a precursor of a powdered lithium adsorbent containing manganese under predetermined temperature conditions. Since the tetravalent manganese has low solubility in water, dissolution of the lithium adsorbent in water can be suppressed when the lithium adsorbent is used.

Description

Technical Field

[0001] The present invention relates to a method for producing a calcined lithium adsorbent precursor and a method for producing lithium adsorbent granules. More specifically, the present invention relates to a method for producing a calcined lithium adsorbent precursor by oxidatively calcining a powdered lithium adsorbent precursor, and a method for producing lithium adsorbent granules containing the calcined lithium adsorbent precursor. Background Art

[0002] Non-Patent Document 1 discloses a system for recovering lithium from brine. This document describes the use of a lithium adsorbent to adsorb lithium from the brine and desorb the adsorbed lithium until high-purity Li2CO3 is produced. This document describes the lithium adsorption process using a column method.

[0003] Furthermore, a method for producing a molded body used in a column is disclosed in Patent Document 1. Patent Document 1 discloses a method for producing a molded body from a precursor of a lithium adsorbent and an inorganic binder such as alumina or silica, or a method for producing a molded body from a precursor of a lithium adsorbent and an organic binder such as chitin or polyvinyl chloride.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2011 / 058841.

[0007] Non-patent literature

[0008] Non-Patent Document 1: Tang Weiping, "Development of a System for Recovering Lithium from Brine," [online], June 11, 2011, Kagawa Industrial Support Foundation, [November 22, 2011], Internet (https: / / www.kagawa-isf.jp / wp-content / uploads / 2022 / 02 / 21tang.pdf). Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, in the case of a molded body using an inorganic binder produced by the method described in Patent Document 1, there is a problem in that the specific surface area decreases as sintering proceeds, thereby reducing the adsorption capacity.

[0011] Furthermore, the molded article produced using an organic binder by the method described in Patent Document 1 suffers from the problem of the organic binder eluting during the elution step using an acidic solution. Consequently, repeated use of the molded article can lead to disintegration of the molded article, a decrease in adsorbent, or clogging of the column by the resulting powder.

[0012] Furthermore, organic binders carbonize when subjected to temperatures of approximately 500°C after forming into a compact, so high temperatures cannot be applied after forming. When the lithium adsorbent contains manganese, there is a problem that divalent manganese cannot be oxidized to tetravalent manganese, which has low solubility in water, unless high temperatures are applied.

[0013] In view of the above circumstances, an object of the present invention is to provide a method for producing a precursor of a calcined lithium adsorbent containing a large amount of tetravalent manganese having low solubility in water, and a method for producing lithium adsorbing granules having high adsorption capacity, stronger granules, and easier shape retention.

[0014] Means for solving problems

[0015] The method for producing a calcined lithium adsorbent precursor of the first invention is characterized by comprising an oxidative calcination step of oxidatively calcining a powdery lithium adsorbent precursor containing manganese at 300° C. to 600° C. to obtain a powdery calcined lithium adsorbent precursor.

[0016] The method for producing a calcined lithium adsorbent precursor according to the second invention is characterized in that, in the first invention, the oxidizing calcination temperature in the oxidizing calcination step is 450° C. or higher and 550° C. or lower.

[0017] The method for producing granules for lithium adsorption of the third invention is characterized in that it includes: a mixing step, in which the precursor of the calcined lithium adsorbent produced by the production method of the first invention or the second invention, an organic binder and a curing agent for promoting the curing of the organic binder are mixed to obtain a mixed product; a granulation step, in which the mixed product is granulated to obtain granules; and a baking step, in which the granules are baked at a temperature of not less than 90°C and not more than 120°C to obtain granules for lithium adsorption.

[0018] A fourth invention of the method for producing lithium adsorbing granules is characterized in that, in the third invention, a drying step of drying the granules at 10° C. to 60° C. is provided after the granulation step and before the baking step.

[0019] The method for producing lithium adsorbing granules according to a fifth invention is characterized in that, in the third invention or the fourth invention, the organic binder is a copolyester.

[0020] The method for producing lithium adsorbing granules according to a sixth invention is characterized in that, in any one of the third to fifth inventions, the curing agent is a polyisocyanate.

[0021] A seventh invention provides a method for producing lithium adsorbing granules according to any one of the third to sixth inventions, wherein the organic binder accounts for 5 wt % to 20 wt % of the calcined powder of the lithium adsorbent precursor.

[0022] Effects of the Invention

[0023] According to the first invention, by oxidatively calcining a precursor of a powdered lithium adsorbent containing manganese under predetermined temperature conditions, divalent manganese can be converted to tetravalent manganese. Since tetravalent manganese has low solubility in water, dissolution of the lithium adsorbent in water can be suppressed when the lithium adsorbent is used.

[0024] According to the second invention, by setting the oxidation roasting temperature to 450° C. or higher and 550° C. or lower, divalent manganese can be converted to tetravalent manganese, and a high lithium adsorption capacity can be maintained.

[0025] According to the third invention, by including a kneading step of kneading an organic binder and a curing agent and a baking step of baking the first granules to obtain second granules, granules for lithium adsorption having high adsorption capacity, strong granules, and easy to maintain their shape can be obtained.

[0026] According to the fourth invention, by providing a drying step for drying the granules under predetermined temperature conditions before the baking step, the granules can be fed to the baking step in a state where the moisture content is low, and the granules become more solid.

[0027] According to the fifth invention, since the organic binder is a copolyester, dissolution into an acidic liquid can be further suppressed, and the granules can be made stronger.

[0028] According to the sixth invention, since the curing agent is polyisocyanate, the bonding strength of the organic binder can be further improved, and the granules can be made stronger.

[0029] According to the seventh invention, the organic binder to be kneaded accounts for 5% by weight or more and 20% by weight or less of the powder of the precursor of the lithium adsorbent, whereby the adsorption capacity of the lithium adsorbent can be maintained at a high level. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a graph showing the relationship between the oxidation calcination temperature of the lithium adsorbent precursor and the amount of manganese eluted.

[0031] Figure 2This is a graph showing the relationship between the oxidation calcination temperature of the lithium adsorbent precursor and the amount of lithium adsorbed.

[0032] Figure 3 This is a flow chart of a method for producing lithium adsorbing granules according to the first embodiment of the present invention.

[0033] Figure 4 This is a flow chart of a method for producing lithium adsorbing granules according to the second embodiment of the present invention.

[0034] Figure 5 This is a graph showing the difference in lithium adsorption amount due to different binders.

[0035] Figure 6 This is a graph showing the transition of granule reduction. DETAILED DESCRIPTION

[0036] Next, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments described below are merely examples of methods for producing a precursor of a calcined lithium adsorbent and a method for producing lithium-adsorbing granules, which embody the technical concept of the present invention. The present invention is not particularly limited to the methods described below.

[0037] The method for producing a calcined lithium adsorbent precursor according to the present invention includes an oxidative calcination step of oxidatively calcining a powdered lithium adsorbent precursor containing manganese at 300° C. to 600° C. to obtain a powdered calcined lithium adsorbent precursor.

[0038] By oxidatively calcining a precursor of a powdered lithium adsorbent containing manganese under predetermined temperature conditions, divalent manganese can be converted to tetravalent manganese. Tetravalent manganese has low solubility in water, so when the lithium adsorbent is used, its dissolution in water can be suppressed.

[0039] In the method for producing a calcined lithium adsorbent precursor according to the present invention, the oxidative calcination temperature in the oxidative calcination step is 450° C. to 550° C. By calcining at a temperature of 450° C. to 550° C., divalent manganese can be converted to tetravalent manganese, and a high lithium adsorption capacity can be maintained.

[0040] In addition, the present invention relates to a method for producing lithium adsorbent granules, comprising: a mixing step in which the precursor of the calcined lithium adsorbent, an organic binder, and a curing agent for promoting the curing of the organic binder are mixed to obtain a mixed product; a granulation step in which the mixed product is granulated to obtain granules; and a baking step in which the granules are baked at a temperature of not less than 90°C and not more than 120°C to obtain granules for lithium adsorption.

[0041] The method for producing lithium adsorbing granules includes a kneading step of kneading an organic binder and a curing agent, and a baking step of baking the granules to obtain lithium adsorbing granules. Thus, lithium adsorbing granules having high adsorption capacity and easy shape retention can be obtained.

[0042] In the method for producing lithium-adsorbing granules according to the present invention, it is preferred that a drying step of drying the granules at a temperature of 10°C to 60°C be provided after the granulation step and before the baking step. This allows the granules to be fed to the baking step with a low moisture content, resulting in a more robust granule.

[0043] In the method for producing lithium adsorbing granules according to the present invention, the organic binder is preferably a copolyester. This further suppresses dissolution in an acidic solution and makes the granules more solid.

[0044] In the method for producing lithium adsorbing granules according to the present invention, the curing agent is preferably a polyisocyanate. This can further enhance the bonding strength of the organic binder and make the granules stronger.

[0045] In the method for producing lithium adsorbing granules according to the present invention, the organic binder preferably accounts for 5% to 20% by weight of the lithium adsorbent precursor powder, thereby maintaining the adsorption capacity of the lithium adsorbent at a high level.

[0046] <Embodiment of the method for producing a calcined lithium adsorbent precursor>

[0047] (Precursor of lithium adsorbent)

[0048] The lithium adsorbent is not particularly limited as long as it contains manganese and selectively adsorbs lithium from a solution containing lithium. Examples of lithium adsorbents include H2O3 obtained from lithium manganate. 1.6 Mn 1.6 O4、H 1.33 Mn 1.67O4, etc. These lithium adsorbents are preferably lithium adsorbents produced by a wet production method. This is because it is easy to obtain the lithium adsorbent in powder form during the production stage. However, this is not limited to this, and there is no problem with lithium adsorbents produced by a dry production method. The lithium adsorbent is obtained by preparing Li 1.6 Mn 1.6 O4、Li 1.33 Mn 1.67 O4 is obtained by replacing Li with hydrogen as shown in formulas 1 and 2.

[0049] [Formula 1]

[0050] Li 1.6 Mn 1.6 O4 + 1.6HCl → H 1.6 Mn 1.6 O4+1.6LiCl

[0051] [Formula 2]

[0052] Li 1.33 Mn 1.67 O4 + 1.33HCl → H 1.33 Mn 1.67 O4+1.33LiCl

[0053] (Oxidation roasting process)

[0054] The precursor of the lithium adsorbent sometimes contains components that are not fully oxidized. Therefore, the method for manufacturing the precursor of the lithium adsorbent after calcination involved in this embodiment has an oxidation roasting step. In the oxidation roasting step, the precursor of the powdered lithium adsorbent containing manganese is oxidation roasted at a temperature of 300°C to 600°C to obtain the precursor of the lithium adsorbent after calcination. The oxidation roasting step uses, for example, an electric furnace. The oxidation roasting time is preferably set to 2 hours to 24 hours. As long as there is oxygen, the environment inside the electric furnace is fine. For example, by supplying the atmosphere into the furnace, a preferred environment can be formed. In order to promote oxidation roasting, the temperature inside the furnace is preferably 300°C to 600°C as described above. In addition, considering the lithium adsorption capacity after oxidation roasting, it is further preferably 450°C to 550°C.

[0055] By oxidizing and calcining the precursor of the powdered lithium adsorbent containing manganese under a predetermined temperature condition, divalent or trivalent manganese can be converted to tetravalent manganese. The compound containing divalent or trivalent manganese contained in the precursor of the lithium adsorbent is Li 0.8 Mn 1.8 O 3.5 For example, the reaction is shown in Formula 3. Tetravalent manganese has low solubility in water, so when a lithium adsorbent is used, the dissolution of the lithium adsorbent in water can be suppressed.

[0056] [Formula 3]

[0057] 4Li 0.8 Mn 1.8 O 3.5 +O2→2Li 1.6 Mn 1.6 O4+4MnO2

[0058] In the method for producing a calcined lithium adsorbent precursor according to the present invention, the oxidative calcination temperature in the oxidative calcination step is 450° C. to 550° C. By calcining at a temperature of 450° C. to 550° C., divalent manganese can be converted to tetravalent manganese, and a high lithium adsorption capacity can be maintained.

[0059] <First embodiment of the method for producing lithium adsorbing granules>

[0060] exist Figure 3 A flow chart of a method for producing lithium adsorbent granules according to the first embodiment of the present invention is shown in FIG. The powder of the lithium adsorbent precursor is used in the oxidative roasting step of the method for producing the calcined lithium adsorbent precursor. The calcined lithium adsorbent precursor obtained is used in the kneading step described below.

[0061] (Organic binder)

[0062] An organic binder is used in the kneading process. Examples of organic binders include copolyesters, which are polyesters, chitin, and PVC (polyvinyl chloride), with copolyesters being preferred. Using a copolyester as the organic binder further suppresses dissolution in acidic solutions, resulting in a more robust granule.

[0063] (Curing Agent)

[0064] Curing agents are used in the mixing process. Curing agents are used to accelerate the curing of the organic binder. "Accelerated curing" means, for example, further hardening or accelerating the hardening of the finished product, thereby enhancing the effectiveness of the organic binder as a binder. There are many types of curing agents, but polyisocyanates are preferred. Hexamethylene diisocyanate-based polyisocyanates are even more preferred. Using a polyisocyanate as the curing agent further enhances the bonding strength of the organic binder, making the granules more durable.

[0065] (Mixing process)

[0066] When commercializing a method for producing a lithium-containing solution from a lithium adsorbent, the most appropriate method is to granulate the lithium adsorbent, store it in a predetermined container, and then pass an acid solution such as hydrochloric acid through the container. In this case, the precursor of the lithium adsorbent needs to be granulated after calcination.

[0067] The method for producing lithium-adsorbing granules according to this embodiment includes a kneading step. In this kneading step, a calcined powder of a lithium adsorbent precursor, an organic binder, and a curing agent are kneaded to produce a kneaded product. In the kneading step, the calcined powder of the lithium adsorbent precursor, the organic binder, and the curing agent are kneaded, but preferably, a liquid such as water is added at this time.

[0068] The amount of the organic binder used in the mixing process is preferably not less than 5% by weight and not more than 20% by weight of the powder of the precursor of the calcined lithium adsorbent. When the amount of the organic binder is less than 5% by weight, the organic binder is too little and does not adhere. In addition, when the amount of the organic binder is greater than 20% by weight, the proportion of the precursor of the calcined lithium adsorbent contained in the final form of the granules becomes smaller, and the specified adsorption capacity cannot be obtained. By keeping the amount of the organic binder within the above range, the adsorption capacity of the lithium adsorbent can be maintained at a high level. In addition, the amount of the curing agent is preferably determined to be a preferred amount relative to the organic binder.

[0069] (Granulation process)

[0070] like Figure 3 As shown, in the granulation step, the kneaded material obtained in the kneading step is granulated to obtain granules. The size of the granules is not particularly limited, but in order to make the particle size of the final lithium adsorption granules be greater than or equal to 0.5 mm and less than or equal to 1.5 mm, the particle size of the granules is preferably greater than or equal to 0.5 mm and less than or equal to 1.5 mm. The particle size of the granules involved in this embodiment is within a specific range, and specifically, it can be confirmed using a sieve with a mesh size corresponding to each particle size based on the JIS Z8801 standard. It should be noted that it is not necessary for all granules to have this particle size, as long as it is a predetermined ratio. For example, the predetermined ratio is preferably 90% or more. When the particle size of the granules is greater than or equal to 0.5 mm, when the granules of the present invention are filled into a container and water is passed through, the granules are not easily clogged in the container, and the pressure loss in the container can be prevented from increasing. When the particle size is larger than 1.5 mm, the lithium adsorption rate slows down and the adsorption efficiency deteriorates. However, by setting the particle size to 1.5 mm or less, the adsorption performance can be improved.

[0071] In the granulation process, granulation is carried out, i.e., extrusion is initially carried out, and the extrudate is made into granules by, for example, stirring and mixing granulation, rolling granulation, extrusion granulation, crushing granulation, fluidized bed granulation, spray drying granulation (spray drying), compression granulation, etc. If it is a material in an extruded state, since its shape has sharp corners, the sharp corners are removed by granulation, so that when it is filled into a column and used, the generation of fragments caused by damage can be suppressed. Granulation is preferably made into a spherical shape. By being made into a spherical shape, since there is no edge, the crushing caused by the contact of granulation bodies can be suppressed. Here, for the granulated granules, when considering 3 mutually orthogonal coordinates from the center of the granule to XYZ, it is preferred that the lengths in the X direction, Y direction and Z direction are roughly the same (for example, the maximum length is less than 3 times the minimum length).

[0072] When the particle size of the lithium adsorbing granules is 0.5 mm or more and 1.5 mm or less, the contact area between the lithium adsorbing granules and the lithium contained in the lithium-containing solution can be further increased, and clogging of the column can be prevented.

[0073] (Drying process)

[0074] like Figure 3 As shown, in this embodiment, the granules obtained in the granulation step are dried for a predetermined time at 10° C. to 60° C. Such drying allows the granules to be fed to the baking step with less water content, making the granules more solid.

[0075] The temperature of the drying step is preferably room temperature. For example, it is more preferably 20° C. or higher and 30° C. or lower. The predetermined time is preferably 20 hours or higher and 30 hours or lower, for example.

[0076] (Baking process)

[0077] like Figure 3 As shown, in the baking step, the granules obtained in the granulation step and subjected to the drying step are baked to obtain lithium-adsorbing granules. The granules are baked, for example, in an electric furnace at a predetermined temperature for a predetermined time to obtain lithium-adsorbing granules. The optimal temperature and time are determined depending on the organic binder and curing agent used.

[0078] The temperature is preferably 90° C. to 120° C., more preferably 100° C. to 110° C. The holding time is preferably 0.5 hours to 2 hours.

[0079] (Processing after baking process and before desorption process)

[0080] The lithium adsorption granules manufactured by the above-mentioned method for manufacturing lithium adsorption granules are preferably washed with acid to rinse out soluble divalent manganese or washed with alkali to rinse out hexavalent and heptavalent manganese before the subsequent desorption process of converting the precursor of the lithium adsorbent into the lithium adsorbent. For example, the acid washing is preferably carried out using 1 mol / L hydrochloric acid, which is about 15 times the concentration of the precursor of the lithium adsorbent. In addition, the alkali washing is preferably carried out by immersing in a 1 mol / L lithium hydroxide solution for 1 hour. In this case, the lithium hydroxide solution is preferably set to 6 times the concentration of the precursor of the lithium adsorbent. In addition, after the alkali washing is completed, it is preferably washed with pure water and dried.

[0081] <Second embodiment of the method for producing lithium adsorbing granules>

[0082] exist Figure 4 A flow chart of a method for producing lithium-adsorbing granules according to a second embodiment of the present invention is shown in FIG. This method differs from the first embodiment in that the drying step between the granulation and baking steps is omitted. Other aspects are the same as those of the first embodiment, and therefore detailed descriptions are omitted.

[0083] In this embodiment, the granules obtained in the granulation step are sent to the baking step without undergoing the drying step. In this case, the materials in the kneading step or the temperature or time in the baking step are adjusted to reduce the moisture content of the granules.

[0084] <Example of a method for producing a calcined lithium adsorbent precursor>

[0085] Hereinafter, specific examples of the method for producing the precursor of the calcined lithium adsorbent according to the present invention will be described, but the present invention is not limited to these examples.

[0086] <Example 1>

[0087] 20 g of a powdery lithium adsorbent precursor L containing manganese produced by a wet production method was prepared. 1.6 Mn 1.6 O4. The precursor of the lithium adsorbent was subjected to an oxidation roasting process. That is, the precursor of the lithium adsorbent was subjected to oxidation roasting at 300°C for 5 hours using an electric furnace. The precursor of the calcined lithium adsorbent was obtained by the oxidation roasting. The obtained precursor of the calcined lithium adsorbent was put into 300ml of pure water and stirred for 10 minutes. After stirring, the supernatant was separated and the amount of manganese in the supernatant was measured using an ICP emission spectrometer. The results are shown in Tables 1 and Figure 1 middle.

[0088] In addition, the precursor of the lithium adsorbent after calcination after separation of the supernatant was directly brought into contact with hydrochloric acid in a powdered form as a pre-adsorption treatment to prepare a lithium adsorbent. This lithium adsorbent weighed 10 g. Using this lithium adsorbent, an adsorption process was performed on a lithium solution containing lithium at a concentration of 0.5%, and an elution process was performed using hydrochloric acid at a concentration of 2%, and the amount of lithium adsorbed per unit weight of the lithium adsorbent was measured. The results are shown in Tables 1 and Figure 2 middle.

[0089] <Example 2>

[0090] The oxidation roasting step was carried out under the same conditions as in Example 1 except that the temperature in the oxidation roasting step was set to 350°C. The amount of manganese is shown in Tables 1 and Figure 1 In addition, the lithium adsorption amount is shown in Table 1 and Figure 2 middle.

[0091] <Example 3>

[0092] The oxidation roasting step was carried out under the same conditions as in Example 1 except that the temperature in the oxidation roasting step was set to 400°C. The amount of manganese is shown in Tables 1 and Figure 1 In addition, the lithium adsorption amount is shown in Table 1 and Figure 2 middle.

[0093] <Example 4>

[0094] The oxidation roasting step was carried out under the same conditions as in Example 1 except that the temperature in the oxidation roasting step was set to 450°C. The amount of manganese is shown in Tables 1 and Figure 1 In addition, the lithium adsorption amount is shown in Table 1 and Figure 2 middle.

[0095] <Example 5>

[0096] The oxidation roasting step was carried out under the same conditions as in Example 1 except that the temperature in the oxidation roasting step was set to 500°C. The amount of manganese is shown in Tables 1 and Figure 1 In addition, the lithium adsorption amount is shown in Table 1 and Figure 2 middle.

[0097] <Example 6>

[0098] The oxidation roasting step was carried out under the same conditions as in Example 1 except that the temperature in the oxidation roasting step was set to 550°C. The amount of manganese is shown in Tables 1 and Figure 1 In addition, the lithium adsorption amount is shown in Table 1 and Figure 2 middle.

[0099] <Example 7>

[0100] The oxidation roasting step was carried out under the same conditions as in Example 1 except that the temperature in the oxidation roasting step was set to 600°C. The amount of manganese is shown in Tables 1 and Figure 1 In addition, the lithium adsorption amount is shown in Table 1 and Figure 2 middle.

[0101] Comparative Example 1

[0102] The oxidation roasting step was carried out under the same conditions as in Example 1 except that the temperature in the oxidation roasting step was set to 250°C. The amount of manganese is shown in Tables 1 and Figure 1 In addition, the lithium adsorption amount is shown in Table 1 and Figure 2 middle.

[0103] Comparative Example 2

[0104] The oxidation roasting step was carried out under the same conditions as in Example 1 except that the temperature in the oxidation roasting step was set to 650°C. The amount of manganese is shown in Tables 1 and Figure 1 In addition, the lithium adsorption amount is shown in Table 1 and Figure 2 middle.

[0105] Comparative Example 3

[0106] The oxidation roasting step was carried out under the same conditions as in Example 1 except that the temperature in the oxidation roasting step was set to 700°C. The amount of manganese is shown in Tables 1 and Figure 1 In addition, the lithium adsorption amount is shown in Table 1 and Figure 2 middle.

[0107] [Table 1]

[0108] Oxidation roasting temperature ℃ 250 300 350 400 450 500 550 600 650 700 Mn dissolution mg 59 37 28 28 30 32 34 40 70 77 Li adsorption capacity mmol / g 3.45 3.5 3.55 3.63 3.73 3.77 3.76 3.5 2.56 1.9

[0109] The standard value of manganese dissolution is 40 mg. Figure 1 As can be seen from Table 1, in Examples 1 to 7, that is, when the oxidation roasting temperature was 300° C. or higher and 600° C. or lower, the amount of manganese elution was suppressed.

[0110] In addition, regarding the Li adsorption amount, Figure 2 The vertical axis represents the amount of Li in mmol relative to the precursor of the calcined lithium adsorbent. 1.6 Mn 1.6 The amount of Li obtained from the number of grams of O4. The reference value at this time is 3.7mmol / g. Figure 2 As can be seen from Table 1, in Examples 4 to 6, that is, when the oxidation roasting temperature is 450° C. or higher and 550° C. or lower, the Li adsorption capacity can be maintained.

[0111] <Example of a method for producing lithium adsorbing granules>

[0112] <Example 1a>

[0113] (Mixing process)

[0114] Example 6 of the method for producing the precursor of the calcined lithium adsorbent, that is, the lithium manganate Li as the precursor of the calcined lithium adsorbent is calcined at an oxidation calcination temperature of 550 degrees. 1.6 Mn 1.6 900 g of O4 powder was placed in a kneader and the kneader was rotated. Next, 451 g of a water-dispersible polyester resin (VYLONAL MD1500, manufactured by Toyobo Co., Ltd.: 30% copolyester content) and 29 g of a hexamethylene diisocyanate-based polyisocyanate (Duranate WM44-L70G, manufactured by Asahi Kasei Corporation: 60-70% blocked polyisocyanate content) as a curing agent were weighed and placed in the kneader. In this case, the organic binder, representing 30% of the 451 g, amounted to 135.3 g, which represented 15.03% by weight of the 900 g lithium manganate powder. The mixed powder was rotated in the kneader for approximately 15-20 minutes to distribute the organic binder throughout the mixture and to form a small number of lumps, thereby obtaining a kneaded product.

[0115] (Granulation process)

[0116] The kneaded product obtained in the kneading step was placed in a granulator to obtain a cylindrical molded body having a diameter of about 1 mm and a length of 1 mm. This molded body was then placed in a rotating tumbling granulator and tumbling granulated (sizing) for about 3 to 10 seconds to obtain granules having a diameter of about 1 mm.

[0117] (Drying process)

[0118] The granules obtained in the granulation step were spread on a square pan (vat) and naturally dried at room temperature for about 1 day.

[0119] (Baking process)

[0120] The granules after the drying step were heated in an electric furnace at 90° C. for 0.5 hours to solidify the organic binder and the like, thereby obtaining granules for lithium adsorption.

[0121] (Desorption process)

[0122] The lithium adsorbing granules after the baking step were placed in a column and desorbed using 0.5 mol / L hydrochloric acid. After desorption, pure water was passed through the column for washing to remove residual hydrochloric acid.

[0123] (Adsorption process)

[0124] After the desorption process, brine with a predetermined lithium concentration is passed through a column containing lithium-adsorbing granules. The lithium contained in the brine is adsorbed by the lithium adsorbent contained in the lithium-adsorbing granules. After the brine has passed through, pure water is passed through the column to remove any remaining brine.

[0125] (Elution process)

[0126] After the adsorption step, 0.5 mol / L hydrochloric acid was passed through the column containing the lithium adsorption granules to elute the lithium adsorbed on the lithium adsorbent. Figure 5 The graph in FIG2 shows the amount of lithium eluted in the elution step. Figure 5 The horizontal axis represents time, and the vertical axis represents the molar amount of lithium obtained relative to the weight of the lithium adsorbent.

[0127] The results of Example 1 are represented by quadrilaterals.

[0128] (repeatedly)

[0129] After the elution step, the column filled with lithium adsorbing granules was used directly, and the adsorption step and elution step were repeated. The proportion of lithium adsorbing granules that could not maintain their morphology was shown in FIG. Figure 6 middle. Figure 6 The horizontal axis represents the number of cycles, and the vertical axis represents the proportion of lithium adsorbing granules that cannot maintain their morphology, that is, the granule reduction rate. The results of Example 1 using the copolyester are represented by squares.

[0130] <Comparative Example 1a>

[0131] (Mixing process)

[0132] As in Example 1a, lithium manganate Li and lithium nitrate as precursors of the calcined lithium adsorbent were weighed. 1.6 Mn 1.6 800g of O4 powder and 200g of alumina, an inorganic binder, were pre-mixed in a plastic bag. 1000g of this mixed powder was placed in a kneader, and water was added while the kneader was rotated. The kneader was rotated for several minutes to distribute the water throughout the kneaded product.

[0133] (Granulation process)

[0134] The kneaded product obtained in the kneading step is extruded and fed into a pelletizer to obtain cylindrical molded bodies with a diameter of about 1 mm to 3 mm from the orifice. The molded pellets are then cut into lengths of 3 mm to 6 mm.

[0135] (Drying process)

[0136] The molded body obtained in the granulation step was spread on a square tray and dried in a dryer at 80° C. or higher for about 1 day.

[0137] (Sintering process)

[0138] The compact after the drying step was sintered in an electric furnace at 500° C. for 1.5 hours to obtain sintered granules.

[0139] (Desorption process)

[0140] The sintered granules were placed in a column and desorbed using 1 mol / L hydrochloric acid. After desorption, pure water was passed through the column for washing to remove residual hydrochloric acid.

[0141] (Adsorption process)

[0142] After the desorption process, brine with a predetermined lithium concentration is passed through a column containing sintered granules, allowing the lithium contained in the brine to be adsorbed by the lithium adsorbent contained in the lithium adsorption granules. After the brine has passed through, pure water is passed through the column to remove any remaining brine.

[0143] (Elution process)

[0144] After the adsorption step, 1 mol / L hydrochloric acid was passed through the column containing the sintered granules to elute the lithium adsorbed on the lithium adsorbent. The amount of lithium eluted in this elution step is shown in FIG. Figure 5 The results of Comparative Example 1 are indicated by circles. In addition, for reference, the case where the lithium adsorbent adsorbed lithium in a powdered state is indicated by triangles.

[0145] Depend on Figure 5 It can be seen that the adsorption capacity of lithium adsorbent granules using copolyester as an organic binder is about 2 mmol per 1 g of the lithium adsorbent precursor, which is worse than the powder state. However, the adsorption capacity of sintered granules using alumina as an inorganic binder is about 1.3 mmol / g. The adsorption force of lithium adsorbent granules using an organic binder is higher than that of the inorganic binder.

[0146] (repeatedly)

[0147] After the elution step, the column containing the sintered granules was used directly to repeat the adsorption step and the elution step. The proportion of the sintered granules that could not maintain their morphology was shown in FIG. Figure 6 The results of Comparative Example 1 using aluminum oxide are indicated by circles.

[0148] like Figure 6As shown, the sintered granules formed using an inorganic alumina binder gradually disintegrate after approximately 50 cycles, and disintegrate rapidly after 60 cycles. On the other hand, the lithium adsorbing granules using the copolyester have a reduction rate of 10% even after 300 cycles, and almost no disintegration is observed.

Claims

1. A method for producing a precursor of a calcined lithium adsorbent, characterized in that: include: The step of oxidizing and calcining the precursor of the powdery lithium adsorbent containing manganese is oxidized and calcined at 300° C. to 600° C. to obtain a powdery calcined precursor of the lithium adsorbent.

2. The method for producing a precursor of a calcined lithium adsorbent according to claim 1, wherein: The temperature of the oxidation roasting in the oxidation roasting step is 450° C. or higher and 550° C. or lower.

3. A method for producing lithium adsorbing granules, characterized in that: include: a kneading step of kneading the precursor of the calcined lithium adsorbent produced by the method for producing a precursor of the calcined lithium adsorbent according to claim 1 or 2, an organic binder, and a curing agent for promoting curing of the organic binder to obtain a kneaded product; a granulation step of granulating the kneaded product to obtain granules; and A baking step of baking the granules at a temperature of 90° C. to 120° C. to obtain granules for lithium adsorption.

4. The method for producing lithium adsorbing granules according to claim 3, wherein: The drying step of drying the granules at 10° C. or higher and 60° C. or lower is provided after the granulation step and before the baking step.

5. The method for producing lithium adsorbing granules according to claim 3 or 4, wherein: The organic binder is copolyester.

6. The method for producing lithium adsorbing granules according to any one of claims 3 to 5, wherein The curing agent is polyisocyanate.

7. The method for producing lithium adsorbing granules according to any one of claims 3 to 6, wherein The organic binder accounts for 5% by weight or more and 20% by weight or less of the powder of the calcined lithium adsorbent precursor.

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