Method for producing precursor of roasted lithium adsorbent and method for producing granules for lithium adsorption

Abstract

Provided is a method for producing a lithium adsorbent precursor after roasting, the precursor comprising a large amount of tetravalent manganese with low solubility in water.　The method for producing a lithium adsorbent precursor after roasting includes an oxidative roasting step for subjecting a powdery lithium adsorbent precursor containing manganese to oxidative roasting at a temperature of 300 °C to 600 °C to obtain a powdery lithium adsorbent precursor after roasting. By subjecting the powdery lithium adsorbent precursor containing manganese to oxidative roasting at a predetermined temperature, divalent manganese can be converted into tetravalent manganese. Since tetravalent manganese has low solubility in water, it is possible to suppress the lithium adsorbent from dissolving in water at the time of use of the lithium adsorbent.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a precursor of a roasted lithium adsorbent and a method for producing granules for adsorbing lithium. More specifically, the present invention relates to a method for producing a precursor of a roasted lithium adsorbent by oxidatively roasting a powdery precursor of a lithium adsorbent, and a method for producing granules for adsorbing lithium, including the precursor of a roasted lithium adsorbent. [Background technology]

[0002] Non-Patent Document 1 discloses a system for recovering lithium from brine. This document discloses the process of using a lithium adsorbent to adsorb lithium from brine, and then desorbing the adsorbed lithium to produce high-purity Li2CO3. This document also describes that lithium adsorption is performed using a column method.

[0003] Patent Document 1 also discloses a method for producing a molded body to be used in a column, which method comprises producing a molded body from a precursor of a lithium adsorbent and an inorganic binder such as alumina or silica, or from a precursor of a lithium adsorbent and an organic binder such as chitin or polyvinyl chloride. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2011 / 058841 [Non-patent literature]

[0005] [Non-Patent Document 1] Yu, Eihei, "Development of a lithium recovery system from brine," [online], June 11, 2010, Kagawa Industrial Support Foundation, [November 22, 2018], Internet (https: / / www.kagawa-isf.jp / wp-content / uploads / 2022 / 02 / 21tang.pdf) Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of a molded body using an inorganic binder produced by the method described in Patent Document 1, the specific surface area decreases as sintering progresses, which causes a problem of a decrease in adsorption capacity. Furthermore, in the case of a compact using an organic binder manufactured by the method described in Patent Document 1, there is a problem that the organic binder elutes during the elution step using an acidic solution, and therefore repeated use of the compact can cause the compact to collapse, reducing the adsorbent and clogging the column with the resulting powder. In addition, for organic binders, if high temperatures of around 500°C are applied after molding, the organic binder will carbonize, so high temperatures cannot be applied after molding. If the lithium adsorbent contains manganese, the problem is that divalent manganese cannot be oxidized to tetravalent manganese, which has low solubility in water, unless high temperatures can be applied.

[0007] In view of the above circumstances, an object of the present invention is to provide a method for producing a precursor of a roasted lithium adsorbent that contains a large amount of tetravalent manganese, which has low solubility in water, and a method for producing granules for adsorbing lithium, which have a high adsorption capacity, are more robust, and can easily maintain their shape. [Means for solving the problem]

[0008] The method for producing a granule for adsorbing lithium according to the first aspect of the present invention comprises the steps of: Bivalent or trivalentThe method includes an oxidizing roasting step of oxidizing roasting a powdered lithium adsorbent precursor containing manganese at 300°C or higher and 600°C or lower to obtain a powdered post-roasted lithium adsorbent precursor containing lithium manganate; a kneading step of kneading the post-roasted lithium adsorbent precursor with an organic binder and a curing agent for accelerating curing of the organic binder to obtain a kneaded mixture; a granulating step of granulating the kneaded mixture to obtain granules; and a baking step of baking the granules at 90°C or higher and 120°C or lower to obtain granules for lithium adsorption, wherein the organic binder is a copolymer polyester and the curing agent is a polyisocyanate. The method for producing a granule for adsorbing lithium according to a second aspect of the present invention is characterized in that, in the method according to the first aspect of the present invention, a drying step of drying the granule at a temperature of 10°C or higher and 60°C or lower is provided after the granulation step and before the baking step. The method for producing a granule for adsorbing lithium according to a third aspect of the present invention is characterized in that, in the first or fourth aspect of the present invention, the organic binder accounts for 5% by weight or more and 20% by weight or less of the powder of the precursor of the roasted lithium adsorbent. [Effects of the Invention]

[0009] According to the first invention, divalent manganese can be converted to tetravalent manganese by oxidizing and roasting a powdered precursor of a lithium adsorbent containing manganese at a predetermined temperature. Tetravalent manganese has low solubility in water, so when the lithium adsorbent is used, dissolution of the lithium adsorbent in water can be suppressed. Furthermore, by including a kneading step of kneading an organic binder and a curing agent together, and a baking step of baking the first granules to obtain second granules, it is possible to obtain granules for adsorbing lithium that have high adsorption capacity, are robust, and can easily maintain their shape. Furthermore, by using a copolymer polyester as the organic binder, elution in an acidic solution can be further suppressed, and the granules become even more robust. Furthermore, by using polyisocyanate as the curing agent, the adhesive strength of the organic binder can be further increased, making the granules even stronger. According to the fourth aspect of the present invention, a drying step in which the granules are dried at a predetermined temperature is provided before the baking step. This allows the granules to be subjected to the baking step with less moisture in the granules, making the granules more durable. According to the seventh invention, the organic binder to be kneaded is 5% by weight or more and 20% by weight or less of the powder of the precursor of the lithium adsorbent, so that the adsorption capacity of the lithium adsorbent can be maintained at a high level. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a graph showing the relationship between the oxidizing roasting temperature and the amount of manganese eluted from a precursor of a lithium adsorbent. [Figure 2] 1 is a graph showing the relationship between the oxidizing roasting temperature and the amount of lithium adsorbed for a precursor of a lithium adsorbent. [Figure 3] FIG. 1 is a flow diagram of a method for producing lithium adsorbing granules according to a first embodiment of the present invention. [Figure 4] FIG. 4 is a flow diagram of a method for producing lithium adsorbing granules according to a second embodiment of the present invention. [Figure 5] 1 is a graph showing the difference in lithium adsorption amount depending on the binder. [Figure 6] 1 is a graph showing the progress of the reduction in granules. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below exemplify a method for producing a precursor of a roasted lithium adsorbent and a method for producing granules for lithium adsorption to embody the technical concept of the present invention, and the present invention does not limit the methods for producing a precursor of a roasted lithium adsorbent and a method for producing granules for lithium adsorption to those described below.

[0012] The method for producing a precursor of a roasted lithium adsorbent according to the present invention includes an oxidizing roasting step of oxidizing roasting a powdered precursor of a lithium adsorbent containing manganese at 300°C or more and 600°C or less to obtain a powdered precursor of a roasted lithium adsorbent.

[0013] Divalent manganese can be converted to tetravalent manganese by oxidizing and roasting a powdered lithium adsorbent precursor containing manganese at a predetermined temperature. Tetravalent manganese has low solubility in water, so when the lithium adsorbent is used, dissolution of the lithium adsorbent in water can be suppressed.

[0014] In addition, in the method for producing a precursor of a roasted lithium adsorbent according to the present invention, the oxidizing roasting temperature in the oxidizing roasting step is 450° C. or more and 550° C. or less. By setting the oxidizing roasting temperature to 450° C. or more and 550° C. or less, divalent manganese can be converted to tetravalent manganese, and the lithium adsorption capacity can be maintained at a high level.

[0015] Furthermore, the method for producing granules for adsorbing lithium according to the present invention includes a kneading step of kneading a precursor of the roasted lithium adsorbent, an organic binder, and a curing agent for accelerating curing of the organic binder to obtain a kneaded mixture; a granulation step of granulating the kneaded mixture to obtain granules; and a baking step of baking the granules at a temperature of 90°C or higher and 120°C or lower to obtain granules for adsorbing lithium.

[0016] The method for producing lithium-adsorbing granules includes a kneading step of kneading an organic binder and a curing agent together, and a baking step of baking the granules to obtain lithium-adsorbing granules. This makes it possible to obtain lithium-adsorbing granules that have high adsorption capacity and that easily maintain their shape.

[0017] Furthermore, in the method for producing granules for lithium adsorption according to the present invention, a drying step of drying the granules at a temperature of 10° C. to 60° C. is preferably performed after the granulation step and before the baking step. This allows the granules to be subjected to the baking step with a low moisture content, making the granules more robust.

[0018] In the method for producing granules for adsorbing lithium according to the present invention, the organic binder is preferably a copolymer polyester, which can further suppress elution in an acidic solution and make the granules even more robust.

[0019] In the method for producing granules for adsorbing lithium according to the present invention, the curing agent is preferably polyisocyanate, which can further increase the bonding strength of the organic binder and make the granules even more robust.

[0020] In the method for producing granules for adsorbing lithium according to the present invention, the organic binder is preferably contained in an amount of 5% by weight to 20% by weight of the powder of the precursor of the lithium adsorbent, thereby enabling the adsorption capacity of the lithium adsorbent to be maintained at a high level.

[0021] <Embodiment of Method for Producing Precursor of Roasted Lithium Adsorbent> (Lithium adsorbent precursor) The lithium adsorbent is not particularly limited as long as it contains manganese and selectively adsorbs lithium from a solution containing lithium. Examples of the lithium adsorbent include H obtained from lithium manganate. 1.6 Mn 1.6 O4, H 1.33 Mn 1.67 O4, etc. These lithium adsorbents are preferably manufactured by a wet manufacturing method, because it is easy to obtain them in powder form at the manufacturing stage. However, this is not limited to this, and there is no problem even if they are manufactured by a dry manufacturing method. The lithium adsorbent is made by using Li, which is a precursor of the lithium adsorbent. 1.6 Mn 1.6 O4, Li 1.33Mn 1.67 It can be obtained by replacing Li with hydrogen from O4 as shown in equations 1 and 2.

[0022] [Number 1] Li 1.6 Mn 1.6 O4 + 1.6HCl → H 1.6 Mn 1.6 O4+1.6LiCl

[0023] [Number 2] Li 1.33 Mn 1.67 O4 + 1.33HCl → H 1.33 Mn 1.67 O4+1.33LiCl

[0024] (Oxidation roasting process) The lithium adsorbent precursor may contain a composition that is not sufficiently oxidized. Therefore, the method for producing a roasted lithium adsorbent precursor according to this embodiment includes an oxidizing roasting step. In the oxidizing roasting step, a powdered lithium adsorbent precursor containing manganese is oxidizing roasted at 300°C to 600°C to obtain a roasted lithium adsorbent precursor. For example, an electric furnace or the like is used for the oxidizing roasting step. The oxidizing roasting time is preferably, for example, 2 hours to 24 hours. The atmosphere inside the electric furnace does not pose a problem as long as oxygen is present. For example, a preferable atmosphere can be achieved by supplying air into the furnace. To promote oxidizing roasting, the temperature inside the furnace is preferably 300°C to 600°C, as described above. Furthermore, considering the lithium adsorption capacity after oxidizing roasting, a temperature of 450°C to 550°C is more preferable.

[0025] By oxidizing and roasting a powdered precursor of a lithium adsorbent containing manganese at a predetermined temperature, divalent or trivalent manganese can be converted to tetravalent manganese. 0.8 Mn 1.8 O 3.5For example, the reaction is as shown in Equation 3. Tetravalent manganese has low solubility in water, so when using a lithium adsorbent, it can prevent the lithium adsorbent from dissolving in water.

[0026] [Number 3] 4Li 0.8 Mn 1.8 O 3.5 +O2 → 2Li 1.6 Mn 1.6 O4+4MnO2

[0027] In addition, in the method for producing a precursor of a roasted lithium adsorbent according to the present invention, the oxidizing roasting temperature in the oxidizing roasting step is 450° C. or more and 550° C. or less. By setting the oxidizing roasting temperature to 450° C. or more and 550° C. or less, divalent manganese can be converted to tetravalent manganese, and the lithium adsorption capacity can be maintained at a high level.

[0028] <First embodiment of the method for producing granules for lithium adsorption> 3 is a flow diagram of a method for producing granules for adsorbing lithium according to a first embodiment of the present invention. The precursor powder of the lithium adsorbent is used in the oxidation roasting step of the method for producing the precursor of the roasted lithium adsorbent, and the obtained precursor of the roasted lithium adsorbent is used in the kneading step described below.

[0029] (organic binder) An organic binder is used in the kneading process. Examples of organic binders include copolymer polyester, which is a type of polyester, chitin, and PVC, but copolymer polyester is preferred. By using copolymer polyester as the organic binder, elution in acidic solutions can be further suppressed, making the granules even more robust.

[0030] (hardening agent) A curing agent is used in the kneading process. The curing agent is used to accelerate the curing of the organic binder. "Accelerating curing" means, for example, making the finished product harder or accelerating the hardening process, thereby increasing the effect of the organic binder as a binder. There are various curing agents, but polyisocyanate is preferred. Hexamethylene diisocyanate-based polyisocyanate is even more preferred. By using polyisocyanate as the curing agent, the bonding strength of the organic binder can be further increased, making the granules even more robust.

[0031] (Kneading process) To commercially realize a production method for obtaining a lithium-containing solution containing lithium from a lithium adsorbent, the most suitable method is to granulate the lithium adsorbent, place it in a predetermined container, and pass an acid solution such as hydrochloric acid through the container. In this case, it is necessary to granulate the precursor of the lithium adsorbent after roasting.

[0032] The method for producing lithium adsorbent granules according to this embodiment includes a kneading step. In this kneading step, a powder of a precursor of the roasted lithium adsorbent, an organic binder, and a curing agent are kneaded together to obtain a kneaded product. In the kneading step, the powder of the precursor of the roasted lithium adsorbent, the organic binder, and the curing agent are kneaded together, and it is preferable that a liquid such as water is added during the kneading step.

[0033] The amount of organic binder used in the kneading step is preferably 5% by weight or more and 20% by weight or less of the powder of the precursor of the roasted lithium adsorbent. If it is less than 5% by weight, the amount of organic binder is too small to bond the powder. If it is more than 20% by weight, the proportion of the precursor of the roasted lithium adsorbent contained in the final granules becomes too small, making it impossible to obtain the desired adsorption capacity. By keeping the amount of organic binder within the above range, the adsorption capacity of the lithium adsorbent can be maintained at a high level. In addition, it is preferable to determine the amount of curing agent to be a preferred amount relative to the organic binder.

[0034] (granulation process) As shown in FIG. 3 , in the granulation step, the kneaded product obtained in the kneading step is granulated to obtain granules. While the size of the granules is not particularly limited, it is preferable that the particle size of the granules be 0.5 mm or more and 1.5 mm or less so that the particle size of the final lithium adsorption granules is 0.5 mm or more and 1.5 mm or less. Specifically, whether the particle size of the granules according to this embodiment is within a specific range can be confirmed using a sieve with openings corresponding to each particle size according to the JIS Z8801 standard. It is not necessary for all of the granules to have this particle size; a predetermined proportion is acceptable. For example, the predetermined proportion is preferably 90% or more. When the granules of the present invention are filled in a container and water is passed through, a particle size of 0.5 mm or more makes the granules less likely to clog the container, preventing an increase in pressure loss within the container. Furthermore, while a particle size larger than 1.5 mm slows the lithium adsorption rate and reduces adsorption efficiency, a particle size of 1.5 mm or less can improve adsorption performance.

[0035] In the granulation process, granulation processing, i.e., extrusion processing, is first performed, and the extruded material is then converted into granules by, for example, stirring and mixing granulation, rolling granulation, extrusion granulation, crushing granulation, fluidized bed granulation, spray drying granulation, compression granulation, etc. Since the as-extruded material has sharp corners, removing the corners by granulation can prevent damage and the generation of fragments when packed into a column for use. The granules are preferably spherical. By making the granules spherical, there are no edges, so crushing due to contact between granules is suppressed. When considering the three mutually orthogonal coordinates X, Y, and Z from the center of the particle, it is preferable that the lengths of the granules in the X, Y, and Z directions are approximately the same (for example, the maximum length is three times or less the minimum length).

[0036] By setting the particle size of the lithium adsorbing granules to 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.

[0037] (drying process) As shown in Fig. 3, in this embodiment, the granules obtained in the granulation step are dried for a predetermined time at a temperature of 10°C to 60°C. By drying in this manner, the granules can be subjected to the baking step with less water content, making the granules more durable.

[0038] The temperature in the drying step is preferably room temperature, and more preferably, for example, 20° C. to 30° C. The predetermined time is preferably, for example, 20 hours to 30 hours.

[0039] (Baking process) As shown in Fig. 3, in the baking process, the granules obtained in the granulation process and that have been through the drying process are baked to obtain granules for lithium adsorption. The granules are baked by, for example, maintaining them in an electric furnace at a predetermined temperature for a predetermined time, to become granules for lithium adsorption. The optimum values ​​for this temperature and time are determined depending on the organic binder and curing agent used.

[0040] The temperature is preferably 90° C. or higher and 120° C. or lower, and more preferably 100° C. or higher and 110° C. or lower. The holding time is preferably 0.5 hours or higher and 2 hours or lower.

[0041] (Treatment after baking process and before desorption process) The lithium adsorption granules produced by the above-described method for producing lithium adsorption granules are preferably subjected to an acid wash to remove readily soluble divalent manganese and an alkali wash to remove hexavalent and heptavalent manganese before the subsequent desorption process in which a precursor of the lithium adsorbent is used as the lithium adsorbent. For example, the acid wash is preferably carried out using 1 mol / L hydrochloric acid in an amount approximately 15 times the amount of the lithium adsorbent precursor. The alkali wash is preferably carried out by immersing the granules in a 1 mol / L lithium hydroxide solution for one hour. In this case, the lithium hydroxide solution is preferably 6 times the amount of the lithium adsorbent precursor. After the alkali wash is completed, the granules are preferably washed with pure water and then dried.

[0042] <Second embodiment of the method for producing granules for lithium adsorption> 4 shows a flow diagram of a method for producing granules for lithium adsorption according to a second embodiment of the present invention. The difference from the first embodiment is that the drying step provided between the granulation step and the baking step is omitted. Since the other points are the same as those in the first embodiment, detailed explanations will be omitted.

[0043] In this embodiment, the granules obtained in the granulation step are subjected to the baking step without undergoing the drying step. In this case, the materials in the kneading step are adjusted, or the temperature or time in the baking step is adjusted, so as to reduce the moisture content in the granules.

[0044] <Example of a method for producing a precursor of a roasted lithium adsorbent> Hereinafter, specific examples of the method for preparing a precursor of a roasted lithium adsorbent according to the present invention will be described, but the present invention is not limited to these examples.

[0045] Example 1 Manganese-containing powdered lithium adsorbent precursor L produced by wet manufacturing method 1.6 Mn 1.6 20 g of O4 was prepared. This lithium adsorbent precursor was subjected to an oxidizing roasting process. Specifically, the lithium adsorbent precursor was oxidizing roasted in an electric furnace at 300°C for 5 hours. This oxidizing roasting yielded a roasted lithium adsorbent precursor. The roasted lithium adsorbent precursor was then added to 300 ml of pure water and stirred for 10 minutes. After stirring, the supernatant was separated, and the manganese content of this supernatant was measured using an ICP atomic emission spectrometer. The results are shown in Table 1 and Figure 1.

[0046] After separating the supernatant, the roasted lithium adsorbent precursor was brought into contact with hydrochloric acid in powder form as a pre-treatment for adsorption to produce a lithium adsorbent. This lithium adsorbent weighed 10 g. Using this lithium adsorbent, an adsorption step was carried out on a lithium solution containing 0.5% lithium, and an elution step was carried out using 2% hydrochloric acid, and the amount of lithium adsorbed per unit weight of the lithium adsorbent was measured. The results are shown in Table 1 and Figure 2.

[0047] <Example 2> The oxidizing roasting step was carried out under the same conditions as in Example 1, except that the temperature in the oxidizing roasting step was set to 350° C. The manganese amount is shown in Table 1 and FIG. 1. The lithium adsorption amount is shown in Table 1 and FIG. 2.

[0048] Example 3 The oxidizing roasting step was carried out under the same conditions as in Example 1, except that the temperature in the oxidizing roasting step was set to 400° C. The manganese amount is shown in Table 1 and FIG. 1. The lithium adsorption amount is shown in Table 1 and FIG. 2.

[0049] Example 4 The oxidizing roasting step was carried out under the same conditions as in Example 1, except that the temperature in the oxidizing roasting step was set to 450° C. The manganese amount is shown in Table 1 and FIG. 1. The lithium adsorption amount is shown in Table 1 and FIG. 2.

[0050] <Example 5> The oxidizing roasting step was carried out under the same conditions as in Example 1, except that the temperature in the oxidizing roasting step was set to 500° C. The manganese amount is shown in Table 1 and FIG. 1. The lithium adsorption amount is shown in Table 1 and FIG. 2.

[0051] Example 6 The oxidizing roasting step was carried out under the same conditions as in Example 1, except that the temperature in the oxidizing roasting step was set to 550° C. The manganese amount is shown in Table 1 and FIG. 1. The lithium adsorption amount is shown in Table 1 and FIG. 2.

[0052] Example 7 The oxidizing roasting step was carried out under the same conditions as in Example 1, except that the temperature in the oxidizing roasting step was set to 600° C. The manganese amount is shown in Table 1 and FIG. 1. The lithium adsorption amount is shown in Table 1 and FIG. 2.

[0053] <Comparative Example 1> The oxidizing roasting step was carried out under the same conditions as in Example 1, except that the temperature in the oxidizing roasting step was set to 250° C. The manganese amount is shown in Table 1 and FIG. 1. The lithium adsorption amount is shown in Table 1 and FIG. 2.

[0054] <Comparative Example 2> The oxidizing roasting step was carried out under the same conditions as in Example 1, except that the temperature in the oxidizing roasting step was set to 650° C. The manganese amount is shown in Table 1 and FIG. 1. The lithium adsorption amount is shown in Table 1 and FIG. 2.

[0055] <Comparative Example 3> The oxidizing roasting step was carried out under the same conditions as in Example 1, except that the temperature in the oxidizing roasting step was set to 700° C. The manganese amount is shown in Table 1 and FIG. 1. The lithium adsorption amount is shown in Table 1 and FIG. 2.

[0056] [Table 1]

[0057] The reference value for the amount of eluted manganese was 40 mg. From Figure 1 and Table 1, it can be seen that the amount of eluted manganese was suppressed in Examples 1 to 7, i.e., when the oxidizing roasting temperature was 300°C or higher and 600°C or lower.

[0058] Regarding the amount of Li adsorption, the vertical axis of Fig. 2 shows the amount of Li adsorbed after roasting. 1.6 Mn 1.6 The amount of Li obtained is expressed in mmol per gram of O4. The reference value is 3.7 mmol / g. Figure 2 and Table 1 show that the Li adsorption capacity is maintained in Examples 4 to 6, i.e., when the oxidizing roasting temperature is 450°C or higher and 550°C or lower.

[0059] <Example of method for producing granules for lithium adsorption> Example 1a (Kneading process) Example 6 of the method for producing the precursor of the roasted lithium adsorbent, that is, lithium manganate Li, which is the precursor of the roasted lithium adsorbent, which is oxidized and roasted at an oxidizing roasting temperature of 550°C. 1.6 Mn 1.6 900 g of O4 powder was placed into a kneader and the kneader was left running. Next, 451 g of the organic binder, a water-dispersible polyester resin (Toyobo Vylonal MD1500: copolymer polyester content 30%), and 29 g of the curing agent, a hexamethylene diisocyanate-based polyisocyanate (Asahi Kasei Duranate WM44-L70G: block polyisocyanate content 60-70%), were weighed and placed into the kneader. In this case, the organic binder was 30% of 451 g, or 135.3 g, which is 15.03 wt % of the 900 g lithium manganate powder. The mixed powder was rotated in the kneader for 15-20 minutes until the organic binder was distributed throughout and a small amount of lumps formed, resulting in a kneaded mixture.

[0060] (granulation process) The kneaded material obtained in the kneading step was placed in a granulator to obtain cylindrical compacts with a diameter of approximately 1 mm and a length of 1 mm. These compacts were then placed in a rotating tumbling granulator and subjected to tumbling granulation (size regulation) for approximately 3 to 10 seconds to obtain granules with a diameter of approximately 1 mm.

[0061] (drying process) The granules obtained in the granulation step were spread in a tray and allowed to dry naturally at room temperature for about one day.

[0062] (Baking process) The granules that had been subjected to the drying step were subjected to a heat treatment in an electric furnace at a temperature of 90° C. for 0.5 hours to harden the organic binder, etc., to obtain granules for lithium adsorption.

[0063] (Desorption process) The lithium adsorption granules that had undergone the baking process were packed into a column and desorbed with 0.5 mol / L hydrochloric acid. After desorption, the column was washed with pure water to remove any remaining hydrochloric acid.

[0064] (Adsorption process) After the desorption step, salt lake brine having a predetermined lithium concentration was passed through a column packed with lithium adsorption granules, and the Li contained in the salt lake brine was adsorbed by the lithium adsorbent contained in the lithium adsorption granules. After the salt lake brine was passed through the column, pure water was passed through the column to remove the remaining salt lake brine.

[0065] (Elution step) After the adsorption step, 0.5 mol / L hydrochloric acid was passed through the column packed with the lithium adsorption granules to elute the lithium adsorbed to the lithium adsorbent. Figure 5 shows a graph of the amount of lithium eluted in the elution step. The horizontal axis of Figure 5 shows time, and the vertical axis shows the molar amount of lithium obtained relative to the weight of the lithium adsorbent. The results of Example 1 are shown by squares.

[0066] (repetition) After the elution step, the column packed with the lithium adsorption granules was used as is to repeatedly perform the adsorption step and the elution step, and the percentage of the lithium adsorption granules that could no longer maintain their shape is shown in Figure 6. The horizontal axis of Figure 6 represents the number of cycles, and the vertical axis represents the percentage of the lithium adsorption granules that could no longer maintain their shape, i.e., the granule reduction rate. The results of Example 1, which used a copolymer polyester, are represented by squares.

[0067] <Comparative Example 1a> (Kneading process) As in Example 1a, after roasting, lithium manganate Li, which is the precursor of the lithium adsorbent, 1.6 Mn 1.6800g of O4 powder and 200g of alumina, an inorganic binder, were weighed out and placed in a vinyl bag for pre-mixing. 1000g of this mixed powder was placed in a kneader, and the kneader was rotated while water was added. The kneader was rotated for several minutes to ensure that the water was distributed evenly throughout the mixture, resulting in a kneaded product.

[0068] (granulation process) The kneaded product obtained in the kneading step was fed into an extrusion granulator, and cylindrical moldings with a diameter of about 1 mm to 3 mm were obtained from the holes. The molded pellets were then cut into lengths of 3 mm to 6 mm.

[0069] (drying process) The compacts obtained in the granulation step were placed in a tray and dried in a dryer at 80°C or higher for about a day.

[0070] (Sintering process) The compacts that had undergone the drying process were sintered in an electric furnace at 500°C for 1.5 hours to obtain sintered granules.

[0071] (Desorption process) The sintered granules were packed into a column and desorbed with 1 mol / L hydrochloric acid. After desorption, the column was washed with pure water to remove the remaining hydrochloric acid.

[0072] (Adsorption process) After the desorption process, salt lake brine with a predetermined lithium concentration was passed through a column packed with the sintered granules, and the Li contained in the salt lake brine was adsorbed by the lithium adsorbent contained in the lithium adsorption granules. After the salt lake brine was passed through, pure water was passed through the column to remove the remaining salt lake brine.

[0073] (Elution step) After the adsorption step, 1 mol / L hydrochloric acid was passed through the column packed with the sintered granules to elute the lithium adsorbed to the lithium adsorbent. The amount of lithium eluted in this elution step is shown in Figure 5. The results of Comparative Example 1 are indicated by circles. In addition, for reference, the case where lithium was adsorbed in the form of a lithium adsorbent powder is indicated by triangles.

[0074] As can be seen from Figure 5, the adsorption capacity of lithium adsorption granules using copolymer polyester, an organic binder, is approximately 2 mmol per 1 g of lithium adsorbent precursor, which is worse than that of the powder state.However, the adsorption capacity of sintered granules using alumina, an inorganic binder, is approximately 1.3 mmol / g, and it can be seen that lithium adsorption granules using an organic binder have a higher adsorption power than inorganic binders.

[0075] (repetition) After the elution step, the column packed with the sintered granules was used as is to repeatedly perform the adsorption step and the elution step, and the percentage of the sintered granules that could no longer maintain their shape is shown in Figure 6. The results of Comparative Example 1, which used alumina, are represented by circles.

[0076] As shown in Figure 6, the sintered granules formed using an inorganic alumina binder gradually began to disintegrate after about 50 cycles, and the disintegration progressed rapidly after 60 cycles. On the other hand, the lithium adsorption granules using copolymer polyester showed a reduction rate of only 10% even after 300 cycles, demonstrating that almost no further disintegration was observed.

Claims

1. An oxidizing roasting process in which a powdered precursor of a lithium adsorbent containing divalent or trivalent manganese is oxidizing roasted at 300°C or higher and 600°C or lower to obtain a powdered precursor of a roasted lithium adsorbent containing lithium manganate; a kneading step of kneading the precursor of the roasted lithium adsorbent, an organic binder, and a curing agent for accelerating curing of the organic binder to obtain a kneaded mixture; a granulation step of granulating the kneaded mixture to obtain granules; a baking step of baking the granules at 90°C or higher and 120°C or lower to obtain granules for lithium adsorption, the organic binder is a copolymer polyester, The curing agent is a polyisocyanate. A method for producing a granule for lithium adsorption, comprising:

2. a drying step of drying the granules at a temperature of 10°C or higher and 60°C or lower, It is provided after the granulation process and before the baking process.

2. The method for producing a granule for adsorbing lithium according to claim 1.

3. the organic binder is 5% by weight or more and 20% by weight or less of the powder of the precursor of the roasted lithium adsorbent; 3. The method for producing a granule for adsorbing lithium according to claim 1 or 2.

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