A lithium adsorbent and its preparation method

Abstract

The present invention relates to the field of lithium extraction by adsorption method, and particularly relates to a lithium adsorbent and a preparation method thereof. The raw materials of the lithium adsorbent include a lithium adsorbent active material and auxiliary materials. Among them, the auxiliary materials include a hydrophilic binder and reinforcing fibers. The use of the reinforcing fibers and the hydrophilic binder effectively prevents the brittle crack propagation caused by volume expansion and contraction of the lithium adsorbent active material during use, significantly improves the strength and cyclic service life of the lithium adsorbent, and at the same time, the use of the hydrophilic binder increases the adsorption rate and capacity of the lithium adsorbent.

Description

Technical Field

[0001] The present invention relates to the field of lithium extraction by adsorption method, and particularly to a lithium adsorbent and a preparation method thereof. Background Art

[0002] Lithium, as the lightest metallic element in the periodic table, due to its unique physical and chemical properties, is widely used in fields such as aviation and navigation, new energy materials, ceramics, lithium batteries, nuclear industry, etc. Especially in recent years, the explosion of the new energy vehicle industry has brought a super large cycle to the lithium resource market, which is also an important reason for the whole industry to compete for lithium mines nowadays. Lithium resources in China mainly exist in solid lithium mines and salt lake brines. The methods for extracting lithium from salt lakes mainly include adsorption method, precipitation method, solvent extraction method, calcination method, membrane separation method, etc. Among them, the adsorption method is considered to be an economical and effective method for extracting lithium from salt lake brines due to its advantages such as low cost, high selectivity, stable cycle and no pollution. At present, most lithium adsorbents are in powder form, and the dissolution loss rate is relatively high during the preparation and regeneration processes, which is not suitable for wide application.

[0003] Therefore, Patent CN 115845825 A provides a method for forming a lithium adsorbent, using polyvinyl chloride, polyurethane TPU and chlorinated polyvinyl chloride as binders, and polyvinylpyrrolidone, polyethylene glycol and polyethylene glycol as pore-forming agents, which are mixed with the lithium adsorbent in a specific proportion, and granulation and forming of the powdery lithium adsorbent are achieved through spinning, coagulation, cleaning and drying. However, the lithium adsorbent prepared by this method has problems of slow adsorption rate and low adsorption capacity. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of slow adsorption rate and low adsorption capacity existing in the lithium adsorbents in the prior art, so as to provide a novel lithium adsorbent and a preparation method thereof.

[0005] The present invention provides a lithium adsorbent, the raw materials of which include a lithium adsorbent active material, a hydrophilic binder and a reinforcing fiber.

[0006] The term lithium adsorbent active material refers to an adsorbent having an adsorption function for lithium ions, and conventional adsorbents in the art can be used, such as aluminum salt lithium adsorbents.

[0007] Furthermore, the hydrophilic binder includes at least one of an inorganic binder and an organic binder.

[0008] Furthermore, the inorganic binder is selected from any one or a combination of two or more of silica sol, aluminum sol, potassium silicate, lithium silicate, sodium silicate, polyaluminum chloride; preferably silica sol;

[0009] The organic binder is a hydrophilic polymer or an aqueous solution containing a hydrophilic polymer. The hydrophilic polymer includes any one or a combination of two or more of urea-formaldehyde resin and polyvinyl alcohol, and is preferably urea-formaldehyde resin.

[0010] Further, based on the dry weight of the lithium adsorbent active material being 100%, the mass percentage of the dry matter in the hydrophilic binder is 5-30%.

[0011] Further, the reinforcing fiber is selected from any one or a combination of two or more of glass fiber, polyacrylonitrile fiber, polypropylene fiber, polyethylene fiber, polyvinyl chloride fiber, polyamide fiber, and polyester fiber;

[0012] Preferably, the diameter of the reinforcing fiber is 1 μm to 50 μm, and the length is 10 μm to 10 mm;

[0013] More preferably, the diameter of the reinforcing fiber is 1 μm to 12 μm, and the length is 0.1 mm to 2 mm.

[0014] Further, the mass of the reinforcing fiber is 1-20% of the dry weight of the lithium adsorbent active material, and is preferably 1-5% of the dry weight of the lithium adsorbent active material.

[0015] Further, the lithium adsorbent active material is an aluminum salt lithium adsorbent, preferably the dry powder of the aluminum salt lithium adsorbent or the wet powder with a water content of less than 60%.

[0016] Further, the lithium adsorbent active material is prepared by gelation, aging, and heat treatment of lithium hydroxide and aluminum sol in the presence of water.

[0017] Further, the mass ratio of lithium hydroxide to aluminum sol is 2-10:100; and / or, the temperature of sealed heating is 80-180 °C; and / or, the heating time is 2-24 h.

[0018] Further, other auxiliary agents are also included in the raw materials of the lithium adsorbent. Preferably, the other auxiliary agents are a combination of one or several of a pore-forming agent, a thickening agent, and a pH regulator.

[0019] Further, the pore-forming agent is selected from one or a combination of several of butanediol, glycerol, and sodium chloride; and / or, the thickening agent is selected from one or a combination of several of guar gum, sesbania powder, starch, and glucose; and / or, the pH regulator is selected from one or a combination of several of calcium carbonate, sodium bicarbonate, ammonium chloride, calcium hydroxide, sodium carbonate, and ammonia water; and / or, the mass of the pore-forming agent is 10-100% of the dry weight of the lithium adsorbent active material; and / or, the mass of the thickening agent is 0.1-2% of the dry weight of the lithium adsorbent active material; and / or, the mass of the pH regulator is 1-20% of the dry weight of the lithium adsorbent active material.

[0020] Further, the raw materials of the lithium adsorbent are composed of an aluminum salt lithium adsorbent, silica sol, guar gum, and glass fiber. Taking the dry weight of the aluminum salt lithium adsorbent as 100%, the dry matter mass of the silica sol accounts for 9%, the guar gum accounts for 1%, and the glass fiber accounts for 2%; or,

[0021] The raw materials of the lithium adsorbent are composed of an aluminum salt lithium adsorbent, silica sol, ammonium chloride, calcium carbonate, and glass fiber. Taking the dry weight of the aluminum salt lithium adsorbent as 100%, the dry matter mass of the silica sol accounts for 9%, the ammonium chloride accounts for 10%, the calcium carbonate accounts for 6%, and the glass fiber accounts for 3%; or,

[0022] The raw materials of the lithium adsorbent are composed of an aluminum salt lithium adsorbent, silica sol, calcium carbonate, sodium bicarbonate, and glass fiber. Taking the dry weight of the aluminum salt lithium adsorbent as 100%, the dry matter mass of the silica sol accounts for 6%, the calcium carbonate accounts for 6%, the sodium bicarbonate accounts for 2%, and the glass fiber accounts for 4%.

[0023] The present invention also provides a preparation method of the lithium adsorbent as described in any one of the above, including the following steps: mixing the raw materials of the lithium adsorbent, and obtaining the lithium adsorbent through extrusion, curing, and drying.

[0024] Further, the temperature of the curing is from room temperature to 80°C.

[0025] Further, the temperature of the drying is 80-150°C, preferably 80-120°C.

[0026] Optionally, the curing time is 12-36 h, and the drying time is 2 h-10 h.

[0027] Further, the prepared lithium adsorbent is a strip. Preferably, the width of the strip is 0.1-2 mm and the length is 1-10 mm.

[0028] The technical solution of the present invention has the following advantages:

[0029] 1. The lithium adsorbent provided by the present invention has raw materials including a lithium adsorbent active material, a hydrophilic binder, and reinforcing fibers. The use of the reinforcing fibers and the hydrophilic binder generates a bond with the microscopic particles of the lithium adsorbent active material through hydrogen bonds or ionic bonds, and the anchoring effect of the reinforcing fibers effectively prevents the brittle crack propagation caused by volume expansion and contraction of the lithium adsorbent active material during use, significantly improving the strength and cyclic service life of the lithium adsorbent. The use of the hydrophilic binder significantly increases the adsorption rate and capacity of the lithium adsorbent.

[0030] 2. For the lithium adsorbent provided by the present invention, the inorganic binder is selected from any one or a combination of two or more of silica sol, aluminum sol, potassium silicate, lithium silicate, sodium silicate, polyaluminum chloride (especially silica sol), the reinforcing fibers are selected from any one or a combination of two or more of glass fiber, polyacrylonitrile fiber, polypropylene fiber, polyethylene fiber, polyvinyl chloride fiber, polyamide fiber, polyester fiber (especially glass fiber), and the aluminum salt lithium adsorbent is prepared by gelation, aging, and heat treatment of lithium hydroxide and aluminum sol in the presence of water. By optimizing the preparation method of the aluminum salt lithium adsorbent and the types and dosages of the hydrophilic binder and the reinforcing fibers, the adsorption rate and capacity can be better improved.

[0031] 3. The preparation method of the lithium adsorbent provided by the present invention has low preparation cost, simple process, no organic solvents throughout the process, is environmentally friendly and pollution-free, is suitable for large-scale production, and has broad application prospects in the extraction of lithium from salt lakes.

[0032] 4. For the preparation method of the lithium adsorbent provided by the present invention, the drying temperature is controlled at 80 - 150 °C. When the drying temperature is lower than 80 °C, the content of crystal water in the prepared lithium adsorbent is too high, the mechanical strength will decrease and the apparent adsorption capacity is relatively low; when the drying temperature is higher than 150 °C, LiCl·2Al(OH) in the aluminum-based lithium adsorbent 3 starts to dehydrate and decompose into LiCl and γ-Al 2 O 3 , and it cannot adsorb lithium ions again, resulting in a decrease in the adsorption capacity of the lithium adsorbent. In the present invention, the drying temperature is preferably 80 - 120 °C, and the lithium adsorbent obtained at this temperature can better improve the adsorption rate and capacity. Specific Embodiments

[0033] The following embodiments are provided to better further understand the present invention, which is not limited to the best embodiment, and does not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features falls within the protection scope of the present invention.

[0034] For those not specifying the specific experimental procedures or conditions in the examples, the operations or conditions of the conventional experimental procedures described in the literature in this field can be followed. For the reagents or instruments not indicating the manufacturer, they are all conventional reagent products that can be obtained through commercial purchase.

[0035] Among them, polyacrylonitrile fiber, manufacturer: Shandong Oude Chemical Fiber Products Co., Ltd., model PD650. Polyethylene fiber, manufacturer: Shandong New Force Engineering Materials Co., Ltd., customized to be fibers with a diameter of 10 μm and a length of 2 mm. Polyvinyl alcohol, manufacturer: Guangzhou Suixin Chemical Industry Co., Ltd., models 0588 and 2499. Urea-formaldehyde resin, manufacturer: Zhengzhou Erqi Leixiang Chemical Industry & Commerce Bank, model 681, solid content 50%. Silica sol, manufacturer: Guangzhou Suize Environmental Protection Technology Co., Ltd., specification is neutral silica sol, particle size 10 - 30 nm, solid content 30%. Glass fiber, manufacturer: Wuhe Weijia Composite Materials Co., Ltd., model WJ03, diameter 12 μm, length 2 mm. Glass fiber, manufacturer: Taishan Fiberglass Inc., model T435N, diameter 10 μm, length 2 mm; model T435TM, diameter 8 μm, length 2 mm. Sesbania powder, manufacturer: Shandong Taihecheng Biotechnology Co., Ltd., specification food grade.

[0036] The aluminum salt lithium adsorbents in each example and comparative example of the present invention were all prepared by the following method:

[0037] (1) Take 8 g of lithium hydroxide and dissolve it in 100 g of water to obtain an aqueous lithium hydroxide solution.

[0038] (2) Take 100 g of aluminum sol (aluminum mass content 12.5%, aluminum-chlorine mass ratio 1.1) and add it to the aqueous lithium hydroxide solution prepared in step (1) and mix quickly until a uniform gel is formed, and age overnight.

[0039] (3) Load the gel into an enamel autoclave and heat it in a sealed manner at 150 °C for 12 hours. Cool and take out the reactant. Distill the water until the water content meets the requirements (30 - 60%), which is the wet powder of the aluminum salt lithium adsorbent used in the example. Place the wet powder in a vacuum dryer at 50 °C and then pulverize it to obtain the dry powder of the aluminum salt lithium adsorbent.

[0040] Example 1

[0041] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0042]

[0043] The preparation method of the above lithium adsorbent includes: weighing each raw material according to the dosage in the above table, adding it to a mixing kettle, and stirring evenly at room temperature to obtain a paste-like premix; transferring the premix to a storage tank to remove air bubbles. The premix is extruded through the die orifice of a twin-screw extruder, and the filaments are extruded onto a conveyor belt and collected to obtain filamentous materials. The filamentous materials are stored and cured at room temperature for 24 h, then cut by a cutting machine, and dried at 100 °C for 2 h to finally obtain a lithium adsorbent with a diameter of 0.6 mm and a length of 2 mm.

[0044] Example 2

[0045] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0046]

[0047] The preparation method of the above lithium adsorbent includes: weighing each raw material according to the dosage in the above table, adding it to a mixing kettle, and stirring evenly at room temperature to obtain a paste-like premix; transferring the premix to a storage tank to remove air bubbles. The premix is extruded through the die orifice of a twin-screw extruder, and the filaments are extruded onto a conveyor belt and collected to obtain filamentous materials. The filamentous materials are stored and cured at 80 °C for 24 h, then cut by a cutting machine, and dried at 120 °C for 2 h to finally obtain a lithium adsorbent with a diameter of 0.6 mm and a length of 2 mm.

[0048] Example 3

[0049] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0050]

[0051]

[0052] The preparation method of the above lithium adsorbent is basically the same as that of Example 2, except that the drying time is adjusted to 4 h.

[0053] Example 4

[0054] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0055]

[0056] The preparation method of the above lithium adsorbent is the same as that of Example 2.

[0057] Example 5

[0058] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0059]

[0060] The preparation method of the above lithium adsorbent is the same as that in Example 1.

[0061] Example 6

[0062] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0063]

[0064] The preparation method of the above lithium adsorbent is basically the same as that in Example 1, except that the drying temperature is adjusted to 90 °C and the time is 6 h.

[0065] Example 7

[0066] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0067]

[0068] The preparation method of the above lithium adsorbent is basically the same as that in Example 1, except that the drying temperature is adjusted to 90 °C and the time is 2 h.

[0069] Example 8

[0070] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0071]

[0072] The preparation method of the above lithium adsorbent is the same as that in Example 2.

[0073] Example 9

[0074] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0075]

[0076] The preparation method of the above lithium adsorbent is the same as that in Example 2.

[0077] Example 10

[0078] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0079]

[0080] The preparation method of the above lithium adsorbent is the same as that in Example 1.

[0081] Example 11

[0082] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0083]

[0084]

[0085] The preparation method of the above lithium adsorbent is the same as that in Example 2.

[0086] Example 12

[0087] This example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0088]

[0089] The preparation method of the above lithium adsorbent is the same as that in Example 2.

[0090] Example 13

[0091] This example provides a lithium adsorbent, whose raw materials and preparation method are basically the same as those in Example 2, except that the drying temperature is adjusted to 70 °C and the drying time is 5 h.

[0092] Example 14

[0093] This example provides a lithium adsorbent, whose raw materials and preparation method are basically the same as those in Example 2, except that the drying temperature is adjusted to 150 °C and the drying time is 2 h.

[0094] Comparative Example 1

[0095] The lithium adsorbent composite particles were prepared by the method steps in Example 1 of Patent CN108722372A.

[0096] Comparative Example 2

[0097] This comparative example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0098]

[0099] The preparation method of the above lithium adsorbent is the same as that in Example 2.

[0100] Comparative Example 3

[0101] This comparative example provides a lithium adsorbent, and its raw materials are shown in the following table.

[0102]

[0103] The preparation method of the above lithium adsorbent is the same as that in Example 2.

[0104] Experimental Example 1 Adsorption Performance Test

[0105] The adsorption performance of the lithium adsorbents prepared in each example and Comparative Example 1 was tested using salt lake brine, including the adsorption capacity at 2 h and 12 h. The specific surface area and pore volume were tested using a Geminni V2380 specific surface area and porosity analyzer.

[0106] The adsorption performance test method was the static adsorption method. 20 g of deionized water and 2 g of the lithium adsorbent were mixed, placed in a shaker, and desorbed for 15 min at room temperature and 150 rpm. The free water was removed by centrifugation, and deionized water was added again for desorption. This was repeated 5 times to obtain the lithium adsorbent after lithium deintercalation treatment. It was added to 200 ml of salt lake brine (lithium content 300 ppm, magnesium content 110 g / L, chlorine content 300 g / L, pH value 5.5), and adsorbed in the shaker at room temperature and 150 rpm for 2 h. Samples were taken, and samples were taken again after 12 h. The test samples were filtered, and the lithium content in the filtrate was tested.

[0107] The adsorption capacity of the adsorbent was:

[0108] Q = V(C 0 - C) / m

[0109] In the formula, Q is the adsorption capacity, mg·g -1 ; V is the volume of the adsorption solution, L; m is the mass of the adsorbent, g; C 0 , C are the lithium ion concentrations in the brine before and after adsorption, respectively, mg·L -1 .

[0110] The test results are as follows:

[0111] Table 1 Test Results

[0112]

[0113] It can be seen from the above results that compared with Comparative Example 1, the lithium adsorbent products provided in each example of the present invention are basically close to the saturated adsorption state after 2 h of adsorption, and have a high adsorption capacity and adsorption rate. Compared with other examples, Examples 7, 9, and 12 of the present invention have significantly increased adsorption amounts at 2 h of adsorption, especially Example 12.

[0114] Experimental Example 2

[0115] The stability of the lithium adsorbents prepared in each example and Comparative Examples 2 - 3 was tested using a shaker experiment and a chromatographic column periodic adsorption and desorption experiment, respectively.

[0116] The specific operation of the shaker experiment was as follows: 2 g of the lithium adsorbent and 100 ml of water were placed in a 250 ml ground glass Erlenmeyer flask, placed in a shaker, and continuously shaken at a speed of 160 rpm for 24 h to observe the fracture of the lithium adsorbent.

[0117] The specific operation of the periodic adsorption and desorption experiment of the chromatography column is as follows: Soak 30 g of lithium adsorbent in 300 ml of pure water for half an hour. Take out the lower-layer lithium adsorbent, measure 30 ml, and load it into a 50-ml chromatography column. Use a peristaltic pump to control the flow rate, and pump 300 ml of the brine in Experimental Example 1 into the chromatography column in the forward direction for 1 hour (adsorption step), and then pump 300 ml of pure water into it for 1 hour (desorption step) to complete one adsorption and desorption cycle. Repeat the above adsorption and desorption steps alternately for 20 cycles.

[0118] It was found that during the shaker experiment, the lithium adsorbents prepared in each embodiment of the present invention did not show fracture and powder falling phenomena within 24 hours, and no fracture and powder falling phenomena were found after 20 cyclic adsorption and desorption cycles. The cyclic service life was more than 20 cycles, meeting the practical requirements.

[0119] For the lithium adsorbents prepared in Comparative Examples 2 and 3, partial fractures occurred during the shaker experiment after soaking in water for 2 minutes and 5 minutes respectively. More than 90% of the lithium adsorbents had fractures after using the first adsorption and desorption cycle, affecting the use, and the service life was less than 1 cycle.

[0120] Obviously, the above embodiments are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A preparation method of a lithium adsorbent, characterized in that, its raw materials include a lithium adsorbent active material and auxiliary materials, wherein the auxiliary materials include a hydrophilic binder and reinforcing fibers, the mass of the reinforcing fibers is 1-5% of the dry weight of the lithium adsorbent active material, the hydrophilic binder includes at least one of an inorganic binder and an organic binder, and the inorganic binder is silica sol; the organic binder is a hydrophilic polymer or an aqueous solution containing a hydrophilic polymer, the hydrophilic polymer is urea-formaldehyde resin, and the preparation method of the lithium adsorbent includes the following steps: Mix the raw materials of the lithium adsorbent, and prepare the lithium adsorbent by extrusion, curing and drying; the lithium adsorbent active material is an aluminum salt lithium adsorbent; the lithium adsorbent active material is prepared by gelation, aging and heat treatment of lithium hydroxide and aluminum sol in the presence of water; the reinforcing fibers are selected from any one or a combination of two or more of polyacrylonitrile fibers, polypropylene fibers, polyethylene fibers, polyvinyl chloride fibers, polyamide fibers, and polyester fibers.

2. The preparation method of the lithium adsorbent according to claim 1, characterized in that, Calculated based on the dry weight of the lithium adsorbent active material being 100%, the mass ratio of the dry matter in the hydrophilic binder is 5-30%.

3. The preparation method of the lithium adsorbent according to claim 1 or 2, characterized in that, the diameter of the reinforcing fibers is 1 μm to 50 μm, and the length is 10 μm to 10 mm.

4. The preparation method of the lithium adsorbent according to claim 3, characterized in that, the diameter of the reinforcing fibers is 1 μm to 12 μm, and the length is 0.1 mm to 2 mm.

5. The preparation method of the lithium adsorbent according to claim 1 or 2, characterized in that, the lithium adsorbent active material is a dry powder of an aluminum salt lithium adsorbent or a wet powder with a water content of less than 60%.

6. The preparation method of the lithium adsorbent according to claim 1 or 2, characterized in that, the mass ratio of lithium hydroxide to aluminum sol is 2-10:100; and / or, the heating temperature is 80-180 °C; and / or, the heating time is 2-24 h.

7. The preparation method of the lithium adsorbent according to claim 1 or 2, characterized in that, other auxiliary agents are also included in the raw materials of the lithium adsorbent.

8. The preparation method of the lithium adsorbent according to claim 7, characterized in that, the other auxiliary agents are one or a combination of a pore-forming agent, a thickening agent, and a pH regulator.

9. The preparation method of the lithium adsorbent according to claim 8, characterized in that, The pore-forming agent is selected from one or a combination of several of butanediol, glycerol, and sodium chloride; and / or, the thickening agent is selected from one or a combination of several of guar gum, sesbania powder, starch, and glucose; and / or, the pH regulator is selected from one or a combination of several of calcium carbonate, sodium bicarbonate, ammonium chloride, calcium hydroxide, sodium carbonate, and ammonia water; and / or, the mass of the pore-forming agent is 10-100% of the dry weight of the lithium adsorbent active material; and / or, the mass of the thickening agent is 0.1-2% of the dry weight of the lithium adsorbent active material; and / or, the mass of the pH regulator is 1-20% of the dry weight of the lithium adsorbent active material.

10. The method for preparing a lithium adsorbent according to claim 1 or 2, characterized in that the temperature for curing is from room temperature to 80°C.

11. The method for preparing a lithium adsorbent according to claim 1 or 2, characterized in that the temperature for drying is 80-150°C.

12. The method for preparing a lithium adsorbent according to claim 11, characterized in that the temperature for drying is 80-120°C.

13. The method for preparing a lithium adsorbent according to claim 1 or 2, characterized in that the prepared lithium adsorbent is a strip.

14. The method for preparing a lithium adsorbent according to claim 13, characterized in that the width of the strip is 0.1-2 mm and the length is 1-10 mm.

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