Composite adsorbent particles, methods of making and using the same

Abstract

The application provides a composite adsorbent particle and a preparation method and application thereof. The composite adsorbent particle comprises carrier-adsorbent powder composite particles and a coating layer covering the carrier-adsorbent powder composite particles, and the carrier and the coating layer each comprise a polycationic electrolyte and / or a polyanionic electrolyte. The application prepares the carrier-adsorbent powder composite particles by a phase separation method, and then coats the carrier-adsorbent powder composite particles by using a layer-by-layer impregnation method to construct the coating layer. The carrier used in the application has excellent chemical stability and hydrophilicity, can reduce the adsorption capacity of the adsorbent powder as much as possible, effectively prevents the leakage of the adsorbent powder in the circulation process, significantly reduces the solution loss rate of the adsorbent, and improves the circulation stability and service life of the composite adsorbent particle. The composite adsorbent particle has a good application prospect in the field of low-lithium brine lithium extraction and the like.

Description

Technical Field

[0001] This invention belongs to the field of adsorption materials technology, specifically relating to a composite adsorbent particle, its preparation method, and its application. Background Technology

[0002] In the field of lithium extraction from low-lithium brine, lithium-ion sieve (LIS) adsorption has proven to be the most effective technology. Titanium-based and manganese-based adsorbents, due to their high theoretical adsorption capacity and fast adsorption kinetics, have become the most promising lithium-ion adsorbents in low-lithium-concentration geothermal brines. Because powdered adsorbents are difficult to process in adsorption / desorption cycles, most researchers employ granulation techniques, embedding the powder into porous composite materials using binders. Literature reports that granulation significantly reduces both adsorption capacity and adsorption rate, which remains a key challenge in preparing high-performance composite adsorbents.

[0003] The choice of binder is a decisive factor. Several studies have explored using different polymers as binders, mainly categorized as hydrophilic and hydrophobic materials. While hydrophobic binders possess high mechanical strength, their closed pores make it difficult for liquids to enter the sieve, resulting in relatively low adsorption capacity and slow adsorption rates. In contrast, hydrophilic binders exhibit superior adsorption performance. However, their tendency to expand and structural instability lead to poor cycle stability, making them unsuitable for industrial applications. Chinese patent application CN116328713A proposes a preparation method that first mixes lithium-ion sieve powder with a hydrophobic polymer (such as polyvinyl chloride) and a porogen, obtaining a precursor with high mechanical strength through a phase inversion method; subsequently, the precursor is further compounded with a hydrophilic polymer (such as chitosan) and subjected to acid leaching. This method aims to utilize the hydrophobic polymer to construct a stable framework, while simultaneously improving the wettability and mass transfer efficiency of the adsorbent through the pores left by the hydrophilic polymer and porogen, thereby increasing the adsorption capacity while maintaining particle strength. However, the aforementioned granulation processes still largely rely on organic solvents, and the long-term stability of the composite structure requires further verification. Therefore, there is an urgent need to develop novel adhesives that combine high adsorption performance, good chemical stability, excellent mechanical strength, and the use of green solvents.

[0004] In the recycling process, composite adsorbent particles are highly susceptible to adsorbent powder leakage, which not only causes adsorbent loss but also leads to secondary water pollution. Simultaneously, manganese-based adsorbents suffer from high solubility, and titanium-based adsorbents exhibit slight solubility. The loss of active components significantly reduces the adsorption performance and cycle life of the adsorbent, limiting its industrial application. To address these issues, some studies have attempted to construct protective layers through surface coating. For example, patent application CN108607503A discloses a magnetic adsorbent that uses zeolite powder as a template to synthesize a LiMn2O4 adsorbent core in situ. Calcium silicate is then generated by reacting nano-silica with calcium chloride, and Fe3O4 magnetic powder is coated onto the particle surface, forming spherical particles with a calcium silicate-coated magnetic powder outer layer. This calcium silicate layer acts as a physical barrier, mitigating manganese solubility to some extent. However, this coating layer has inherent limitations: the total mass of the outer calcium silicate and magnetic powder is limited to less than 5% of the total adsorbent mass, resulting in an excessively thin coating layer that is difficult to form a dense protection; at the same time, the calcium silicate layer lacks mechanical stability, posing a risk of peeling off during long-term cycling. Therefore, it is still necessary to develop a novel protective structure that combines high stability and good mass transfer performance. By forming a dense protective layer on the surface of the adsorbent particles, the direct damage to the particles from the external environment can be effectively isolated, thereby inhibiting powder shedding and dissolution of active components, ensuring the integrity and long-term effectiveness of the adsorbent during cycling. Summary of the Invention

[0005] This invention addresses the aforementioned problems in existing technologies by proposing a composite adsorbent particle, its preparation method, and its application. Using polyelectrolytes as both the loading and coating materials, titanium-based / manganese-based adsorbent powders are efficiently loaded and stably coated, solving problems such as decreased adsorption performance, powder leakage, and loss of active components that occur in titanium-based / manganese-based powder composite adsorbents during recycling.

[0006] In one aspect, the present invention provides composite adsorbent particles.

[0007] In one or more embodiments, the composite adsorbent particles comprise carrier-adsorbent powder composite particles and a coating on the surface of the carrier-adsorbent powder composite particles. The carrier-adsorbent powder composite particles comprise a carrier and adsorbent powder loaded on the carrier. The carrier comprises a first polycationic electrolyte and a first polyanionic electrolyte. The coating comprises one or more polyelectrolyte layers, each polyelectrolyte layer independently comprising a second polycationic electrolyte and / or a second polyanionic electrolyte.

[0008] In one or more embodiments, the adsorbent powder is selected from one or both of layered titanium-based lithium ion sieve adsorbent Li2TiO3 and spinel-like manganese-based lithium ion sieve adsorbent LiMn2O4.

[0009] In one or more embodiments, the particle size D50 of the adsorbent powder is 0.01. m~300 μm.

[0010] In one or more embodiments, the particle size D50 of the carrier-adsorbent powder composite particles is 0.1 mm to 5 mm.

[0011] In one or more embodiments, the particle size D50 of the composite adsorbent particles is 0.1 mm to 5 mm.

[0012] In one or more embodiments, the mass ratio of the carrier to the adsorbent powder in the carrier-adsorbent powder composite particles is 1:4 to 4:1.

[0013] In one or more embodiments, the degree of dissociation of the quaternary ammonium salt group of the first polycationic electrolyte is ≥ 95%.

[0014] In one or more embodiments, the first polycationic electrolyte is selected from one or more of polydimethyldiallyl ammonium chloride, polymethacryloyloxyethyltrimethylammonium chloride, quaternized poly(4-vinylpyridine) and hydroxypropyltrimethylammonium chloride chitosan, preferably polydimethyldiallyl ammonium chloride.

[0015] In one or more embodiments, the degree of dissociation of the sulfonic acid groups of the first polyanionic electrolyte is ≥ 95%.

[0016] In one or more embodiments, the first polyanion is selected from one or more of sodium polystyrene sulfonate, sodium poly(2-acryloyl-2-methylpropanesulfonate), and sodium polyvinyl sulfate, preferably sodium polystyrene sulfonate.

[0017] In one or more embodiments, the molar ratio of the first polycationic electrolyte to the first polyanionic electrolyte in the carrier is (1-4):1, preferably (1-1.2):1.

[0018] In one or more embodiments, the coating comprises two or more polyelectrolyte layers, with adjacent polyelectrolyte layers carrying positive and negative charges, respectively.

[0019] In one or more embodiments, in two adjacent polyelectrolyte layers of the coating, one layer contains a polycationic electrolyte but not a polyanionic electrolyte, and the other layer contains a polyanionic electrolyte but not a polycationic electrolyte.

[0020] In one or more embodiments, in the coating, each polyelectrolyte layer contains the same or different second polycationic electrolyte and second polyanionic electrolyte.

[0021] In one or more embodiments, the second polycationic electrolyte is selected from one or more of polydimethyldiallyl ammonium chloride, polyacrylamide hydrochloride, polyethyleneimine, and polyethyleneamine, preferably one or two of polydimethyldiallyl ammonium chloride and polyacrylamide hydrochloride.

[0022] In one or more embodiments, the second polyanionic electrolyte is selected from one or more of sodium polystyrene sulfonate, sodium polyacrylate, sodium polyvinyl sulfonate, and sulfonated polyether ether ketone, preferably sodium polystyrene sulfonate.

[0023] In one or more embodiments, the coating comprises 1 to 40 polyelectrolyte layers, preferably 2 to 7 layers, more preferably 3 to 7 polyelectrolyte layers.

[0024] In one or more embodiments, the innermost polyelectrolyte layer in the coating that is in contact with the carrier-adsorbent powder composite particles is formed of a polyanionic electrolyte or a polycationic electrolyte.

[0025] In one or more embodiments, the innermost polyelectrolyte layer is formed of a second polyanionic electrolyte.

[0026] In one or more embodiments, the outermost polyelectrolyte layer in the coating is formed of a polyanionic electrolyte or a polycationic electrolyte.

[0027] In one or more embodiments, the outermost polyelectrolyte layer is formed of a second polyanionic electrolyte.

[0028] In one or more embodiments, the initial adsorption capacity of the composite adsorbent particles for lithium ions is ≥18 mg / g; In one or more embodiments, the adsorption capacity of the composite adsorbent particles for lithium ions in the 10th cycle of adsorption is more than 93% of the initial adsorption capacity.

[0029] In one or more embodiments, after the composite adsorbent particles undergo 10 cycles of adsorption, the total titanium / manganese dissolution rate in the adsorbent powder is no greater than 9%.

[0030] Another aspect of the present invention provides a method for preparing composite adsorbent particles, comprising the following steps: (1) Provide a polyelectrolyte slurry containing a first polycationic electrolyte, a first polyanionic electrolyte, and a salt; (2) The adsorbent powder is uniformly dispersed in the polyelectrolyte slurry of step (1) to obtain a composite slurry containing adsorbent powder; (3) The composite slurry obtained in step (2) is dropped into water and the carrier-adsorbent powder composite particles are formed by phase separation method; (4) Provide a salt solution containing a second polycationic electrolyte and / or a salt solution containing a second polyanionic electrolyte, and contact the surface of the carrier-adsorbent powder composite particles obtained in step (3) with the salt solution containing the second polycationic electrolyte or the salt solution containing the second polyanionic electrolyte, and then wash in water to form the innermost polyelectrolyte layer. When the coating comprises two or more polyelectrolyte layers, the preparation method further includes the following steps: (5) Contact the surface of the second polyelectrolyte layer containing the second polycationic electrolyte or the second polyanionic electrolyte with the salt solution, and then clean it to form the Nth polyelectrolyte layer. The N-1th polyelectrolyte layer refers to a polyelectrolyte layer that is adjacent to the Nth polyelectrolyte layer but closer to the carrier-adsorbent powder composite particles; N is preferably an integer from 2 to 40.

[0031] In one or more embodiments, in step (1), the molar ratio of the first polycationic electrolyte and the first polyanionic electrolyte in the polyelectrolyte slurry is (1-4):1, preferably (1-1.2):1.

[0032] In one or more embodiments, in step (1), the polyelectrolyte slurry is composed of a salt solution containing a first cationic electrolyte and a salt solution containing a first anionic electrolyte.

[0033] In one or more embodiments, in step (1), the salt solution containing the first polycationic electrolyte comprises the first polycationic electrolyte and the salt.

[0034] In one or more embodiments, in step (1), the salt solution containing the first polyanionic electrolyte comprises the first polyanionic electrolyte and the salt.

[0035] In one or more embodiments, in step (1), the salts in the salt solution containing the first polycationic electrolyte and the salt solution containing the first polyanionic electrolyte are each independently selected from one or more of NaCl, NaNO3, NaF, NaBr, KCl and KBr, preferably NaCl, and the concentration of the salt is 0.5~6 mol / L, preferably 5~6 mol / L.

[0036] In one or more embodiments, in step (1), the concentrations of the first polycationic electrolyte and the first polyanionic electrolyte in the salt solution containing the first polycationic electrolyte and the salt solution containing the first polyanionic electrolyte are independently 10 wt% to 25 wt%, preferably 15 wt% to 19 wt%.

[0037] In one or more embodiments, in step (2), the mass ratio of the polyelectrolyte slurry to the adsorbent powder is (0.2-2):1, preferably 1:3 to 2:1.

[0038] In one or more embodiments, in step (3), when the composite slurry is dripped into water, the temperature of the composite slurry is 15°C to 100°C, preferably 40°C.

[0039] In one or more embodiments, in step (3), the composite slurry is dripped into deionized water using a syringe or dropper, wherein the inner diameter of the syringe or dropper is preferably 0.1 mm to 5 mm, more preferably 2 ± 0.5 mm; the distance between the needle tip of the syringe or the bottom of the dropper and the water surface is 5 to 100 cm, more preferably 20 ± 5 cm; and the dripping rate is 1 to 60 drops / min, preferably 30 ± 5 drops / min.

[0040] In one or more embodiments, in step (3), water is used as the coagulation bath for the phase separation method, and the temperature of the coagulation bath is 0℃~100℃, preferably 0℃~50℃; when the composite slurry is added dropwise, the coagulation bath is stirred to prevent particle adhesion, and the stirring rate is 50~800 rpm, preferably 100±20 rpm.

[0041] In one or more embodiments, in step (4), the salt solution containing the second polycationic electrolyte comprises the second polycationic electrolyte and the salt.

[0042] In one or more embodiments, in step (4), the salt solution containing the second polyanionic electrolyte comprises the second polyanionic electrolyte and salt.

[0043] In one or more embodiments, in step (4), the concentrations of the second polycationic electrolyte and the second polyanionic electrolyte in the salt solution containing the second polycationic electrolyte and the salt solution containing the second polyanionic electrolyte are independently 0.001~2 mol / L, preferably 0.001~0.1 mol / L.

[0044] In one or more embodiments, in step (4), the salts in the salt solution containing the second polycationic electrolyte and the salt solution containing the second polyanionic electrolyte are each independently selected from one or more of NaCl, NaNO3, NaF, NaBr, KCl and KBr, preferably NaCl, and the salt concentration is 0.01~6 mol / L, preferably 0.025~2.5 mol / L.

[0045] In one or more embodiments, the carrier-adsorbent powder composite particles or the carrier-adsorbent powder composite particles with a polyelectrolyte layer on the surface are contacted with the salt solution containing the second polycationic electrolyte or the salt solution containing the second polyanionic electrolyte by an impregnation method, and the contact time is 0-30 min, excluding 0 min, preferably 10±2 min.

[0046] In one or more embodiments, the preparation method further includes acid treatment of the composite adsorbent particles obtained in step (4) or (5) with an acid solution, wherein the acid solution is a hydrochloric acid solution and / or a sulfuric acid solution, preferably a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 0.01-1 mol / L, preferably 0.1±0.02 mol / L; the temperature of the hydrochloric acid solution during acid treatment is 30 ℃-80 ℃, preferably 60±5 ℃; and the acid treatment time is 0.5-24 h, preferably 10±2 h.

[0047] A lithium extraction device comprising composite adsorbent particles according to any embodiment of the present invention or composite adsorbent particles obtained by the method described in any embodiment of the present invention.

[0048] Another aspect of the invention provides the following uses: (1) Use of composite adsorbent particles as described in any embodiment of the present invention or composite adsorbent particles obtained by the method described in any embodiment of the present invention in reducing adsorbent powder leakage and / or metal ion dissolution; (2) Use of composite adsorbent particles as described in any embodiment of the present invention or composite adsorbent particles obtained by the method described in any embodiment of the present invention in improving lithium extraction stability and / or adsorption performance. Attached Figure Description

[0049] Figure 1 SEM image of the inner cross section of the composite adsorbent particles prepared in Example 1; Figure 2 This is a magnified SEM image of the cavities within the cross-section of the composite adsorbent particles prepared in Example 1. Figure 3 This is a magnified SEM image of the pores inside the composite adsorbent particles prepared in Example 1. Figure 4 SEM image of the outer surface of the composite adsorbent particles prepared in Example 1; Figure 5 Here is a magnified SEM image of the outer surface of the composite adsorbent particles prepared in Example 1; Figure 6 This is a magnified SEM image of the outer surface of the composite adsorbent particles prepared in Example 10 after coating. Figure 7The image shows the turbidity of the adsorption solution after ten cycles of lithium extraction from the composite adsorbent particles prepared in Example 1. Figure 8 The image shows the turbidity of the adsorption solution after ten cycles of lithium extraction from the composite adsorbent particles prepared in Example 10. Detailed Implementation

[0050] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used herein are explained and defined in general terms below. Unless otherwise specified, all technical and scientific terms used herein have the common meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0051] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0052] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0053] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0054] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0055] In this article, the sum of the percentages of all components in the composition is 100%.

[0056] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope of this invention.

[0057] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0058] This invention provides lithium extraction composite adsorbent particles, their preparation method, and applications. The surface of the lithium extraction composite adsorbent particles is a layer-by-layer self-assembled polyelectrolyte coating, which effectively protects the adsorbent powder inside the particles and prevents leakage and dissolution. The composite adsorbent particles of this invention exhibit good recyclability; after 10 cycles, the adsorption capacity is more than 93% of the initial adsorption capacity, and the total titanium / manganese dissolution rate is less than 9%.

[0059] Composite adsorbent particles

[0060] The composite adsorbent particles of the present invention comprise carrier-adsorbent powder composite particles and a coating on the surface of the carrier-adsorbent powder composite particles. The carrier-adsorbent powder composite particles comprise a carrier and adsorbent powder loaded on the carrier. The carrier comprises a first polycationic electrolyte and a first polyanionic electrolyte. The coating comprises one or more polyelectrolyte layers, and each polyelectrolyte layer independently comprises a second polycationic electrolyte and / or a second polyanionic electrolyte.

[0061] In this invention, the adsorbent powder is selected from one or both of layered titanium-based lithium ion sieve adsorbent (Li2TiO3) and spinel-like manganese-based lithium ion sieve adsorbent (LiMn2O4).

[0062] In this invention, the lithium-ion sieve is a type of inorganic functional material with a specific crystal cavity structure, which mainly achieves the storage of Li-ion ions through ion exchange and molecular memory effects. + Highly selective recognition and adsorption of lithium ions. Lithium-ion sieve powder has a large specific surface area and fully exposed active sites, enabling selective adsorption of Li from systems where multiple ions coexist. + This includes manganese-based lithium ion sieves (HMO) and titanium-based lithium ion sieves (HTO).

[0063] In this invention, the particle size D50 of the adsorbent powder is 0.01. m~300 μm, for example 0.01 m, 0.05 m, 0.08 m, 0.1 m, 0.2 m, 0.25 m, 0.3 m, 0.5 m 0.8 m、1 m, 1.5 m、2 m、3 m, 5 m, 10 m, 20 m, 50 m, 100 m, 200 m, 300 m.

[0064] In this invention, the particle size D50 of the carrier-adsorbent powder composite particles is 0.1 mm to 5 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 1 mm, 1.2 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, and 5 mm.

[0065] In this invention, the particle size D50 of the composite adsorbent particles is 0.1 mm to 5 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 1 mm, 1.2 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm, 3 mm, 4 mm, and 5 mm. In this invention, the coating thickness is very thin relative to the particle size of the composite adsorbent particles, only about 1 nm to 200 nm. Therefore, the particle size D50 of the composite adsorbent particles, measured by a digital vernier caliper (accuracy 0.1 mm), is very close to the particle size D50 of the carrier-adsorbent powder composite particles, which is 0.1 mm to 5 mm.

[0066] In this invention, the mass ratio of carrier to adsorbent powder in the carrier-adsorbent powder composite particles is 1:4-4:1, such as 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, or 4:1.

[0067] In this invention, the first polycationic electrolyte is a strong polycationic electrolyte, and the degree of dissociation of the quaternary ammonium salt group of the first polycationic electrolyte is ≥ 95%.

[0068] In this invention, the first polycationic electrolyte is selected from one or more of polydimethyldiallyl ammonium chloride, polymethacryloyloxyethyltrimethylammonium chloride, quaternized poly(4-vinylpyridine) and hydroxypropyltrimethylammonium chloride chitosan, preferably polydimethyldiallyl ammonium chloride.

[0069] In this invention, the first polyanionic electrolyte is a strong polyanionic electrolyte, and the degree of dissociation of the sulfonic acid groups in the first polyanionic electrolyte is ≥ 95%.

[0070] In this invention, the first polyanion is selected from one or more of sodium polystyrene sulfonate, sodium poly(2-acryloyl-2-methylpropanesulfonate), and sodium polyvinyl sulfate, preferably sodium polystyrene sulfonate.

[0071] In this invention, the first polycationic electrolyte is a strong polycationic electrolyte, and the second polyanionic electrolyte is a strong polyanionic electrolyte. Their charges are stable and unaffected by pH, allowing for free switching between homogeneous solutions and phase separation through salt addition / control. For example, under low-salt conditions, electrostatic complexation forms a stable and homogeneous polyelectrolyte composite solution; under high-salt conditions, the small ion charge shielding and salting-out effect synergistically induce liquid-liquid phase separation. In contrast, weak polyelectrolytes can only be controlled by adjusting the acidity and alkali levels to change the charge, which is limited by conditions and has poor stability. The strong polyelectrolyte salts used in this invention are simpler to control, have a wider range of applications, are resistant to high salt levels, and are reversible and controllable.

[0072] In this invention, the molar ratio of the first polycationic electrolyte to the first polyanionic electrolyte in the carrier is (1-4):1, preferably (1-1.2):1, such as 1:1, 1.2:1, 2:1, 3:1, 4:1.

[0073] In this invention, the coating comprises two or more polyelectrolyte layers, with adjacent polyelectrolyte layers carrying positive and negative charges, respectively.

[0074] In this invention, among two adjacent polyelectrolyte layers of the coating, one layer contains a polycationic electrolyte but not a polyanionic electrolyte, and the other layer contains a polyanionic electrolyte but not a polycationic electrolyte.

[0075] In this invention, the second polycationic electrolyte and the second polyanionic electrolyte contained in each polyelectrolyte layer of the coating may be the same or different.

[0076] In this invention, the second polycationic electrolyte is selected from one or more of polydimethyldiallyl ammonium chloride, polyacrylamide hydrochloride, polyethyleneimine, and polyethyleneamine, preferably one or two of polydimethyldiallyl ammonium chloride and polyacrylamide hydrochloride.

[0077] In this invention, the second polyanionic electrolyte is selected from one or more of sodium polystyrene sulfonate, sodium polyacrylate, sodium polyvinyl sulfonate, and sulfonated polyether ether ketone, preferably sodium polystyrene sulfonate.

[0078] In this invention, the coating comprises 1 to 40 polyelectrolyte layers, preferably 2 to 7 layers, more preferably 3 to 7 layers, such as 3, 4, 5, 6, or 7 layers.

[0079] In this invention, a coating with 3 to 7 polyelectrolyte layers has better technical effects. This is because this number of layers can form a continuous and dense protective film, which can effectively block the leakage of active particle powder and inhibit the dissolution of titanium ions, while ensuring the rapid passage of lithium ions. If the coating contains fewer than 3 polyelectrolyte layers, the coating coverage is incomplete, the powder is easily leaked during the cycle, the interception effect of titanium ions is poor, resulting in a decrease in the cycle stability and a shortened life of the adsorbent. If the coating contains more than 7 polyelectrolyte layers, the film layer is too thick, which will seriously hinder the transport of lithium ions, and at the same time, the adsorption sites will be buried, and the adsorption performance will be weakened.

[0080] In this invention, preferably, the outermost polyelectrolyte layer of the coating is a polyelectrolyte layer formed from a second polyanionic electrolyte. Therefore, the outermost polyelectrolyte layer of the coating is negatively charged and can effectively adsorb lithium ions through electrostatic attraction, thereby improving the migration rate and interface enrichment effect of lithium ions and alleviating the decline in lithium ion transport kinetics caused by the physical barrier of the coating.

[0081] In this invention, the innermost polyelectrolyte layer in the coating that is in contact with the carrier-adsorbent powder composite particles is formed of a polyanionic electrolyte or a polycationic electrolyte.

[0082] In this invention, the innermost polyelectrolyte layer is formed from a second polyanionic electrolyte.

[0083] In this invention, the outermost polyelectrolyte layer in the coating is formed of a polyanionic electrolyte or a polycationic electrolyte.

[0084] In this invention, the outermost polyelectrolyte layer is formed from a second polyanionic electrolyte.

[0085] In this invention, the initial adsorption capacity of the composite adsorbent particles for lithium ions is ≥20 mg / g, such as 20 mg / g, 20.17 mg / g, 20.70 mg / g, 23.05 mg / g, 24.58 mg / g, 24.86 mg / g, 25.58 mg / g, 25.70 mg / g, 25.74 mg / g, 27.50 mg / g, 28.47 mg / g, 28.66 mg / g, 31.11 mg / g, 34.77 mg / g, 35 mg / g, 40 mg / g, and 50 mg / g.

[0086] In this invention, the adsorption capacity of the composite adsorbent particles for lithium ions in the 10th cycle of adsorption is more than 93% of the initial adsorption capacity.

[0087] In this invention, after the composite adsorbent particles undergo 10 cycles of adsorption, the total titanium / manganese dissolution rate in the adsorbent powder is no greater than 9%.

[0088] In this invention, a polyelectrolyte layer forms a bilayer with an adjacent polyelectrolyte layer. For example, the surface of the carrier-adsorbent powder composite particles is first contacted with a salt solution containing a second polyanionic electrolyte, and after cleaning, a polyelectrolyte layer is formed; the surface of the formed polyelectrolyte layer is then contacted with a salt solution containing a second polycationic electrolyte, and after cleaning, another polycationic layer is formed. These two polyelectrolyte layers constitute a bilayer.

[0089] Preparation method of composite adsorbent particles

[0090] In this invention, the preparation method of the composite adsorbent particles includes the following steps: (1) Provide a polyelectrolyte slurry containing a first polycationic electrolyte, a first polyanionic electrolyte, and a salt; (2) The adsorbent powder is uniformly dispersed in the polyelectrolyte slurry of step (1) to obtain a composite slurry containing adsorbent powder; (3) The composite slurry obtained in step (2) is dropped into water and the carrier-adsorbent powder composite particles are formed by phase separation method; (4) Provide a salt solution containing a second polycationic electrolyte and / or a salt solution containing a second polyanionic electrolyte, and contact the surface of the carrier-adsorbent powder composite particles obtained in step (3) with the salt solution containing the second polycationic electrolyte or the salt solution containing the second polyanionic electrolyte, and then wash in water to form the innermost polyelectrolyte layer. When the coating comprises two or more polyelectrolyte layers, the preparation method further includes the following steps: (5) Contact the surface of the second polyelectrolyte layer containing the second polycationic electrolyte or the second polyanionic electrolyte with the salt solution, and then clean it to form the Nth polyelectrolyte layer. The N-1th polyelectrolyte layer refers to a polyelectrolyte layer that is adjacent to the Nth polyelectrolyte layer but closer to the carrier-adsorbent powder composite particles; N is preferably an integer from 2 to 40.

[0091] In this invention, the solvent in the polyelectrolyte slurry, the salt solution containing the second polycationic electrolyte, and the salt solution containing the second polyanionic electrolyte is water.

[0092] In this invention, in step (1), the molar ratio of the first polycationic electrolyte and the first polyanionic electrolyte in the polyelectrolyte slurry is (1-4):1, preferably (1-1.2):1, such as 1:1, 1.2:1, 1.5:1, 2:1, 3:1, 4:1.

[0093] In this invention, in step (1), the polyelectrolyte slurry is formed by mixing a salt solution containing a first cationic electrolyte and a salt solution containing a first anionic electrolyte.

[0094] In this invention, in step (1), the salt solution containing the first polyanionic electrolyte comprises the first polyanionic electrolyte and salt.

[0095] In this invention, in step (1), the salt solution containing the first polycationic electrolyte comprises the first polycationic electrolyte and the salt.

[0096] In this invention, in step (1), the salts in the salt solution containing the first polycationic electrolyte and the salt solution containing the first polyanionic electrolyte are independently selected from one or more of NaCl, NaNO3, NaF, NaBr, KCl and KBr, preferably NaCl, and the salt concentration is 0.5~6 mol / L, preferably 5~6 mol / L, such as 5 mol / L, 5.5 mol / L, and 6 mol / L.

[0097] In this invention, in step (1), the concentrations of the first polycationic electrolyte and the first polyanionic electrolyte in the salt solution containing the first polycationic electrolyte and the salt solution containing the first polyanionic electrolyte are independently 10 wt% to 25 wt%, preferably 15 wt% to 19 wt%, such as 15 wt%, 16 wt%, 17 wt%, 18 wt%, and 19 wt%.

[0098] In this invention, in step (1), the first polycationic electrolyte is selected from one or more of polydimethyldiallyl ammonium chloride, polymethacryloyloxyethyltrimethylammonium chloride, quaternized poly(4-vinylpyridine) and hydroxypropyltrimethylammonium chloride chitosan, preferably polydimethyldiallyl ammonium chloride.

[0099] In this invention, in step (1), the first polyanionic electrolyte may be one or more of sodium polystyrene sulfonate, sodium poly(2-acryloyl-2-methylpropanesulfonate) and sodium polyvinyl sulfate, preferably an aqueous solution of sodium polystyrene sulfonate with a mass concentration of 10 wt% to 40 wt%.

[0100] In this invention, in step (2), the mass ratio of polyelectrolyte slurry to adsorbent powder is (0.2-2):1, preferably 1:3 to 2:1, such as 1:3, 0.4:1, 1:2, 3:5, 0.7:1, 4:5, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1.

[0101] In this invention, in step (3), when the composite slurry is dripped into the water, the temperature of the composite slurry is 15℃~100℃, preferably 40℃.

[0102] In this invention, in step (3), a syringe or dropper can be used to drip the composite slurry into deionized water. The inner diameter of the syringe or dropper is preferably 0.1 mm to 5 mm, more preferably 2 ± 0.5 mm, such as 1.5 mm, 2 mm, or 2.5 mm. The distance between the needle tip of the syringe or the bottom of the dropper and the water surface is 5 to 100 cm, more preferably 20 ± 5 cm, such as 15 cm, 20 cm, or 25 cm. The dripping rate is 1 to 60 drops / min, preferably 30 ± 5 drops / min, such as 25 drops / min, 30 drops / min, or 35 drops / min.

[0103] In this invention, in step (3), water is used as the coagulation bath for phase separation. The temperature of the coagulation bath is 0℃~100℃, preferably 0℃~50℃, such as 0℃, 19℃, 20℃, 30℃, 40℃, 45℃, 50℃. When the composite slurry is added, the coagulation bath is stirred to prevent particle adhesion. The stirring speed is 50~800 rpm, preferably 100±20 rpm, such as 80 rpm, 100 rpm, 120 rpm.

[0104] In this invention, in step (4), the salt solution containing the second polycationic electrolyte comprises the second polycationic electrolyte and the salt.

[0105] In this invention, in step (4), the salt solution containing the second polyanionic electrolyte comprises the second polyanionic electrolyte and salt.

[0106] In this invention, in step (4), the concentrations of the second polycationic electrolyte and the second polyanionic electrolyte in the salt solution containing the second polycationic electrolyte and the salt solution containing the second polyanionic electrolyte are independently 0.001~2 mol / L, preferably 0.001~0.1 mol / L, such as 0.001 mol / L, 0.01 mol / L, 0.02 mol / L, 0.05 mol / L, and 0.1 mol / L.

[0107] In this invention, in step (4), the salts in the salt solution containing the second polycationic electrolyte and the salt solution containing the second polyanionic electrolyte are independently selected from one or more of NaCl, NaNO3, NaF, NaBr, KCl and KBr, preferably NaCl, and the salt concentration is 0.01~6 mol / L, preferably 0.025~2.5 mol / L, such as 0.025 mol / L, 0.25 mol / L, 0.5 mol / L, 2.5 mol / L.

[0108] In this invention, an impregnation method is used to contact carrier-adsorbent powder composite particles or carrier-adsorbent powder composite particles with a polyelectrolyte layer on the surface with a salt solution containing a second polycationic electrolyte or a second polyanionic electrolyte. The contact time is 0-30 min, excluding 0 min, preferably 10 ± 2 min, such as 8 min, 10 min, or 12 min. In this invention, by using the impregnation method, a single contact with a salt solution containing a second polycationic or second polyanionic electrolyte for 10 minutes can form a thin, orderly, and dense layer on the surface of the carrier-adsorbent powder composite particles or the carrier-adsorbent powder composite particles with a polyelectrolyte layer on the surface, thereby ensuring effective coating. Under this condition, multiple cycles of impregnation to a certain number of layers can achieve the required interception effect without hindering ion transport.

[0109] In this invention, the method for preparing composite adsorbent particles further includes acid treatment of the composite adsorbent particles obtained in step (4) or step (5) using an acid solution, wherein the acid solution is a hydrochloric acid solution and / or a sulfuric acid solution, preferably a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 0.01-1 mol / L, preferably 0.1±0.02 mol / L, such as 0.08 mol / L, 0.1 mol / L, 1.2 mol / L; the temperature of the hydrochloric acid solution during acid treatment is 30℃-80℃, preferably 60±5℃, such as 55℃, 60℃, 65℃; the acid treatment time is 0.5-24 h, preferably 10±2 h, such as 8 h, 10 h, 12 h.

[0110] A lithium extraction device comprising composite adsorbent particles according to any embodiment of the present invention or composite adsorbent particles obtained by the method according to any embodiment of the present invention.

[0111] The use of composite adsorbent particles according to any embodiment of the present invention, or composite adsorbent particles obtained by the method according to any embodiment of the present invention, in reducing adsorbent powder leakage and / or metal ion dissolution.

[0112] The use of composite adsorbent particles of any embodiment of the present invention or composite adsorbent particles obtained by the method of any embodiment of the present invention in improving lithium extraction stability and / or adsorption performance.

[0113] Compared with the prior art, the present invention has the following beneficial effects: 1. The particle matrix prepared by this invention exhibits a porous structure on its surface, possessing excellent chemical stability and hydrophilicity, thus restoring the powder adsorption capacity as much as possible; the preparation method of this invention does not require the use of organic solvents, making the preparation process more environmentally friendly. 2. This invention constructs a coating on the surface of the adsorbent particle matrix through a layer-by-layer impregnation method, which firmly encapsulates the adsorbent inside. This effectively prevents the leakage of adsorbent powder during the cycle, significantly reduces the dissolution rate of titanium-based, especially easily soluble manganese-based active components, and improves the cycle stability and service life of the adsorbent particles. The resulting adsorbent particles have good application prospects in fields such as lithium extraction from low-lithium brine.

[0114] The present invention will be described below by way of specific embodiments. It should be understood that these embodiments are merely illustrative and are not intended to limit the scope of the invention. The methods, reagents, and materials used in the embodiments and comparative examples are conventional methods, reagents, and materials in the art, unless otherwise stated. The starting material compounds in the embodiments and comparative examples are all commercially available.

[0115] Test Example 1

[0116] This test example demonstrates a method for testing the cyclic stability of composite adsorbent particles, specifically testing their equilibrium adsorption capacity.

[0117] The adsorption conditions for the cycle stability test were as follows: LiCl solution concentration of 30 mg / L (pH=12), adsorbent particle concentration (solid-liquid ratio) of 1 g / L; reaction in a shaker at a temperature of 60℃ for 12 h and a rotation speed of 180 rpm.

[0118] The desorption conditions for the cyclic stability test were as follows: HCl solution concentration of 0.1 mg / L, solid-liquid ratio of 1 g / L; reaction in a shaker at a temperature of 60℃ for 2 h and a rotation speed of 180 rpm.

[0119] Equilibrium adsorption capacity q e Defined as: the amount of lithium ions adsorbed by a unit mass of active adsorbent component when adsorption equilibrium is reached, expressed by formula (1). (1) In formula (1), C 0 (mg / L) C e (mg / L) represent Li before adsorption and at adsorption equilibrium, respectively. + concentration, m (g) represents the mass of the active component (adsorbent powder) in the composite adsorbent particles. V 1 (L) represents the volume of the adsorption solution.

[0120] Test Example 2

[0121] This test example demonstrates the solubility loss rate of the active component in composite adsorbent particles during the adsorption process.

[0122] Titanium dissolution DL Ti Defined as: the degree of titanium dissolution loss in the active component of the composite adsorbent particles after desorption, expressed by formula (2) and calculated as follows: (2) In formula (2), C Ti (mg / L) indicates the concentration of Ti in the desorption solution (HCl solution) after desorption. 4+ The concentration; V 2 (L) represents the volume of the desorption solution; m Ti (mg) indicates the Ti content in the adsorbent 4+ The quality.

[0123] Test Example 3

[0124] Adsorbent powder particle size test: Dynamic light scattering (DLS) was used. An appropriate amount of adsorbent powder was dispersed in deionized water (concentration 0.1~0.5 mg / mL), and after ultrasonic dispersion for 5 min, the volume average particle size (D50) was measured using a Bettersize 2600 laser particle size analyzer at 25℃. Each sample was tested in triplicate and the average value was taken.

[0125] Test Example 4

[0126] Carrier-adsorbent powder composite particles, particle size D50 test of composite adsorbent particles: Direct measurement was performed using vernier calipers. Twenty dry carrier-adsorbent powder composite particles or composite adsorbent particles were randomly selected, and the longest axis dimension of each particle was measured using a digital vernier caliper (accuracy 0.1 mm). The particle diameter D50 was then calculated.

[0127] Example 1

[0128] Slurry preparation: 5 g of the first polyanionic electrolyte, sodium polystyrene sulfonate aqueous solution (PSS, Mw = 1000 kDa, 30 wt.% in water), was added to 5 g of saturated NaCl aqueous solution (5.5 mol / L, 25℃). After dissolution, a 15% PSS salt aqueous solution was obtained, denoted as solution A. 1.18 g of dried first polycationic electrolyte, polydimethyldiallylammonium chloride (PDADMAC, Mw = 150~200 kDa), was added to 6.62 g of saturated NaCl aqueous solution to obtain a 15% PDADMAC salt aqueous solution, denoted as solution B. A non-bound homogeneous solution, denoted as solution C, was prepared by mixing solutions A and B. The molar ratio of PSS to PDADMAC was 1:1. 2.68 g of titanium-based adsorbent powder (particle size D50 = 0.36) was taken. m) is added to solution C, wherein the mass ratio of polyelectrolyte slurry to titanium-based adsorbent is 1:1, to obtain a composite slurry.

[0129] Preparation of composite titanium-based adsorbent particles: The coagulation bath temperature was maintained at 0℃, and a magnetic stirring speed of 100 rpm was set to create a swirling flow as the droplets fell, preventing them from sticking together or adhering to the cup wall. The prepared composite slurry was heated to 40℃ and loaded into a 2 mL medical syringe with a 2 mm diameter needle. The syringe was vertically fixed above the coagulation bath, with the syringe outlet approximately 20 cm above the liquid surface. The syringe piston was pushed at a uniform speed, controlling the composite slurry to be dropped dropwise into the 0℃ deionized water coagulation bath at a rate of 30 drops / min. After all the slurry had been added, mechanical stirring was maintained, and the mixture was solidified in 0℃ deionized water for 2 hours to ensure complete phase separation and composite precipitation, and to ensure complete diffusion of NaCl. Subsequently, the formed spherical particles were collected with a sieve and repeatedly washed with a large amount of deionized water to remove residual free NaCl, finally obtaining spherical carrier-adsorbent powder composite particles with a porous structure and a particle size D50 of 1.8 mm.

[0130] The above-mentioned composite titanium-based adsorbent particles were added to a 0.1 mol / L hydrochloric acid solution, and the solid-liquid ratio was controlled at 5 g / L. The solution was then activated for 10 h at 60 °C and 180 rpm in a shaker.

[0131] Cyclic stability test: The adsorption capacity in the first cycle was 28.66 mg / g. After 10 cycles, the adsorption capacity was 83.99% of the first adsorption capacity, and the total titanium loss was 12.27%.

[0132] Experimental Example 2

[0133] The only difference from Example 1 is that: an aqueous solution of the first polyanionic electrolyte, sodium polystyrene sulfonate (PSS, Mw = 1000 kDa, 30 wt.% in water), was mixed into a saturated NaCl solution to prepare a 17% PSS salt aqueous solution, denoted as solution A. Based on the molar content of PSS in solution A, an equimolar amount of dried first polycationic electrolyte, polydimethyldiallylammonium chloride (PDADMAC, Mw = 150~200 kDa), was dissolved in a saturated NaCl solution to obtain a 17% PDADMAC salt aqueous solution, denoted as solution B. The remaining steps are the same as in Example 1, and the particle size D50 of the obtained carrier-adsorbent powder composite particles is 1.8 mm.

[0134] Cyclic stability test: The adsorption capacity in the first cycle was 25.74 mg / g. After 10 cycles, the adsorption capacity was 83.34% of the first adsorption capacity, and the total titanium loss was 12.08%.

[0135] Example 3

[0136] The only difference from Example 1 is that: an aqueous solution of the first polyanionic electrolyte, sodium polystyrene sulfonate (PSS, Mw = 1000 kDa, 30 wt.% in water), was mixed into a saturated NaCl solution to obtain a 19% PSS salt aqueous solution, denoted as solution A. Based on the molar content of PSS in solution A, an equimolar amount of dried first polycationic electrolyte, polydimethyldiallylammonium chloride (PDADMAC, Mw = 150~200 kDa), was dissolved in a saturated NaCl solution to obtain a 19% PDADMAC salt aqueous solution, denoted as solution B. The remaining steps are the same as in Example 1, and the particle size D50 of the obtained carrier-adsorbent powder composite particles is 1.8 mm.

[0137] Cyclic stability test: The adsorption capacity in the first cycle was 23.05 mg / g. After 10 cycles, the adsorption capacity was 83.22% of the first adsorption capacity, and the total titanium loss was 11.96%.

[0138] Example 4

[0139] The only difference from Example 1 is that a 2 mL syringe was used to drop the slurry into 19°C deionized water. The remaining steps were the same as in Example 1, and the resulting carrier-adsorbent powder composite particles had a particle size D50 of 2.5 mm.

[0140] Cyclic stability test: The adsorption capacity in the first cycle was 25.58 mg / g. After 10 cycles, the adsorption capacity was 75.44% of the first adsorption capacity, and the total titanium loss was 15.53%.

[0141] Example 5

[0142] The only difference from Example 1 is that a 2 mL syringe was used to drop the slurry into 45°C deionized water. The remaining steps were the same as in Example 1, and the resulting carrier-adsorbent powder composite particles had a particle size D50 of 3.0 mm.

[0143] Cyclic stability test: The adsorption capacity in the first cycle was 20.70 mg / g. After 10 cycles, the adsorption capacity was 62.04% of the first adsorption capacity, and the total titanium loss was 15.06%.

[0144] Example 6

[0145] The only difference from Example 1 is that the mass ratio of polyelectrolyte slurry to titanium-based adsorbent in the adsorbent particles is 2:1. The remaining steps are the same as in Example 1, and the resulting carrier-adsorbent powder composite particles have a particle size D50 of 1.8 mm.

[0146] Cyclic stability test: The adsorption capacity in the first cycle was 28.47 mg / g. After 10 cycles, the adsorption capacity was 83.69% of the first adsorption capacity, and the total titanium loss was 12.20%.

[0147] Example 7

[0148] The only difference from Example 1 is that the mass ratio of polyelectrolyte slurry to titanium-based adsorbent in the adsorbent particles is 1:2. The remaining steps are the same as in Example 1, and the resulting carrier-adsorbent powder composite particles have a particle size D50 of 1.8 mm.

[0149] Cyclic stability test: The adsorption capacity in the first cycle was 24.86 mg / g. After 10 cycles, the adsorption capacity was 86.53% of the first adsorption capacity, and the total titanium loss was 11.89%.

[0150] Example 8

[0151] The only difference from Example 1 is that the mass ratio of polyelectrolyte slurry to titanium-based adsorbent in the adsorbent particles is 1:3. The remaining steps are the same as in Example 1, and the resulting carrier-adsorbent powder composite particles have a particle size D50 of 1.8 mm.

[0152] Cyclic stability test: The adsorption capacity in the first cycle was 18.80 mg / g. After 10 cycles, the adsorption capacity was 87.78% of the first adsorption capacity, and the total titanium loss was 11.00%.

[0153] Example 9

[0154] The only difference from Example 1 is that the manganese-based adsorbent powder (particle size D50 is 0.25) m) was added to solution C to finally obtain a manganese-based adsorbent slurry. The remaining steps were the same as in Example 1, and the particle size D50 of the obtained carrier-adsorbent powder composite particles was 1.6 mm.

[0155] Cyclic stability test: The adsorption capacity in the first cycle was 34.77 mg / g. After 10 cycles, the adsorption capacity was 50.23% of the first adsorption capacity, and the total manganese loss reached 38.50%.

[0156] Example 10

[0157] A coating was prepared on the surface of the carrier-adsorbent powder composite particles obtained in Example 1. Using 0.5 M NaCl as the background salt solution, coating solutions of 0.02 M PSS (1000 kDa) and 0.02 M PDADMAC (500-600 kDa) were prepared. The carrier-adsorbent powder composite particles obtained in Example 1 were sequentially immersed in PSS aqueous solution, deionized water, PDADMAC aqueous solution, deionized water, PSS aqueous solution, and deionized water, each immersion lasting 10 minutes. This sequence constituted 1.5 bilayer coatings (i.e., 3 polyelectrolyte layers). After coating, acid treatment was performed, following the same steps as in Example 1. The obtained composite adsorbent particles had a particle size D50 of 1.8 mm.

[0158] Cyclic stability test: The adsorption capacity in the first cycle was 27.50 mg / g. After 10 cycles, the adsorption capacity was 93.67% of the first adsorption capacity, and the total titanium loss was 7.59%.

[0159] Example 11

[0160] A coating was prepared on the surface of the carrier-adsorbent powder composite particles obtained in Example 1. Using 0.5 M NaCl as the background salt solution, a coating solution was prepared consisting of 0.02 M sodium polystyrene sulfonate (PSS, 1000 kDa, powder) and 0.02 M polycationic polyacrylamide hydrochloride (PAH, 10-20 kDa). The carrier-adsorbent powder composite particles obtained in Example 1 were sequentially immersed in PSS salt solution, deionized water, PAH salt solution, and then in deionized water, PSS salt solution, and deionized water, each immersion lasting 10 minutes. This sequence constituted 1.5 bilayer coatings. After coating, acid treatment was performed, following the same steps as in Example 1. The obtained composite adsorbent particles had a particle size D50 of 1.8 mm.

[0161] Cyclic stability test: The adsorption capacity in the first cycle was 25.70 mg / g. After 10 cycles, the adsorption capacity was 95.69% of the first adsorption capacity, and the total titanium loss was 6.09%.

[0162] Example 12

[0163] The only difference from Example 1 is that manganese-based adsorbent powder is added to solution C to obtain a manganese-based adsorbent slurry. For the outer coating of the composite adsorbent particles: using 0.5 M NaCl as the background salt solution, coating solutions of 0.02 M PSS (1000 kDa) and 0.02 M PDADMAC (500-600 kDa) were prepared. The carrier-adsorbent powder composite particles were sequentially immersed in PSS salt solution, deionized water, PDADMAC salt solution, deionized water, PSS salt solution, and deionized water, each immersion lasting 10 minutes. This sequence constitutes 1.5 bilayer coatings. After coating, acid treatment was performed, following the same steps as in Example 1. The obtained composite adsorbent particles had a particle size D50 of 1.6 mm.

[0164] Cyclic stability test: The adsorption capacity in the first cycle was 31.11 mg / g. After 10 cycles, the adsorption capacity was 93.26% of the first adsorption capacity, and the total manganese loss reached 8.67%.

[0165] Example 13

[0166] The difference from Example 10 is that, during coating preparation, 2.5 bilayer coatings, i.e., 5 polyelectrolyte layers, were prepared in the following order: contact with the salt solution of the polyanionic electrolyte, the salt solution of the polycationic electrolyte, the salt solution of the polyanionic electrolyte, and so on. After coating, acid treatment was performed, following the same steps as in Example 1. The obtained composite adsorbent particles had a particle size D50 of 1.8 mm.

[0167] Cyclic stability test: The adsorption capacity in the first cycle was 24.58 mg / g. After 10 cycles, the adsorption capacity was 94.67% of the first adsorption capacity, and the total titanium loss was 7.09%.

[0168] Example 14

[0169] The difference from Example 10 is that, during coating preparation, 3.5 bilayer coatings, i.e., 7 polyelectrolyte layers, were prepared in the order of contacting the polyanionic electrolyte salt solution, the polycationic electrolyte salt solution, the polyanionic electrolyte salt solution, and so on. After coating, acid treatment was performed, following the same steps as in Example 1. The obtained composite adsorbent particles had a particle size D50 of 1.8 mm.

[0170] Cyclic stability test: The adsorption capacity in the first cycle was 20.17 mg / g. After 10 cycles, the adsorption capacity was 94.99% of the first adsorption capacity, and the total titanium loss was 7.00%.

[0171] Comparative Example 1

[0172] The difference between this comparative example and Example 10 is that the carrier-adsorbent powder composite particles obtained in Example 1 were sequentially immersed in PSS brine solution, deionized water, PDADMAC brine solution, and deionized water, with each immersion lasting 10 minutes. This sequence forms a double-layer coating (i.e., two polyelectrolyte layers). After coating, acid treatment was performed, following the same steps as in Example 1. The obtained composite adsorbent particles had a particle size D50 of 1.8 mm.

[0173] Cyclic stability test: The adsorption capacity in the first cycle was 27.98 mg / g. After 10 cycles, the adsorption capacity was 88.99% of the first adsorption capacity, and the total titanium loss was 10.78%.

[0174] Comparative Example 2

[0175] The difference between this comparative example and Example 10 is that the carrier-adsorbent powder composite particles were sequentially immersed in PDADMAC salt solution, deionized water, PSS salt solution, deionized water, PDADMAC salt solution, and deionized water, each immersion lasting 10 minutes, to prepare 1.5 bilayer coatings (i.e., 3 polyelectrolyte layers). After coating, acid treatment was performed. The remaining steps were the same as in Example 10. The obtained composite adsorbent particles had a particle size D50 of 1.8 mm.

[0176] Cyclic stability test: The adsorption capacity in the first cycle was 25.55 mg / g. After 10 cycles, the adsorption capacity was 93.99% of the first adsorption capacity, and the total titanium loss was 7.44%.

[0177] The adsorption capacity and cycling test results of Examples 1-14 and Comparative Examples 1-2 are summarized in Table 1: Table 1. Adsorption capacity and cycle test results

[0178] Examples 1-3 show that the adsorption capacity tends to decrease with increasing polyelectrolyte concentration. This is because the slurry viscosity increases with increasing polyelectrolyte concentration, leading to powder accumulation, which results in partial coverage of adsorption sites and a decrease in adsorption capacity. However, the cycling stability and titanium dissolution do not change significantly with polyelectrolyte concentration.

[0179] Examples 1, 4, and 5 show that the adsorption capacity decreases with increasing water bath temperature. This is because the particle size decreases with increasing water bath temperature; smaller adsorbent particles have shorter diffusion distances, larger specific surface areas, and higher adsorption capacities. Larger adsorbent particles are more prone to powder leakage during adsorption. The leaked powder is more susceptible to titanium dissolution in the adsorption solution, leading to increased total titanium loss and ultimately decreased cycle stability.

[0180] As shown in Examples 1 and 6-8, the adsorption capacity initially remains stable and then decreases as the proportion of adsorbent powder increases. This is because, with a fixed solid-liquid ratio, when the powder is present in an appropriate or even small amount, its uniform distribution within the carrier reduces powder accumulation, and the active sites of the powder can reach saturation, resulting in a large adsorption capacity. However, excessive powder wastes adsorption sites and accumulates, covering the adsorption sites. Cyclic stability and titanium dissolution only change slightly with the polyelectrolyte concentration.

[0181] As can be seen from Examples 1, 10, 11 and Examples 9, 12, the coating improves cycle stability and reduces titanium dissolution at the cost of sacrificing a small amount of adsorption capacity.

[0182] A comparison of Example 10 and Comparative Example 1 reveals that fewer dip-coating cycles (e.g., one double-layer coating in Comparative Example 1) resulted in incomplete coating coverage, leading to continued powder leakage during cycling. Titanium ion dissolution was not significantly suppressed, resulting in decreased adsorption performance and limited improvement in cycling stability.

[0183] Comparing Example 10 and Comparative Example 2, it was found that when the coating surface of the dip-coated material is a polycationic electrolyte, the coating surface carries a positive charge, which is not conducive to lithium ion adsorption. As a result, although the composite adsorbent particles prepared in Comparative Example 2 have good cycle stability, their adsorption performance has decreased.

[0184] The principle for evaluating the performance of composite adsorbent particles in this invention is based on selecting composite adsorbent particles with fewer coating layers while ensuring optimal overall performance in terms of adsorption capacity, total titanium / manganese dissolution rate, and leakage resistance. The adsorption capacity and total titanium / manganese dissolution rate show a gradually decreasing trend with increasing coating layer count, which is a key technical point requiring careful consideration and optimization. As the number of coating layers increases, the coating significantly hinders lithium ion absorption, affecting the adsorption capacity, but the dense coating surface results in good total titanium / manganese dissolution rate and cycle stability. Conversely, when the number of coating layers is very small, the coating has low lithium ion resistance and high initial adsorption capacity, but the thin coating and insufficient surface density lead to poor total titanium / manganese dissolution rate, severe adsorbent powder dissolution, and poor cycle stability.

[0185] With the same number of coating layers (Example 10 and Comparative Example 2), the composite adsorbent particles prepared by first contacting the carrier-adsorbent powder composite particles with a polycationic electrolyte (such as polydimethyldiallylammonium chloride) (Comparative Example 2) have better cycle stability, but their adsorption performance is not high because their coating has a stronger barrier effect on lithium ions. On the other hand, the composite adsorbent particles prepared by first contacting the carrier-adsorbent powder composite particles with a polyanionic electrolyte (such as sodium polystyrene sulfonate) (Example 10) have a negatively charged coating surface, which is conducive to the adsorption of lithium ions and has a higher adsorption capacity.

[0186] Figure 1 The image shows a cross-sectional SEM image of the composite adsorbent particles prepared in Example 1. The image reveals a few large pores inside. The pores within the particles primarily exhibit a sponge-like structure. Figure 2 The exterior of the cavity exhibits a honeycomb-like structure, such as... Figure 3 In summary, the adsorbent particles have a rich internal pore structure, which is beneficial for adsorption.

[0187] Figure 4 The image shows the SEM image of the outer surface of the composite adsorbent particles prepared in Example 1. Figure 5 The image shown is a magnified SEM image of the outer surface of the adsorbent particles in Example 1, which shows that there are a few defects on the outer surface.

[0188] Figure 6 This is a magnified SEM image of the outer surface of the composite adsorbent particles prepared in Example 10 after coating, compared to... Figure 4 The defect disappeared, and the coating filled it.

[0189] Figure 7 The image shows the turbidity of the adsorption solution after ten cycles of the composite adsorbent particles in Example 1. The turbidity indicates that the uncoated composite adsorbent particles experienced adsorbent powder leakage, which will shorten the particle cycle life.

[0190] Figure 8 The image shows the turbidity of the solution after ten cycles of the composite adsorbent particles in Example 10. The solution became clear, indicating that the coating firmly fixed the active component within the load. Although the adsorption capacity decreased compared to before coating, no powder leakage occurred. Furthermore, the coating prevented titanium ion leakage, resulting in a high titanium concentration within the particles and thus inhibiting titanium dissolution. Therefore, the adsorption capacity after cycling reached 93.67% of the initial capacity, compared to only 83% after cycling before coating, demonstrating a significant improvement in cycling stability.

Claims

1. A composite adsorbent particle, characterized in that, The composite adsorbent particles comprise carrier-adsorbent powder composite particles and a coating on the surface of the carrier-adsorbent powder composite particles. The carrier-adsorbent powder composite particles comprise a carrier and adsorbent powder loaded on the carrier. The carrier comprises a first polycationic electrolyte and a first polyanionic electrolyte. The coating comprises one or more polyelectrolyte layers, and each polyelectrolyte layer independently comprises a second polycationic electrolyte and / or a second polyanionic electrolyte.

2. The composite adsorbent particles as described in claim 1, characterized in that, The composite adsorbent particles have one or more of the following characteristics: The adsorbent powder is selected from one or two of layered titanium-based lithium ion sieve adsorbent Li2TiO3 and spinel-like manganese-based lithium ion sieve adsorbent LiMn2O4. The particle size D50 of the adsorbent powder is 0.

01. m~300 μm; The particle size D50 of the carrier-adsorbent powder composite particles is 0.1 mm to 5 mm; The particle size D50 of the composite adsorbent particles is 0.1 mm-5 mm; In the carrier-adsorbent powder composite particles, the mass ratio of carrier to adsorbent powder is 1:4-4:1; The first polycationic electrolyte is selected from one or more of polydiallyl ammonium chloride, polymethacryloyloxyethyltrimethylammonium chloride, quaternized poly(4-vinylpyridine) and hydroxypropyltrimethylammonium chloride chitosan, preferably polydiallyl ammonium chloride; The first polyanion is selected from one or more of sodium polystyrene sulfonate, sodium poly-2-acryloyl-2-methylpropanesulfonate and polyethylene sulfate, preferably sodium polystyrene sulfonate; In the carrier, the molar ratio of the first polycationic electrolyte to the first polyanionic electrolyte is (1-4):1, preferably (1-1.2):1; The coating comprises two or more polyelectrolyte layers, with adjacent polyelectrolyte layers carrying positive and negative charges, respectively; preferably, one of the adjacent polyelectrolyte layers contains a polycationic electrolyte but not a polyanionic electrolyte, and the other layer contains a polyanionic electrolyte but not a polycationic electrolyte; In the coating, the second polycationic electrolyte and the second polyanionic electrolyte contained in each polyelectrolyte layer may be the same or different; preferably, the second polycationic electrolyte is selected from one or more of polydimethyldiallyl ammonium chloride, polyacrylamide hydrochloride, polyethyleneimine and polyethyleneamine, and more preferably one or two of polydimethyldiallyl ammonium chloride and polyacrylamide hydrochloride; preferably, the second polyanionic electrolyte is selected from one or more of sodium polystyrene sulfonate, sodium polyacrylate, sodium polyvinyl sulfonate and sulfonated polyether ether ketone, and more preferably sodium polystyrene sulfonate; The coating comprises 1 to 40 polyelectrolyte layers, preferably 2 to 7 layers, more preferably 3 to 7 polyelectrolyte layers.

3. The composite adsorbent particles as described in claim 1, characterized in that, The coating has one or both of the following characteristics: The innermost polyelectrolyte layer in the coating that is in contact with the carrier-adsorbent powder composite particles is formed of a polyanionic electrolyte or a polycationic electrolyte; preferably, the innermost polyelectrolyte layer is formed of a second polyanionic electrolyte. The outermost polyelectrolyte layer in the coating is formed of a polyanionic electrolyte or a polycationic electrolyte; preferably, the outermost polyelectrolyte layer is formed of a second polyanionic electrolyte.

4. The composite adsorbent particles according to any one of claims 1-3, characterized in that, The composite adsorbent particles have one or more of the following characteristics: The initial adsorption capacity of the composite adsorbent particles for lithium ions is ≥20 mg / g; The adsorption capacity of the composite adsorbent particles for lithium ions in the 10th cycle of adsorption is more than 93% of the initial adsorption capacity. After the 10th cycle of adsorption, the total titanium / manganese dissolution rate in the adsorbent powder is no more than 9%.

5. A method for preparing composite adsorbent particles according to any one of claims 1-4, characterized in that, The method includes the following steps: (1) Provide a polyelectrolyte slurry containing a first polycationic electrolyte, a first polyanionic electrolyte, and a salt; (2) The adsorbent powder is uniformly dispersed in the polyelectrolyte slurry of step (1) to obtain a composite slurry containing adsorbent powder; (3) The composite slurry obtained in step (2) is dropped into water and the carrier-adsorbent powder composite particles are formed by phase separation method; (4) Provide a salt solution containing a second polycationic electrolyte and / or a salt solution containing a second polyanionic electrolyte, and contact the surface of the carrier-adsorbent powder composite particles obtained in step (3) with the salt solution containing the second polycationic electrolyte or the salt solution containing the second polyanionic electrolyte, and then wash in water to form the innermost polyelectrolyte layer; When the coating comprises two or more polyelectrolyte layers, the preparation method further includes the following steps: (5) Contact the surface of the N-1th polyelectrolyte layer with a salt solution containing a second polycationic electrolyte or a salt solution containing a second polyanionic electrolyte, and then clean it to form the Nth polyelectrolyte layer. The N-1th polyelectrolyte layer refers to a polyelectrolyte layer that is adjacent to the Nth polyelectrolyte layer but closer to the carrier-adsorbent powder composite particles; N is preferably an integer from 2 to 40.

6. The method as described in claim 5, characterized in that, The method step (1) has one or more of the following characteristics: The molar ratio of the first polycationic electrolyte and the first polyanionic electrolyte in the polyelectrolyte slurry is (1-4):1, preferably (1-1.2):1; The polyelectrolyte slurry is composed of a salt solution containing a first cationic electrolyte and a salt solution containing a first anionic electrolyte; preferably, the salt solution containing the first polycationic electrolyte comprises the first polycationic electrolyte and a salt; preferably, the salt solution containing the first anionic electrolyte comprises the first anionic electrolyte and a salt; preferably, the salt in the salt solution containing the first polycationic electrolyte and the salt solution containing the first anionic electrolyte are each independently selected from one or more of NaCl, NaNO3, NaF, NaBr, KCl, and KBr, preferably NaCl, and the salt concentration is 0.5~6 mol / L, preferably 5~6 mol / L; preferably, the concentrations of the first polycationic electrolyte and the first anionic electrolyte in the salt solution containing the first polycationic electrolyte and the salt solution containing the first anionic electrolyte are each independently 10 wt%~25 wt%, preferably 15 wt%~19 wt%.

7. The method as described in claim 5, characterized in that, In step (2) of the method, the mass ratio of the polyelectrolyte slurry to the adsorbent powder is (0.2-2):1, preferably 1:3 to 2:

1.

8. The method as described in claim 5, characterized in that, The method step (3) has one or more of the following characteristics: When the composite slurry is dropped into water, the temperature of the composite slurry is 15℃~100℃, preferably 40℃; The composite slurry is dripped into water using a syringe or dropper, wherein the inner diameter of the syringe or dropper is preferably 0.1 mm to 5 mm, more preferably 2 ± 0.5 mm; the distance between the needle tip of the syringe or the bottom of the dropper and the water surface is 5 to 100 cm, more preferably 20 ± 5 cm; and the dripping rate is 1 to 60 drops / min, preferably 30 ± 5 drops / min. Water is used as the coagulation bath in the phase separation method, and the temperature of the coagulation bath is 0℃~100℃, preferably 0℃~50℃; when the composite slurry is added dropwise, the coagulation bath is stirred at a stirring rate of 50~800 rpm, preferably 100±20 rpm.

9. The method as described in claim 5, characterized in that, The method steps (4) and (5) have one or more of the following characteristics: The salt solution containing the second polycationic electrolyte comprises the second polycationic electrolyte and salt; The salt solution containing the second polyanionic electrolyte comprises the second polyanionic electrolyte and salt; The concentrations of the second polycationic electrolyte and the second polyanionic electrolyte in the salt solution containing the second polycationic electrolyte and the salt solution containing the second polyanionic electrolyte are independently 0.001~2 mol / L, preferably 0.001~0.1 mol / L; The salts in the salt solution containing the second polycationic electrolyte and the salt solution containing the second polyanionic electrolyte are each independently selected from one or more of NaCl, NaNO3, NaF, NaBr, KCl and KBr, preferably NaCl, and the salt concentration is 0.01~6 mol / L, preferably 0.025~2.5 mol / L; The carrier-adsorbent powder composite particles or carrier-adsorbent powder composite particles with a polyelectrolyte layer on the surface are contacted with the salt solution containing the second polycationic electrolyte or the salt solution containing the second polyanionic electrolyte by impregnation. The contact time is 0-30 min (excluding 0 min), preferably 10±2 min.

10. The method as described in claim 5, characterized in that, The method further includes acid treatment of the composite adsorbent particles obtained in step (4) or step (5) with an acid solution, wherein the acid solution is a hydrochloric acid solution and / or a sulfuric acid solution, preferably a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 0.01-1 mol / L, preferably 0.1±0.02 mol / L; the temperature of the hydrochloric acid solution during acid treatment is 30 ℃-80 ℃, preferably 60±5 ℃; and the acid treatment time is 0.5-24 h, preferably 10±2 h.

11. A lithium extraction device, characterized in that, The lithium extraction device comprises composite adsorbent particles as described in any one of claims 1-4 or composite adsorbent particles obtained by the method described in any one of claims 5-10.

12. Selected for the following uses: (1) The use of composite adsorbent particles as described in any one of claims 1-4 or composite adsorbent particles obtained by the method as described in any one of claims 5-10 in reducing adsorbent powder leakage and / or metal ion dissolution; (2) The use of composite adsorbent particles as described in any one of claims 1-4 or composite adsorbent particles obtained by the method as described in any one of claims 5-10 in improving the lithium extraction stability and / or adsorption performance of adsorbent materials.

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