Zirconium / aluminum co-doped hierarchical pore titanium-based lithium ion sieve composite microspheres, and preparation method and application thereof

Abstract

This invention belongs to the field of lithium adsorption material technology, specifically relating to a zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microsphere, its preparation method, and its application. The innovative surface modification step of this invention utilizes a modifier containing a catechol structure to construct a dense protective layer on the powder surface, effectively blocking the direct erosion of active sites by acid. Combined with a subsequent phase inversion granulation process using a pore-forming agent and a polymer binder, a hierarchical pore structure connecting micropores to macropores is successfully constructed, completely solving the problem of limited mass transfer caused by pore blockage in traditional granulation techniques. Experimental data confirm that this multi-level synergistic mechanism produces an unexpectedly high synergistic effect; the composite microspheres prepared in the example exhibit an adsorption capacity retention rate as high as 92.3%, far exceeding the comparative examples (below 70%) of single or dual techniques.

Description

Technical Field

[0001] This invention belongs to the field of lithium adsorption material technology, specifically relating to a zirconium / aluminum co-doped hierarchical porous titanium-based lithium ion sieve composite microsphere, its preparation method, and its application. Background Technology

[0002] Lithium, as a core strategic resource in the modern energy system, holds an irreplaceable position in new energy vehicles, large-scale energy storage, and consumer electronics. With the acceleration of global carbon neutrality, the demand for lithium resources is experiencing explosive growth. Currently, global lithium resources are mainly found in salt lake brines and seawater. Although reserves are vast, they are characterized by a high magnesium-to-lithium ratio and low concentration, making traditional precipitation and extraction methods insufficient for efficient and green extraction. Ion sieve adsorption, due to its specific recognition ability for lithium ions, large adsorption capacity, and good cycle stability, is considered the most ideal technical route for extracting lithium from low-grade brines. Among these, titanium-based lithium ion sieves (such as Li4Ti5O) are particularly valuable. 12 Because of its superior chemical stability compared to manganese-based materials and its relatively low titanium dissolution rate during cycling, titanium (and its hydrogen form) has become the preferred adsorbent material for industrial lithium extraction.

[0003] The industrial application of titanium-based lithium-ion sieves typically faces the challenge of bridging the gap between powder synthesis and engineered molding. While laboratory-prepared ion sieve powders exhibit fast adsorption rates and high capacities, their extremely small particle size leads to significant fluid resistance when directly applied to industrial adsorption columns, and they are prone to loss at high flow rates. Therefore, it is essential to engineer granulation by mixing the powder with a polymeric binder. However, this process presents a triple challenge: adsorption capacity, mechanical strength, and mass transfer rate. While the binder imparts a macroscopic shape to the microspheres, it can easily encapsulate active sites and clog micropores, resulting in a significant decrease in adsorption capacity after granulation (typically only 50%-60% of that of the powder). Simultaneously, purely physical pore formation often results in insufficient mechanical strength of the microspheres, making them unable to withstand the high pressure drops of dynamic column operations. Furthermore, the titanium-based framework still faces a certain risk of dissolution during repeated acid elution, limiting the long-term lifespan of the adsorbent. Developing a composite microsphere that simultaneously achieves high capacity, high strength, and long lifespan is a critical technical problem urgently needing to be solved in the field of lithium adsorption materials.

[0004] Chinese patent document CN201811040974.7 discloses a metatitanate-type lithium adsorbent, which improves the lattice stability of the material to a certain extent by introducing elements such as zirconium (Zr) doping. However, this method has obvious defects: its modification is mainly limited to the powder synthesis stage, and it fails to solve the problem of physical blockage of active channels by hydrophobic binders during the engineering granulation process; moreover, this single doping system lacks the synergistic pinning effect of aluminum (Al) on the oxygen framework, resulting in a significant decrease in the effective adsorption capacity and long-term cycling stability of the material under strong acid elution environment.

[0005] Chinese patent document CN202410249795.3 discloses a method for preparing lithium-ion adsorbent particles by adding a pore-forming agent, which attempts to improve mass transfer performance through physical pore formation. However, such techniques that rely solely on pore-forming agents often struggle to achieve both high porosity and high mechanical strength. The prepared microspheres are prone to forming poorly interconnected macropores (dead pores), resulting in low utilization of deep active sites. Simultaneously, due to the lack of an interface enhancement mechanism, the density and mechanical strength of the microspheres decrease significantly, making them highly susceptible to breakage and pulverization under high-flow-rate (>5 BV / h) dynamic adsorption conditions in industrial applications, leading to bed blockage and adsorbent loss. Summary of the Invention

[0006] The purpose of this invention is to provide a hierarchical porous zirconium / aluminum co-doped titanium-based lithium-ion sieve composite microsphere with good mechanical strength, high adsorption capacity and low solubility, so as to solve the technical problems of limited mass transfer during granulation, easy dissolution of the framework and difficulty in connecting the pore structure in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres, the method comprising the following steps: S1. Lithium source, titanium source, zirconium source and aluminum source are dissolved in a solution containing organic solvent and mixed evenly to form a sol. After aging and calcination, precursor powder is obtained. S2. The precursor powder is immersed in an acid solution to remove lithium, and after washing and drying, hydrogen-type Zr / Al co-doped titanium-based lithium ion sieve powder is obtained. S3. Disperse the hydrogen-type Zr / Al co-doped titanium-based lithium ion sieve powder in a weakly alkaline buffer solution, then add a surface modifier containing catechol structure and stir. After filtration and drying, the modified powder is obtained. S4. Add the modified powder, pore-forming agent and polymer binder to the organic solvent and stir evenly. Let stand to degas and obtain the slurry. S5. The slurry is dripped into a coagulation bath to solidify into spheres, then dried, and finally heated to obtain composite microspheres.

[0008] In the above-mentioned method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres, the molar ratio of lithium source, titanium source, zirconium source and aluminum source is (3.5-5.0):(4.0-4.9):(0.05-0.4):(0.05-0.2).

[0009] Preferably, the solution containing organic solvent in step S1 is a homogeneous solution containing alcohol or ester.

[0010] Further preferably, the solution containing the organic solvent is an aqueous solution containing ethanol.

[0011] In the above-mentioned method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium ion sieve composite microspheres, step S1, aging specifically includes: stirring vigorously at 55-65℃ for 3-5 hours to form a uniform sol, and then aging at 70-90℃ for 20-30 hours to form a dry gel. And / or calcination specifically includes: heating to 600-800℃ at a heating rate of 2-10℃ / min and holding at that temperature for 2-6 hours.

[0012] In the above-mentioned method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium ion sieve composite microspheres, in step S2, the concentration of the acid solution is 0.1-1.0 mol / L, and the solid-liquid ratio of the precursor powder soaking is 1g:(50-200)mL, wherein the acid solution includes one of hydrochloric acid solution, nitric acid solution, and acetic acid solution.

[0013] In the above-mentioned method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium ion sieve composite microspheres, in step S3, the pH value of the weakly alkaline buffer solution is 7.5-9.0, and the weakly alkaline buffer solution includes one of sodium bicarbonate / sodium carbonate buffer solution and boric acid / sodium borate buffer solution. And / or the surface modifier containing the catechol structure includes at least one of dopamine hydrochloride and tannic acid, wherein the concentration of the surface modifier containing the catechol structure in the weakly alkaline buffer is 1.5-2.5 mg / mL.

[0014] Here, the main function of the weakly alkaline buffer solution is to provide a mild and stable slightly alkaline oxidative environment (pH 7.5-9.0) to induce spontaneous oxidative cross-linking and polymerization reactions of hydroxyl groups in catechol-containing structures (such as dopamine and tannic acid), thereby depositing a uniform modified layer in situ on the surface of the titanium-based powder. Simultaneously, using a buffer system without primary amines, such as sodium bicarbonate / sodium carbonate or boric acid / sodium borate, can effectively prevent buffer molecules from participating in polymerization side reactions, ensuring the purity and density of the surface modified layer.

[0015] The surface modifier containing catechol structure used in this invention has the following significant advantages: On the one hand, the catechol group has extremely strong biomimetic interface adhesion ability, and can form a stable bond on the surface of the inorganic titanium-based skeleton through interactions such as coordination bonds and hydrogen bonds, which is not easy to fall off during subsequent high-intensity dynamic scouring and repeated acid elution; on the other hand, the dense hydrophilic modified layer formed by in-situ polymerization constructs a dual barrier of "anti-clogging and anti-dissolution", which can not only act as a physical isolation layer to prevent the hydrophobic polymer binder from excessively penetrating into and clogging the internal active micropores of the ion sieve during granulation, but also effectively block the direct erosion of the internal titanium-based skeleton by strong acid solution during desorption. Moreover, the hydrophilic functional groups rich in the modified layer itself fully ensure the rapid mass transfer and diffusion of lithium ions.

[0016] Furthermore, this invention strictly controls the concentration of the surface modifier containing the catechol structure in the weakly alkaline buffer solution to 1.5-2.5 mg / mL. If too little is added (concentration below 1.5 mg / mL), a complete and continuous coating layer cannot be formed on the powder surface. Powder with exposed defects will still have its active pores blocked by the binder during granulation, and the acid solution will easily erode the titanium skeleton from the coating defects during acid elution, failing to achieve the purpose of reducing the titanium dissolution rate. If too much is added (concentration above 2.5 mg / mL), the excessive polymerization of the modifier will lead to an excessively thick coating layer on the powder surface. The excessively thick polymer layer will directly cover or even completely block the adsorption active sites of the titanium-based lithium ion sieve itself, and drastically increase the internal diffusion resistance of lithium ions at the solid-liquid interface, ultimately resulting in a significant reduction in the effective adsorption capacity of the composite microspheres and a slower adsorption rate.

[0017] In the above-mentioned method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres, in step S3, the mass ratio of hydrogen-type Zr / Al co-doped titanium-based lithium-ion sieve powder to surface modifier containing catechol structure is (5-15):1.

[0018] In the above-mentioned method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres, in step S4, the mass ratio of modified powder, pore-forming agent, and polymeric binder is (5-15):(0.5-2.0):(1.0-2.0); wherein the pore-forming agent includes at least one of polyethylene glycol, polyvinylpyrrolidone, and nano-calcium carbonate; and the polymeric binder includes at least one of polyethersulfone, polyvinylidene fluoride, and polysulfone.

[0019] Preferably, the organic solvent in step S4 includes one of N-methylpyrrolidone, dimethylformamide, and dimethylacetamide.

[0020] Preferably, the viscosity of the slurry in step S4 is 2000-3500 mPa·s. (Viscosity test conditions: using a rotational viscometer, rotor speed 30-60 rpm).

[0021] In the above-mentioned method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres, in step S5, the heating temperature is 180-280℃ and the time is 2-6 hours. Excessive heating temperature can cause the binder to decompose, leading to the collapse of the hierarchical pore channels.

[0022] Preferably, in step S5, a phase inversion method is used, in which the slurry from step S3 is dropped into a water or aqueous ethanol coagulation bath at a temperature of 10-40℃, and phase separation is induced by solvent-non-solvent exchange. Through the selective dissolution of the pore-forming agent in the coagulation bath, a through-hole hierarchical pore structure is formed inside the microspheres.

[0023] Further optimization involves dripping the solution into a deionized water coagulation bath at 20-30°C using a needle with an inner diameter of 0.5-0.8 mm at a rate of 1-3 mL / min.

[0024] A zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microsphere is prepared by the above method.

[0025] An apparatus for extracting lithium from seawater or brine from salt lakes, the apparatus being filled with the aforementioned zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres.

[0026] Compared with the prior art, the present invention has the following advantages: 1. This invention employs a synergistic three-pronged strategy of "dual-doped lattice control, surface interface isolation, and phase transformation hierarchical pore formation," cleverly utilizing a zirconium source to expand lattice channels and enhance lithium-ion diffusion rates, while simultaneously introducing an aluminum source to strengthen the stability of Ti-O bonds. These two elements complement each other at the atomic scale, fundamentally suppressing titanium skeleton dissolution during acidic elution. As a result, the titanium dissolution rate of the material is as low as 0.2% after 50 adsorption-desorption cycles, demonstrating excellent cycle stability.

[0027] 2. The innovative surface modification step of this invention utilizes a modifier containing a catechol structure to construct a dense protective layer on the powder surface, effectively blocking the direct erosion of active sites by acid. Combined with the subsequent phase inversion granulation process using a pore-forming agent and a polymer binder, a hierarchical pore structure connecting micropores to macropores is successfully constructed, completely solving the problem of limited mass transfer caused by pore blockage in traditional granulation techniques. Experimental data confirms that this multi-level synergistic mechanism produces an unexpectedly strong synergistic effect. The composite microspheres prepared in the example exhibit an adsorption capacity retention rate as high as 92.3%, far exceeding the comparative examples (below 70%) of single or dual techniques.

[0028] 3. The microspheres of this invention, after thermosetting, possess excellent mechanical strength, with a single particle crushing strength greater than 20N. They can withstand the high-pressure impact and fluid shear force in industrial dynamic column operations, avoiding the problems of easy breakage and high bed resistance of traditional powder materials. This not only achieves a perfect balance of high adsorption capacity, low solubility, and high strength, but also significantly improves the applicability and lifespan of the material in complex brine environments. It provides key material support for large-scale industrial lithium extraction with both high efficiency and high reliability, and has extremely high application value. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the preparation process of the zirconium / aluminum co-doped titanium-based lithium-ion sieve composite microspheres described in Example 1 of the present invention.

[0030] Figure 2 The image shows the dynamic adsorption-throughput curve fitting diagram of the composite microspheres prepared in Example 1 at different flow rates. Detailed Implementation

[0031] The present invention will be described in detail below through specific embodiments. The embodiments listed in the present invention are only some embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Example 1: according to Figure 1 The process flow shown is used to prepare zirconium / aluminum co-doped titanium-based lithium-ion sieve composite microspheres: S1. Synthesis of Lattice-Controlled Precursor: Lithium carbonate (Li₂CO₃), tetrabutyl titanate (Ti(OBu)₄), zirconium oxychloride (ZrOCl₂·8H₂O), and aluminum nitrate (Al(NO₃)₃·9H₂O) were dissolved in a mixed solvent of ethanol and deionized water (volume ratio 1:1) at a molar ratio of Li:Ti:Zr:Al = 4:4.7:0.2:0.1. The solution was vigorously stirred at 60°C for 4 h to form a homogeneous sol, which was then aged in an 80°C forced-air drying oven for 24 h to form a dry gel. The dry gel was ground and placed in a muffle furnace, air was introduced, and the temperature was increased to 700°C at a rate of 5°C / min for calcination for 4 h, followed by natural cooling to room temperature. This process ensured the complete oxidative decomposition of the organic components and the complete construction of the spinel lattice, yielding Zr / Al co-doped titanium-based lithium-ion sieve precursor powder.

[0033] S2. Mild acid elution: The precursor powder obtained in step S1 was placed in a 0.5 mol / L HCl solution with a solid-liquid ratio of 1 g:100 mL and stirred at 25°C for 24 h to elute Li⁺. After elution, the powder was repeatedly filtered and washed with deionized water until the pH of the filtrate was neutral, and then vacuum dried at 60°C to obtain hydrogen-form Zr / Al co-doped titanium-based lithium ion sieve powder (H-LIS).

[0034] S3. Interface modification and slurry preparation: (a) Weigh 10g of H-LIS powder and disperse it in 500mL of sodium bicarbonate / sodium carbonate buffer solution with pH 8.5 and a concentration of 0.05 mol / L. Add 1.0g of dopamine hydrochloride (so that the concentration of dopamine in the system is 2.0mg / mL), stir at room temperature for 4h, so that dopamine is oxidized and polymerized in situ on the surface of the powder to form a hydrophilic modified polydopamine (PDA) layer with a thickness of about 5nm. Filter, wash and dry to obtain modified H-LIS powder.

[0035] (b) 10g of modified H-LIS powder, 1.5g of polyethersulfone (PES) as a binder, and 1.0g of polyethylene glycol (PEG-4000) as a pore-forming agent were added to 30mL of N-methylpyrrolidone (NMP). The mixture was mechanically stirred at 60℃ for 2h, then cooled to 25℃. The viscosity of the slurry was measured and adjusted to 2500mPa·s using a rotational viscometer (30rpm). After standing to remove bubbles, the casting slurry was obtained.

[0036] S4. Phase Transformation and In-situ Pore Formation: Using a precision peristaltic pump, the slurry is dripped into a 25°C deionized water coagulation bath at a rate of 2 mL / min through a 0.7 mm inner diameter needle. Phase separation is induced by the exchange of solvent (NMP) and non-solvent (water), while PEG-4000 dissolves in water to form channels, and the microspheres solidify. The microspheres are then immersed in flowing water for 24 hours to completely dissolve PEG-4000 and residual solvent.

[0037] S5. Structural thermosetting: Drain the wet microspheres and place them in a programmed temperature oven. Heat the oven to 200℃ at a rate of 2℃ / min and keep it at that temperature for 4 hours to allow the binder to undergo physical cross-linking and solidify the structure, ultimately obtaining composite microspheres.

[0038] Test Results: The microspheres prepared in Example 1 had an initial adsorption capacity of 38.5 mg / g (capacity retention rate of 92.3%), a total titanium dissolution rate of 0.12% after 50 cycles, and a single-sphere crushing strength of 25.6 N. BET testing showed a specific surface area of ​​38.2 m² / g. These results indicate that the formulation achieved an optimal balance in terms of capacity, stability, and strength. In simulated brine with a high magnesium-to-lithium ratio of Mg / Li = 20, the composite microspheres prepared in Example 1 exhibited a specific recognition ability for lithium ions. Test data are shown in Table 2.

[0039] Figure 2 The figure shows the fitted curves of the dynamic adsorption-throughput of the composite microspheres prepared in Example 1 at different flow rates. As can be seen from the figure, the dynamic adsorption-throughput curves at different flow rates all exhibit a distinct typical "S"-shaped characteristic. With increasing flow rate, the breakthrough time is correspondingly shortened. It is noteworthy that even at higher flow rates, the breakthrough curves maintain a good steepness, indicating a narrow mass transfer region. This fully demonstrates that the interconnected hierarchical pore structure constructed by the synergistic use of phase transformation and in-situ pore formation plays a crucial role. This structure significantly reduces fluid resistance and lithium ion diffusion resistance within the microspheres, providing excellent mass transfer kinetics performance for the composite microspheres. This allows for the efficient utilization of deep adsorption active sites within the microspheres, indicating that the composite microspheres can adapt to industrial-grade high-flow-rate, high-space-velocity dynamic column extraction lithium extraction conditions.

[0040] Example 2: S1. Synthesis of Lattice-Controlled Precursor: Lithium carbonate, tetrabutyl titanate, zirconium oxychloride, and aluminum nitrate were dissolved in a mixed solvent of ethanol and deionized water (volume ratio 1:1) at a molar ratio of Li:Ti:Zr:Al = 4:4.5:0.4:0.1. The solution was vigorously stirred at 60°C for 4 hours to form a homogeneous sol, which was then aged in an 80°C forced-air drying oven for 24 hours to form a dry gel. The dry gel was ground and placed in a muffle furnace, where it was calcined at 700°C at a rate of 5°C / min for 4 hours to obtain a highly Zr-doped titanium-based lithium-ion sieve precursor powder.

[0041] S2. Mild acid elution: The precursor powder obtained in step S1 was placed in a 0.5 mol / L HCl solution with a solid-liquid ratio of 1 g:100 mL and stirred at 25°C for 24 h to elute Li⁺. After elution, the powder was repeatedly filtered and washed with deionized water until the pH of the filtrate was neutral, and then vacuum dried at 60°C to obtain hydrogen-form H-LIS powder.

[0042] S3. Interface modification and slurry preparation: (a) Weigh 10g of H-LIS powder and disperse it in 500mL of sodium bicarbonate / sodium carbonate buffer solution with pH 8.5 and a concentration of 0.05 mol / L. Add 1.0g of dopamine hydrochloride and stir at room temperature for 4h. The hydrophilic modified layer is formed by in-situ polymerization on the surface of the powder. Filter and dry to obtain modified H-LIS powder.

[0043] (b) Add 10g of modified H-LIS powder, 1.5g of polyethersulfone (PES), and 1.0g of polyethylene glycol (PEG-4000) to 30mL of NMP. Mechanically stir at 60℃ for 2h, adjust the slurry viscosity to 2500mPa·s, and allow to stand to degas to obtain the casting slurry.

[0044] S4. Phase Transformation and In-situ Pore Creation: The slurry was dripped into a 25°C deionized water coagulation bath through a 0.7 mm inner diameter needle using a peristaltic pump. Solvent exchange was used to solidify the microspheres, simultaneously dissolving PEG-4000 to create pores. The microspheres were then immersed in flowing water for 24 hours.

[0045] S5. Structural thermosetting: Drain the wet microspheres, place them in an oven, heat them to 200℃ at a rate of 2℃ / min, and keep them at that temperature for 4 hours.

[0046] Test Results and Analysis: The microspheres prepared in Example 2 had an initial adsorption capacity of 34.5 mg / g, a total titanium dissolution rate of 0.10% after 50 cycles, and a single-sphere crushing strength of 26.2 N. Compared to Example 1, increasing the Zr content further reduced the titanium dissolution rate, but due to the large atomic mass of Zr and its occupation of some lattice sites, the theoretical adsorption capacity per unit mass decreased slightly. This demonstrates that the doping ratio within the scope of protection of this invention can be finely adjusted between capacity and stability according to requirements.

[0047] Example 3: S1. Synthesis of Lattice-Controlled Precursor: Lithium carbonate, tetrabutyl titanate, zirconium oxychloride, and aluminum nitrate were dissolved in a mixed solvent of ethanol and deionized water at a molar ratio of Li:Ti:Zr:Al = 4:4.7:0.2:0.1. The solution was stirred at 60°C for 4 hours to form a sol, and then aged at 80°C for 24 hours. After grinding, the solution was calcined at 700°C for 4 hours to obtain Zr / Al co-doped precursor powder.

[0048] S2. Mild acid elution: The precursor powder was placed in a 0.5 mol / L HCl solution and stirred at 25°C for 24 h to elute Li⁺. The solution was washed until neutral and dried to obtain H-LIS powder.

[0049] S3. Interface modification and slurry preparation: (a) Weigh 10g of H-LIS powder and disperse it in 500mL of sodium bicarbonate / sodium carbonate buffer solution with pH 8.5 and concentration of 0.1 mol / L. Add dopamine hydrochloride (2mg / mL) and stir for 4h to form a PDA modified layer. Dry to obtain modified H-LIS.

[0050] (b) 10g of modified H-LIS powder, 1.5g of polyvinylidene fluoride (PVDF) as a binder, and 0.5g of nano-calcium carbonate (CaCO3) as a pore-forming agent were added to 30mL of NMP. The mixture was stirred at 60℃ for 2h, and the viscosity was adjusted to 2800mPa·s. The slurry was then degassed to obtain the final product.

[0051] S4. Phase Transformation and In-situ Pore Formation: The slurry was dripped into a 25°C deionized water coagulation bath to solidify into spheres. After soaking for 24 hours to remove the solvent, an additional post-treatment step was added: the microspheres were soaked in 0.1 mol / L dilute hydrochloric acid for 2 hours to dissolve the CaCO3 particles inside the microspheres, generating CO2 gas in situ and forming pores. The microspheres were then washed with deionized water until neutral.

[0052] S5. Structural thermosetting: Drain the microspheres, place them in an oven, heat them to 180℃ at a rate of 2℃ / min, and keep them at that temperature for 4 hours.

[0053] Test Results and Analysis: The microspheres prepared in Example 3 had an initial adsorption capacity of 37.8 mg / g, a total titanium dissolution rate of 0.13% after 50 cycles, and a single-sphere crushing strength of 24.1 N. These results demonstrate that the hierarchical pore construction strategy proposed in this invention is universally applicable, suitable not only for water-soluble organic porogens (PEG) but also for acid-soluble inorganic porogens (CaCO3), enabling the construction of interconnected pore structures and achieving excellent adsorption performance.

[0054] Example 4: The difference from Example 1 is that in step S1, lithium carbonate, tetrabutyl titanate, zirconium oxychloride and aluminum nitrate are dissolved in a mixed solvent of ethanol and deionized water in a molar ratio of Li:Ti:Zr:Al=4:4.9:0.05:0.05, and the low-doped precursor powder is obtained by sol-gel process and calcination at 700°C for 4 hours.

[0055] Test Results and Analysis: The microspheres prepared in Example 4 had an initial adsorption capacity of 40.1 mg / g, a total titanium dissolution rate of 0.18% after 50 cycles, and a crushing strength of 25.0 N. At low doping levels, the adsorption capacity was very high (>40 mg / g) due to the high content of active Ti in the lattice. Although the titanium dissolution rate was slightly higher than in Example 1, it was still significantly lower than the undoped comparative example (>2%), fully meeting the standards for industrial applications.

[0056] Example 5: The difference from Example 1 is that in step S3, 10g of modified H-LIS powder, 1.5g of PES, and 2.0g of PEG-4000 are added to 30mL of NMP, stirred at 60℃ for 2h, and the viscosity is adjusted to 3000mPa·s to remove bubbles.

[0057] Test Results and Analysis: The microspheres prepared in Example 5 had an initial adsorption capacity of 39.5 mg / g, a total titanium dissolution rate of 0.13% after 50 cycles, and a single-sphere crushing strength of 20.8 N. Increasing the amount of pore-forming agent significantly improved the porosity of the microspheres, bringing the adsorption capacity close to the theoretical value of the powder. Although the mechanical strength decreased somewhat, it was still higher than the industrially required threshold of 20 N.

[0058] Example 6: The only difference from Example 1 is that the surface modifier containing the catechol structure is tannic acid, and the coagulation bath is an aqueous solution containing 30 v% ethanol.

[0059] Test Results and Analysis: The microspheres prepared in Example 6 had an initial adsorption capacity of 36.5 mg / g, a total titanium dissolution rate of 0.12% after 50 cycles, and a single-sphere crushing strength of 26.5 N. Tannic acid, as another modifier containing a catechol structure, also played a role in preventing pore blockage and aiding dispersion. The use of an ethanol coagulation bath fine-tuned the pore structure, resulting in a slight increase in microsphere strength. This demonstrates the diversity in the selection of modifiers and coagulation baths in this invention.

[0060] Comparative Example 1: S1. Synthesis of Lattice-Controlled Precursor: Lithium carbonate (Li₂CO₃), tetrabutyl titanate (Ti(OBu)₄), zirconium oxychloride (ZrOCl₂·8H₂O), and aluminum nitrate (Al(NO₃)₃·9H₂O) were dissolved in a mixed solvent of ethanol and deionized water (volume ratio 1:1) at a molar ratio of Li:Ti:Zr:Al = 4:4.7:0.2:0.1. The solution was vigorously stirred at 60°C for 4 h to form a homogeneous sol, which was then aged in an 80°C forced-air drying oven for 24 h to form a dry gel. The dry gel was ground and placed in a muffle furnace, air was introduced, and the temperature was increased to 700°C at a heating rate of 5°C / min for 4 h. The furnace was then cooled to obtain Zr / Al co-doped titanium-based lithium-ion sieve precursor powder.

[0061] S2. Mild acid elution: The precursor powder obtained in step S1 was placed in a 0.5 mol / L HCl solution with a solid-liquid ratio of 1 g:100 mL and stirred at 25°C for 24 h to elute Li⁺. After elution, the powder was repeatedly filtered and washed with deionized water until the pH of the filtrate was neutral, and then vacuum dried at 60°C to obtain hydrogen-form Zr / Al co-doped titanium-based lithium ion sieve powder (H-LIS).

[0062] S3. Slurry Preparation: Weigh 10g of H-LIS powder (unmodified with dopamine hydrochloride) obtained in step S2, 1.5g of polyethersulfone (PES) as a binder, and 1.0g of polyethylene glycol (PEG-4000) as a pore-forming agent and add them to 30mL of N-methylpyrrolidone (NMP). Mechanically stir at 60℃ for 2h, then cool to 25℃, adjust the slurry viscosity to 2500mPa·s, and allow to stand to degas to obtain the casting slurry.

[0063] S4. Phase Transformation and In-situ Pore Formation: Using a precision peristaltic pump, the slurry was dripped into a 25°C deionized water coagulation bath at a rate of 2 mL / min through a 0.7 mm inner diameter needle. Solvent exchange induced phase separation, while PEG-4000 dissolved in water to form channels, and the microspheres solidified. The microspheres were then immersed in flowing water for 24 hours to completely dissolve PEG-4000 and residual solvent.

[0064] S5. Structural thermosetting: Drain the wet microspheres and place them in a programmed temperature oven. Heat the oven to 200℃ at a rate of 2℃ / min and keep it at that temperature for 4 hours to allow the binder to undergo physical cross-linking and solidify the structure, ultimately obtaining composite microspheres.

[0065] Test results: Adsorption capacity 21.6 mg / g, capacity retention rate only 51.8%. This indicates a lack of PDA isolation layer and severe blockage of active micropores by the binder.

[0066] Comparative Example 2: S1. Precursor Synthesis: Lithium carbonate (Li₂CO₃) and tetrabutyl titanate (Ti(OBu)₄) were dissolved in a mixed solvent of ethanol and deionized water at a molar ratio of Li:Ti = 4:5. The solution was vigorously stirred at 60°C for 4 hours to form a homogeneous sol, which was then aged in an 80°C forced-air drying oven for 24 hours to form a dry gel. The dry gel was ground and placed in a muffle furnace, air was introduced, and the temperature was increased to 700°C at a rate of 5°C / min for calcination for 4 hours. The furnace was then cooled to obtain pure lithium titanate precursor powder.

[0067] S2. Mild acid elution: The precursor powder obtained in step S1 was placed in a 0.5 mol / L HCl solution with a solid-liquid ratio of 1 g:100 mL and stirred at 25°C for 24 h to elute Li⁺. After elution, the powder was repeatedly filtered and washed with deionized water until the pH of the filtrate was neutral, and then vacuum dried at 60°C to obtain hydrogen-form lithium titanate powder (H-LIS).

[0068] S3. Interface modification and slurry preparation: (a) Weigh 10g of H-LIS powder and disperse it in 500mL of sodium bicarbonate / sodium carbonate buffer solution at pH 8.5. Add 1.0g of dopamine hydrochloride and stir at room temperature for 4h to form a PDA modified layer. Filter, wash and dry to obtain modified H-LIS powder.

[0069] (b) Add 10g of modified H-LIS powder, 1.5g of polyethersulfone (PES), and 1.0g of polyethylene glycol (PEG-4000) to 30mL of NMP. Mechanically stir at 60℃ for 2h, adjust the slurry viscosity to 2500mPa·s, and allow to stand to degas to obtain the casting slurry.

[0070] S4. Phase Transformation and In-situ Pore Formation: Using a precision peristaltic pump, the slurry was dripped into a 25°C deionized water coagulation bath at a rate of 2 mL / min through a 0.7 mm inner diameter needle. Solvent exchange induced phase separation, while PEG-4000 dissolved in water to form channels, and the microspheres solidified. The microspheres were then immersed in flowing water for 24 hours.

[0071] S5. Structural thermosetting: Drain the wet microspheres, place them in a programmed temperature oven, heat them to 200℃ at a rate of 2℃ / min and keep them at that temperature for 4 hours to obtain composite microspheres.

[0072] Test results: The initial capacity was 39.0 mg / g, but after 50 cycles, the titanium dissolution rate reached as high as 2.85%, and the microspheres began to pulverize. This indicates a lack of doping and poor acid resistance of the framework.

[0073] Comparative Example 3: S1. Synthesis of Lattice-Controlled Precursor: Lithium carbonate, tetrabutyl titanate, zirconium oxychloride, and aluminum nitrate were dissolved in a mixed solvent of ethanol and deionized water at a molar ratio of Li:Ti:Zr:Al = 4:4.7:0.2:0.1. The solution was vigorously stirred at 60°C for 4 hours to form a homogeneous sol, which was then aged in an 80°C forced-air drying oven for 24 hours to form a dry gel. The dry gel was ground and placed in a muffle furnace, air was introduced, and the temperature was increased to 700°C at 5°C / min for 4 hours to obtain Zr / Al co-doped titanium-based lithium-ion sieve precursor powder.

[0074] S2. Mild acid elution: The precursor powder was placed in a 0.5 mol / L HCl solution at a solid-liquid ratio of 1 g:100 mL and stirred at 25 °C for 24 h to elute Li⁺. After washing to neutrality and drying, hydrogen-form Zr / Al co-doped titanium-based lithium ion sieve powder (H-LIS) was obtained.

[0075] S3. Interface modification and slurry preparation: (a) Weigh 10g of H-LIS powder and disperse it in 500mL of sodium bicarbonate / sodium carbonate buffer solution with pH 8.5. Add 1.0g of dopamine hydrochloride and stir at room temperature for 4h to form a PDA modified layer. Dry to obtain modified H-LIS powder.

[0076] (b) Add 10g of modified H-LIS powder and 1.5g of polyethersulfone (PES) to 30mL of NMP (without adding PEG-4000 or other porogens). Mechanically stir at 60℃ for 2h, adjust the slurry viscosity to 2500mPa·s, and allow to stand to degas to obtain the casting slurry.

[0077] S4. Phase Inversion: Using a precision peristaltic pump, the slurry is dripped into a 25°C deionized water coagulation bath through a 0.7 mm inner diameter needle at a rate of 2 mL / min. Solvent exchange induces phase separation, and the microspheres solidify and form the desired shape. The microspheres are then soaked in flowing water for 24 hours to remove residual solvent.

[0078] S5. Structural thermosetting: Drain the wet microspheres, place them in a programmed temperature oven, heat them to 200℃ at a rate of 2℃ / min and keep them at that temperature for 4 hours to obtain composite microspheres.

[0079] Test results: Adsorption capacity 22.5 mg / g, liquid film diffusion rate extremely slow. This indicates a lack of macroporous channels and impaired mass transfer.

[0080] Comparative Example 4: S1. Synthesis of Lattice-Controlled Precursor: Lithium carbonate, tetrabutyl titanate, zirconium oxychloride, and aluminum nitrate were dissolved in a mixed solvent of ethanol and deionized water at a molar ratio of Li:Ti:Zr:Al = 4:4.7:0.2:0.1. The solution was vigorously stirred at 60°C for 4 hours to form a homogeneous sol, which was then aged in an 80°C forced-air drying oven for 24 hours to form a dry gel. The dry gel was ground and placed in a muffle furnace, air was introduced, and the temperature was increased to 700°C at 5°C / min for 4 hours to obtain Zr / Al co-doped titanium-based lithium-ion sieve precursor powder.

[0081] S2. Mild acid elution: The precursor powder was placed in a 0.5 mol / L HCl solution at a solid-liquid ratio of 1 g:100 mL and stirred at 25 °C for 24 h to elute Li⁺. After washing to neutrality and drying, hydrogen-form Zr / Al co-doped titanium-based lithium ion sieve powder (H-LIS) was obtained.

[0082] S3. Interface modification and slurry preparation: (a) Weigh 10g of H-LIS powder and disperse it in 500mL of sodium bicarbonate / sodium carbonate buffer solution with pH 8.5. Add 1.0g of dopamine hydrochloride and stir at room temperature for 4h to form a PDA modified layer. Dry to obtain modified H-LIS powder.

[0083] (b) Add 10g of modified H-LIS powder, 1.5g of polyethersulfone (PES), and 1.0g of polyethylene glycol (PEG-4000) to 30mL of NMP. Mechanically stir at 60℃ for 2h, adjust the slurry viscosity to 2500mPa·s, and allow to stand to degas to obtain the casting slurry.

[0084] S4. Phase Transformation and In-situ Pore Formation: Using a precision peristaltic pump, the slurry was dripped into a 25°C deionized water coagulation bath at a rate of 2 mL / min through a 0.7 mm inner diameter needle. Solvent exchange induced phase separation, while PEG-4000 dissolved in water to form channels, and the microspheres solidified. The microspheres were then immersed in flowing water for 24 hours.

[0085] S5. Structural thermosetting: Drain the wet microspheres, place them in a programmed temperature oven, heat them to 350℃ at a rate of 2℃ / min and keep them at that temperature for 4 hours.

[0086] Test results: The microspheres turned dark brown, with an adsorption capacity of only 20.5 mg / g and a crushing strength of 12.4 N. This indicates that high temperature caused the binder to decompose and carbonize, the pore structure to collapse, and the performance to deteriorate.

[0087] Comparative Example 5: S1. Synthesis of Lattice-Controlled Precursor: Lithium carbonate, tetrabutyl titanate, zirconium oxychloride, and aluminum nitrate were dissolved in a mixed solvent of ethanol and deionized water at a molar ratio of Li:Ti:Zr:Al = 4:4.7:0.2:0.1. The solution was vigorously stirred at 60°C for 4 hours to form a homogeneous sol, which was then aged in an 80°C oven for 24 hours to form a dry gel. The dry gel was ground and placed in a muffle furnace, air was introduced, and the temperature was increased to 700°C at 5°C / min for 4 hours to obtain Zr / Al co-doped titanium-based lithium-ion sieve precursor powder.

[0088] S2. Mild acid elution: The precursor powder was placed in a 0.5 mol / L HCl solution at a solid-liquid ratio of 1 g:100 mL and stirred at 25 °C for 24 h to elute Li⁺. After washing to neutrality and drying, hydrogen-form Zr / Al co-doped titanium-based lithium ion sieve powder (H-LIS) was obtained.

[0089] S3. Interface modification and slurry preparation: (a) 10 g of H-LIS powder was weighed and dispersed in 500 mL of 0.05 mol / L citric acid / sodium citrate buffer solution with a pH of 4.5. 1.0 g of dopamine hydrochloride was added, and the mixture was stirred at room temperature for 4 h. Due to the acidic environment inhibiting the oxidative polymerization of dopamine, an effective polydopamine modified layer failed to form on the powder surface. The powder was then filtered, washed, and dried to obtain the final powder.

[0090] (b) Add the above powder, 1.5 g polyethersulfone (PES), and 1.0 g polyethylene glycol (PEG-4000) to 30 mL NMP. Mechanically stir at 60 °C for 2 h, adjust the slurry viscosity to 2500 mPa·s, and allow to stand to remove bubbles to obtain the casting slurry.

[0091] S4. Phase Transformation and In-situ Pore Formation: Using a precision peristaltic pump, the slurry was dripped into a 25°C deionized water coagulation bath at a rate of 2 mL / min through a 0.7 mm inner diameter needle. Solvent exchange induced phase separation, while PEG-4000 dissolved in water to form channels, and the microspheres solidified. The microspheres were then immersed in flowing water for 24 hours.

[0092] S5. Structural thermosetting: Drain the wet microspheres, place them in a programmed temperature oven, heat them to 200℃ at a rate of 2℃ / min, and keep them at that temperature for 4 hours.

[0093] Test results: The adsorption capacity was 22.3 mg / g, and the capacity retention rate was only 53.5%. This indicates that dopamine cannot undergo spontaneous oxidative cross-linking and polymerization reactions in an acidic environment, and cannot build an "anti-clogging" barrier on the powder surface. This leads to excessive penetration of the hydrophobic polymer binder during granulation, which clogs the active micropores.

[0094] Comparative Example 6: S1. Synthesis of Lattice-Controlled Precursor: Lithium carbonate, tetrabutyl titanate, zirconium oxychloride, and aluminum nitrate were dissolved in a mixed solvent of ethanol and deionized water at a molar ratio of Li:Ti:Zr:Al = 4:4.7:0.2:0.1. The solution was vigorously stirred at 60°C for 4 hours to form a homogeneous sol, which was then aged in an 80°C oven for 24 hours to form a dry gel. The dry gel was ground and placed in a muffle furnace, air was introduced, and the temperature was increased to 700°C at 5°C / min for 4 hours to obtain Zr / Al co-doped titanium-based lithium-ion sieve precursor powder.

[0095] S2. Mild acid elution: The precursor powder was placed in a 0.5 mol / L HCl solution at a solid-liquid ratio of 1 g:100 mL and stirred at 25 °C for 24 h to elute Li⁺. After washing to neutrality and drying, hydrogen-form Zr / Al co-doped titanium-based lithium ion sieve powder (H-LIS) was obtained.

[0096] S3. Interface modification and slurry preparation: (a) Weigh 10g of H-LIS powder and disperse it in 500mL of sodium bicarbonate / sodium carbonate buffer solution with a concentration of 0.05mol / L and a pH of 8.5. Add 1.0g of polyvinyl alcohol (PVA 1788) without catechol structure and stir at room temperature for 4h. PVA only covers the powder surface through physical adsorption and lacks in-situ polymerization ability and chemical coordination. Filter and dry to obtain modified powder.

[0097] (b) Add the modified powder, 1.5 g of polyethersulfone (PES), and 1.0 g of polyethylene glycol (PEG-4000) to 30 mL of NMP. Mechanically stir at 60 °C for 2 h, adjust the slurry viscosity to 2500 mPa·s, and allow to stand to remove bubbles to obtain the casting slurry.

[0098] S4. Phase Transformation and In-situ Pore Formation: Using a precision peristaltic pump, the slurry was dripped into a 25°C deionized water coagulation bath at a rate of 2 mL / min through a 0.7 mm inner diameter needle. Solvent exchange induced phase separation, while PEG-4000 dissolved in water to form channels, and the microspheres solidified. The microspheres were then immersed in flowing water for 24 hours.

[0099] S5. Structural thermosetting: Drain the wet microspheres, place them in a programmed temperature oven, heat them to 200℃ at a rate of 2℃ / min, and keep them at that temperature for 4 hours.

[0100] Test results: The initial adsorption capacity was 24.8 mg / g, and the titanium dissolution rate after 50 cycles was 0.85%. This indicates that the non-catechol structure modifier lacks strong biomimetic interfacial adhesion and chemical bonding capabilities, and is prone to detachment and failure during slurry preparation or subsequent acid elution, thus failing to construct a stable dual barrier against pore clogging and dissolution.

[0101] Test method description: 1. Pore structure parameters: Specific surface area was determined using a fully automated specific surface area and pore size analyzer (BET method); macropore size distribution and porosity were determined using mercury intrusion porosimetry (MIP).

[0102] 2. Surface element and thickness analysis: X-ray photoelectron spectroscopy (XPS) was used to detect the nitrogen element signal on the surface of the microspheres to verify the coating of the modified layer; transmission electron microscopy (TEM) was used to measure the thickness of the modified layer on the powder surface.

[0103] 3. Slurry viscosity determination: The apparent viscosity of the casting slurry was determined using a rotational viscometer (such as Brookfield DV-II) with an appropriate range rotor (such as 63#) under constant temperature of 25 ℃ and rotation speed of 30 rpm.

[0104] 4. Adsorption capacity and capacity retention rate: Adsorption capacity: The adsorption capacity was determined by ICP-OES after adsorption in simulated brine with a Li⁺ concentration of 500 mg / L for 24 h and solid-liquid separation.

[0105] Capacity retention rate: defined as (microsphere adsorption capacity / corresponding powder adsorption capacity) × 100%.

[0106] Adsorption selectivity test: A simulated brine containing multiple competing cations was prepared, with the ion concentrations set as follows: Li⁺ 500 mg / L, Mg 2+ 10000 mg / L, Na⁺ 5000 mg / L, K⁺ 1000 mg / L (Mg / Li ratio = 20). 0.1 g of the composite microspheres were placed in 100 mL of the above simulated brine and incubated at 25°C with shaking for 24 h. After centrifugation, the concentration changes of each ion before and after adsorption were determined using ICP-OES. The partition coefficient Kd and separation coefficient α were calculated. ; ; Where C0 is the initial concentration, C eTo balance the concentration, V is the solution volume, m is the adsorbent mass, and Me represents competing ions (Mg, Na, K).

[0107] 6. Titanium dissolution rate: The adsorbed microspheres were desorbed with 0.5 mol / L HCl, and the concentration of Ti in the desorbent was determined by ICP-OES. The dissolution rate of a single cycle was calculated, and the total dissolution rate of 50 cycles was calculated cumulatively.

[0108] 7. Crushing strength: 20 dry microspheres were randomly selected and compressed using a microparticle strength tester. The maximum force value when the microspheres broke was recorded and the average value was taken.

[0109] Table 1: Performance test results of composite microspheres prepared in the examples and comparative examples

[0110] Table 2: Adsorption selectivity of composite microspheres in multi-ion coexistence system in Example 1

[0111] The results above demonstrate that the zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres and their preparation method proposed in this invention successfully prepare high-performance adsorbent materials with interconnected hierarchical pore structures through a synergistic technique of "dual-doping lattice control, surface interface isolation, and phase transformation hierarchical pore formation." This method not only solves the bottleneck problems of significant decrease in adsorption capacity and insufficient mechanical strength caused by pore blockage by binders in traditional granulation processes, but also significantly reduces the framework dissolution rate during acid cycling by utilizing the synergistic effect of zirconium / aluminum elements, achieving an effective balance between high adsorption capacity, high mechanical strength, and long cycle life.

[0112] The embodiments described herein cover all points not exhaustively within the scope of the technical claims of this invention, as well as new technical solutions formed by equivalent substitutions of single or multiple technical features in the embodiments. These are also within the scope of protection of this invention. Furthermore, in all listed and unlisted embodiments of this invention, each parameter in the same embodiment merely represents an instance (i.e., a feasible solution), and there is no strict coordination or limitation relationship between the parameters. Parameters can be substituted for each other without violating axioms and the claims of this invention, unless otherwise stated. The technical means disclosed in this invention are not limited to those disclosed above, but also include technical solutions composed of any combination of the above technical features. The above descriptions are specific embodiments of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. The specific embodiments described herein are merely illustrative examples of the spirit of this invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, but without departing from the spirit of this invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres, characterized in that, The method includes the following steps: S1. Lithium source, titanium source, zirconium source and aluminum source are dissolved in a solution containing organic solvent and mixed evenly to form a sol. After aging and calcination, precursor powder is obtained. S2. The precursor powder is immersed in an acid solution to remove lithium, and after washing and drying, hydrogen-type Zr / Al co-doped titanium-based lithium ion sieve powder is obtained. S3. Disperse the hydrogen-type Zr / Al co-doped titanium-based lithium ion sieve powder in a weakly alkaline buffer solution, then add a surface modifier containing catechol structure and stir. After filtration and drying, the modified powder is obtained. S4. Add the modified powder, pore-forming agent and polymer binder to the organic solvent and stir evenly. Let stand to degas and obtain the slurry. S5. The slurry is dripped into a coagulation bath to solidify into spheres, then dried, and finally heated to obtain composite microspheres.

2. The method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres according to claim 1, characterized in that, The molar ratio of the lithium source, titanium source, zirconium source and aluminum source is (3.5-5.0):(4.0-4.9):(0.05-0.4):(0.05-0.2).

3. The method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres according to claim 1, characterized in that, In step S1, the aging process specifically includes: stirring vigorously at 55-65°C for 3-5 hours to form a uniform sol, and then aging at 70-90°C for 20-30 hours to form a dry gel; And / or the calcination specifically includes: heating to 600-800℃ at a heating rate of 2-10℃ / min and holding at that temperature for 2-6 hours.

4. The method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres according to claim 1, characterized in that, In step S2, the concentration of the acid solution is 0.1-1.0 mol / L, and the solid-liquid ratio of the precursor powder soaking is 1g:(50-200)mL, wherein the acid solution includes one of hydrochloric acid solution, nitric acid solution, and acetic acid solution.

5. The method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres according to claim 1, characterized in that, In step S3, the pH value of the weakly alkaline buffer solution is 7.5-9.0, and the weakly alkaline buffer solution includes one of sodium bicarbonate / sodium carbonate buffer solution and boric acid / sodium borate buffer solution. And / or the surface modifier containing the catechol structure includes at least one of dopamine hydrochloride and tannic acid, wherein the concentration of the surface modifier containing the catechol structure in the weakly alkaline buffer is 1.5-2.5 mg / mL.

6. The method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres according to claim 1, characterized in that, In step S3, the mass ratio of the hydrogen-type Zr / Al co-doped titanium-based lithium-ion sieve powder to the surface modifier containing the catechol structure is (5-15):

1.

7. The method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres according to claim 1, characterized in that, In step S4, the mass ratio of the modified powder, porogen, and polymer binder is (5-15):(0.5-2.5):(1.0-2.0); wherein the porogen includes at least one of polyethylene glycol, polyvinylpyrrolidone, and nano-calcium carbonate; and the polymer binder includes at least one of polyethersulfone, polyvinylidene fluoride, and polysulfone.

8. The method for preparing zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres according to claim 1, characterized in that, In step S5, the heating treatment temperature is 180-280℃ and the time is 2-6h.

9. A zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microsphere, characterized in that, The composite microspheres are prepared by the method described in any one of claims 1-8.

10. An apparatus for extracting lithium from seawater or salt lake brine, characterized in that, The device is filled with zirconium / aluminum co-doped hierarchical porous titanium-based lithium-ion sieve composite microspheres as described in claim 9.

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