Method for improving comprehensive performance of lithium ion sieve type adsorbent

Abstract

The invention belongs to the technical field of preparation of lithium ion sieve type adsorbents, and particularly relates to a method for improving the comprehensive performance of a lithium ion sieve type adsorbent. The preparation method comprises the following steps: mixing transition metal ions, a lithium ion sieve and a polymer binder, then introducing an additive capable of generating a polymerization reaction, then mixing with an oxidizing agent hydrogen peroxide, then performing a polymerization reaction, and finally curing into particles by utilizing a phase inversion principle to obtain the lithium ion sieve type adsorbent. Compared with a traditional lithium ion sieve type adsorbent granulation forming technology based on liquid-solid phase conversion, the method does not need any pretreatment or aftertreatment or additional auxiliary equipment, hydrogen peroxide and an additive capable of being subjected to polymerization reaction are directly introduced, transition metal ion complexing and catalytic action are assisted, and therefore the lithium ion sieve type adsorbent granulation forming technology is obtained. And a polymer with a rigid structure, adhesiveness and hydrophilicity is formed in situ, so that the hydrophilicity, porosity and mechanical strength of the lithium ion sieve type adsorbent and the binding force of the binding agent and the ion sieve are synchronously improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion sieve adsorbent preparation technology, specifically relating to a method for improving the overall performance of lithium-ion sieve adsorbents. Background Technology

[0002] The booming development of the electronics and new energy vehicle industries continues to drive global demand for lithium carbonate. From a resource structure perspective, approximately 60% of the world's lithium resources are found in salt lake brines, making the development of salt lake lithium resources a strategic choice to ensure lithium supply. However, salt lake brines are chemically complex systems, containing not only high concentrations of inorganic ions such as Na⁺, K⁺, Mg²⁺, and Ca²⁺, but also dissolved organic matter such as humic substances, proteins, and polysaccharides. This environment of multiple components coexisting and ions with similar properties makes the separation of relatively low-concentration lithium ions difficult. Therefore, achieving efficient and highly selective extraction of lithium from salt lake brines has become a core technological challenge for the industry.

[0003] Among numerous lithium extraction technologies, adsorption has become the mainstream process for the efficient separation and enrichment of lithium from complex salt lake brines due to its advantages such as high selectivity, good recovery rate, and strong adaptability to different brines. The core of this process lies in using adsorbent materials with specific recognition capabilities for Li⁺ to achieve selective capture and enrichment of lithium ions through physical or chemical reactions. Therefore, the performance of the adsorbent directly determines the lithium extraction efficiency and is crucial to the development of this technology. Currently, lithium adsorbent materials are mainly divided into three categories: organic, inorganic, and composite adsorbents. Among them, inorganic adsorbents, represented by manganese-based and titanium-based lithium ion sieves, are the most promising material systems for lithium extraction from salt lake brines due to their excellent adsorption capacity, high selectivity, and good chemical stability.

[0004] Manganese-based and titanium-based lithium-ion sieves exhibit excellent "memory effect" and high selectivity for lithium ions primarily due to their unique chemical structures, making them highly sought after in lithium extraction. However, both are nanoscale powders, and direct application to liquid systems such as salt lake brine presents challenges such as filtration difficulties, high fluid resistance, and easy loss, failing to meet industrial production requirements. Therefore, granulation is essential to transform them into particles with a certain size and mechanical strength, a crucial prerequisite for engineering applications. Against this backdrop, a granulation technology for lithium-ion sieve adsorbents based on liquid-solid phase transformation has emerged. This technology involves dissolving manganese-based or titanium-based lithium-ion sieve powder with polymeric binders and pore-forming agents in a solvent to form a homogeneous slurry. This slurry is then shaped through extrusion, spheroidization, or spray drying, followed by curing and elution to obtain adsorbent particles with macroscopic dimensions (typically 1.0 mm to 2.0 mm). This method is simple to operate, has mature technology, and produces particles with high mechanical strength, making it one of the most widely used lithium-ion sieve forming technologies in industrial applications. However, it still faces the following core technological challenges:

[0005] 1) Insufficient hydrophilicity of the adsorbent surface: During granulation, polymeric binders such as polyvinyl chloride, polyvinylidene fluoride, and polysulfone are commonly used to construct the adsorbent's framework structure. These materials all have strong hydrophobicity, and lithium-ion sieves mainly adhere to the surface and internal pores of this hydrophobic framework. Due to the hydrophobic properties of the framework, brine cannot effectively wet the deep pores inside the adsorbent, resulting in a large number of lithium-ion sieves encapsulated inside the particles failing to fully contact lithium ions, forming an "isolated" state. Consequently, the adsorption capacity of the granulated adsorbent is far lower than the theoretical value. To address this problem, some studies (such as CN116786076A) have introduced hydrophilic components into hydrophobic polymer systems to improve hydrophilicity. However, the hydrophilic components in the resulting adsorbent particles are prone to swelling, hydrolysis, or degradation in acidic desorption solutions, leading to particle pulverization, binder loss, and severely reducing the stability of the adsorbent.

[0006] 2) Trade-off between adsorbent porosity and mechanical strength: The filling and embedding of polymeric binders result in low porosity of lithium-ion sieve adsorbent particles. Traditional processes use hydrophilic pore-forming agents (such as PEG, PVP, etc.) to create pores. While this has made progress in increasing porosity, problems remain, including insufficient pore structure development, poor pore connectivity, and the easy formation of closed or narrow pores. A key challenge is that within a limited particle volume, increasing the porosity inevitably reduces the share of the polymeric binder skeleton, leading to fewer skeleton connection points, thinner pore walls, and a sharp decline in adsorption force and particle mechanical strength. Adsorbents with insufficient strength are easily broken or collapsed under water flow impact, inter-particle friction, and packing pressure. Therefore, traditional pore-forming methods cannot simultaneously improve porosity and mechanical strength.

[0007] 3) Weak bonding between binder and ion sieve interface: Manganese-based and titanium-based lithium ion sieves are both strongly hydrophilic inorganic oxides with highly polar hydroxyl groups on their surfaces; while commonly used binders are mostly hydrophobic polymers. The significant difference in interfacial energy between the two makes it difficult for the ion sieve powder to effectively spread and wet the binder framework surface. Only a physical "point contact" is formed between the two phases, rather than a continuous and tight "surface bond," making the interface prone to defects and stress concentration. Furthermore, due to the lack of chemical "anchoring" effects such as hydrogen bonds and coordination bonds, the interfacial bonding is weak. Under the continuous impact of fluid shear force during the adsorption-desorption process, nanoscale ion sieve particles are easily detached from the polymer framework, causing irreversible physical loss of active components, i.e., "ion sieve dissolution," which ultimately leads to a decrease in the cycle stability of the adsorbent and a shortened service life.

[0008] To address the aforementioned technical bottlenecks, existing modification strategies are mostly limited to localized optimization of a single property of lithium-ion sieve adsorbents, often leading to a trade-off: improving hydrophilicity and mass transfer efficiency often comes at the cost of mechanical strength and long-term stability; increasing porosity to improve kinetics makes it difficult to maintain the structural strength of the adsorbent particles; strengthening the interfacial bonding between the binder and the ion sieve weakens the overall hydrophilicity. This trade-off between multiple indicators makes it difficult to achieve synergistic optimization among the core elements of "hydrophilicity, porosity, mechanical strength, and binder-ion sieve bonding," becoming a key technical bottleneck restricting its long-term stable operation and large-scale engineering applications. Summary of the Invention

[0009] To address the technical bottlenecks of the existing technologies, this invention provides a method for improving the overall performance of lithium-ion sieve adsorbents. Compared to traditional granulation techniques for lithium-ion sieve adsorbents based on liquid-solid phase transformation, this invention requires no pretreatment or post-treatment, nor additional auxiliary equipment. It directly introduces hydrogen peroxide and additives capable of polymerization, supplemented by transition metal ion complexation and catalysis, to form a polymer in situ possessing a rigid structure, adhesiveness, and hydrophilicity. This achieves a simultaneous improvement in the hydrophilicity, porosity, mechanical strength, and binder-ion sieve bonding force of the lithium-ion sieve adsorbent. The method of this invention features simple operation steps, mild reaction conditions, and high efficiency, making it suitable for the large-scale production of lithium-ion sieve adsorbents.

[0010] To achieve the aforementioned technical objectives, the technical solution adopted by this invention is as follows: Step 1) At room temperature, the transition metal ions are first dissolved in an organic solvent, and then lithium ion sieves and polymer binders are introduced in sequence. The mixture is stirred at 250 r / min to 300 r / min until completely dissolved to obtain the first mixture.

[0011] Step 2) Further introduce an additive capable of polymerization into the first mixture and stir and dissolve it at 300 r / min to 400 r / min for 20 min to 30 min to obtain the second mixture.

[0012] Step 3) Introduce hydrogen peroxide into the second mixture and immediately seal the container containing the mixture. Stir at 600 r / min to 800 r / min for 5 min to 10 min to promote mass transfer and diffusion and form a homogeneous oxidation system. Then, continue stirring and reacting at 40℃ to 60℃ and 60 r / min to 100 r / min for 8 h to 12 h to form a homogeneous slurry. Under oxidation conditions, on the one hand, oxidation induces the self-aggregation of free dopamine and forms 30 nm to 60 nm polydopamine particles. On the other hand, the complexing ability of transition metal ions induces the two-dimensional directional self-polymerization of dopamine and triterpenes surrounding the polymer binder molecular chain, forming a hydrophilic rigid film at the polymer binder interface to obtain a homogeneous slurry, which is the granulation slurry liquid. Rigid films formed in situ around the binder molecular chains, possessing both a large π-conjugated structure and abundant hydroxyl, amino, and aldehyde functional groups, can form hydrogen bonds and π-π stacking interactions with the solid interface, exhibiting "universal glue" properties, thus efficiently anchoring lithium-ion sieves to their surface. There are hydrogen bonding cross-linking and physical coating effects between the rigid film and the polymer binder, specifically: Hydrogen bonding: The polymer binder molecular chains contain strongly electronegative atoms (such as F, N, and O), which can form hydrogen bonds with dopamine monomers and tripterene (and the films formed by their polymerization); Uniform coating (forming a cross-linking network): Under the complexation and oxidation of transition metal ions, dopamine and tripterene undergo directional two-dimensional polymerization on the surface of the binder molecular chains, forming a "planar" rigid structure. This rigid film, like "armor," uniformly coats and encapsulates the surface of the flexible polymer binder molecular chains, significantly enhancing the binder's resistance to deformation and cohesive force.

[0013] Step 4) The homogeneous slurry is dripped into a coagulation bath at 45℃~60℃ through a mold and solidified into particles using the principle of phase inversion. After thorough rinsing and drying, it is then acid-washed with a dilute hydrochloric acid solution to obtain lithium ion sieve spherical adsorbent.

[0014] Preferably, the transition metal ion is selected from any one of FeCl2, CuCl2, and ZnCl2.

[0015] Preferably, the organic solvent is selected from any one of N-N'-dimethylacetamide, ethylene glycol ether, ethyl acetoacetate, and triethyl phosphate.

[0016] Preferably, lithium ions are screened from Li2TiO3 and Li4Ti5O3. 12 , LiMn2O4, Li2Mn2O5, Li4Mn5O 12 Any one of them.

[0017] Preferably, the polymeric binder is selected from polyvinylidene fluoride, polyvinyl chloride, ethylene-vinyl alcohol, or polyethersulfone.

[0018] Preferably, the additive capable of undergoing polymerization is a mixture of dopamine monomer and tripterene.

[0019] Preferably, the coagulation bath is a mixture of organic solvent and water.

[0020] Preferably, the hydrogen peroxide is a 30% (w / w) aqueous solution of hydrogen peroxide.

[0021] Preferably, the mass percentages of each component in the granulation slurry are as follows: transition metal ions 0.08%~0.2%, lithium ion sieve 28%~35%, polymer binder 10%~15%, additives 1%~3%, and hydrogen peroxide 0.05%~0.2%. The amount of organic solvent is adjusted according to the amount of other components added to the system so that the sum of the mass percentages of each component is 100%.

[0022] Preferably, in the additive, the mass ratio of dopamine monomer to tripterene is 5~12:1.

[0023] Preferably, the molar concentration of transition metal ions (M) 离子 ) and the molar concentration of hydrogen peroxide in hydrogen peroxide (M H2O2 M satisfies the following relationship: 离子 =M H2O2 ×0.75.

[0024] Preferably, the mass ratio of lithium ion sieve to additive is 15~28:1.

[0025] Preferably, the dopamine mass m Da The mass m of hydrogen peroxide in hydrogen peroxide H2O2 The following relationship must be satisfied: 25 <m Da / m H2O2 <120.

[0026] Preferably, the coagulation bath contains the same organic solvent as the homogeneous slurry, and the volume concentration of the organic solvent in the coagulation bath is 2% to 10%.

[0027] Compared with the prior art, the beneficial effects of the present invention are: Addressing the technical bottlenecks encountered in the granulation process of traditional lithium-ion sieve adsorbents, this invention proposes a method to improve the overall performance of lithium-ion sieve adsorbents, achieving the following beneficial effects: 1. Simultaneous Improvement of Hydrophilicity, Porosity, and Mechanical Strength: This invention constructs a weakly oxidizing liquid phase system by introducing transition metal ions, hydrogen peroxide, and self-polymerizing additives into the granulation slurry. This system induces partial dopamine self-aggregation to form hydrophilic particles of 30nm~60nm, which migrate towards the coagulation bath during solidification, effectively increasing porosity. Simultaneously, transition metal ions, through complexation and catalysis, guide the two-dimensional directional self-polymerization of dopamine surrounding the polymer binder with tripterene, forming a 5nm~10nm thick hydrophilic rigid film, thereby achieving a simultaneous improvement in the hydrophilicity and mechanical strength of the adsorbent particles.

[0028] 2. In-situ formation of a "universal adhesive" to enhance the interfacial bonding between the lithium-ion sieve and the binder: In a homogeneous slurry system, a rigid film formed in situ around the binder molecular chains possesses both a large π-conjugated structure and abundant hydroxyl, amino, and aldehyde functional groups, enabling it to form hydrogen bonds and π-π stacking interactions with the solid interface, thus exhibiting "universal adhesive" properties. This film forms a strong bond with the polymeric binder on one hand, and on the other hand, under the thermodynamic drive of the granulation process, efficiently anchors the lithium-ion sieve to its surface, thereby significantly enhancing the interfacial bonding strength between the lithium-ion sieve and the polymeric binder; effectively suppressing the peeling of active components and the loss of ion sieve adsorbent powder that may occur during dynamic adsorption or multiple cycles.

[0029] 3. Significantly Improved Overall Performance of Lithium-ion Sieve Adsorbents: Compared to traditional lithium-ion sieve granulation technology based on liquid-solid phase conversion, the method of this invention requires no pretreatment, post-treatment, additional equipment, or extra time investment, and does not change the original granulation process. By synthesizing pore-forming agents, rigid framework substances, hydrophilic substances, and binders in situ in the granulation slurry, the hydrophilicity, porosity, mechanical strength, and binder-ion sieve bonding force of the adsorbent are simultaneously improved.

[0030] 4. The method of this invention is simple, highly applicable, and has significant effects. Compared with existing lithium-ion sieve adsorbents, the hydrophilicity is increased by a maximum of 33.0%, the mechanical strength is increased by a maximum of 129.5%, the porosity is increased by a maximum of 76.9%, and the adsorption capacity is not lost after 30 cycles of operation. Attached Figure Description

[0031] Figure 1 These are appearance diagrams of the lithium-ion sieve adsorbents obtained in Comparative Example 2 (left) and Example 1 (right). Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0033] As analyzed in the background section of this invention, the traditional lithium-ion sieve adsorbent granulation process suffers from technical bottlenecks such as insufficient hydrophilicity of the adsorbent surface, trade-off between adsorbent porosity and mechanical strength, and weak bonding force between the binder and the ion sieve interface. To solve these problems, this invention provides a method for improving the overall performance of lithium-ion sieve adsorbents.

[0034] In a typical embodiment of the present invention, the method includes the following steps: Step 1) At room temperature, transition metal ions are dissolved in an organic solvent, followed by the sequential introduction of a lithium ion sieve and a polymer binder. The mixture is stirred at 250-300 rpm until completely dissolved, yielding the first mixture. Room temperature operation ensures that all components achieve purely physical homogeneous mixing and complexation anchoring before polymerization, forming a necessary process gradient with the subsequent polymerization reaction stage at 40-60°C. Introducing high temperatures at this stage would lead to excessive solvent evaporation or affect the molecular chain extension state of the polymer binder. This gradient temperature control—"initial room temperature purely physical homogeneous dispersion" + "later isothermal chemical polymerization"—combined with high-speed deentanglement in the initial stage and low-speed, gentle reaction in the later stage, ensures that the additive can undergo controlled two-dimensional directional self-polymerization around the polymer chain, rather than disordered explosive polymerization. Step 2) Further introduce the additive that can undergo polymerization reaction into the first mixture, and stir and dissolve it for 20 min to 30 min at 300 r / min to 400 r / min to obtain the second mixture; Step 3) Introduce hydrogen peroxide into the second mixture and immediately seal the container. First stir for 5 min to 10 min at 600 r / min to 800 r / min to promote mass transfer and diffusion and form a homogeneous oxidation system. Then continue stirring and reacting at 40℃ to 60℃ and 60 r / min to 100 r / min for 8 h to 12 h to form a homogeneous slurry, which is the granulation slurry liquid; Step 4) Drop the homogeneous slurry into a coagulation bath at 45℃ to 60℃ through a mold, solidify it into granules using the principle of phase inversion, rinse and dry thoroughly, and then acid wash with dilute hydrochloric acid solution to obtain a lithium ion sieve adsorbent.

[0035] This invention achieves multi-step in-situ modification by sequentially introducing multiple non-solvent phases into an organic solvent under different stirring conditions, utilizing the synergistic effect of the organic solvent's solubility and physical stirring.

[0036] In steps 1) and 2), transition metal ions, lithium ion sieves, and additives capable of polymerization are uniformly dispersed around the polymer binder molecular chains, laying the foundation for subsequent performance modification at the molecular chain level. In step 3), after introducing the oxidant hydrogen peroxide, mass transfer and diffusion are first promoted under strong stirring to form a homogeneous oxidation system. Then, under constant temperature and low stirring conditions, on the one hand, oxidation induces dopamine self-aggregation to form 30nm~60nm polydopamine particles, providing a prerequisite for improving the porosity of the lithium ion sieve adsorbent; on the other hand, the complexing ability of transition metal ions is synergistically induced to induce two-dimensional directional self-polymerization of dopamine and trimelline surrounding the binder molecular chains, forming a hydrophilic rigid film, thereby ensuring the hydrophilicity and mechanical strength of the lithium ion sieve adsorbent. In step 4), the homogeneous slurry is dripped into a coagulation bath at 45℃~60℃ through a mold. Organic solvents and nano-hydrophilic substances in the slurry migrate into the coagulation bath, while water molecules in the coagulation bath migrate into the liquid phase of the slurry. By controlling the temperature and composition of the coagulation bath, the migration rates of different phases are controlled, thereby achieving precise control over the formation and pore structure of the lithium-ion sieve-type adsorbent. In the granulation slurry preparation stage, this invention, on the one hand, forms a hydrophilic substance with pore-forming effect through in-situ self-polymerization; on the other hand, it constructs a hydrophilic rigid film around the polymer binder molecular chains. This film not only enhances the hydrophilicity and mechanical strength of the lithium-ion sieve-type adsorbent, but its polydopamine component also imparts strong adhesion properties to the film, thus tightly bonding the lithium-ion sieve to the binder. The overall process of this invention is simple to operate, low in cost, and highly applicable. It is not only suitable for the performance modification of lithium-ion sieve-type adsorbents but can also be extended to the interface control of other types of adsorbents.

[0037] In step 1) above, the transition metal ions are selected from any one of FeCl2, CuCl2, and ZnCl2. These metal ions (Fe²⁺, Cu²⁺, or Zn²⁺) can provide empty orbitals to complex with the active functional groups in the additives dopamine and trimerene, anchoring them around the polymer binder molecular chains. In addition, the transition metal ions can also activate the adjacent hydrogen peroxide through catalysis, enhancing the oxidation capacity within the microenvironment; on the one hand, they promote the self-aggregation of free dopamine to form polydopamine particles with a particle size of 30nm~60nm; on the other hand, they initiate the polymerization reaction of dopamine and trimerene anchored around the binder molecular chains, generating a hydrophilic rigid film in situ. In this process, the selected metal ions are the key prerequisite for regulating the oxidation reaction rate and the formation space of the hydrophilic rigid film.

[0038] In step 1) above, the organic solvent is selected from any one of N-N'-dimethylacetamide, ethylene glycol ether, ethyl acetoacetate, and triethyl phosphate. The non-solvent phase of this invention includes transition metal ions, lithium ion sieves, polymeric binders, mixed component additives, and the oxidant hydrogen peroxide. To achieve effective preparation of the granulation slurry, the selected solvent must have good compatibility with these non-solvent phases, which have significantly different properties. Based on the performance characteristics and solubility properties of the non-solvent phase, aprotic polar organic solvents rich in amide or alcohol ester structures are selected. This solvent can not only dissolve the polymeric binder but also generate strong interactions with transition metal ions, lithium ion sieves, additives, and oxidants, ensuring effective mass transfer of each component in the granulation slurry, thereby preparing a homogeneous granulation slurry.

[0039] In step 1) above, lithium ions are screened from Li2TiO3 and Li4Ti5O3. 12 , LiMn2O4, Li2Mn2O5, Li4Mn5O 12 Any one of the following. This invention designs an improvement in the performance of lithium-ion sieve-type adsorbents. These five materials cover the two most mature lithium-ion sieve systems: titanium-based and manganese-based. As powder functional fillers, they can be well combined with the in-situ modification system (transition metal ions, binders, and additives) of this invention, providing an ideal carrier for the simultaneous improvement of hydrophilicity, porosity, mechanical strength, and interfacial bonding through subsequent in-situ polymerization.

[0040] In step 1) above, the polymer binder is selected from polyvinylidene fluoride, polyvinyl chloride, ethylene-vinyl alcohol, and polyethersulfone. In the granulation slurry system, dopamine monomer and trimelline are the core components for adsorbent modification, and their polymerization behavior and structural morphology play a decisive role in the final adsorbent performance. Specifically, if the two can polymerize along the two-dimensional direction on the binder molecular chain, a hydrophilic rigid film can be formed, achieving uniform modification; conversely, if the free dopamine monomer undergoes bulk polymerization to generate polydopamine particles with a size of hundreds of nanometers, large-sized defect pores are easily formed on the surface and cross-section of the adsorbent during phase separation; if polydopamine exists in a dissolved small molecule form (molecular weight of about several hundred Daltons), only micropores can be formed after phase separation, and the modification effect is not ideal. Therefore, it can be seen that how to control the polymerization path of dopamine monomer and trimelline and the morphology and size of polydopamine is the key to improving the overall performance of the adsorbent. Based on this, the present invention selects polyvinylidene fluoride, polyvinyl chloride, ethylene-vinyl alcohol copolymer, and polyethersulfone as binders. These polymers contain strongly electronegative atoms (such as F, N, and O) in their molecular chains, which can form hydrogen bonds with dopamine monomers and tripterene, guiding them to surround the polymer chains. An oxidant is then introduced to induce directional two-dimensional polymerization of dopamine and tripterene at adjacent sites, forming a rigid "planar" structure that uniformly coats the surface of the binder molecular chains. This mechanism effectively inhibits the formation of particulate aggregates and the loss of small molecules, achieving stable and uniform modification of the polymer binder, thereby significantly optimizing the microstructure and macroscopic properties of the lithium-ion sieve-type adsorbent.

[0041] In step 2) above, the additive that can undergo polymerization is a mixture of dopamine monomer and tripterene.

[0042] This invention aims to simultaneously improve four core performance indicators of lithium-ion sieve adsorbents: mechanical strength, porosity, hydrophilicity, and the binding force between the lithium-ion sieve and the binder. It selects a mixture of dopamine monomer and tripterene, which can undergo polymerization reaction, as an additive, and utilizes the synergistic effect of the two to achieve the purpose of this invention.

[0043] Dopamine, rich in catechol groups, introduces a large number of hydroxyl and amino groups after polymerization, significantly enhancing the hydrophilicity and mass transfer efficiency of polar substances on the surface of the lithium-ion sieve adsorbent. Triptene, with its unique rigid three-dimensional framework, acts as a "pillar" during polymerization, preventing the polymer chains from densely packing together, thereby inducing the formation of "self-contained micropores" in the matrix and greatly improving the specific surface area and pore regularity. Crucially, the two undergo directional two-dimensional copolymerization under the induction of hydrogen bonds on the surface of the binder molecular chains, forming a uniform "planar" rigid coating layer. This effectively avoids the large-size defect pores caused by the easy self-polymerization of single dopamine into particles of hundreds of nanometers, and also suppresses the micropore problem caused by the loss of small molecules. This rigid layer, like "armor," encases the flexible polymer chains, and together with the hydrogen bond cross-linking network formed by dopamine and the binder (containing F, N, and O atoms), significantly enhances the binder's resistance to deformation and cohesive force. In summary, this combined design achieves an organic unity of introducing hydrophilic functional groups, constructing rigid micropores, and suppressing structural defects, enabling lithium-ion sieve adsorbents to possess high mechanical stability, high porosity, and excellent hydrophilicity, while also enhancing the binding ability between the binder and the lithium-ion sieve.

[0044] In step 3) above, the oxidant is a 30% (w / w) aqueous solution of hydrogen peroxide. To achieve the regulation of polymerization rate and morphology of dopamine monomers and trimerenes in the granulation slurry, this invention, based on the redox potential, oxidation mechanism, and mass transfer kinetics of typical oxidants in the granulation slurry, selects a 30% (w / w) aqueous solution of hydrogen peroxide to construct a weak oxidizing environment. Its mechanism of action is as follows: ① Hydrogen peroxide diffuses slowly in the granulation slurry, effectively preventing the rapid local aggregation of dopamine monomers, maintaining system stability, and preventing strong oxidation from damaging the binder and additive structure; ② Hydrogen peroxide is rich in hydrogen bond donors, easily forming hydrogen bonds with dopamine monomers and trimerenes, thereby promoting local oxidation at the molecular chain ends and strengthening the directional aggregation of adjacent additive molecules along the two-dimensional direction; ③ During the granulation slurry formation stage, hydrogen peroxide continuously and slowly releases oxygen, which diffuses rapidly in the slurry, providing a stable oxidation source for the self-aggregation of free dopamine monomers and the gradual construction of particulate matter.

[0045] In step 4) above, the coagulation bath is a mixed solution of organic solvent and water. This invention uses a mixed solution of organic solvent and water as the coagulation bath, which has a multi-dimensional regulatory effect on the reaction rate, the pore structure of the lithium-ion sieve adsorbent, and the migration direction of the additives during the granulation process. At the reaction rate level, water, as a polar non-solvent, can induce instantaneous solid-liquid phase separation, inducing instantaneous formation of the interface between the granulation slurry dripped into the mold, ensuring the morphology of the lithium-ion sieve adsorbent particles is controllable. The addition of organic solvent can reduce the polarity of the system, slowing down the exchange rate between water and the organic solvent in the already formed granulation slurry in the coagulation bath, avoiding explosive polymerization of the formed hydrophilic additives, and achieving a gradual and controllable polymerization rate of the additives. At the pore structure control level, the mixed coagulation bath influences the phase separation process by adjusting the dual diffusion rates: rapid water diffusion tends to form instantaneous phase separation, easily generating a dense skin layer; slow organic solvent diffusion promotes delayed phase separation, which is beneficial for forming an open porous network. Adjusting the ratio of the two can balance mass transfer kinetics, optimize pore size distribution and pore connectivity, thereby reducing the probability of closed pores and dead pores. At the same time, the hydrogen bonding effect of the organic solvent regulates the molecular chain arrangement, further improving the specific surface area and structural stability of the lithium-ion sieve adsorbent. At the additive migration direction level, based on the difference between the hydrophilicity of dopamine and the hydrophobicity of triterpenes, the concentration gradient formed by the mixed solvent drives the directional distribution of additives, thereby controlling the outward migration rate of macromolecular polydopamine and promoting its dispersion and enrichment within the granulation slurry.

[0046] To obtain a stable granulation slurry system and successfully prepare lithium-ion sieve-type adsorbents, the mass percentages of each component in the homogeneous slurry are as follows: transition metal ions 0.08%~0.2%, lithium-ion sieve 28%~35%, polymer binder 10%~15%, additives 1%~3%, hydrogen peroxide 0.05%~0.2%, and the remainder is solvent.

[0047] Based on the polymerization mechanism and morphological structure control requirements of additives in the granulation slurry system, further optimization is performed. In step 2), the mass ratio of dopamine monomer to tripterene in the additive is limited to 5~12:1. This not only ensures the effective synthesis of particulate polydopamine and hydrophilic rigid polydopamine-tripterene films in the granulation slurry system and their improvement on the porosity, hydrophilicity, mechanical strength and lithium ion sieve-binder bonding force of the adsorbent, but also avoids the presence of too much tripterene from masking the hydrophilicity, adhesion and pore-forming advantages of polydopamine.

[0048] Based on the complexation behavior of transition metal ions with dopamine monomers and their catalytic mechanism for hydrogen peroxide, further optimization is made regarding the molar concentration (M) of transition metal ions in step 1). 离子 The molar concentration of hydrogen peroxide in the hydrogen peroxide solution (M) in step 3) H2O2 Limited to M 离子 =M H2O2×0.75 is used to reduce the steric hindrance effect of the polymer binder in the liquid phase of the granulation slurry, enhance the self-polymerization driving force between dopamine monomers, and thus ensure the effective synthesis of hydrophilic polydopamine particles.

[0049] Further optimization involves limiting the mass ratio of the lithium-ion sieve in step 1) to the additive in step 2) to 15~28:1. Under this mass ratio condition, the final residual hydrophilic rigid film in the granulation slurry is within a reasonable range. It is neither too thin to achieve an effective improvement in hydrophilicity, adhesion, and mechanical strength, nor too thick to cover up the performance of the lithium-ion sieve itself, thereby destroying the selective adsorption capacity of the lithium-ion sieve.

[0050] Based on the degradation behavior of dopamine monomers in the additive, the oxidation mechanism of free radical generation catalyzed by hydrogen peroxide in the organic phase, and the synthesis mechanism of polydopamine, further optimization is achieved by limiting the mass ratio of dopamine in the additive in step 2) to hydrogen peroxide in the oxidant in step 3) to 50. <m Da / m H2O2 <120, under this condition, it can avoid the degradation and mineralization of dopamine monomers and the formation of large-size polydopamine by oxidants, and ensure the oxidative aggregation of dopamine monomers and tripterene around the binder molecular chain in two dimensions.

[0051] Further optimization involves limiting the organic solvent in the coagulation bath in step 4) to the same component as the homogeneous slurry. This avoids introducing new components and thus slows down the intense double diffusion rate during the adsorbent solidification process. Furthermore, controlling the volume percentage of the organic solvent in the coagulation bath within the range of 2% to 10% effectively creates a "weakly solvent-free" environment. Under this concentration, the lower organic solvent content reduces the chemical potential gradient between the coagulation bath and the slurry, delaying the phase separation process and promoting the formation of a sponge-like porous structure. Simultaneously, this concentration range avoids the problem of delayed solidification or even failure to form due to excessively high concentrations (>10%), thus achieving an effective balance between forming rate and structural uniformity.

[0052] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0053] Example 1 A method for improving the overall performance of lithium-ion sieve adsorbents includes the following steps: Step 1) At room temperature, FeCl2 (providing transition metal ions) is first dissolved in the organic solvent N-N'-dimethylacetamide at 0.17% of the mass of the granulation slurry system (the mass percentage of the organic solvent in the granulation slurry system is 57.63%). Then, the lithium ion sieve Li2TiO3 and the polymer binder polyvinylidene fluoride are introduced sequentially at 30% and 10% of the mass of the granulation slurry system, respectively. The mixture is stirred at 300 r / min until completely dissolved to obtain the first mixture.

[0054] Step 2) To the first mixture, further introduce an additive capable of polymerization, namely a mixture of dopamine monomer and trimerene, at 2% of the mass of the granulation slurry system, wherein the mass ratio of dopamine monomer to trimerene is 5:1 (mass percentage of dopamine monomer in the granulation slurry system (m...). Da The percentage of triterpenes was 1.666%, and the mass percentage of triterpenes (m) was... TP The concentration of the first solution was 0.334%, and the solution was stirred at 400 r / min for 30 min to obtain the second mixture.

[0055] Step 3) Introduce hydrogen peroxide into the second mixture at 0.2% of the mass of the granulation slurry system. The hydrogen peroxide mass concentration in the hydrogen peroxide is 30% (the mass percentage of hydrogen peroxide in the granulation slurry system is 0.06%). Immediately seal the container containing the mixture, stir at 800 r / min for 10 min, and then continue stirring and reacting at 60℃ and 100 r / min for 10 h to form a homogeneous slurry, i.e., the granulation slurry.

[0056] Step 4) The homogeneous slurry is dripped through a mold into a 60°C coagulation bath. The coagulation bath is a mixture of water and N-N'-dimethylacetamide, wherein the volume percentage of N-N'-dimethylacetamide is 2%. The mixture is solidified into particles using the phase inversion principle. After thorough rinsing and drying, it is then acid-washed with a dilute hydrochloric acid solution. Besides acting as an eluent to extract lithium ions and obtain lithium-ion memory vacancies to obtain the final adsorbent, the acid also plays another important role: this acid washing step demonstrates that the hydrophilic rigid film synthesized in situ in this invention possesses extremely strong chemical stability and a "universal glue"-like strong binding force. Unlike traditional materials, it will not degrade or cause the active component to peel off in an acidic desorption environment, resulting in a lithium-ion sieve-shaped adsorbent, such as... Figure 1 As shown in Figure (b) of the document.

[0057] Comparative Example 1 The difference between this comparative example and Example 1 is that the multi-step speed-controlled stirring process has been changed. Instead, a "one-pot method" is used to simultaneously add all non-solvent phase substances to the solvent, and the mixture is continuously stirred at a constant temperature at a conventional speed (300 r / min). Specifically: FeCl2 (providing transition metal ions), lithium-ion sieve Li2TiO3, polymer binder polyvinylidene fluoride, additives, and hydrogen peroxide were added to the organic solvent N-N'-dimethylacetamide. The mixture was stirred continuously at 300 r / min and 60℃ for 10 h to form a granulated slurry. Subsequently, the granulated slurry was dripped through a mold into a 60℃ coagulation bath (the coagulation bath was a mixture of water and N-N'-dimethylacetamide, with a volume concentration of 2% N-N'-dimethylacetamide). The mixture was solidified into granules using the principle of phase inversion. After thorough rinsing and drying, the spherical adsorbent was acid-washed with dilute hydrochloric acid solution to finally obtain the lithium-ion sieve adsorbent.

[0058] Effect Analysis: Uniformly dispersing transition metal ions, lithium ion sieves, and additives around the polymer binder molecular chains is fundamental to achieving performance modification at the molecular chain level. Due to the lack of a gradient stirring process, the initial high-speed (600 r / min~800 r / min) was insufficient to forcefully shear and disentangle the polymer binder and its components, hindering homogenization. Furthermore, the subsequent low-speed (60 r / min~100 r / min) was not used to ensure a gentle microenvironment for slow polymerization. This ultimately led to severe agglomeration of the lithium ion sieves and excessive local dopamine polymerization, forming gel blocks. This resulted in poor slurry stability, easy stratification, uneven particle pore distribution after molding, and numerous dead pores, severely restricting adsorption kinetics. Therefore, it is essential to strictly adhere to the specific multi-step feeding sequence of this invention; only through synergy can the optimal effect be achieved. Any reversal of the timing or premature mixing will disrupt the microscopic homogeneity of the system and the rate-controlling mechanism of the polymerization reaction.

[0059] Example 2 A method for improving the overall performance of lithium-ion sieve adsorbents includes the following steps: Step 1) At room temperature, ZnCl2 (providing transition metal ions) is first dissolved in the organic solvent N-N'-dimethylacetamide at 0.08% of the mass of the granulation slurry system (the mass percentage of the organic solvent in the granulation slurry system is 55.8313%). Then, the lithium ion sieve Li2TiO3 and the polymer binder polyvinylidene fluoride are introduced sequentially at 28% and 15% of the mass of the granulation slurry system, respectively. The mixture is stirred at 250 r / min until completely dissolved to obtain the first mixture.

[0060] Step 2) To the first mixture, further introduce an additive capable of polymerization, namely a mixture of dopamine monomer and trimerene, at 1% of the mass of the granulation slurry system, wherein the mass ratio of dopamine monomer to trimerene is 5:1 (the mass percentage of dopamine monomer in the granulation slurry system is m...). Da The percentage of triterpenes (m) was 0.8333%. TPThe concentration of the first solution was 0.1667%, and the solution was stirred at 300 r / min for 30 min to obtain the second mixture.

[0061] Step 3) Introduce hydrogen peroxide into the second mixture at 0.0887% of the mass of the granulation slurry system. The hydrogen peroxide mass concentration in the hydrogen peroxide is 30% (the mass percentage of hydrogen peroxide in the granulation slurry system is 0.02661%). Immediately seal the container containing the mixture, stir at 600 r / min for 10 min, and then continue stirring and reacting at 50℃ and 60 r / min for 10 h to form a homogeneous slurry, i.e., the granulation slurry.

[0062] Step 4) The homogeneous slurry is dripped into a 60°C coagulation bath through a mold. The coagulation bath is a mixture of water and N-N'-dimethylacetamide, wherein the volume percentage of N-N'-dimethylacetamide is 5%. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, it is then acid-washed with a dilute hydrochloric acid solution to obtain a lithium ion sieve spherical adsorbent.

[0063] Comparative Example 2 The difference between this comparative example and Example 2 is that dopamine and triterpenoid additives, hydrogen peroxide, and transition metal ions ZnCl2 were not introduced; the corresponding mass fractions were made up by organic solvents, specifically: The lithium-ion sieve Li2TiO3 and the polymer binder polyvinylidene fluoride were introduced into the organic solvent N-N'-dimethylacetamide at 28% and 15% of the mass of the granulation slurry system, respectively, and stirred at 300 r / min until completely dissolved to obtain a mixture.

[0064] The mixture is dripped through a mold into a 60°C coagulation bath, which is a mixture of water and N-N'-dimethylacetamide, wherein the volume percentage of N-N'-dimethylacetamide is 5%. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, it is then acid-washed with a dilute hydrochloric acid solution to obtain a lithium ion sieve adsorbent.

[0065] Performance Analysis: As this was a purely physical blend blank system, no dopamine-related oxidative polymerization or coordination crosslinking processes occurred. The resulting adsorbent particles had poor surface hydrophilicity and a large water contact angle; the internal structure lacked a self-contained microporous structure, leading to high mass transfer resistance; furthermore, the binder and lithium-ion sieve relied only on weak physical interlocking, resulting in weak interfacial bonding. Consequently, the lithium-ion adsorption capacity and particle mechanical strength of the final material were both at low levels, making it prone to pulverization during actual cycling.

[0066] Example 3 A method for improving the overall performance of lithium-ion sieve adsorbents includes the following steps: Step 1): At room temperature, firstly, dissolve CuCl2 (providing transition metal ions) at 0.12% of the mass of the granulation slurry system in the organic solvent ethylene glycol ether (the mass percentage of the organic solvent in the granulation slurry system is 56.2451%). Then, add the lithium ion sieve Li4Ti5O... 12 Polyvinyl chloride (PVC) and a polymeric binder were introduced sequentially at 30% and 12% of the mass of the granulation slurry system, respectively, and stirred at 300 r / min until completely dissolved to obtain the first mixture.

[0067] Step 2) To the first mixture, further introduce an additive capable of polymerization, namely a mixture of dopamine monomer and trimerene, at 1.5% of the mass of the granulation slurry system, wherein the mass ratio of dopamine monomer to trimerene is 8:1 (the mass percentage of dopamine monomer in the granulation slurry system is m...). Da The percentage of triterpenes (m) was 1.3333%. TP The concentration of the first solution was 0.1667%, and the solution was stirred at 400 r / min for 20 min to obtain the second mixture.

[0068] Step 3) Introduce hydrogen peroxide into the second mixture at 0.1349% of the mass of the granulation slurry system. The hydrogen peroxide mass concentration in the hydrogen peroxide is 30% (the mass percentage of hydrogen peroxide in the granulation slurry system is 0.04047%). Immediately seal the container containing the mixture, stir at 800 r / min for 5 min, and then continue stirring and reacting at 60℃ and 90 r / min for 10 h to form a homogeneous slurry, i.e., the granulation slurry.

[0069] Step 4) The homogeneous slurry is dripped into a 60°C coagulation bath through a mold. The coagulation bath is a mixture of water and ethylene glycol ether, wherein the volume concentration of ethylene glycol ether is 8%. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, it is then acid-washed with a dilute hydrochloric acid solution to obtain a lithium ion sieve spherical adsorbent.

[0070] Comparative Example 3-1 The difference between this comparative example and Example 3 is that the additive (a mixture of dopamine monomer and tripterene, mass ratio 8:1, total 1.5%) was retained, but hydrogen peroxide and transition metal ions CuCl2 were not added. The corresponding missing mass fraction was made up by the organic solvent (ethylene glycol ether), specifically: At room temperature, lithium ion sieve Li4Ti5O 12 Polyvinyl chloride (PVC) and ethylene glycol ether (ethylene glycol ether) were added to the organic solvent at 30% and 12% of the mass of the granulation slurry system, respectively, and stirred at 300 r / min until completely dissolved to obtain the first mixture.

[0071] To the first mixture, at 1.5% of the mass of the granulation slurry system, a polymerization-reactive additive, namely a mixture of dopamine monomer and trimerene, is further introduced, wherein the mass ratio of dopamine monomer to trimerene is 8:1 (the mass percentage of dopamine monomer in the granulation slurry system is m...). Da The percentage of triterpenes (m) was 1.3333%. TP The concentration of the first solution was 0.1667%, and the solution was stirred at 400 r / min for 20 min to obtain the second mixture.

[0072] The second mixture is dripped through a mold into a 60°C coagulation bath, which is a mixture of water and ethylene glycol ether, with a volume concentration of 8% for the ethylene glycol ether. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, the particles are then acid-washed with a dilute hydrochloric acid solution to obtain the lithium ion sieve adsorbent.

[0073] Effect Analysis: The system lacks the synergistic catalytic effect of hydrogen peroxide and metal ions. Dopamine self-polymerization relies solely on the extremely slow self-oxidation process of dissolved oxygen in the system. This modification process is time-consuming and has low polymerization efficiency. After molding, although a certain degree of polydopamine functional layer can still be formed on the surface and inside the material, compared to the blank system without any additives (such as Comparative Example 2), its contact angle is reduced (hydrophilicity improved), and the adsorption capacity is also somewhat increased; however, due to the lack of Cu... 2+ Due to the multi-orbital coordination crosslinking and the directional induction of hydrogen peroxide, dopamine and tripterene cannot undergo two-dimensional directional copolymerization on the surface of the binder molecular chain, and cannot form a uniform hydrophilic rigid film "armor". Ultimately, the improvement of micro porosity is very limited, and the overall deformation resistance and mechanical strength of the particles are significantly inferior to those in Example 3.

[0074] Comparative Example 3-2 The difference between this comparative example and Example 3 is that only 1.5% of dopamine monomer was introduced into the additive, without the addition of triterpenes, hydrogen peroxide (an oxidizing agent), and CuCl2 (a transition metal ion). The missing mass fraction was made up by the organic solvent (ethylene glycol ether), specifically: At room temperature, lithium ion sieve Li4Ti5O 12 Polyvinyl chloride (PVC) and ethylene glycol ether (ethylene glycol ether) were added to the organic solvent at 30% and 12% of the mass of the granulation slurry system, respectively, and stirred at 300 r / min until completely dissolved to obtain the first mixture.

[0075] To the first mixture, an additive capable of polymerization, namely dopamine monomer, is further introduced at 1.5% of the mass of the granulation slurry system, and stirred and dissolved at 400 r / min for 20 min to obtain the second mixture.

[0076] The second mixture is dripped through a mold into a 60°C coagulation bath, which is a mixture of water and ethylene glycol ether, with a volume concentration of 8% for the ethylene glycol ether. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, the particles are then acid-washed with a dilute hydrochloric acid solution to obtain the lithium ion sieve adsorbent.

[0077] Effect Analysis: This system removes the rigid three-dimensional framework of tripterene. Due to the slow auto-oxidation of only free dopamine monomers, the polydopamine segments lack tripterene to act as spatial "pillars" during the molding process, leading to tight packing of the polymer binder chains. Although dopamine introduces hydrophilic hydroxyl and amino groups, improving the interfacial wettability of the particles to some extent, it cannot induce the formation of an open "self-porous" network in the polymer matrix. This directly results in a significant reduction in the specific surface area of ​​the adsorbent, obstruction of internal mass transfer channels, and disordered self-polymerization of large dopamine molecules, even blocking some micropores. Ultimately, this manifests as: although the material surface has some hydrophilicity, the adsorption kinetics are poor, the actual effective adsorption capacity is low, and due to the lack of a rigid framework, the particles are prone to deformation during stirred adsorption.

[0078] Comparative Example 3-3 The difference between this comparative example and Example 3 is that only 1.5% by mass of triterpenesene was introduced into the additive, and no dopamine monomer was added. Furthermore, no oxidant hydrogen peroxide or transition metal ion CuCl2 was added. The missing mass fraction was compensated by an organic solvent (ethylene glycol ether), specifically: At room temperature, lithium ion sieve Li4Ti5O 12 Polyvinyl chloride (PVC) and ethylene glycol ether (ethylene glycol ether) were added to the organic solvent at 30% and 12% of the mass of the granulation slurry system, respectively, and stirred at 300 r / min until completely dissolved to obtain the first mixture.

[0079] Additives capable of polymerization, namely triterene, are further introduced into the first mixture at 1.5% of the mass of the granulation slurry system, and stirred and dissolved at 400 r / min for 20 min to obtain the second mixture.

[0080] The second mixture is dripped through a mold into a 60°C coagulation bath, which is a mixture of water and ethylene glycol ether, with a volume concentration of 8% for the ethylene glycol ether. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, the particles are then acid-washed with a dilute hydrochloric acid solution to obtain the lithium ion sieve adsorbent.

[0081] Performance Analysis: This system lacks dopamine monomers rich in catechol groups. Triptene itself is a highly hydrophobic rigid molecule. Without dopamine copolymerization and metal ion complexation anchoring, triptene is prone to agglomeration during phase inversion molding and may even be lost with the solvent phase. Not only can it not form uniform rigid micropores inside the polymer matrix, but it also leads to severe macroscopic phase separation and structural defects. Due to the lack of strong adhesion properties (hydrogen bond cross-linking network) provided by polydopamine, the interfacial bonding force between the polymer binder and the lithium ion sieve is weak. The final test results show that the particles obtained in this comparative example have poor surface hydrophilicity (large water contact angle) and are difficult to wet with real salt lake brine. Moreover, the particle structure is loose, and the mechanical compressive strength drops sharply. Under the flushing of industrial simulated fluids, it will quickly pulverize and fall off, completely losing its engineering application value as an adsorbent.

[0082] Example 4 A method for improving the overall performance of lithium-ion sieve adsorbents includes the following steps: Step 1) At room temperature, FeCl2 (providing transition metal ions) is first dissolved in ethyl acetoacetate, an organic solvent, at 0.15% of the mass of the granulation slurry system (the mass percentage of the organic solvent in the granulation slurry system is 52.8711%). Then, lithium ion sieve LiMn2O4 and polymer binder ethylene-vinyl alcohol are introduced sequentially at 32% and 13% of the mass of the granulation slurry system, respectively. The mixture is stirred at 300 r / min until completely dissolved to obtain the first mixture.

[0083] Step 2) To the first mixture, further introduce an additive capable of polymerization, namely a mixture of dopamine monomer and trimerene, at 1.8% of the mass of the granulation slurry system, wherein the mass ratio of dopamine monomer to trimerene is 10:1 (mass percentage of dopamine monomer in the granulation slurry system (m...). Da The percentage of triterpenes (m) was 1.6364%. TP The concentration of the first solution was 0.1636%, and the solution was stirred at 400 r / min for 30 min to obtain the second mixture.

[0084] Step 3) Introduce hydrogen peroxide into the second mixture at 0.1789% of the mass of the granulation slurry system. The hydrogen peroxide mass concentration in the hydrogen peroxide is 30% (the mass percentage of hydrogen peroxide in the granulation slurry is 0.05367%). Immediately seal the container containing the mixture, stir at 800 r / min for 5 min, and then continue stirring and reacting at 60℃ and 60 r / min for 10 h to form a homogeneous slurry, i.e., the granulation slurry.

[0085] Step 4) The homogeneous slurry is dripped into a 60°C coagulation bath through a mold. The coagulation bath is a mixture of water and ethyl acetoacetate, with a volume concentration of 10%. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, it is then acid-washed with a dilute hydrochloric acid solution to obtain a lithium ion sieve spherical adsorbent.

[0086] Comparative Example 4 The difference between this comparative example and Example 4 is that the additives and hydrogen peroxide were retained, but transition metal ions were not added (i.e., a non-coordinating crosslinking system). Effect analysis: The oxidative polymerization process of dopamine in the system was significantly accelerated by hydrogen peroxide, and the hydrophilic properties of the material's surface interface were further improved compared to the system relying solely on dissolved oxygen self-oxidation. However, due to the lack of complexation and catalytic effects from transition metal ions, dopamine monomers and trimelline could not be effectively anchored around the polymer binder molecular chains, thus failing to undergo two-dimensional directional copolymerization and form a 5nm~10nm hydrophilic rigid film. Furthermore, free dopamine monomers directly underwent bulk polymerization in the slurry system, generating larger polydopamine particles and initiating a certain degree of agglomeration. This disordered polymerization limited the long-term stability of the resulting modified layer; simultaneously, the large-sized polymers easily caused local micro-phase separation of the matrix structure during phase inversion molding, forming large-sized defect pores. Therefore, although the hydrophilicity, effective adsorption capacity and particle compressive strength of the adsorbent obtained by this system are better than those of the system without oxidant, the overall performance is still significantly lower than that of the system in Example 4 with the synergistic effect of "dopamine & tripterene-hydrogen peroxide-metal transition ions".

[0087] Example 5 A method for improving the overall performance of lithium-ion sieve adsorbents includes the following steps: Step 1) At room temperature, ZnCl2 (providing transition metal ions) is first dissolved in triethyl phosphate, an organic solvent, at 0.17% of the mass of the granulation slurry system (the mass percentage of the organic solvent in the granulation slurry system is 48.8415%). Then, lithium ion sieve Li2Mn2O5 and polymer binder polyethersulfone are introduced sequentially at 34.5% and 14% of the mass of the granulation slurry system, respectively. The mixture is stirred at 300 r / min until completely dissolved to obtain the first mixture.

[0088] Step 2) To the first mixture, further introduce an additive capable of polymerization, namely a mixture of dopamine monomer and trimerene, at 2.3% of the mass of the granulation slurry system, wherein the mass ratio of dopamine monomer to trimerene is 7:1 (mass percentage of dopamine monomer in the granulation slurry system (m...). Da The percentage of triterpenes (m) was 2.0125%. TPThe concentration of the first solution was 0.2875%, and the solution was stirred at 400 r / min for 30 min to obtain the second mixture.

[0089] Step 3) Introduce hydrogen peroxide into the second mixture at 0.1885% of the mass of the granulation slurry system. The hydrogen peroxide mass concentration in the hydrogen peroxide is 30% (the mass percentage of hydrogen peroxide in the granulation slurry system is 0.05655%). Immediately seal the container containing the mixture, stir at 800 r / min for 10 min, and then continue stirring and reacting at 40℃ and 60 r / min for 10 h to form a homogeneous slurry, i.e., the granulation slurry.

[0090] Step 4) The homogeneous slurry is dripped into a 60°C coagulation bath through a mold. The coagulation bath is a mixture of water and triethyl phosphate, in which the volume percentage of triethyl phosphate is 2%. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, it is then acid-washed with a dilute hydrochloric acid solution to obtain a lithium ion sieve spherical adsorbent.

[0091] Comparative Example 5 The difference between this comparative example and Example 5 is that the coagulation bath was replaced with pure water at 25°C (no organic solvent was added, and it was not heated to 45°C~60°C). Effect analysis: The temperature and composition of the coagulation bath directly determine the migration rate of different phases, which is the core of molding and precise control of pore structure. When using pure water at 25°C, at the instant the granulation slurry is dropped into the water, the diffusion rate of water (a strong non-solvent) into the droplet is much greater than the diffusion rate of the solvent to the outside. This intense "instantaneous phase separation" causes the particle surface to shrink rapidly, forming a dense skin layer, while finger-like macropores form inside. This dense skin layer easily blocks the channels for lithium ions to enter the particle interior. Even with internal hydrophilic modification, the actual working adsorption capacity and adsorption rate drop precipitously.

[0092] Example 6 A method for improving the overall performance of lithium-ion sieve adsorbents includes the following steps: Step 1): At room temperature, firstly, dissolve ZnCl2 (providing transition metal ions) at 0.18% of the mass of the granulation slurry system in the organic solvent N-N'-dimethylacetamide (the mass percentage of the organic solvent in the granulation slurry system is 50.6203%). Then, add the lithium ion sieve Li4Mn5O... 12 Polyethersulfone (PSS) and polyether sulfone (PES) were introduced sequentially at 35% and 12% of the mass of the granulation slurry system, respectively, and stirred at 300 r / min until completely dissolved to obtain the first mixture.

[0093] Step 2) To the first mixture, further introduce an additive capable of polymerization, namely a mixture of dopamine monomer and trimerene, at 2.0% of the mass of the granulation slurry system, wherein the mass ratio of dopamine monomer to trimerene is 9:1 (mass percentage of dopamine monomer in the granulation slurry system (m...). Da The content of triterpenes was 1.8%, and the mass percentage of triterpenes (m) TP The solution was prepared by stirring at 400 rpm for 30 minutes to obtain a second mixture (0.2%).

[0094] Step 3) Introduce hydrogen peroxide into the second mixture at 0.1997% of the mass of the granulation slurry system. The hydrogen peroxide mass concentration in the hydrogen peroxide is 30% (the mass percentage of hydrogen peroxide in the granulation slurry system is 0.05991%). Immediately seal the container containing the mixture, stir at 800 r / min for 10 min, and then continue stirring and reacting at 60℃ and 60 r / min for 8 h to form a homogeneous slurry, i.e., the granulation slurry.

[0095] Step 4) The homogeneous slurry is dripped into a 45°C coagulation bath through a mold. The coagulation bath is a mixture of water and N-N'-dimethylacetamide, wherein the volume percentage of N-N'-dimethylacetamide is 2%. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, it is then acid-washed with a dilute hydrochloric acid solution to obtain a lithium ion sieve spherical adsorbent.

[0096] Comparative Example 6 The difference between this comparative example and Example 6 is that the transition metal ion ZnCl2 is replaced with an equimolar amount of the non-transition metal salt NaCl. Effect analysis: The selected metal ion is a key prerequisite for controlling the oxidation reaction rate and the formation space of the hydrophilic rigid film. Zn 2+ As a moderately strong Lewis acid, it can form dynamic coordination complexes with the phenolic hydroxyl or amino groups in dopamine and triterpenes, thereby regulating the dopamine oxidation rate and constructing a spatial cross-linked network. In contrast, Na⁺ is a highly hydrated monovalent alkali metal ion with extremely weak coordination ability, unable to form stable complex structures, and therefore loses its regulatory role in the oxidation process and membrane structure formation; at the same time... It lacks the ability to catalyze and activate hydrogen peroxide. This prevents the additive from undergoing two-dimensional directional copolymerization around the polymer binder molecular chains, resulting in disordered bulk polymerization within the system. This leads to the loss of free small molecules and the aggregation of large particles, failing to form a protective "armor." Ultimately, the mechanical compressive strength of the adsorbent is significantly reduced, making it prone to breakage during stirred adsorption tests.

[0097] Example 7 A method for improving the overall performance of lithium-ion sieve adsorbents includes the following steps: Step 1) At room temperature, FeCl2 (providing transition metal ions) is first dissolved in the organic solvent ethylene glycol ether at 0.09% of the mass of the granulation slurry system (the mass percentage of the organic solvent in the granulation slurry system is 52.5527%). Then, lithium ion sieve LiMn2O4 and polymer binder polyvinyl chloride are introduced sequentially at 34.95% and 10% of the mass of the granulation slurry system, respectively. The mixture is stirred at 300 r / min until completely dissolved to obtain the first mixture.

[0098] Step 2) To the first mixture, further introduce an additive capable of polymerization, namely a mixture of dopamine monomer and trimerene, at 2.3% of the mass of the granulation slurry system, wherein the mass ratio of dopamine monomer to trimerene is 9:1 (mass percentage of dopamine monomer in the granulation slurry system (m...). Da The percentage of triterpenes was 2.097%, and the mass percentage of triterpenes was (m TP The concentration of the first solution was 0.233%, and the solution was stirred at 400 r / min for 30 min to obtain the second mixture.

[0099] Step 3) Introduce hydrogen peroxide into the second mixture at 0.1073% of the mass of the granulation slurry system. The hydrogen peroxide mass concentration in the hydrogen peroxide is 30% (the mass percentage of hydrogen peroxide in the granulation slurry system is 0.03219%). Immediately seal the container containing the mixture, stir at 800 r / min for 10 min, and then continue stirring and reacting at 60℃ and 60 r / min for 12 h to form a homogeneous slurry, i.e., the granulation slurry.

[0100] Step 4) The homogeneous slurry is dripped into a 60°C coagulation bath through a mold. The coagulation bath is a mixture of water and ethylene glycol ether, wherein the volume percentage of ethylene glycol ether is 4%. The mixture is solidified into particles using the principle of phase inversion. After thorough rinsing and drying, it is then acid-washed with a dilute hydrochloric acid solution to obtain a lithium ion sieve spherical adsorbent.

[0101] Comparative Example 7 The difference between this comparative example and Example 7 is that a conventional volatile solvent (such as tetrahydrofuran, THF) was used instead of the specific aprotic polar organic solvent (ethyl acetoacetate). Effect analysis: The solvent must have good compatibility with the non-solvent phase, which has significantly different properties. Although THF can dissolve some binders, it lacks the strong polarity and hydrogen bond donor-acceptor capacity of amide or alcohol ester structures. This results in extremely weak interactions with dopamine, trimelline, and hydrogen peroxide, hindering mass transfer among the components in the slurry and making it difficult to form a homogeneous system. Before being added to the coagulation bath, the slurry underwent visible macroscopic phase separation and could not be solidified into well-structured spherical particles by phase inversion, demonstrating the irreplaceable role of specific organic solvents in in-situ modification and granulation processes.

[0102] Table 1. Mass fraction ratio of different components in various embodiments of the present invention Through systematic cross-validation of the above seven sets of examples and comparative examples, it is fully demonstrated that there is a deep synergistic effect mechanism among the components and process conditions described in this invention. The indispensability of each core technical feature is summarized as follows: Table 2. Performance Comparison of Lithium-ion Sieve-type Adsorbents Obtained in the Embodiments and Comparative Examples of the Invention Kinetic assurance of multi-step speed-controlled gradient stirring process (verification by Comparative Example 1): Conventional "one-pot" constant-speed stirring cannot simultaneously meet the strong shear forces required for polymer de-entanglement and the mild microenvironment required for uniform polymerization. This invention effectively avoids lithium-ion sieve agglomeration and localized excessive polymerization of dopamine by combining high-speed forced homogenization in the early stage with low-speed gentle reaction in the later stage. This is a key process prerequisite for achieving uniform modification of lithium-ion sieve adsorbents.

[0103] The necessity of multi-component in-situ catalytic crosslinking systems: Pure physical blending (Comparative Example 2) cannot improve interfacial hydrophilicity and binding force. If only the oxidant and metal ions are missing (Comparative Example 3-1), the modification is slow and inefficient; if tripterene is missing (Comparative Example 3-2), the matrix lacks a rigid framework, easily leading to blocked internal mass transfer channels and tight polymer chain stacking; if dopamine is missing (Comparative Example 3-3), hydrophilicity and chemical anchoring of the bonding interface are lost. Anchoring effect of transition metals: Under conditions with an oxidant, if transition metal ions are missing (Comparative Example 4), free dopamine will undergo uncontrolled bulk polymerization, forming large-sized finger-like defect pores; even with metal ions present, if replaced with monovalent alkali metal ions with weak coordination ability (such as Na⁺, Comparative Example 6), it is impossible to stably form dynamic coordination complexes and spatial crosslinking networks, resulting in a significant decrease in the mechanical strength of the adsorbent. This confirms the core role of the synergistic effect of "dopamine & tripterene-hydrogen peroxide-transition metal ions" in two-dimensional directional copolymerization.

[0104] The decisive role of the coagulation bath microenvironment in pore structure: Conventional room temperature pure water coagulation baths induce intense "instantaneous phase separation" (Comparative Example 5), resulting in the formation of a dense, non-porous skin on the particle surface, blocking mass transfer channels. This invention innovatively introduces a heated "water-polar organic phase" mixed coagulation bath, successfully constructing a "weakly non-solvent" environment, slowing down the dual diffusion rate, thereby ensuring a sponge-like porous network structure that is interconnected inside and outside the particles.

[0105] Prerequisites for solvent system compatibility: (Verification by Comparative Example 7) If conventional volatile solvents (such as THF) are used, due to the lack of polarity and hydrogen bond acceptor capacity of amide or alcohol ester structures, their interaction with dopamine, triterpenes and hydrogen peroxide is weak. Mass transfer of each component in the slurry is hindered, and effective mass transfer of each functional non-solvent phase cannot be achieved. This directly leads to the failure of macroscopic phase separation and molding, proving the stringency and specificity of the specific aprotic polar organic solvent selected in this invention.

[0106] In summary, addressing the technical bottlenecks in existing technologies such as insufficient hydrophilicity of adsorbent surfaces, difficulty in balancing porosity and mechanical strength, and weak interfacial bonding, this invention provides a novel method for improving the overall performance of lithium-ion sieve-type adsorbents. Compared to traditional granulation techniques based on liquid-solid phase transformation, this invention completely eliminates the reliance on complex pretreatment, post-treatment processes, and additional auxiliary equipment. The core advantages of this invention lie in: directly introducing polymerizable additives and hydrogen peroxide during the granulation slurry preparation stage, cleverly supplemented by the complexation, anchoring, and catalytic activation effects of transition metal ions, and constructing a weak oxidation system to induce dopamine self-aggregation, forming in-situ polydopamine hydrophilic nanoparticles with a particle size of 30nm~60nm. This provides the necessary prerequisite for effective dissolution and improved overall macroporous porosity of the adsorbent during subsequent phase transformation; simultaneously, the triterpenoid monomer, with its unique three-dimensional rigid framework, constructs a rich "self-microporous" structure within the copolymerization network. Ultimately, through the strong synergistic effect of the aforementioned multi-components, a polymer-modified layer with a three-dimensional rigid structure, strong adhesion, and excellent hydrophilicity was precisely constructed in situ within the slurry. This multi-scale structural regulation from the molecular chain to the macroscopic interface fundamentally breaks through the limitations of existing technologies, achieving a simultaneous leap in the hydrophilicity, effective porosity, particle mechanical strength, and binder-ion sieve interface bonding of the lithium-ion sieve adsorbent. Furthermore, the method of this invention not only effectively solves the problem of the difficulty in achieving a balanced comprehensive performance of traditional adsorbents, but also features simplified overall operation steps, mild reaction conditions, and high modification efficiency, making it fully capable of large-scale continuous industrial application in the field of lithium resource extraction. Moreover, its multi-component synergistic regulation strategy can also be extended to the preparation and modification of other polymer-based composite porous materials.

[0107] Although specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the spirit and scope of the present invention, which is defined only by the appended claims.

Claims

1. A method for improving the overall performance of lithium-ion sieve-type adsorbents, characterized in that, Includes the following steps: At room temperature, transition metal ions are dissolved in an organic solvent, and then lithium ion sieves and polymer binders are introduced in sequence and stirred until completely dissolved to obtain the first mixture. Among them, the organic solvent is an aprotic polar organic solvent rich in amide or alcohol ester structures; Additives capable of polymerization are introduced into the first mixture and stirred at 300 r / min to 400 r / min to dissolve them, so that the transition metal ions, lithium ion sieves and additives are uniformly dispersed around the polymer binder molecular chains to obtain the second mixture. Among them, the additive that can undergo polymerization reaction is a mixture of dopamine monomer and tripterene; Hydrogen peroxide, an oxidant, is introduced into the second mixture. The mixture is first stirred and mixed evenly at 600 rpm to 800 rpm, and then a polymerization reaction is carried out at 40°C to 60°C and 60 rpm to 100 rpm. Under oxidizing conditions, free dopamine molecules in the second mixture undergo self-aggregation to form 30 nm to 60 nm polydopamine particles. These particles, along with the complexing ability of transition metal ions, induce two-dimensional directional self-polymerization of dopamine and triterpenes surrounding the polymer binder molecular chains, forming a hydrophilic rigid film at the polymer binder interface. Finally, a homogeneous slurry is obtained. The homogeneous slurry is dropped into a coagulation bath at 45℃~60℃. The organic solvent and nano-hydrophilic substances in the homogeneous slurry migrate to the coagulation bath, while water molecules in the coagulation bath migrate to the liquid phase of the slurry. The slurry is solidified into particles by utilizing the principle of phase transformation, thus obtaining a lithium ion sieve adsorbent. The coagulation bath consists of water and organic solvent, with the organic solvent accounting for 2% to 10% of the volume.

2. The method for improving the overall performance of lithium-ion sieve-type adsorbents according to claim 1, characterized in that, In the homogeneous slurry, the mass percentages of each component are as follows: transition metal ions 0.08%~0.2%, lithium ion sieve 28%~35%, polymer binder 10%~15%, additives 1%~3%, hydrogen peroxide 0.05%~0.2%, and the remainder is solvent.

3. The method for improving the overall performance of lithium-ion sieve-type adsorbents according to claim 1, characterized in that, The organic solvent is selected from any one of N-N'-dimethylacetamide, ethylene glycol ether, ethyl acetoacetate, and triethyl phosphate.

4. The method for improving the overall performance of lithium-ion sieve-type adsorbents according to claim 1, characterized in that, The transition metal ions are selected from any one of FeCl2, CuCl2, and ZnCl2.

5. The method for improving the overall performance of lithium-ion sieve-type adsorbents according to claim 1, characterized in that, Lithium ions were screened from Li2TiO3 and Li4Ti5O3. 12 , LiMn2O4, Li2Mn2O5, Li4Mn5O 12 Any one of them.

6. The method for improving the overall performance of lithium-ion sieve-type adsorbents according to claim 1, characterized in that, The polymeric binder is selected from one of polyvinylidene fluoride, polyvinyl chloride, ethylene-vinyl alcohol, and polyethersulfone.

7. The method for improving the overall performance of lithium-ion sieve-type adsorbents according to claim 1, characterized in that, The mass ratio of dopamine monomer to tripterene is 5~12:

1.

8. The method for improving the overall performance of lithium-ion sieve-type adsorbents according to claim 1, characterized in that, The mass ratio of lithium ion sieve to additive is 15~28:

1.

9. The method for improving the overall performance of lithium-ion sieve-type adsorbents according to claim 1, characterized in that, The oxidizing agent, hydrogen peroxide, has a hydrogen peroxide mass fraction of 30%, and the mass ratio of dopamine to hydrogen peroxide is 50. <m Da / m H2O2 <120.

10. The method for improving the overall performance of lithium-ion sieve-type adsorbents according to claim 1, characterized in that, The relationship between the molar concentration of transition metal ions and the molar concentration of hydrogen peroxide in hydrogen peroxide is: M 离子 =M H2O2 ×0.75.

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