Composite porous lithium ion sieve adsorbent and preparation method and application thereof

Abstract

The present application relates to salt lake lithium extraction technical field, disclose a kind of composite porous lithium ion sieve adsorbent and its preparation method and application, including the following steps: lithium ion sieve adsorbent precursor, fluorine-containing polymer, binder, pore-forming agent, solvent are mixed uniformly to obtain slurry;The slurry of step S1 is added to crosslinking agent, and the composite porous lithium ion sieve adsorbent precursor is obtained after standing crosslinking;The composite porous lithium ion sieve adsorbent precursor of step S2 is eluted using eluent, and the composite porous lithium ion sieve adsorbent is obtained.The adsorbent prepared by the present application is easy to recover, and has certain mechanical strength, can show better cycle stability, is conducive to long-term cyclic use, is a kind of lithium adsorption material easy to realize industrial application;Fluorine atom in fluorine-containing polymer as a kind of atom with strong electronegativity, has high affinity for lithium ion in aqueous phase, can assist to realize efficient, fast lithium adsorption.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from salt lakes, and in particular to a composite porous lithium-ion sieve adsorbent, its preparation method, and its application. Background Technology

[0002] Lithium and its compounds, due to their unique physicochemical properties, have wide applications in energy storage, nuclear industry, medical, aerospace, ceramics, and glass, among other fields. Especially in energy storage, lithium occupies a crucial position and is known as the "white oil" of modern energy. Currently, we are at a critical juncture in the world, facing a food crisis, environmental pollution control, and the transformation and upgrading of "dual-carbon" industrial structures. Against this backdrop, developing emerging industries has become an inevitable choice to address energy resource scarcity and the ecological crisis. With the rapid development of new energy batteries, the demand for lithium, as a key raw material in the downstream industrial chain, is showing a dramatic upward trend.

[0003] Salt lake brines, as one of the world's important sources of lithium resources, have attracted attention due to their abundant lithium reserves and relatively low production costs. However, factors such as low lithium concentration, high magnesium-to-lithium ratio, and complex associated environments pose challenges to the effective development of lithium resources in salt lake brines. These factors collectively affect the selectivity and efficiency of the lithium extraction process, making efficient extraction technologies for liquid lithium resources a key research focus in the future development of lithium resources. Currently, the main technologies for extracting lithium from salt lake brines include precipitation, solvent extraction, electrochemical methods, and adsorption methods. Among them, adsorption is considered a promising lithium extraction technology due to its simplicity, high selectivity, and environmental friendliness. Adsorption separates lithium from other ions by utilizing the selective adsorption of lithium ions by adsorbents. However, the selection and design of adsorbents are crucial for the successful application of this technology, requiring comprehensive consideration of the adsorption capacity, selectivity, stability, and regeneration capacity of the adsorbent.

[0004] Currently, adsorbents are mainly classified into two categories: organic adsorbents and inorganic adsorbents. Among them, lithium-ion sieve adsorbents (LIS) have attracted much attention due to their ability to specifically recognize lithium ions. These adsorbents have advantages such as controllable production costs and simple synthesis processes, and possess the potential for large-scale production and application in industry, making them a current research hotspot. Currently, lithium-ion sieve adsorbent materials mainly include titanium-based adsorbents (LTO) and manganese-based adsorbents (LMO). LTO and LMO are usually in powder form, which faces problems such as difficult powder recovery and significant losses in practical applications, limiting their efficiency and economic viability in industrial-scale lithium extraction. Therefore, adsorbent molding has become one of the most important research directions, with existing molding technologies including granulation, magnetization, foaming, and film formation.

[0005] Chinese invention patent CN116786076A, entitled "A Granulation and Forming Method for Lithium-ion Screens for Liquid Lithium Recovery," describes a method of mixing lithium-ion screen precursor powder with a dual binder and pore-forming agent to prepare a slurry for granulation, followed by elution to obtain the formed lithium-ion screen. The spherical lithium-ion screen prepared by this invention possesses a certain mechanical strength, overcoming the current difficulties in the direct application and recycling of powdered lithium-ion screens. However, compared to powdered adsorbents, its adsorption capacity loss exceeds 40%. Currently, lithium-ion screen forming technologies mostly use organic polymers as binders or additives, which have the drawback of blocking some adsorption sites, leading to adsorption capacity loss and a decrease in adsorption rate, thus weakening the overall adsorption performance of the adsorbent.

[0006] To achieve a sustainable supply of lithium, there is an urgent need for a composite porous lithium-ion sieve adsorbent, its preparation method, and its application to solve the aforementioned technical problems. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a composite porous lithium-ion sieve adsorbent, its preparation method and application, which, while shaping the powder adsorbent into a granular form more suitable for industrial applications, minimizes the negative impact of the use of binders on lithium adsorption performance, thereby obtaining a lithium adsorbent material with excellent performance.

[0008] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0009] A method for preparing a composite porous lithium-ion sieve adsorbent includes the following steps:

[0010] S1, a slurry is obtained by uniformly mixing lithium-ion sieve adsorbent precursor, fluoropolymer, binder, pore-forming agent and solvent;

[0011] S2, add the slurry obtained in step S1 to the crosslinking agent, and after standing and crosslinking, obtain the composite porous lithium ion sieve adsorbent precursor.

[0012] S3, the composite porous lithium ion sieve adsorbent precursor obtained in step S2 is eluted with lithium using an eluent to obtain the composite porous lithium ion sieve adsorbent.

[0013] Preferably, in step S1, the slurry obtained comprises a mixture of lithium-ion sieve adsorbent precursor, fluoropolymer, binder, and pore-forming agent, wherein the mixture comprises the following components in the following mass fractions: 20-40 wt% lithium-ion sieve adsorbent precursor, 10-40 wt% fluoropolymer, 10-40 wt% binder, and 5-20 wt% pore-forming agent; the mass ratio of the mixture to the solvent is 1:(2-10).

[0014] Preferably, in step S1, the lithium-ion sieve adsorbent precursor is at least one of titanium-based adsorbent precursor and manganese-based adsorbent precursor.

[0015] Preferably, the titanium-based adsorbent precursor is Li2TiO3 or Li4Ti5O3. 12 At least one of the following; the manganese-based adsorbent precursor is LiMn2O4 or Li4Mn5O4. 12 Li 1.6 Mn 1.6 At least one of O5.

[0016] Preferably, in step S1, the viscosity-average molecular weight of the fluoropolymer is 1,000 to 50,000; the fluoropolymer is at least one of polyvinylidene fluoride (PVDF), perfluoroethylene propylene (FEP), perfluoroalkoxy polymer (PFA), and polytetrafluoroethylene (PTFE).

[0017] More preferably, the viscosity-average molecular weight of the fluoropolymer is 2000 to 10000.

[0018] Preferably, in step S1, the average molecular weight of the adhesive is 1,000 to 200,000; the adhesive is at least one of sodium alginate (SA), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), and polyacrylonitrile (PAN).

[0019] Preferably, in step S1, the pore-forming agent is at least one of nano-calcium carbonate, nano-magnesium carbonate, nano-manganese carbonate, and nano-zinc carbonate.

[0020] Preferably, in step S1, the solvent is at least one of water, N,N-dimethylformamide (DMF), ethanol, N-methylpyrrolidone (NMP), and dimethylacetamide (DMAC).

[0021] Preferably, in step S2, the crosslinking agent is at least one of water, calcium chloride solution, and boric acid solution; the volume ratio of crosslinking agent to slurry is (5-10):1; and the concentrations of calcium chloride solution and boric acid solution do not exceed 1 mol / L.

[0022] Preferably, in step S2, after the slurry is added to the crosslinking agent, it is allowed to stand for crosslinking for 8 to 12 hours, and then filtered, washed, and dried to obtain the composite porous lithium ion sieve adsorbent precursor; the drying temperature is 50 to 80°C, and the drying time is 4 to 12 hours.

[0023] Preferably, in step S2, the slurry is added to the crosslinking agent by dripping, with a dripping rate of 30-40 drops / min.

[0024] Preferably, in step S3, the eluent is at least one of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution; the concentration of the eluent is 0.1 to 0.5 mol / L.

[0025] Preferably, in step S3, the composite porous lithium-ion sieve adsorbent is eluted with an eluent to remove lithium ions; subsequently, it is filtered, washed, and dried to obtain the composite porous lithium-ion sieve adsorbent; the solid-liquid ratio of the composite porous lithium-ion sieve adsorbent precursor to the eluent is (1-50):1, and the unit of the solid-liquid ratio is g:L; the elution temperature is 20-60℃, the elution time is 2-24h, the stirring speed during the elution process is 100-600r / min; the drying temperature is 50-80℃, and the drying time is 4-12h.

[0026] The present invention also includes a composite porous lithium-ion sieve adsorbent, which is prepared by the above preparation method.

[0027] The composite porous lithium-ion sieve adsorbent prepared by this invention is in granular form.

[0028] The present invention also includes the application of composite porous lithium-ion sieve adsorbents in lithium extraction from salt lakes.

[0029] Mechanism of action:

[0030] The method of this invention uses a fluoropolymer as an additive, which, together with a binder and a powdered adsorbent precursor (referring to the "lithium-ion sieve adsorbent precursor" used in this invention), synergistically constructs a molded composite porous lithium-ion sieve adsorbent with certain mechanical properties and excellent adsorption performance. The fluorine atoms in the fluoropolymer have a high affinity for lithium, and can form fluorine-lithium bonds with lithium ions in the aqueous phase with a certain binding force, achieving rapid capture of lithium ions and effectively improving the overall adsorption capacity of the composite porous lithium-ion sieve adsorbent. Simultaneously, it reduces the lithium adsorption capacity loss caused by the use of organic binders during the molding process. The composite porous lithium-ion sieve adsorbent possesses a certain mechanical strength due to molding, exhibiting excellent cycle stability, which is beneficial for long-term cyclic use. At the same time, this composite porous lithium-ion sieve adsorbent exhibits a certain selectivity, achieving highly selective adsorption of lithium in complex aqueous environments.

[0031] Beneficial effects:

[0032] (1) The composite porous lithium ion sieve adsorbent prepared by the present invention is easy to recycle and has a certain mechanical strength. It can exhibit good cycle stability and is conducive to long-term cycle use. It is a lithium adsorbent material that is easy to realize industrial application.

[0033] (2) Fluorine atoms in fluoropolymers are highly electronegative atoms and have a high affinity for lithium ions in the aqueous phase, which can help achieve efficient and rapid lithium adsorption.

[0034] (3) Fluoropolymers can selectively adsorb lithium ions together with lithium ion sieve adsorbents, making the composite porous lithium ion sieve adsorbent exhibit high adsorption selectivity.

[0035] (4) The preparation method is simple and environmentally friendly, and does not require high temperature and high pressure, which reduces energy consumption and environmental pollution. Attached Figure Description

[0036] Figure 1 The selectivity of the adsorbent samples prepared in Example 1 and Comparative Example 1 for different metal ions in brine solution E is shown.

[0037] Figure 2 The graph shows the lithium ion adsorption capacity of the adsorbent samples prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention in brine solution A at different times. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0039] There are no particular restrictions on the purity of any raw materials used in this invention. However, it is preferred to use industrial-grade or conventionally pure materials used in this field.

[0040] Unless otherwise specified, the apparatus used in this invention employs commonly used devices in the field.

[0041] Example 1

[0042] A method for preparing a composite porous lithium-ion sieve adsorbent specifically includes the following steps:

[0043] Weigh 1g of SA with a molecular weight of 20000, add 49mL of deionized water to prepare 50mL of SA solution with a concentration of 2wt%. After complete dissolution, add 2g of titanium-based adsorbent precursor Li2TiO3, 2g of PVDF with a molecular weight of 5000 and 1g of nano-calcium carbonate. Stir at 300r / min for 4h at room temperature to obtain a slurry. Slowly add the slurry dropwise to 500mL of 0.1mol / L calcium chloride solution at a rate of 30-40 drops / min to form gel spheres. After standing for cross-linking for 12h, wash three times with pure water and dry the product in a 50℃ oven for 12h to obtain the shaped composite porous lithium-ion sieve adsorbent precursor. Weigh an appropriate amount of the composite precursor according to a solid-liquid ratio of 10g:1L and place it in a 0.2mol / L dilute HCl solution for elution to remove lithium ions. The elution temperature is 30℃, the elution time is 8h, and the stirring speed is 200r / min. After acid elution, the product is washed with pure water until the washing solution is neutral. It is then dried in a 60℃ oven for 8 hours to obtain the composite porous titanium-based lithium-ion sieve adsorbent.

[0044] Example 2

[0045] A method for preparing a composite porous lithium-ion sieve adsorbent specifically includes the following steps:

[0046] Weigh 4g of PVA with a molecular weight of 74800 and mix it with 36mL of deionized water to prepare 40mL of PVA solution with a concentration of 10wt%. After complete dissolution, add 4g of Li4Mn5O 12 2g of PVDF with a molecular weight of 5000 and 1g of nano-magnesium carbonate were added, and the mixture was stirred at 500r / min for 6 hours at 25℃ to obtain a homogeneous slurry. The slurry was added dropwise to 250mL of 0.8mol / L boric acid solution at a rate of 30-40 drops / min to form gel spheres. After standing in the solution for cross-linking for 8 hours, the product was washed three times with pure water and then dried in an oven at 80℃ for 4 hours to obtain the shaped composite porous lithium-ion sieve adsorbent precursor. An appropriate amount of the composite precursor was weighed according to a solid-liquid ratio of 20g:1L and eluted in a 0.3mol / L dilute HCl solution to remove lithium ions. The elution temperature was 40℃, the elution time was 4 hours, and the stirring speed was 200r / min. After acid elution, the product was washed with pure water until the washing solution was neutral. The product was then dried in an oven at 80℃ for 4 hours to obtain the composite porous manganese-based lithium-ion sieve adsorbent.

[0047] Example 3:

[0048] A method for preparing a composite porous lithium-ion sieve adsorbent specifically includes the following steps:

[0049] Weigh 2g of PVC and dissolve it in 38mL of DMF to prepare 40mL of 5wt% PVC solution. After complete dissolution, add 3g of titanium-based adsorbent precursor Li4Ti5O. 12 Two g of perfluoroethylene propylene (PFEP) with a molecular weight of 7000 and one g of nano-manganese carbonate were stirred at 300 r / min for 8 hours at 60℃ to obtain a homogeneous slurry. The slurry was added dropwise to 500 mL of deionized water at a rate of 30–40 drops / min to form gel spheres. After standing for 12 hours for cross-linking, the spheres were washed three times with pure water and anhydrous ethanol, respectively. The product was then dried in a 60℃ oven for 8 hours to obtain the shaped composite porous lithium-ion sieve adsorbent precursor. An appropriate amount of the composite precursor was weighed according to a solid-liquid ratio of 40 g: 1 L and eluted in a 0.5 mol / L dilute HNO3 solution to remove lithium ions. The elution temperature was 30℃, the elution time was 2 hours, and the stirring speed was 100 r / min. After acid elution, the product was washed with pure water until the washing solution was neutral. The product was then dried in a 60℃ oven for 8 hours to obtain the composite porous titanium-based lithium-ion sieve adsorbent.

[0050] Example 4

[0051] A method for preparing a composite porous lithium-ion sieve adsorbent specifically includes the following steps:

[0052] 3g of PAN was dissolved in 27mL of DMAC to prepare 30mL of 10wt% PAN solution. After complete dissolution, 2g of manganese-based adsorbent precursor LiMn2O4, 2g of perfluoroalkoxy polymer with a molecular weight of 4000, and 1g of nano-zinc carbonate were added. The mixture was stirred at 300r / min for 6h at 80℃ to obtain a homogeneous slurry. The slurry was added dropwise to 250mL of deionized water at a rate of 30-40 drops / min to form gel spheres. After standing for cross-linking for 12h, the mixture was washed three times with pure water and anhydrous ethanol, and then dried in an 80℃ oven for 6h to obtain the shaped composite porous lithium-ion sieve adsorbent precursor. A suitable amount of the composite precursor was weighed according to a solid-liquid ratio of 5g:1L and eluted in a 0.1mol / L dilute H₂SO₄ solution to remove lithium ions. The elution temperature was 20℃, the elution time was 24h, and the stirring speed was 400r / min. After acid elution, the product was washed with pure water until the washing solution was neutral. The product was then dried in a 50℃ oven for 12h to obtain the composite porous manganese-based lithium ion sieve adsorbent.

[0053] Example 5

[0054] A method for preparing a composite porous lithium-ion sieve adsorbent specifically includes the following steps:

[0055] Weigh 1g of SA with a molecular weight of 20000, add 49mL of deionized water to prepare 50mL of SA solution with a concentration of 2wt%. After complete dissolution, add 2g of manganese-based adsorbent precursor Li. 1.6 Mn 1.6 O5, 2g of PTFE with a molecular weight of 8000, and 1g of nano-calcium carbonate were stirred at 300 rpm for 4 hours at room temperature to prepare a slurry. The slurry was added dropwise to 550mL of 0.1mol / L calcium chloride solution at a rate of 30-40 drops / min to form gel spheres. After standing for cross-linking for 12 hours, the spheres were washed three times with pure water and then dried in a 60℃ oven for 10 hours to obtain the shaped composite porous lithium-ion sieve adsorbent precursor. An appropriate amount of the composite precursor was weighed according to a solid-liquid ratio of 2g:1L and eluted in a 0.1mol / L dilute HCl solution to remove lithium ions. The elution temperature was 60℃, the elution time was 6 hours, and the stirring speed was 600 rpm. After acid elution, the product was washed with pure water until the washing solution was neutral. The product was then dried in a 60℃ oven for 6 hours to obtain the composite porous manganese-based lithium-ion sieve adsorbent.

[0056] Comparative Example 1

[0057] The only difference between this comparative example and Example 1 is that the shaped titanium adsorbent was prepared without the addition of fluoropolymer PVDF; all other conditions and parameters were exactly the same as in Example 1.

[0058] Comparative Example 2

[0059] The only difference between this comparative example and Example 1 is that no pore-forming agent was added to prepare the shaped titanium adsorbent; all other conditions and parameters are exactly the same as in Example 1.

[0060] Comparative Example 3

[0061] In this comparative example, an appropriate amount of powdered titanium-based precursor Li₂TiO₃ was weighed at a solid-liquid ratio of 10 g / L and eluted in a 0.2 mol / L dilute HCl solution to remove lithium ions. The elution temperature was 30℃, the elution time was 8 h, and the stirring speed was 200 r / min. After acid elution, the product was washed with pure water until the washing solution was neutral. The product was then dried in a 60℃ oven for 8 h to obtain the powdered titanium-based lithium ion sieve adsorbent.

[0062] Comparative Example 4

[0063] In this comparative example, an appropriate amount of powdered manganese precursor Li4Mn5O was weighed according to a solid-liquid ratio of 20 g / L. 12Lithium ions were removed by elution in a 0.3 mol / L dilute HCl solution at 40°C for 4 hours, with a stirring speed of 100 r / min. After acid elution, the product was washed with pure water until the washing solution was neutral. The product was then dried in an 80°C oven for 4 hours to obtain the powdered manganese-based lithium ion sieve adsorbent.

[0064] Testing and Characterization:

[0065] Adsorption experiments: The adsorption performance of the adsorbents prepared in Examples 1 to 5 and Comparative Examples 1 to 4 was studied and compared through adsorption experiments. Several lithium halide aqueous solutions with different ionic compositions were prepared, and their compositions are listed in Table 1.

[0066] Table 1. Composition of the solution used in the adsorption experiment

[0067] <![CDATA[Li + (g / L)]]> 1.06 0.38 1.74 1.79 0.40 <![CDATA[Na + (g / L)]]> - 55.13 44.58 3.15 1.35 <![CDATA[K + (g / L)]]> - 8.68 0.87 1.86 0.48 <![CDATA[Mg 2+ (g / L)]]> - - - 86.40 120.33 pH 12.5 9.6 12.6 7.2 6.2

[0068] In the table above, a "-" indicates that the brine solution does not contain the corresponding ion.

[0069] The prepared adsorbents (1g each from the above examples and comparative examples) were added to 500mL of lithium-containing solution, and lithium adsorption experiments were conducted in a 30℃ water bath with a shaking speed of 200r / min. Samples were taken periodically until the lithium concentration remained constant and adsorption reached equilibrium. The lithium ion concentration in the solution before and after adsorption was measured using inductively coupled plasma optical emission spectrometry (ICP-OES), and the lithium adsorption capacity was calculated. The formula for calculating the adsorption capacity of the composite adsorbent is: In the formula, Q p To convert the mass of the composite adsorbent to the lithium adsorption capacity of the powdered lithium ion sieve, in mg / g; C0 and C e , respectively, are the lithium ion concentrations in the solution at the initial and equilibrium states of adsorption, mg / L; V is the volume of the lithium-containing solution, L; m is the mass of the composite adsorbent, g; w is the content of powdered lithium ion sieves in the composite adsorbent, %. Separation factor The calculation formula is: M represents other metal ions, K d This is the allocation coefficient.

[0070] The adsorption of lithium ions by various prepared adsorbents in different brines was tested, and the relevant adsorption experimental data are summarized in Table 2.

[0071] Table 2 Summary of Adsorption Data

[0072]

[0073]

[0074] In the table above, entries with relevant results indicate that relevant adsorption tests were conducted; entries with no relevant results marked with "-" indicate that no relevant adsorption tests were conducted.

[0075] During the process of forming a gel network through cross-linking between powdered adsorbents and binders, some adsorption sites are covered by the organic binder, which hinders effective contact between the adsorbent and lithium ions in the solution. Furthermore, the cross-linking process may affect the pore structure of the adsorbent, thereby affecting the diffusion and transport of lithium ions within it. Therefore, powdered adsorbents often experience a decrease in adsorption capacity after molding. Adsorption capacity, as an important indicator for evaluating the adsorption performance of an adsorbent, can vary significantly under different adsorption conditions. For lithium ion sieves, the adsorption capacity increases with increasing initial lithium concentration and solution pH. In the adsorption experiment of pure lithium solution A at pH 12.5, the adsorption capacity of the sample in Example 1 was 50.42 mg / g, while that of the sample in Comparative Example 1 was 44.65 mg / g. In Example 1, the added fluoropolymer, due to the affinity of fluorine atoms for lithium, can adsorb lithium ions in the solution based on the lithium bond formation principle. This not only assists in achieving efficient and rapid lithium adsorption but also, to some extent, compensates for the loss of adsorption capacity of powdered LTO caused by the molding process. Cyclic adsorption experiments were conducted on the sample prepared in Example 1. After ten cycles, its adsorption capacity remained at 98.33% of the initial adsorption capacity. The results indicate that the composite porous lithium-ion sieve adsorbent prepared in this invention has certain cyclic stability, which is beneficial for long-term cyclic use in industrial applications.

[0076] The adsorption selectivity of the samples from Example 1 and Comparative Example 1 in brine solution E was compared and investigated. Figure 1 The figure shows the selectivity of the adsorbent samples prepared in Example 1 and Comparative Example 1 for different metal ions in brine solution E. It can be seen that the molded composite porous lithium-ion sieve adsorbent prepared by adding fluoropolymer in Example 1 exhibits excellent selectivity for lithium ions. The composite porous lithium-ion sieve adsorbent still has excellent lithium selective extraction and separation ability in solutions with a high magnesium-to-lithium ratio, showing good application prospects.

[0077] Figure 2This figure shows the lithium-ion adsorption capacity of the adsorbent samples prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention in brine solution A at different times. As can be seen from the figure, the adsorption capacity of all samples gradually increases with time. Rapid adsorption occurs within the first 6 hours, and the adsorption capacity reaches 86.1%, 79.1%, and 81.7% of their equilibrium adsorption capacity at 6 hours, respectively. In the initial stage of adsorption, the sample surface has many adsorption sites, which can rapidly adsorb free lithium ions in the aqueous phase. The adsorption kinetics of the samples were analyzed using a pseudo-second-order kinetic equation, and the relevant parameters are listed in Table 3. Rate constant k2: Example 1 > Comparative Example 2 > Comparative Example 1, with the sample of Example 1 exhibiting the fastest adsorption rate. The fluoropolymer incorporated in the sample of Example 1 has a certain affinity for lithium, and the added pore-forming agent promotes the formation of a rich pore structure inside the adsorbent, thus exhibiting a relatively fast adsorption rate.

[0078] Table 3 Fitting parameters for pseudo-second-order adsorption kinetics

[0079] Example 1 50.42 0.0153 55.31 0.9975 Comparative Example 1 42.65 0.0099 48.19 0.9940 Comparative Example 2 47.02 0.0121 52.47 0.9957

[0080] This invention uses a binder to prepare a molded composite adsorbent from powdered adsorbents, avoiding material loss during subsequent recycling and effectively ensuring the recyclability of the adsorbent. It also provides a certain level of mechanical strength, improving the stability and service life of the molded material, which is beneficial for long-term recycling in industry.

[0081] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite porous lithium-ion sieve adsorbent, characterized in that: Includes the following steps: S1, a slurry is obtained by uniformly mixing lithium-ion sieve adsorbent precursor, fluoropolymer, binder, pore-forming agent and solvent; S2, the slurry obtained in step S1 is added dropwise to the crosslinking agent to form gel spheres. After static crosslinking, a composite porous lithium ion sieve adsorbent precursor is obtained. S3, the composite porous lithium ion sieve adsorbent precursor obtained in step S2 is eluted with lithium using an eluent to obtain the composite porous lithium ion sieve adsorbent. In step S1, the obtained slurry is a mixture of lithium-ion sieve adsorbent precursor, fluoropolymer, binder, and pore-forming agent. The mixture comprises the following components in the following mass fractions: lithium-ion sieve adsorbent precursor 20-40 wt%, fluoropolymer 10-40 wt%, binder 10-40 wt%, and pore-forming agent 5-20 wt%. The mass ratio of the mixture to the solvent is 1:(2-10). In step S1, the lithium-ion sieve adsorbent precursor is at least one of titanium-based adsorbent precursor and manganese-based adsorbent precursor. In step S1, the viscosity-average molecular weight of the fluoropolymer is 1000~50000; the fluoropolymer is at least one of polyvinylidene fluoride, perfluoroethylene propylene, perfluoroalkoxy polymer, and polytetrafluoroethylene. In step S1, the average molecular weight of the adhesive is 1,000 to 200,000; the adhesive is at least one of sodium alginate, polyvinyl alcohol, polyvinyl chloride, and polyacrylonitrile. In step S1, the pore-forming agent is at least one of nano-calcium carbonate, nano-magnesium carbonate, nano-manganese carbonate, and nano-zinc carbonate. In step S1, the solvent is at least one of water, N,N-dimethylformamide, ethanol, N-methylpyrrolidone, and dimethylacetamide.

2. The method for preparing a composite porous lithium-ion sieve adsorbent according to claim 1, characterized in that: In step S2, the crosslinking agent is at least one of water, calcium chloride solution, and boric acid solution; the volume ratio of crosslinking agent to slurry is (5~10):1; and the concentration of calcium chloride solution and boric acid solution does not exceed 1 mol / L.

3. The method for preparing a composite porous lithium-ion sieve adsorbent according to claim 1, characterized in that: In step S2, the slurry is added to the crosslinking agent and allowed to stand for crosslinking for 8-12 hours. Then, it is filtered, washed, and dried to obtain the composite porous lithium ion sieve adsorbent precursor. The drying temperature is 50-80℃ and the drying time is 4-12 hours.

4. The method for preparing a composite porous lithium-ion sieve adsorbent according to claim 1, characterized in that: In step S3, the eluent is at least one of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution; the concentration of the eluent is 0.1~0.5 mol / L.

5. The method for preparing a composite porous lithium-ion sieve adsorbent according to claim 1, characterized in that: In step S3, the composite porous lithium-ion sieve adsorbent is eluted with an eluent to remove lithium ions; then it is filtered, washed, and dried to obtain the composite porous lithium-ion sieve adsorbent. The solid-liquid ratio of the composite porous lithium-ion sieve adsorbent precursor to the eluent is (1~50):1, and the unit of the solid-liquid ratio is g:L; the elution temperature is 20~60℃, the elution time is 2~24 h, and the stirring speed during the elution process is 100~600 r / min. The drying temperature is 50~80℃, and the drying time is 4~12 h.

6. A composite porous lithium-ion sieve adsorbent, characterized in that: It is prepared by the preparation method according to any one of claims 1-5.

7. The application of the composite porous lithium-ion sieve adsorbent as described in claim 6 in lithium extraction from salt lakes.

Images