Lithium ion sieve adsorbent and preparation method and application thereof
By combining a polymer framework and a titanium-based lithium-ion sieve in the lithium-ion sieve adsorbent to form an interpenetrating network, and by modifying it with Gd doping, the problem of low adsorption capacity and selectivity of the lithium-ion sieve adsorbent is solved, and a highly efficient lithium-ion extraction effect is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2026-04-14
AI Technical Summary
Existing lithium-ion sieve adsorbents have low adsorption capacity and low selectivity, making it difficult to efficiently extract lithium resources from salt lake brines.
A combination of polymer framework and titanium-based lithium-ion sieve is adopted. An interpenetrating network is formed by polyacrylonitrile molecular chains and polymer molecular chains A, and the titanium-based lithium-ion sieve is dispersed in the framework. Furthermore, the diffusion kinetics of the lithium-ion sieve are improved by Gd doping modification.
This improved the adsorption performance and selectivity of the lithium-ion sieve adsorbent, reduced titanium dissolution loss, and achieved efficient lithium-ion adsorption and selective extraction.
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Figure CN121847097A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of adsorption materials, specifically to a lithium-ion sieve adsorbent, its preparation method, and its application. Background Technology
[0002] With the rapid development of the lithium battery industry, the demand for lithium resources from various sectors is continuously increasing, and the importance of lithium production is also growing. Currently, lithium resources are mainly distributed in lithium ore and salt lake brine, but lithium ore resources are constantly decreasing, and development costs are constantly increasing; in contrast, lithium resources in salt lake brine are low-cost and abundant. my country has abundant liquid lithium resources, but extracting lithium from lithium lake brine is a challenging task.
[0003] Currently, lithium extraction methods from salt lakes mainly include adsorption, precipitation, extraction, electrodialysis, and calcination. Among these, adsorption offers advantages such as simple process, energy efficiency, and high selectivity, outperforming other methods in terms of time and cost, and thus has broad application prospects. Since salt lake brine often suffers from low lithium content, the core of lithium extraction using adsorption methods is the preparation of highly selective adsorbents. Highly selective lithium adsorbents mainly include ion sieve adsorbents and amorphous hydroxide adsorbents. Manganese-based lithium ion sieves have large adsorption capacity but suffer from manganese dissolution loss; titanium-based lithium ion sieves have low dissolution loss and broad market prospects. However, compared to manganese-based lithium ion sieves, titanium-based lithium ion sieve adsorbents have lower adsorption capacity and lower selectivity. Therefore, there is an urgent need to develop highly efficient titanium-based lithium ion sieves. Summary of the Invention
[0004] The purpose of this invention is to overcome the problems of low adsorption capacity and low selectivity of existing lithium-ion sieve adsorbents, and to provide a lithium-ion sieve adsorbent, its preparation method, and its application. This lithium-ion sieve adsorbent comprises polyacrylonitrile molecular chains, polymer molecular chains A, and a titanium-based lithium-ion sieve dispersed in the polymer framework.
[0005] To achieve the above objectives, the first aspect of the present invention provides a lithium-ion sieve adsorbent, wherein the lithium-ion sieve adsorbent comprises a polymer framework and a lithium-ion sieve dispersed in the polymer framework;
[0006] The polymer backbone comprises a polyacrylonitrile molecular chain and a polymer molecular chain A, wherein the polymer molecular chain A comprises structural units represented by Formula I and / or Formula II; the lithium ion sieve is a titanium-based lithium ion sieve.
[0007]
[0008] In this configuration, R1 and R2 are each independently H or methyl; R3 is H, methyl, or isopropyl.
[0009] A second aspect of the present invention provides a method for preparing a lithium-ion sieve adsorbent, wherein the preparation method includes the following steps:
[0010] (1) Mix polyacrylonitrile, monomer A shown in Formula 1 and / or Formula 2 with a first solvent to obtain a first mixture;
[0011] (2) Add the titanium-based lithium-ion sieve to the first mixture for a second mixing to obtain the second mixture;
[0012] (3) The initiator and the third solvent are mixed in a third mixture to obtain a third mixture;
[0013] (4) The second mixture is added dropwise to the third mixture to carry out the polymerization reaction, and a lithium ion sieve adsorbent is obtained;
[0014]
[0015] In this configuration, R1 and R2 are each independently H or methyl; R3 is H, methyl, or isopropyl.
[0016] A third aspect of the present invention provides a lithium-ion sieve adsorbent prepared by the above-described preparation method.
[0017] The fourth aspect of the present invention provides an application of the above-mentioned lithium-ion sieve adsorbent in lithium extraction, preferably in lithium extraction in a liquid environment.
[0018] Through the above technical solutions, the lithium-ion sieve adsorbent, its preparation method, and its application provided by the present invention achieve the following beneficial effects:
[0019] (1) The lithium-ion sieve adsorbent provided by the present invention comprises polymer molecular chain A and polyacrylonitrile molecular chain of specific structural unit, which form an interpenetrating network and together serve as the skeleton of the lithium-ion sieve adsorbent. The titanium-based lithium-ion sieve is dispersed in the skeleton, thereby further improving the adsorption performance of the lithium-ion sieve adsorbent.
[0020] (2) In this invention, some titanium atoms in the titanium-based lithium-ion sieve are modified by Gd doping to form defects, which improves the diffusion dynamics of lithium ions in the unit cell. The titanium loss of the lithium-ion sieve adsorbent containing the doped and modified titanium-based lithium-ion sieve is significantly lower than that of the lithium-ion sieve adsorbent containing the unmodified titanium-based lithium-ion sieve.
[0021] (3) Further, monomer A can form ether-oxygen segments through self-polymerization or copolymerization, forming a semi-interpenetrating network structure with the polymer backbone of polyacrylonitrile, thereby enabling the titanium-based lithium-ion sieve to be uniformly dispersed in the polymer backbone containing ether-oxygen bonds. The network structure formed by ether-oxygen bonds in the vinyl polymer segments containing ether-oxygen bonds has a significant impact on the Li-ion sieve. + It has an affinity effect, so the lithium ion sieve adsorbent has a strong selectivity for lithium ions. Attached Figure Description
[0022] Figure 1 This is a SEM image of the lithium-ion sieve adsorbent from Example 1. Detailed Implementation
[0023] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0024] The first aspect of the present invention provides a lithium-ion sieve adsorbent, wherein the lithium-ion sieve adsorbent comprises a polymer framework and a lithium-ion sieve dispersed in the polymer framework;
[0025] The polymer backbone comprises a polyacrylonitrile molecular chain and a polymer molecular chain A, wherein the polymer molecular chain A comprises structural units represented by Formula I and / or Formula II; the lithium ion sieve is a titanium-based lithium ion sieve.
[0026]
[0027] In this configuration, R1 and R2 are each independently H or methyl; R3 is H, methyl, or isopropyl.
[0028] In this invention, the lithium-ion sieve adsorbent comprises polymer molecular chains A and polyacrylonitrile molecular chains of specific structural units, which form an interpenetrating network and together serve as the skeleton of the lithium-ion sieve adsorbent. The titanium-based lithium-ion sieve is dispersed in the skeleton, thereby further improving the adsorption performance of the lithium-ion sieve adsorbent.
[0029] Furthermore, R1, R2, and R3 are all H.
[0030] According to the present invention, preferably, the titanium-based lithium-ion sieve is a Gd-doped titanium-based lithium-ion sieve.
[0031] In this invention, some titanium atoms in the titanium-type lithium-ion sieve are modified by Gd doping to form defects, which improves the diffusion kinetics of lithium ions in the unit cell. The titanium dissolution loss of the doped and modified lithium-ion sieve adsorbent is significantly lower than that of the unmodified lithium-ion sieve adsorbent.
[0032] In one specific embodiment of the present invention, the titanium-based lithium-ion sieve has a composition of Li₂Gd. x Ti 1-x O3, 0.01≤x≤0.12.
[0033] In this invention, when the titanium-based lithium-ion sieve has the above-mentioned composition, the titanium-based lithium-ion sieve has low titanium dissolution loss, which makes the lithium-ion sieve adsorbent containing the titanium-based lithium-ion sieve have high adsorption capacity.
[0034] Furthermore, 0.06 ≤ x ≤ 0.1.
[0035] In this invention, there is no particular limitation on the source of the titanium-based lithium-ion sieve; it can be commercially available or prepared in-house using conventional methods in the field.
[0036] In one specific embodiment of the present invention, the preparation method of the titanium-based lithium-ion sieve includes: mixing a lithium source, a titanium source, and a Gd source, and then sintering them in an air atmosphere to obtain the titanium-based lithium-ion sieve.
[0037] According to the present invention, the amounts of the lithium source, the titanium source and the Gd source are such that n(Li):n(Ti):n(Gd) = 1:(0.44-0.495):(0.005-0.06).
[0038] Furthermore, the amounts of the lithium source, the titanium source, and the Gd source are such that n(Li):n(Ti):n(Gd) = 1:(0.45-0.47):(0.03-0.05).
[0039] According to the present invention, preferably, the sintering conditions include: heating from room temperature to 600-800°C at a heating rate of 1-5°C / min, and holding at that temperature for 6-8 hours.
[0040] In this invention, there is no particular limitation on the lithium source, and conventional lithium sources in the art can be used, such as lithium carbonate, lithium nitrate, lithium chloride, lithium sulfate, etc.
[0041] In this invention, there is no particular limitation on the titanium source; conventional titanium sources in the art, such as titanium dioxide, can be used.
[0042] In this invention, there is no particular limitation on the Gd source; conventional Gd sources in the art, such as gadolinium oxide, can be used.
[0043] According to the present invention, the average particle size of the titanium-based lithium ion sieve is 50-1000 nm.
[0044] In this invention, when the average particle size of the titanium-based lithium ion sieve is controlled to meet the above-mentioned range, the titanium-based lithium ion sieve has low titanium dissolution loss, which makes the lithium ion sieve adsorbent containing the titanium-based lithium ion sieve have high adsorption capacity.
[0045] In this invention, the average particle size of the titanium-based lithium ion sieve was measured using SEM electron microscopy.
[0046] Furthermore, the average particle size of the titanium-based lithium-ion sieve is 100-400 nm.
[0047] According to the present invention, based on the total weight of the lithium-ion sieve adsorbent, the content of polyacrylonitrile molecular chains is 10-25 wt%; the content of polymer molecular chain A is 0.2-9 wt%; and the content of the titanium-based lithium-ion sieve is 70-85 wt%.
[0048] In this invention, when the contents of polyacrylonitrile molecular chains, polymer molecular chains A, and titanium-based lithium-ion sieves in the lithium-ion sieve adsorbent meet the above-mentioned ranges, the lithium-ion sieve adsorbent can have a high adsorption capacity, as well as excellent structural stability and stability for long-term cyclic use.
[0049] In this invention, the contents of polyacrylonitrile molecular chains, polymer molecular chain A, and titanium-based lithium-ion sieves in the lithium-ion sieve adsorbent are determined by the following method, specifically:
[0050] The content of titanium-based lithium ion sieves was determined by X-ray photoelectron spectroscopy (XPS). The content of titanium-based lithium ion sieves was calculated from the content of metallic Ti (mass percentage of titanium-based lithium ion sieves (%) = mass percentage of titanium (%) / relative atomic mass of titanium (g / mol) × relative molecular mass of titanium-based lithium ion sieves (g / mol)).
[0051] The relative molecular mass of the titanium-based lithium ion sieve was determined by the following method: the titanium-based lithium ion sieve sample was dissolved in nitric acid, and the content of its metal ions was determined by ICP-MS to determine the composition of the titanium-based lithium ion sieve and obtain the relative molecular mass of the titanium-based lithium ion sieve.
[0052] Content of polyacrylonitrile molecular chain, polymer molecular chain A, and titanium-based lithium ion sieve: The mass percentage of cyano (-CN) is obtained by peak separation of fine spectrum. The content of structural units from polyacrylonitrile is calculated by the content of cyano (mass percentage of polyacrylonitrile structural units (%) = mass percentage of cyano (%) / relative molecular mass of cyano (g / mol) × relative molecular mass of polyacrylonitrile (g / mol)). The content of structural unit A of polymer molecular chain (%) = 1 - mass percentage of polyacrylonitrile structural units (%) - mass percentage of titanium-based lithium ion sieve (%).
[0053] Furthermore, based on the total weight of the lithium-ion sieve adsorbent, the content of polyacrylonitrile molecular chains is 12-20 wt%; the content of polymer molecular chain A is 3-8 wt%; and the content of the titanium-based lithium-ion sieve is 75-80 wt%.
[0054] According to the present invention, the average particle size of the lithium-ion sieve adsorbent is 1-5 mm.
[0055] In this invention, when the average particle size of the lithium-ion sieve adsorbent meets the above-mentioned range, the granular lithium-ion sieve adsorbent can have a high adsorption capacity.
[0056] Furthermore, the average particle size of the lithium-ion sieve adsorbent is 2-4 mm.
[0057] In this invention, the average particle size of the lithium-ion sieve adsorbent is measured using vernier calipers. Specifically, the testing method involves placing the adsorbent between the two clips of the vernier caliper, with the clips holding the diameter of the adsorbent in place, and then taking the reading. Each particle of the adsorbent is measured using the vernier caliper, and then the average value is taken.
[0058] According to the present invention, the average pore size of the lithium-ion sieve adsorbent is 0.1-10 μm.
[0059] In this invention, when the average pore size of the lithium-ion sieve adsorbent meets the above-mentioned range, the lithium-ion sieve adsorbent can have a high adsorption capacity.
[0060] Furthermore, the average pore size of the lithium-ion sieve adsorbent profile is 0.5-2.5 μm.
[0061] In this invention, the average pore size of the lithium-ion sieve adsorbent profile was measured using a scanning electron microscope. Specifically, the testing method involved randomly selecting 10 observation points for scanning electron microscopy, with each observation area being no less than 500 × 500 μm, and then calculating the average value.
[0062] According to the present invention, the specific surface area of the lithium-ion sieve adsorbent is 10-100 m². 2 / g.
[0063] In this invention, when the specific surface area of the lithium-ion sieve adsorbent meets the above-mentioned range, the lithium-ion sieve adsorbent can have a faster water mass transfer rate.
[0064] In this invention, the specific surface area of the lithium-ion sieve adsorbent is determined using the BET method.
[0065] Furthermore, the specific surface area of the lithium-ion sieve adsorbent is 20-50 m². 2 / g.
[0066] A second aspect of the present invention provides a method for preparing a lithium-ion sieve adsorbent, wherein the preparation method includes the following steps:
[0067] (1) Mix polyacrylonitrile, monomer A shown in Formula 1 and / or Formula 2 with a first solvent to obtain a first mixture;
[0068] (2) Add the titanium-based lithium-ion sieve to the first mixture for a second mixing to obtain the second mixture;
[0069] (3) The initiator and the third solvent are mixed in a third mixture to obtain a third mixture;
[0070] (4) The second mixture is added dropwise to the third mixture to carry out the polymerization reaction, and a lithium ion sieve adsorbent is obtained;
[0071]
[0072] In this configuration, R1 and R2 are each independently H or methyl; R3 is H, methyl, or isopropyl.
[0073] In this invention, a mixed solution containing polyacrylonitrile, monomer A as shown in Formula 1 and / or Formula 2, and a titanium-based lithium-ion sieve undergoes a phase inversion in a second mixed solution containing an initiator. Monomer A as shown in Formula 1 and / or Formula 2 can form ether-oxygen segments through self-polymerization or copolymerization, forming a semi-interpenetrating network structure with the polymer backbone of polyacrylonitrile, thereby ensuring uniform dispersion of the lithium-ion sieve within the polymer backbone containing ether-oxygen bonds. Furthermore, the network structure formed by ether-oxygen bonds in the resulting vinyl polymer segments with ether-oxygen bonds affects the lithium-ion sieve. + Due to its affinity, the titanium-based lithium-ion sieve adsorbent exhibits strong selectivity for lithium ions. By employing the specific mixing sequence described above, the dispersion of the titanium-based lithium-ion sieve within the polymer framework becomes more uniform, resulting in a high adsorption capacity.
[0074] In one specific embodiment of the present invention, monomer A is N-acryloylmorpholine, i.e., in Formula 1, R1 is H.
[0075] In another specific embodiment of the present invention, monomer A is N-(2-morpholinoethyl)acrylamide, that is, in formula 2, R2 and R3 are H.
[0076] In this invention, the conditions for the first mixing and the second mixing each independently include: a temperature of 40-90°C and a time of 12-30h.
[0077] In this invention, the first solvent is a conventional organic solvent in the art, such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, etc. There is no particular limitation on the amount of the first solvent used, as long as it ensures that the polyacrylonitrile, monomer A, and titanium-based lithium-ion sieve are thoroughly and uniformly mixed.
[0078] According to the present invention, the titanium-based lithium-ion sieve is a Gd-doped titanium-based lithium-ion sieve.
[0079] In this invention, some titanium atoms in the titanium-based lithium-ion sieve are modified by Gd doping to form defects, which improves the diffusion kinetics of lithium ions in the unit cell. The titanium dissolution loss of the doped lithium-ion sieve adsorbent is significantly lower than that of the unmodified lithium-ion sieve adsorbent.
[0080] According to the present invention, the titanium-based lithium-ion sieve has the composition Li₂Gd. x Ti 1-x O3, 0.01≤x≤0.12.
[0081] Furthermore, 0.06 ≤ x ≤ 0.1.
[0082] According to the present invention, the average particle size of the titanium-based lithium ion sieve is 50-1000 nm.
[0083] Furthermore, the average particle size of the titanium-based lithium-ion sieve is 100-400 nm.
[0084] According to the present invention, the weight-average molecular weight of the polyacrylonitrile is 50,000 to 250,000 g / mol.
[0085] In this invention, when the weight-average molecular weight of polyacrylonitrile meets the above-mentioned range, it forms an interpenetrating network with polymer molecular chain A, which together serve as the skeleton of the lithium-ion sieve adsorbent. The titanium-based lithium-ion sieve is dispersed in the skeleton, which can result in a lithium-ion sieve adsorbent with high adsorption capacity and magnesium-lithium selectivity.
[0086] Furthermore, the weight-average molecular weight of the polyacrylonitrile is 80,000-100,000 g / mol.
[0087] According to the present invention, based on the total weight of polyacrylonitrile, monomer A and titanium-based lithium ion sieve, the amount of polyacrylonitrile is 10-25 wt%; the amount of monomer A is 0.2-9 wt%; and the amount of titanium-based lithium ion sieve is 70-85 wt%.
[0088] In this invention, by controlling the amounts of polyacrylonitrile, monomer A, and titanium-based lithium-ion sieve to meet the above-mentioned ranges, the resulting lithium-ion sieve adsorbent can achieve high adsorption capacity and magnesium-lithium selectivity.
[0089] In this invention, when monomer A includes both monomer A1 as shown in Formula 1 and monomer A2 as shown in Formula 2, there are no special requirements for the amount of monomer A1 and monomer A2 used respectively, as long as the total amount of monomer A used meets the requirements of this invention.
[0090] Furthermore, based on the total weight of polyacrylonitrile, monomer A, and titanium-based lithium-ion sieve, the amount of polyacrylonitrile is 12-20 wt%; the amount of monomer A is 3-8 wt%; and the amount of titanium-based lithium-ion sieve is 75-80 wt%.
[0091] According to the present invention, the initiator is selected from at least one of potassium persulfate, ammonium persulfate and azobisisobutyronitrile.
[0092] In this invention, there is no particular limitation on the type of the second solvent, as long as it can ensure that the initiator is fully and uniformly mixed. For example, the second solvent is water.
[0093] According to the present invention, the concentration of the initiator in the third mixture is 1-5 wt%.
[0094] Furthermore, the concentration of the initiator in the third mixture is 1-3 wt%.
[0095] According to the present invention, the amounts of the second mixture and the third mixture are such that, based on the amount of monomer A, the amount of initiator is 0.5-3 wt%.
[0096] In this invention, when the amounts of monomer A and initiator are controlled to satisfy the above relationship, the lithium-ion sieve adsorbent formed after the polymerization reaction can have high adsorption capacity and magnesium-lithium selectivity.
[0097] Furthermore, based on the amount of monomer A, the amount of initiator is 1-2 wt%.
[0098] According to the present invention, the conditions for the polymerization reaction include: a polymerization temperature of 50-80°C and a polymerization time of 12-24 h.
[0099] In this invention, the polymerization reaction carried out under the above conditions enables the titanium-based lithium ion sieve to be uniformly dispersed in the framework of the prepared lithium ion sieve adsorbent, thereby making the lithium ion sieve adsorbent hydrophilic and improving the adsorption capacity and selectivity of the lithium ion sieve adsorbent.
[0100] Furthermore, the conditions for the polymerization reaction include: a polymerization temperature of 60-70℃ and a polymerization time of 14-20h.
[0101] In this invention, there are no special requirements for the dripping rate of the second mixture into the third mixture, as long as it can make the particles form and have a certain strength so that they can be recycled multiple times. Preferably, the dripping rate is 0.5-5 mL / min, and more preferably 1-3 mL / min.
[0102] According to the present invention, the method further includes the step of washing the lithium-ion sieve adsorbent with an acidic solution.
[0103] In this invention, the lithium-ion sieve adsorbent is a titanium-based lithium-ion sieve precursor. The lithium-ion sieve adsorbent is washed with an acidic solution to remove the Li+ in the precursor. + and H + The precursor is activated by exchange to obtain H-type lithium ion sieve adsorbent, which has a specific adsorption effect on lithium ions.
[0104] Furthermore, the lithium-ion sieve adsorbent is circulated and washed using an acidic solution under the action of a peristaltic pump.
[0105] Furthermore, the acidic solution is selected from at least one of hydrochloric acid, phosphoric acid, and sulfuric acid.
[0106] Furthermore, with H + The concentration of the acidic solution is calculated to be 0.1-1 mol / L.
[0107] Furthermore, the flow rate of the peristaltic pump is 1-6 BV / h, and the circulation time is 1-24h.
[0108] A third aspect of the present invention provides a lithium-ion sieve adsorbent prepared by the above-described preparation method.
[0109] The fourth aspect of the present invention provides an application of the above-mentioned lithium-ion sieve adsorbent in lithium extraction, preferably in lithium extraction in a liquid environment.
[0110] The present invention will be described in detail below through embodiments.
[0111] Test case
[0112] The lithium-ion sieve adsorbents prepared in the examples and comparative examples were subjected to the following measurements:
[0113] Adsorption capacity: The obtained granulated particles (4g) were packed into a glass column and acid-washed (using H2O). + The adsorption-desorption cycle was performed for 24 hours using 0.5 mol / L hydrochloric acid at a flow rate of 2 mL / min. A mixture of lithium chloride, sodium chloride, and magnesium chloride (lithium ion concentration 1000 mg / L, magnesium ion concentration 1000 mg / L, sodium ion concentration 1000 mg / L, pH adjusted to 9.5 with ammonia-ammonium chloride buffer, V = 400 mL) was then pumped in at a flow rate of 2 mL / min using a peristaltic pump for 24 hours to desorb lithium ions from the particles. The particles were then washed with deionized water until neutral, constituting one cycle. During one adsorption process, the change in adsorption capacity over time was monitored, and the saturated adsorption capacity Q was calculated using the following formula:
[0114]
[0115] Where Q is the saturated adsorption capacity in mg / g, reflecting the amount of adsorption at equilibrium; C0 and C are the initial and saturated ion concentrations in the solution, respectively, in mg / L; V is the volume of the adsorption solution in L; and m is the mass of the particulate adsorbent in g. Ion concentrations were determined using ion chromatography (ICS-1100, DIONEX, America).
[0116] Test method for Ti dissolution:
[0117] (1) Take 0.5 g of the titanium-based lithium ion sieves from Preparation Examples 1-6, add them to 50 mL of 5 M hydrochloric acid, stir for 24 h, centrifuge, and test the concentration of Ti in the supernatant by ICP-MS. Ti Unit: mg / L. Dissolution rate η = (c Ti *V) / m Ti *100%, where m Ti V represents the mass of Ti in 0.5g of titanium-based lithium-ion sieve, and V is the volume of hydrochloric acid (L).
[0118] (2) Pack 4 g of the lithium-ion sieve adsorbent prepared in the examples and comparative examples into a column, and pump 500 mL of 5 M hydrochloric acid at a flow rate of 2 mL / min using a peristaltic pump, circulating for 24 h. The concentration of Ti in the circulating solution, c, was measured by ICP-MS. Ti The unit is mg / L. Dissolution rate η = (c Ti *V) / m Ti *100%, where m Ti V represents the mass of Ti in 4g of lithium-ion sieve adsorbent, and V represents the volume of hydrochloric acid (L).
[0119] The morphology of the lithium-ion sieve adsorbent and the average pore size of the lithium-ion sieve adsorbent profile were characterized by scanning electron microscopy (SEM, S-4800).
[0120] The specific surface area was determined by the BET method. Specifically, the adsorption-desorption isotherm of N2 by the lithium-ion sieve adsorbent was measured at 77 K, and the BET specific surface area was obtained by fitting the isotherm.
[0121] Average particle size of lithium-ion sieve adsorbent: The average particle size of the lithium-ion sieve adsorbent is measured using vernier calipers. Specifically, the test method involves placing the adsorbent between the two clips of the vernier caliper, with the clips holding the diameter of the adsorbent in place, and then taking the reading. Each adsorbent particle is measured using the vernier caliper, and the average value is then calculated.
[0122] The content of each component was determined by X-ray photoelectron spectroscopy (XPS). The content of titanium-based lithium-ion sieves was calculated from the metallic Ti content (mass percentage of titanium-based lithium-ion sieves (%) = mass percentage of titanium (%) / relative atomic mass of titanium (g / mol) × relative molecular mass of titanium-based lithium-ion sieves (g / mol)). After dissolving the titanium-based lithium-ion sieve sample in nitric acid, the content of metal ions was determined by ICP-MS to determine the composition of the titanium-based lithium-ion sieves and obtain their relative molecular mass.
[0123] Content of polyacrylonitrile molecular chain, polymer molecular chain A, and titanium-based lithium ion sieve: The mass percentage of cyano (-CN) is obtained by peak separation of fine spectrum. The content of structural units from polyacrylonitrile is calculated by the content of cyano (mass percentage of polyacrylonitrile structural units (%) = mass percentage of cyano (%) / relative molecular mass of cyano (g / mol) × relative molecular mass of polyacrylonitrile (g / mol)). The content of structural unit A of polymer molecular chain A = 1 - mass percentage of polyacrylonitrile structural units (%) - mass percentage of titanium-based lithium ion sieve (%).
[0124] In the following examples and comparative examples: all reagents were purchased from Bailingwei Technology Co., Ltd.
[0125] Preparation Example 1
[0126] Lithium carbonate, titanium dioxide, and gadolinium oxide were ground in a mortar for 30 min at a Li:Gd:Ti molar ratio of 1:0.05:0.46. The mixed sample was then placed in a crucible, which was placed in a muffle furnace and heated to 700℃ at a rate of 3℃ / min, held at that temperature for 8 h, and then cooled to room temperature. This yielded a titanium-based lithium-ion sieve, T1. The Ti dissolution rate in T1 was 0.8%.
[0127] Preparation Example 2
[0128] Lithium carbonate, titanium dioxide, and gadolinium oxide were ground in a mortar for 30 min at a Li:Gd:Ti molar ratio of 1:0.03:0.48. The mixed sample was then placed in a crucible and placed in a muffle furnace. The temperature was increased to 800℃ at a rate of 3℃ / min and held for 6 h, then cooled to room temperature. This yielded a titanium-based lithium-ion sieve, T2. The Ti dissolution rate in T2 was 1.2%.
[0129] Preparation Example 3
[0130] Lithium carbonate, titanium dioxide, and gadolinium oxide were ground in a mortar for 30 min at a Li:Gd:Ti molar ratio of 1:0.06:0.45. The mixed sample was then placed in a crucible and placed in a muffle furnace. The temperature was increased to 600℃ at a rate of 3℃ / min, held for 6 h, and then cooled to room temperature. This yielded a titanium-based lithium-ion sieve, T3. The Ti dissolution rate in T3 was 1.4%.
[0131] Preparation Example 4
[0132] Lithium carbonate, titanium dioxide, and gadolinium oxide were ground in a mortar for 30 min at a Li:Gd:Ti molar ratio of 1:0.25:0.3. The mixed sample was then placed in a crucible, which was placed in a muffle furnace and heated to 600℃ at a rate of 3℃ / min, held at that temperature for 6 h, and then cooled to room temperature. This yielded a titanium-based lithium-ion sieve, T4. The Ti dissolution rate in T4 was 1.6%.
[0133] Preparation Example 5
[0134] Lithium carbonate and titanium dioxide were ground in a mortar for 30 min at a Li:Ti molar ratio of 1:0.5. The mixed sample was then placed in a crucible, which was placed in a muffle furnace and heated to 600℃ at a rate of 3℃ / min, held at that temperature for 6 h, and then cooled to room temperature. This yielded a titanium-based lithium-ion sieve, T5. The Ti dissolution rate in T5 was 1.8%.
[0135] Preparation Example 6
[0136] Lithium carbonate, titanium dioxide, and calcium chloride were ground in a mortar for 30 min at a Li:Ca:Ti molar ratio of 1:0.05:0.46. The mixed sample was then placed in a crucible and placed in a muffle furnace. The temperature was increased to 600℃ at a rate of 3℃ / min, held at that temperature for 6 h, and then cooled to room temperature. Titanium-based lithium-ion sieve T6 was obtained. The Ti dissolution rate in T6 was 2.6%.
[0137] The composition, average particle size, and titanium dissolution loss of the titanium-based lithium-ion sieve prepared in the preparation example were tested, and the results are shown in Table 1.
[0138] Table 1
[0139] composition Average particle size / nm Ti dissolution loss% Preparation Example 1 (T1) <![CDATA[Li2Gd 0.1 Ti 0.9 O3]]> 300 0.8 Preparation Example 2 (T2) <![CDATA[Li2Gd 0.06 Ti 0.94 O3]]> 320 1.2 Preparation Example 3 (T3) <![CDATA[Li2Gd 0.12 Ti 0.88 O3]]> 290 1.4 Preparation Example 4 (T4) <![CDATA[Li2Gd 0.5 Ti 0.5 O3]]> 310 1.6 Preparation Example 5 (T5) <![CDATA[Li2TiO3]]> 315 1.8 Preparation Example 6 (T6) <![CDATA[Li2Ca 0.1 Ti 0.9 O3]]> 350 2.6
[0140] Example 1
[0141] (1) Dissolve polyacrylonitrile powder and N-acryloylmorpholine (R1 is H in Formula 1) in DMF and stir at 60°C for 24 h to obtain the first mixture.
[0142] (2) Add T1 to the first mixture from (1) and stir at 60°C for 24 hours to obtain the second mixture. The total weight of polyacrylonitrile, monomer A, and titanium-based lithium-ion sieve is 19.2 wt%, monomer A is 3.8 wt%, and titanium-based lithium-ion sieve T1 is 77 wt%. The weight-average molecular weight of polyacrylonitrile is 85,000 g / mol.
[0143] (3) Ammonium persulfate is mixed with water to obtain a third mixture, wherein the concentration of ammonium persulfate in the third mixture is 1 wt%.
[0144] (4) Take the second mixture and add it dropwise to the third mixture at a rate of 1 mL / min. Soak at 60°C for 12 h, then rinse thoroughly with deionized water to obtain lithium ion sieve adsorbent M1. The amount of initiator is 1 wt%, based on the amount of monomer A.
[0145] Example 2
[0146] (1) Prepare polyacrylonitrile powder and N-acryloylmorpholine (R1 is H in Formula 1) and dissolve them in DMF. Stir at 60°C for 24 hours to obtain the first mixture.
[0147] (2) Add T1 to the first mixture from (1) and stir at 60°C for 24 hours to obtain the second mixture. The total weight of polyacrylonitrile, monomer A, and titanium-based lithium-ion sieve is used as the basis, with polyacrylonitrile accounting for 12 wt%, monomer A for 8 wt%, and titanium-based lithium-ion sieve T1 for 80 wt%. The weight-average molecular weight of polyacrylonitrile is 85,000 g / mol.
[0148] (3) Ammonium persulfate is mixed with water to obtain a third mixture, wherein the concentration of ammonium persulfate in the third mixture is 1 wt%.
[0149] (4) Take the second mixture and add it dropwise to the third mixture at a rate of 1 mL / min. Soak at 60°C for 12 h, then rinse thoroughly with deionized water to obtain lithium ion sieve adsorbent M2. The amount of initiator is 1 wt%, based on the amount of monomer A.
[0150] Example 3
[0151] (1) Prepare polyacrylonitrile powder and N-acryloylmorpholine (R1 is H in Formula 1) and dissolve them in DMF. Stir at 60°C for 24 hours to obtain the first mixture.
[0152] (2) Add T1 to the first mixture from (1) and stir at 60°C for 24 hours to obtain the second mixture. The total weight of polyacrylonitrile, monomer A, and titanium-based lithium-ion sieve is used as the basis, with polyacrylonitrile accounting for 23 wt%, monomer A for 0.2 wt%, and titanium-based lithium-ion sieve T1 for 76.8 wt%. The weight-average molecular weight of polyacrylonitrile is 85,000 g / mol.
[0153] (3) Ammonium persulfate is mixed with water to obtain a third mixture, wherein the concentration of ammonium persulfate in the third mixture is 1 wt%.
[0154] (3) Take the second mixture and add it dropwise to the third mixture at a rate of 1 mL / min. Soak at 60°C for 12 h, then rinse thoroughly with deionized water to obtain lithium ion sieve adsorbent M3. The amount of initiator is 1 wt%, based on the amount of monomer A.
[0155] Example 4
[0156] Similar to Example 1, except that an equal mass of N-(2-morpholinoethyl)acrylamide (R2 and R3 in Formula 2 are H) was used to replace monomer A in Example 1 to obtain lithium ion sieve adsorbent M4.
[0157] Example 5
[0158] Similar to Example 1, except that an equal mass of titanium-based lithium-ion sieve T2 was used instead to obtain lithium-ion sieve adsorbent M5.
[0159] Example 6
[0160] Similar to Example 1, except that an equal mass of titanium-based lithium-ion sieve T3 was used instead to obtain lithium-ion sieve adsorbent M6.
[0161] Example 7
[0162] Similar to Example 1, except that an equal mass of titanium-based lithium-ion sieve T4 was used instead to obtain lithium-ion sieve adsorbent M7.
[0163] Example 8
[0164] Similar to Example 1, except that the total weight of polyacrylonitrile, monomer A, and titanium-based lithium-ion sieve was used as the basis, with polyacrylonitrile accounting for 58 wt%, monomer A for 11 wt%, and titanium-based lithium-ion sieve T1 for 31 wt%. This yielded lithium-ion sieve adsorbent M8.
[0165] Example 9
[0166] Similar to Example 1, except that an equal mass of titanium-based lithium-ion sieve T5 was used instead to obtain lithium-ion sieve adsorbent M9.
[0167] Example 10
[0168] Similar to Example 1, except that an equal mass of titanium-based lithium-ion sieve T6 was used instead to obtain lithium-ion sieve adsorbent M10.
[0169] Comparative Example 1
[0170] Similar to Example 1, except that monomer A was not added in step (1) to obtain lithium ion sieve adsorbent N1.
[0171] Comparative Example 2
[0172] (1) Dissolve polyacrylonitrile powder in DMF and stir at 60°C for 24 hours to obtain the first mixture.
[0173] (2) Add T5 to the first mixture from (1) and stir at 60°C for 24 hours to obtain the second mixture. The amount of polyacrylonitrile (PAI) is 20 wt%, and the amount of titanium-based lithium-ion sieve T5 is 80 wt%, based on the total weight of the PAI and T5. The weight-average molecular weight of PAI is 85,000 g / mol.
[0174] (3) Ammonium persulfate is mixed with water to obtain a third mixture, wherein the concentration of ammonium persulfate in the third mixture is 1 wt%.
[0175] (4) Take the second mixture and add it dropwise to the third mixture at a rate of 1 mL / min. Soak at 60°C for 12 h, then rinse thoroughly with deionized water to obtain lithium ion sieve adsorbent N2. The amount of initiator is 1 wt%, based on the amount of monomer A.
[0176] The titanium-based lithium-ion sieve adsorbents prepared in the examples and comparative examples were tested. The contents of polyacrylonitrile molecular chains, ether-oxygen-containing polymer molecular chains A, titanium-based lithium-ion sieve content, specific surface area, average pore size and average particle size of the lithium-ion sieve adsorbent are shown in Table 2.
[0177] Table 2
[0178]
[0179] Test case
[0180] The saturated adsorption capacity, magnesium-lithium selectivity coefficient, and titanium dissolution loss of the lithium-ion sieve adsorbent were tested, and the results are shown in Table 3.
[0181] Table 3
[0182] Saturated adsorption capacity (mg / g) Magnesium-lithium selectivity coefficient Ti dissolution loss% Example 1 18.2 5209 1 Example 2 18.1 5347 1.1 Example 3 14.6 4536 1.6 Example 4 15.1 4365 1.5 Example 5 18 5412 1.2 Example 6 16.2 4789 1.5 Example 7 15.5 4621 1.6 Example 8 12.1 3546 1.8 Example 9 12.8 4125 1.7 Example 10 11.5 3090 2.3 Comparative Example 1 11.3 2894 1.9 Comparative Example 2 10.9 1575 2.5
[0183] Figure 1 The image shows the SEM image of the lithium-ion sieve adsorbent in Example 1. N-Acryloylmorpholine can form ether oxygen segments through self-polymerization, which form a semi-interpenetrating network structure with the polymer backbone of polyacrylonitrile, thereby enabling the titanium-based lithium-ion sieve to be uniformly dispersed in the polymer backbone containing ether oxygen bonds.
[0184] Compared with Comparative Examples 1-2, in the embodiments provided by the present invention, N-acryloylmorpholine and the like form ether oxygen segments through self-polymerization, which form a semi-interpenetrating network structure with the polymer backbone of polyacrylonitrile. The titanium-based lithium ion sieve is uniformly dispersed in the polymer backbone containing ether oxygen bonds, thus resulting in a larger adsorption capacity and stronger selectivity.
[0185] Compared to Example 1, Comparative Example 1 did not provide ether oxygen-containing segments, resulting in a low selectivity coefficient for magnesium and lithium in the lithium-ion sieve adsorbent. The network structure formed by the ether oxygen bonds in the vinyl polymer segments containing ether oxygen bonds in the examples exhibits poor selectivity for Li... + It has an affinity effect, so the adsorbent particles are highly selective for lithium ions.
[0186] Compared with Comparative Example 2, in the embodiments provided by the present invention, some titanium atoms in the titanium-based lithium-ion sieve are modified by Gd doping to form defects, which improves the diffusion kinetics of lithium ions in the unit cell.
[0187] I93704BHY
[0188] The titanium loss of the modified lithium-ion sieve adsorbent is significantly lower than that of the unmodified lithium-ion sieve adsorbent, and the selectivity coefficient for magnesium and lithium is higher.
[0189] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A lithium-ion sieve adsorbent, characterized in that, The lithium-ion sieve adsorbent comprises a polymer framework and a lithium-ion sieve dispersed in the polymer framework; The polymer backbone comprises a polyacrylonitrile molecular chain and a polymer molecular chain A, wherein the polymer molecular chain A comprises structural units represented by Formula I and / or Formula II; the lithium ion sieve is a titanium-based lithium ion sieve. In this configuration, R1 and R2 are each independently H or methyl; R3 is H, methyl, or isopropyl.
2. The lithium-ion sieve adsorbent according to claim 1, wherein, R1, R2, and R3 are all H. Preferably, the titanium-based lithium-ion sieve is a Gd-doped titanium-based lithium-ion sieve; Preferably, the titanium-based lithium-ion sieve has a composition of Li₂Gd. x Ti 1-x O3, 0.01≤x≤0.12; Preferably, the average particle size of the titanium-based lithium ion sieve is 50-1000 nm.
3. The lithium-ion sieve adsorbent according to claim 1 or 2, wherein, Based on the total weight of the lithium-ion sieve adsorbent, the content of polyacrylonitrile molecular chains is 10-25 wt%; the content of polymer molecular chain A is 0.2-9 wt%; and the content of titanium-based lithium-ion sieve is 70-85 wt%. Preferably, based on the total weight of the lithium-ion sieve adsorbent, the content of polyacrylonitrile molecular chains is 12-20 wt%; the content of polymer molecular chain A is 3-8 wt%; and the content of the titanium-based lithium-ion sieve is 75-80 wt%.
4. The lithium-ion sieve adsorbent according to any one of claims 1-3, wherein, The average particle size of the lithium-ion sieve adsorbent is 1-5 mm. Preferably, the lithium-ion sieve adsorbent has an average pore size of 0.1-10 μm; Preferably, the specific surface area of the lithium-ion sieve adsorbent is 10-100 m². 2 / g.
5. A method for preparing a lithium-ion sieve adsorbent, characterized in that, The preparation method includes the following steps: (1) Polyacrylonitrile, monomer A shown in Formula 1 and / or Formula 2 are mixed with a first solvent to obtain a first mixture; (2) Add the titanium-based lithium-ion sieve to the first mixture and mix it again to obtain the second mixture; (3) The initiator and the third solvent are mixed in a third mixture to obtain a third mixture; (4) The second mixture is added dropwise to the third mixture to carry out the polymerization reaction, and a lithium ion sieve adsorbent is obtained; In this configuration, R1 and R2 are each independently H or methyl; R3 is H, methyl, or isopropyl.
6. The preparation method according to claim 5, wherein, The titanium-based lithium-ion sieve is a Gd-doped titanium-based lithium-ion sieve. Preferably, the titanium-based lithium-ion sieve has a composition of Li₂Gd. x Ti 1-x O3, 0.01≤x≤0.12; Preferably, the average particle size of the titanium-based lithium ion sieve is 50-1000 nm.
7. The preparation method according to claim 5 or 6, wherein, The weight-average molecular weight of the polyacrylonitrile is 50,000-250,000 g / mol; Preferably, the initiator is selected from at least one of potassium persulfate, ammonium persulfate, and azobisisobutyronitrile; Preferably, the concentration of the initiator in the third mixture is 1-5 wt%.
8. The preparation method according to any one of claims 5-7, wherein, In step (1), based on the total weight of polyacrylonitrile, monomer A and titanium-based lithium ion sieve, the amount of polyacrylonitrile is 10-25 wt%; the amount of monomer A is 0.2-9 wt%; and the amount of titanium-based lithium ion sieve is 70-85 wt%. Preferably, the amount of initiator is 0.5-3 wt%, based on the amount of monomer A.
9. The preparation method according to any one of claims 5-8, wherein, The conditions for the polymerization reaction include: a polymerization temperature of 50-80℃ and a polymerization time of 12-24h.
10. The preparation method according to any one of claims 5-9, wherein, The preparation method of the titanium-based lithium-ion sieve includes: The titanium source, lithium source and Gd source are mixed and sintered in air atmosphere to obtain the titanium-based lithium ion sieve. Preferably, the amounts of the lithium source, the titanium source, and the Gd source are such that n(Li):n(Ti):n(Gd) = n(Li):n(Ti):n(Gd) = 1:(0.44-0.495):(0.005-0.06); Preferably, the sintering conditions include: heating from room temperature to 600-800°C at a heating rate of 1-5°C / min, and holding at that temperature for 6-8 hours.
11. The preparation method according to any one of claims 5-10, wherein, The method further includes the step of washing the lithium-ion adsorbent with an acidic solution; Preferably, the lithium-ion adsorbent is circulated and washed using an acidic solution under the action of a peristaltic pump; Preferably, the acidic solution is selected from at least one of hydrochloric acid, phosphoric acid, and sulfuric acid; Preferably, H + The concentration of the acidic solution is calculated to be 0.1-1 mol / L; Preferably, the flow rate of the peristaltic pump is 1-6 BV / h, and the circulation time is 1-24h.
12. A lithium-ion sieve adsorbent prepared by the preparation method according to any one of claims 5-11.
13. The application of the lithium-ion sieve adsorbent according to any one of claims 1-4 and 12 in lithium extraction, preferably in a liquid environment.