Double-site doped titanium lithium ion sieve adsorbent as well as preparation method and application thereof

Abstract

The invention discloses a double-site doped titanium lithium ion sieve adsorbent as well as a preparation method and application thereof. The adsorbent is a lithium removal product of a double-site doped titanium lithium ion sieve adsorbent precursor, the chemical general formula of the double-site doped titanium lithium ion sieve adsorbent precursor is Li (2-x) MxTi (1-y) NyOz, M is at least one of Na < + >, K < + >, Zn < 2 + >, Co < 2 + >, Ni < 2 + >, Mg < 2 + > and Al < 3 + > and occupies Li site, N is at least one of Cr < 3 + >, Fe < 3 + >, Zr < 4 + >, Nb < 5 + >, Ta < 5 + >, V < 5 + >, Mo < 6 + > and W < 6 + > and occupies Ti site, x is larger than or equal to 0.001 and smaller than or equal to 0.5, and y is larger than or equal to 0.001 and smaller than or equal to 0.5. Metal cations are introduced to replace Li sites and Ti sites at the same time, Li site substitution enlarges interlayer spacing and improves Li < + > diffusion rate, Ti site substitution regulates local chemical bond and electron distribution, stabilizes lattice structure and enhances electron conduction, and through double-site doping, 'ion-electron 'double channels are constructed, so that a collaborative optimization effect is achieved. The double-site doped titanium lithium ion sieve adsorbent disclosed by the invention is applied to adsorption and extraction of lithium in a Bayer process sodium aluminate solution, and the adsorbent shows excellent adsorption performance.

Description

Technical Field

[0001] The present invention belongs to the field of preparation and application of lithium ion sieve adsorbents, and specifically relates to a dual-site doped titanium-based lithium ion sieve adsorbent and a preparation method and application thereof. Background Art

[0002] Lithium, known as the "energy metal of the 21st century," is widely used in new energy vehicles, glass, ceramics, aerospace, and medicine due to its unique physical and chemical properties. The development of traditional solid lithium mineral resources is facing high costs, high energy consumption, and severe environmental challenges, gradually exposing its sustainability limitations. Against this backdrop, liquid lithium resources have become a new focus of global lithium resource development due to their abundant reserves, low energy consumption, and environmental friendliness. Currently, the main methods for extracting lithium from solutions include precipitation, extraction, membrane, and adsorption. Among them, adsorption has become one of the most commonly used lithium extraction methods due to its low cost, high efficiency, environmental friendliness, and suitability for lithium extraction from low-concentration solutions. The core of the adsorption method is the preparation of adsorbents with high adsorption capacity, high adsorption rate, excellent ion selectivity, and cyclic stability.

[0003] At present, organic adsorbents have low selectivity for lithium ions and high costs, which limit their application. Inorganic adsorbents are more studied, mainly including aluminum-based lithium adsorbents and lithium ion sieve adsorbents. Among them, aluminum-based lithium adsorbents have low adsorption capacity and poor ion selectivity, and manganese-based lithium ion sieves have low Mn in the elution process. 3+ The dissolution problem is serious, affecting its adsorption performance. Titanium-based lithium ion sieves have advantages such as high theoretical adsorption capacity, good ion selectivity, and good cyclic stability, and are considered to be the most promising and research-worthy lithium adsorbents. However, the ion adsorption rate of titanium-based lithium ion sieves is low, and the alternating acid-base environment during the adsorption / desorption process will destroy the structural stability of the material, making its adsorption performance unable to be effectively exerted, resulting in a low lithium extraction rate in actual applications. Therefore, there is an urgent need for a titanium-based lithium ion sieve adsorbent with high ion adsorption rate and good stability. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a dual-site doped titanium-based lithium ion sieve adsorbent, which simultaneously replaces the Li and Ti sites by introducing metal cations. The Li site substitution expands the interlayer spacing and increases the Li + Diffusion rate, Ti substitution regulates local chemical bonds and electron distribution, stabilizes lattice structure, enhances electron conduction, and double-site doping constructs "ion-electron" dual channels to achieve synergistic optimization effects. At the same time, ion doping can form defects inside the material, provide abundant active sites and ion diffusion channels, and reduce Li + The resistance to mass transfer in the interior.

[0005] The second object of the present invention is to provide a method for preparing the dual-site doped titanium-based lithium ion sieve adsorbent, which has a simple process and is suitable for industrial production.

[0006] The third object of the present invention is to provide an application of the dual-site doped titanium-based lithium ion sieve adsorbent.

[0007] The present invention provides a dual-site doped titanium-based lithium ion sieve adsorbent, wherein the dual-site doped titanium-based lithium ion sieve adsorbent is a delithiation product of a dual-site doped titanium-based lithium ion sieve adsorbent precursor; the chemical formula of the dual-site doped titanium-based lithium ion sieve adsorbent precursor is Li 2-x M x Ti 1-y N y O z , where M is Na + , K + 、Zn 2+ 、Co 2+ 、Ni 2+ Mg 2+ 、Al 3+ At least one of them occupies the Li position, and N is Cr 3+ 、Fe 3+ 、Zr 4+ 、Nb 5+ 、Ta 5+ 、V 5+ 、Mo 6+ 、W 6+ At least one of them occupies the Ti position, 0.001≤x≤0.5, 0.001≤y≤0.5.

[0008] The precursor of the dual-site doped titanium-based lithium ion sieve adsorbent is a layered structure; the crystal framework of the dual-site doped titanium-based lithium ion sieve adsorbent precursor is inherited from pure phase Li2TiO3; pure phase Li2TiO3 is composed of alternating pure Li layers and LiTi2 layers; the LiTi2 layers are formed by edge-shared [TiO6] octahedra arranged in a three-dimensional network;

[0009] The preparation method of the dual-site doped titanium-based lithium ion sieve adsorbent precursor is specifically as follows:

[0010] The Li and Ti sites in pure Li2TiO3 are doped at two sites, where M ions replace the Li sites in the pure Li layer, expand the interlayer spacing and serve as interlayer pillars of the Li layer; N ions replace the Ti sites in the [TiO6] octahedron, regulate the electron distribution around Ti and strengthen the Ti-O bond, forming a defect-rich modified Li layer and a modified LiTi2 layer, thereby obtaining a two-site doped titanium-based lithium ion sieve adsorbent precursor; the layered structure of the two-site doped titanium-based lithium ion sieve adsorbent precursor is a plurality of modified Li layers and modified LiTi2 layers arranged alternately.

[0011] The adsorption mechanism of titanium-based lithium ion sieve H2TiO3 is based on the "ion sieve effect". The layered lithium titanate precursor (Li2TiO3) is treated with acid to make Li + and H + When multiple ions coexist in the solution, the H2TiO3 adsorbent has the ability to screen and memorize, and can selectively adsorb Li + The H2TiO3 precursor can be expressed as Li[Li 1 / 3 Ti 2 / 3 ]O2, where Ti and O atoms form a [TiO6] octahedron structure, and Li is located in two adjacent [TiO6] octahedra, forming alternating (Li) layers and (LiTi2) layers. The (Li) layers are filled only with Li atoms, accounting for 2 / 3 of the total lithium in the H2TiO3 structure, and the remaining 1 / 3 of Li is located in the (LiTi2) layers.

[0012] The dual-site doped titanium-based lithium ion sieve adsorbent of the present invention is a delithiation product of a dual-site doped titanium-based lithium ion sieve adsorbent precursor. By introducing metal cations into the precursor to replace the Li and Ti positions at the same time, an "ion-electron" dual channel is constructed to achieve a synergistic optimization effect. Specifically, metal cations are introduced into the Li position of the (Li) layer to act as interlayer pillars, expand the interlayer spacing, and optimize the Li + Diffusion channel, improve Li + The diffusion rate is increased by introducing metal cations into the Ti site of the [TiO6] octahedron in the (LiTi2) layer to regulate the local chemical bonds, stabilize the lattice oxygen, and thus improve the stability of the lattice structure. At the same time, the doping of metal cations can form defects inside the material, regulate the electron distribution around Ti, enhance the electron conduction ability, provide abundant active sites and ion diffusion channels, reduce the mass transfer resistance of Li+ inside, and facilitate Li + and H + Therefore, the ion diffusion rate and structural stability of the adsorbent are synergistically improved by dual-site doping.

[0013] The present invention also provides a method for preparing the dual-site doped titanium-based lithium ion sieve adsorbent, comprising the following steps:

[0014] S1. The lithium source, titanium source, dopant ion source M, dopant ion source N are mixed in a preset ratio to obtain a mixed raw material;

[0015] S2. The mixed raw materials are ball-milled and dried to obtain a pretreated material;

[0016] S3. The pretreated material is calcined in two steps to obtain a precursor material;

[0017] S4. Grinding the precursor material, acid washing, filtering and drying to obtain the titanium-based lithium ion sieve adsorbent.

[0018] Furthermore, in step S1, the lithium source is at least one of lithium carbonate, lithium acetate dihydrate, lithium chloride, lithium nitrate, lithium oxalate, lithium sulfate, lithium fluoride, lithium hydroxide monohydrate, lithium dihydrogen phosphate, lithium hexafluorophosphate and lithium trifluoromethanesulfonimide.

[0019] The titanium source is at least one of titanium dioxide, titanium sulfate, ilmenite, titanium foil, tetrabutyl titanate, titanium tetrachloride, and isopropyl titanate, and more preferably at least one of titanium dioxide, titanium sulfate, ilmenite, and titanium foil.

[0020] The dopant ion M source includes Na + , K + 、Zn 2+ 、Co 2+ 、Ni 2+ Mg 2+ 、Al 3+ At least one of the corresponding nitrates, sulfates, oxalates, acetates and acetylacetonates.

[0021] The dopant ion N source includes Zr 4+ 、Nb 5+ 、Ta 5+ 、V 5+ 、Mo 6+ 、W 6+ At least one of the corresponding nitrates, sulfates, oxalates, acetates and acetylacetonates.

[0022] The molar ratio of the lithium source to the titanium source is (1.5-2.5): (0.8-1).

[0023] When there is too much lithium source or titanium source, by-products will be generated and performance will be reduced; when there is too little lithium source or titanium source, the reaction will be incomplete and the layered structure will be incomplete.

[0024] The molar ratio of the doping ion M source to the lithium source is (0.001-0.5):1.

[0025] The appropriate Li doping amount can optimize the Li + Diffusion channel, improve Li + However, if the amount of doping ion source M added is too much, too much doping ion will replace too much Li + , which leads to the generation of more lithium vacancies, which in turn hinders the migration of lithium ions. At the same time, the reduction of Li sites will also reduce the adsorption capacity of the adsorbent. When the addition amount is too small, the doping effect is not obvious and the material performance improvement is not obvious.

[0026] The molar ratio of the doping ion N source to the titanium source is (0.001-0.5):1.

[0027] The appropriate Ti doping amount can enhance the structural stability of the material and improve the electronic conductivity of the material. However, if the amount of N doping ion source added is too much, too much doping ion will replace too much Ti 4+ , causing lattice distortion, destroying the integrity of the layered structure, and worsening the material properties. When the addition amount is too small, the doping effect is not obvious and the material performance improvement is not obvious.

[0028] Furthermore, in step S2, the ball milling time is 1 to 20 hours, the ball milling speed is 100 to 1000 rpm, and the ball-to-material ratio is (5 to 50):1.

[0029] Furthermore, in step S3, the two-step calcination includes low-temperature calcination and high-temperature calcination; the conditions for the low-temperature calcination are: temperature of 100-400°C, time of 1-8 hours, and atmosphere of air or oxygen; the conditions for the high-temperature calcination are: temperature of 500-1000°C, time of 1-8 hours, and atmosphere of air or oxygen.

[0030] The calcination conditions in the present invention will affect the crystallinity of the precursor, thereby affecting the adsorption performance of the lithium ion sieve adsorbent. The present invention adopts a two-step calcination method, first pre-calcining at a low temperature to achieve a preliminary uniform distribution of the doping elements, which can effectively avoid the problems of lithium volatilization and uneven components caused by direct high-temperature calcination; the second step is calcination at a high temperature to improve the crystallinity of the precursor material. During the calcination process, calcination temperatures that are too high or too low will have a significant impact on the material properties. Too high a calcination temperature will lead to increased lithium volatilization and abnormal grain growth, while too low a calcination temperature will lead to incomplete reaction and uneven doping. At the same time, the calcination time will also significantly affect the crystal structure, particle morphology and particle size distribution of the material. Too short a calcination time will result in incomplete crystal structure of the material, irregular particle morphology, and uneven particle size distribution. Too long a calcination time will cause excessive particle growth and a reduction in specific surface area, thereby affecting the adsorption performance of the adsorbent.

[0031] Furthermore, in step S4, the pickling solution used in the pickling is at least one of hydrochloric acid, sulfuric acid, nitric acid, citric acid, and persulfate.

[0032] Preferably, the persulfate is at least one of (NH4)2S2O8, K2S2O8, and Na2S2O8.

[0033] The acid concentration of the pickling solution is 0.02-1.0 mol / L.

[0034] Appropriate acid wash solution concentration is one of the key factors in preparing high-performance adsorbents. If the acid wash solution concentration is too low, H + He Li + Unable to be fully exchanged, Li in the Li2TiO3 precursor + cannot be completely eluted, the maximum adsorption capacity of the adsorbent is reduced, and at the same time, H + Low concentration will lead to slow ion exchange kinetics; if the pickling solution concentration is too high, it will cause Ti4 + dissolution loss, which in turn affects the structural stability of the adsorbent.

[0035] The pickling temperature is 10-90° C. and the pickling time is 1-48 hours.

[0036] Pickling temperature affects the ion diffusion rate. At low temperature, H + Diffusion and Li + Dissolution kinetics are limited, and the processing time must be significantly extended to achieve a high exchange rate; the higher the temperature, the faster the ion diffusion, which will accelerate the H + He Li + However, if the temperature is too high, it may cause partial phase transformation. + Failure to fully replace Li in the Li layer + , resulting in the retention of part of the precursor phase in the product, and the unexchanged Li + It will occupy the active sites and reduce the subsequent Li + If the pickling time is long, excessive acid etching may destroy the stability of the [TiO6] octahedral layer, resulting in the breakage of Ti-O bonds and the formation of amorphous TiO2 or titanic acid.

[0037] The present invention also provides an application of the dual-site doped titanium-based lithium ion sieve adsorbent in adsorbing lithium in a liquid lithium solution.

[0038] The liquid lithium solution is a sodium aluminate solution purified by high-pressure dissolution during the Bayer process for producing alumina.

[0039] Due to the high lithium content in my country's bauxite, 80% of the lithium released during the Bayer process for alumina production enters the sodium aluminate solution. After separation and high-temperature calcination, it ultimately forms the alumina product. When using this lithium-rich alumina as a raw material to produce metallic aluminum, the accumulation of lithium in the electrolyte reduces the electrolyte temperature and the solubility of the alumina, leading to increased energy consumption during the aluminum electrolysis process and reduced quality of the metallic aluminum product. Therefore, extracting lithium from the purified sodium aluminate solution after high-pressure dissolution during the Bayer process for alumina production is of great significance in addressing production difficulties and improving the economic efficiency of aluminum electrolysis companies.

[0040] Furthermore, the sodium aluminate solution contains Li + The content of the titanium-based lithium ion sieve adsorbent is 20 mg / L to 200 mg / L, the adsorption temperature of the titanium-based lithium ion sieve adsorbent in the sodium aluminate solution is 55° C. to 95° C., the adsorption time of the titanium-based lithium ion sieve adsorbent in the sodium aluminate solution is 1 h to 24 h, and the solid-liquid ratio of the titanium-based lithium ion sieve adsorbent to the sodium aluminate solution is 0.5-10 g / L.

[0041] When using titanium-based lithium ion sieve adsorbents for lithium extraction from sodium aluminate solutions, the choice of adsorption time is crucial. If the adsorption time is too short, the lithium ion sieve will not reach saturated adsorption capacity, resulting in low adsorption efficiency. If the adsorption time is too long, the sodium aluminate solution will be unstable and prone to decomposition, resulting in the precipitation of aluminum hydroxide, which will affect the subsequent separation process.

[0042] Beneficial effects of the present invention:

[0043] (1) The dual-site doped titanium-based lithium ion sieve adsorbent disclosed in the present invention constructs an "ion-electron" dual channel by doping the Li and Ti sites of the adsorbent precursor, providing abundant active sites and reducing Li + The mass transfer resistance inside the material increases the Li + The adsorption rate is fast; by stabilizing the lattice oxygen of the precursor, the structural stability of the adsorbent is improved, and it has high adsorption capacity, fast adsorption rate, good structural stability, and exhibits excellent adsorption performance;

[0044] (2) The preparation method of the dual-site doped titanium-based lithium ion sieve adsorbent disclosed in the present invention adopts a two-step calcination method to achieve dual-site doping of the precursor, and a high-performance adsorbent can be obtained by acid treatment transformation. The preparation process is simple, easy to control, and has good application prospects;

[0045] (3) The application of the dual-site doped titanium-based lithium ion sieve adsorbent disclosed in the present invention realizes the efficient extraction of lithium from sodium aluminate solution by adsorption method, which can not only eliminate the negative impact of lithium-rich alumina production on the aluminum electrolysis process and solve the production difficulties of aluminum electrolysis enterprises, but also realize the value-added utilization of associated lithium resources in bauxite without affecting alumina production, avoid the waste of lithium resources, and improve my country's lithium resource self-sufficiency capacity, and has very considerable application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the process flow of the method of the present invention;

[0047] Figure 2 The saturated adsorption capacity and Ti content of the dual-site doped lithium ion sieve adsorbent obtained in Example 1 in 10 adsorption / desorption cycles in sodium aluminate solution are shown in FIG. 4+ Dissolution loss rate change curve;

[0048] Figure 3 The saturated adsorption capacity and Ti content of the adsorbent obtained in Comparative Example 1 after 10 adsorption / desorption cycles in sodium aluminate solution 4+ Dissolution loss rate change curve;

[0049] Figure 4 The graph shows the change of adsorption capacity of the adsorbents obtained in Example 1 and Comparative Example 1 in sodium aluminate solution over time. DETAILED DESCRIPTION

[0050] The present invention will be described in detail below with reference to the accompanying drawings and specific operating examples; the embodiments are carried out under the conditions described in the present invention and are intended to further illustrate the contents of the present invention, but do not limit the scope of protection of the present invention.

[0051] In the following examples and comparative examples, the simulated sodium aluminate solution used had a caustic ratio of 1.5, a sodium oxide concentration of 170 g / L, and a Li + The concentration is 150mg / L.

[0052] Example 1

[0053] (1) Weigh 9.9645 g of lithium acetate dihydrate and 3.7936 g of titanium dioxide in a molar ratio of 1.95:0.95, add 0.5488 g of zinc acetate dihydrate and 1.0733 g of zirconium nitrate pentahydrate, place the mixture in a ball mill, add 15.38 ml of ethanol solution, and ball mill at 300 rpm for 6 h (ball-to-material ratio is 20:1).

[0054] (2) After ball milling, the ethanol was evaporated and dried in an oven at 90°C. After cooling to room temperature, the raw material was sieved using a 100-mesh sieve.

[0055] (3) The obtained raw materials were placed in a muffle furnace in an air atmosphere and calcined at 400°C for 2 h, then calcined at 800°C for 4 h (heating rate of 5°C / min), and then cooled to room temperature to obtain a precursor.

[0056] (4) The obtained precursor was ground evenly, and the precursor was weighed at a liquid-to-solid ratio of 80:1 and placed in a 0.3M hydrochloric acid solution and acid-washed at 25°C for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent was obtained.

[0057] (5) 0.2 g of titanium-based lithium ion sieve adsorbent was added to 200 ml of simulated sodium aluminate solution and adsorbed at 90 °C for 4 h. The adsorbed liquid was sampled and the Li in the solution was tested using an inductively coupled plasma emission spectrometer. + and Ti 4+ concentration.

[0058] (6) The lithium absorbing residue was dried in an oven at 60°C, and then acid-washed in a 0.3M hydrochloric acid solution at a liquid-to-solid ratio of 80:1 at 25°C for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent having been recycled once was obtained. Based on the above acid washing and adsorption conditions, 10 adsorption / desorption cycles were completed.

[0059] The results showed that Zn 2+ 、Zr 4+ The co-doped titanium lithium ion sieve adsorbent reached adsorption equilibrium in the simulated sodium aluminate solution after 25 minutes of adsorption, with a saturated adsorption capacity of 80 mg / g and an adsorption rate of 95%. 4+ The dissolution loss rate is 0.04%, the capacity retention rate after 10 cycles is 80%, and the Ti 4+ The dissolution loss rate was 0.08%, showing excellent adsorption performance.

[0060] Comparative Example 1

[0061] This comparative example is substantially the same as Example 1, except that in step (1), zinc acetate dihydrate and zirconium nitrate pentahydrate are not added.

[0062] Comparative Example 2

[0063] This comparative example is substantially the same as Example 1, except that zinc acetate dihydrate is not added in step (1).

[0064] Comparative Example 3

[0065] This comparative example is substantially the same as Example 1, except that zirconium nitrate pentahydrate is not added in step (1).

[0066] Comparative Example 4

[0067] This comparative example is basically the same as Example 1, except that in step (3), a one-step calcination method is used to calcine at 1000° C. for 4 h in an air atmosphere.

[0068] Comparative Example 5

[0069] This comparative example is basically the same as Example 1, except that in step (3), the second calcination temperature is 1200°C.

[0070] Comparative Example 6

[0071] This comparative example is substantially the same as Example 1, except that in step (4), the concentration of hydrochloric acid is 2M.

[0072] Comparative Example 7

[0073] This comparative example is substantially the same as Example 1, except that in step (4), the concentration of hydrochloric acid is 0.001 M.

[0074] Comparative Example 8

[0075] This comparative example is basically the same as Example 1, except that in step (4), the pickling time is 80 hours.

[0076] Comparative Example 9

[0077] This comparative example is basically the same as Example 1, except that in step (4), the pickling time is 15 minutes.

[0078] Comparative Example 10

[0079] This comparative example is basically the same as Example 1, except that in step (5), the adsorption temperature is 25°C.

[0080] Comparative Example 11

[0081] This comparative example is basically the same as Example 1, except that in step (5), the adsorption temperature is 150°C.

[0082] Comparative Example 12

[0083] This comparative example is basically the same as Example 1, except that in step (5), the adsorption time is 10 minutes.

[0084] Comparative Example 13

[0085] This comparative example is basically the same as Example 1, except that in step (5), the adsorption time is 48 hours.

[0086] Example 2

[0087] (1) Weigh 10.118 g of lithium acetate dihydrate and 3.9534 g of titanium dioxide in a molar ratio of 1.98:0.99, add 0.2195 g of zinc acetate dihydrate and 0.2147 g of zirconium nitrate pentahydrate, place the mixture in a ball mill, add 14.51 ml of ethanol solution, and ball mill at a speed of 400 rpm for 4 h (ball-to-material ratio is 20:1).

[0088] (2) After ball milling, the ethanol was evaporated and dried in an oven at 90°C. After cooling to room temperature, the raw material was sieved using a 100-mesh sieve.

[0089] (3) The obtained raw materials were placed in a muffle furnace in an air atmosphere and calcined at 400°C for 2 h, then calcined at 800°C for 4 h (heating rate of 5°C / min), and then cooled to room temperature to obtain a precursor.

[0090] (4) The obtained precursor was ground evenly, and the precursor was weighed at a liquid-to-solid ratio of 80:1, placed in a 0.25M hydrochloric acid solution and acid-washed at 30°C for 24 hours, and then filtered and dried to obtain a titanium-based lithium ion sieve adsorbent.

[0091] (5) 0.2 g of titanium-based lithium ion sieve adsorbent was added to 200 ml of simulated sodium aluminate solution and adsorbed at 95 °C for 4 h. The adsorbed liquid was sampled and the Li in the solution was tested using an inductively coupled plasma emission spectrometer. + and Ti 4+ concentration.

[0092] (6) The lithium absorbing residue was dried in an oven at 60°C, and then acid-washed in a 0.25M hydrochloric acid solution at 30°C with a liquid-to-solid ratio of 80:1 for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent having been recycled once was obtained. Based on the above acid washing and adsorption conditions, 10 adsorption / desorption cycles were completed.

[0093] The results showed that Zn 2+ 、Zr 4+ The co-doped titanium lithium ion sieve adsorbent reached adsorption equilibrium in the simulated sodium aluminate solution after 28 minutes of adsorption, with a saturated adsorption capacity of 75 mg / g and an adsorption rate of 94%. 4+ The dissolution loss rate is 0.05%, the capacity retention rate after 10 cycles is 78%, and the Ti 4+ The dissolution loss rate was 0.09%, showing excellent adsorption performance.

[0094] Example 3

[0095] (1) Weigh 10.016 g of lithium acetate dihydrate and 3.7537 g of titanium dioxide in a molar ratio of 1.96:0.94, add 0.439 g of zinc acetate dihydrate and 1.288 g of zirconium nitrate pentahydrate, mix and place in a ball mill, add 15.5 ml of ethanol solution, and ball mill at a speed of 450 rpm for 5 h (ball-to-material ratio is 20:1).

[0096] (2) After ball milling, the ethanol was evaporated and dried in an oven at 90°C. After cooling to room temperature, the raw material was sieved using a 100-mesh sieve.

[0097] (3) The obtained raw materials were placed in a muffle furnace in an air atmosphere and calcined at 400°C for 2 h, then calcined at 800°C for 4 h (heating rate of 5°C / min), and then cooled to room temperature to obtain a precursor.

[0098] (4) The obtained precursor was ground evenly, and the precursor was weighed at a liquid-to-solid ratio of 80:1, placed in a 0.2M hydrochloric acid solution and acid-washed at 40°C for 24 hours, and then filtered and dried to obtain a titanium-based lithium ion sieve adsorbent.

[0099] (5) 0.2 g of titanium-based lithium ion sieve adsorbent was added to 200 ml of simulated sodium aluminate solution and adsorbed at 95 °C for 6 h. The adsorbed liquid was sampled and the Li in the solution was tested using an inductively coupled plasma emission spectrometer. + and Ti 4+ concentration.

[0100] (6) The lithium absorbing residue was dried in an oven at 60°C, and then acid-washed in a 0.2M hydrochloric acid solution at 40°C with a liquid-to-solid ratio of 80:1 for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent having been recycled once was obtained. Based on the above acid washing and adsorption conditions, 10 adsorption / desorption cycles were completed.

[0101] The results showed that Zn 2+ 、Zr 4+ The co-doped titanium lithium ion sieve adsorbent reached adsorption equilibrium in the simulated sodium aluminate solution after 28 minutes of adsorption, with a saturated adsorption capacity of 78 mg / g and an adsorption rate of 96%. 4+ The dissolution loss rate is 0.03%, the capacity retention rate after 10 cycles is 79%, and the Ti 4+ The dissolution loss rate was 0.1%, showing excellent adsorption performance.

[0102] Example 4

[0103] (1) 3.6391 g of lithium carbonate and 3.9134 g of titanium dioxide were weighed in a molar ratio of 0.985:0.98, 0.3733 g of nickel acetate tetrahydrate and 0.538 g of niobium oxalate were added, the mixture was placed in a ball mill, 8.46 ml of ethanol solution was added, and the mixture was ball milled at a speed of 300 rpm for 5 h (ball-to-material ratio was 20:1).

[0104] (2) After ball milling, the ethanol was evaporated and dried in an oven at 90°C. After cooling to room temperature, the raw material was sieved using a 100-mesh sieve.

[0105] (3) The obtained raw materials were placed in a muffle furnace in an air atmosphere and calcined at 300°C for 3 h, and then calcined at 800°C for 4 h (heating rate of 5°C / min), and then cooled to room temperature to obtain a precursor.

[0106] (4) The obtained precursor was ground evenly, and the precursor was weighed at a liquid-to-solid ratio of 80:1, placed in a 0.3M hydrochloric acid solution and acid-washed at 30°C for 24 hours, and then filtered and dried to obtain a titanium-based lithium ion sieve adsorbent.

[0107] (5) 0.2 g of titanium-based lithium ion sieve adsorbent was added to 200 ml of simulated sodium aluminate solution and adsorbed at 90 °C for 4 h. The adsorbed liquid was sampled and the Li in the solution was tested using an inductively coupled plasma emission spectrometer. + and Ti 4+ concentration.

[0108] (6) The lithium absorbing residue was dried in an oven at 60°C, and then acid-washed in a 0.3M hydrochloric acid solution at 30°C with a liquid-to-solid ratio of 80:1 for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent having been recycled once was obtained. Based on the above acid washing and adsorption conditions, 10 adsorption / desorption cycles were completed.

[0109] The results showed that Ni 2+ 、Nb 5+ The co-doped titanium lithium ion sieve adsorbent reached adsorption equilibrium in the simulated sodium aluminate solution after 31 minutes of adsorption, with a saturated adsorption capacity of 80 mg / g and an adsorption rate of 92%. 4+ The dissolution loss rate is 0.06%, the capacity retention rate after 10 cycles is 75%, and the Ti 4+ The dissolution loss rate was 0.11%, showing excellent adsorption performance.

[0110] Example 5

[0111] (1) 3.6021 g of lithium carbonate and 3.8735 g of titanium dioxide were weighed in a molar ratio of 0.975:0.97, 0.6221 g of nickel acetate tetrahydrate and 0.8071 g of niobium oxalate were added, the mixture was placed in a ball mill, 8.91 ml of ethanol solution was added, and the mixture was ball milled at a speed of 500 rpm for 4 h (ball-to-material ratio was 20:1).

[0112] (2) After ball milling, the ethanol was evaporated and dried in an oven at 90°C. After cooling to room temperature, the raw material was sieved using a 100-mesh sieve.

[0113] (3) The obtained raw materials were placed in a muffle furnace in an air atmosphere and calcined at 400°C for 2 h, then calcined at 800°C for 4 h (heating rate of 5°C / min), and then cooled to room temperature to obtain a precursor.

[0114] (4) The obtained precursor was ground evenly, and the precursor was weighed at a liquid-to-solid ratio of 80:1, placed in a 0.25M hydrochloric acid solution and acid-washed at 25°C for 24 hours, and then filtered and dried to obtain a titanium-based lithium ion sieve adsorbent.

[0115] (5) 0.2 g of titanium-based lithium ion sieve adsorbent was added to 200 ml of simulated sodium aluminate solution and adsorbed at 95 °C for 4 h. The adsorbed liquid was sampled and the Li in the solution was tested using an inductively coupled plasma emission spectrometer. + and Ti 4+ concentration.

[0116] (6) The lithium absorbing residue was dried in an oven at 60°C, and then acid-washed in a 0.25M hydrochloric acid solution at a liquid-to-solid ratio of 80:1 at 25°C for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent having been recycled once was obtained. Based on the above acid washing and adsorption conditions, 10 adsorption / desorption cycles were completed.

[0117] The results showed that Ni 2+ 、Nb 5+ The co-doped titanium lithium ion sieve adsorbent reached adsorption equilibrium in the simulated sodium aluminate solution after 32 minutes of adsorption, with a saturated adsorption capacity of 76 mg / g and an adsorption rate of 94%. 4+ The dissolution loss rate is 0.04%, and the capacity retention rate after 10 cycles is 74%. 4+ The dissolution loss rate was 0.09%, showing excellent adsorption performance.

[0118] Example 6

[0119] (1) Weigh 5.3871 g of lithium sulfate and 3.8735 g of titanium dioxide in a molar ratio of 0.98:0.97, add 0.5622 g of cobalt sulfate heptahydrate and 0.4215 g of ferric sulfate, place the mixture in a ball mill, add 10.67 ml of ethanol solution, and ball mill at 400 rpm for 4 h (ball-to-material ratio is 20:1).

[0120] (2) After ball milling, the ethanol was evaporated and dried in an oven at 90°C. After cooling to room temperature, the raw material was sieved using a 100-mesh sieve.

[0121] (3) The obtained raw materials were placed in a muffle furnace in an air atmosphere and calcined at 420°C for 2 h, then calcined at 800°C for 4 h (heating rate of 5°C / min), and then cooled to room temperature to obtain a precursor.

[0122] (4) The obtained precursor was ground evenly, and the precursor was weighed at a liquid-to-solid ratio of 80:1, placed in a 0.3M hydrochloric acid solution and acid-washed at 30°C for 24 hours, and then filtered and dried to obtain a titanium-based lithium ion sieve adsorbent.

[0123] (5) 0.2 g of titanium-based lithium ion sieve adsorbent was added to 200 ml of simulated sodium aluminate solution and adsorbed at 90 °C for 4 h. The adsorbed liquid was sampled and the Li in the solution was tested using an inductively coupled plasma emission spectrometer. + and Ti 4+ concentration.

[0124] (6) The lithium absorbing residue was dried in an oven at 60°C, and then acid-washed in a 0.3M hydrochloric acid solution at 30°C with a liquid-to-solid ratio of 80:1 for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent having been recycled once was obtained. Based on the above acid washing and adsorption conditions, 10 adsorption / desorption cycles were completed.

[0125] The results showed that Co 2+ 、Fe 3+ The co-doped titanium lithium ion sieve adsorbent reached adsorption equilibrium in the simulated sodium aluminate solution after 34 minutes of adsorption, with a saturated adsorption capacity of 78 mg / g and an adsorption rate of 93%. 4+ The dissolution loss rate is 0.05%, the capacity retention rate after 10 cycles is 78%, and the Ti 4+ The dissolution loss rate was 0.09%, showing excellent adsorption performance.

[0126] Example 7

[0127] (1) Weigh 5.442 g of lithium sulfate and 3.7537 g of titanium dioxide in a molar ratio of 0.99:0.94, add 0.2811 g of cobalt sulfate heptahydrate and 0.843 g of ferric sulfate, place the mixture in a ball mill, add 11.16 ml of ethanol solution, and ball mill at 450 rpm for 4 h (ball-to-material ratio is 20:1).

[0128] (2) After ball milling, the ethanol was evaporated and dried in an oven at 90°C. After cooling to room temperature, the raw material was sieved using a 100-mesh sieve.

[0129] (3) The obtained raw materials were placed in a muffle furnace in an air atmosphere and calcined at 420°C for 2 h, then calcined at 800°C for 4 h (heating rate of 5°C / min), and then cooled to room temperature to obtain a precursor.

[0130] (4) The obtained precursor was ground evenly, and the precursor was weighed at a liquid-to-solid ratio of 80:1, placed in a 0.25M hydrochloric acid solution and acid-washed at 25°C for 24 hours, and then filtered and dried to obtain a titanium-based lithium ion sieve adsorbent.

[0131] (5) 0.2 g of titanium-based lithium ion sieve adsorbent was added to 200 ml of simulated sodium aluminate solution and adsorbed at 95 °C for 4 h. The adsorbed liquid was sampled and the Li in the solution was tested using an inductively coupled plasma emission spectrometer. + and Ti 4+ concentration.

[0132] (6) The lithium absorbing residue was dried in an oven at 60°C, and then acid-washed in a 0.25M hydrochloric acid solution at a liquid-to-solid ratio of 80:1 at 25°C for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent having been recycled once was obtained. Based on the above acid washing and adsorption conditions, 10 adsorption / desorption cycles were completed.

[0133] The results showed that Co 2+ 、Fe 3+ The co-doped titanium lithium ion sieve adsorbent reached adsorption equilibrium in the simulated sodium aluminate solution after 30 minutes of adsorption, with a saturated adsorption capacity of 80 mg / g and an adsorption rate of 95%. 4+ The dissolution loss rate is 0.03%, the capacity retention rate after 10 cycles is 72%, and the Ti 4+ The dissolution loss rate was 0.08%, showing excellent adsorption performance.

[0134] Example 8

[0135] (1) Weigh 4.133 g of lithium hydroxide monohydrate and 3.8735 g of titanium dioxide in a molar ratio of 1.97:0.97, add 0.36971 g of magnesium sulfate heptahydrate and 0.4215 g of ferric sulfate, place the mixture in a ball mill, add 8.8 ml of ethanol solution, and ball mill at 400 rpm for 4 h (ball-to-material ratio is 20:1).

[0136] (2) After ball milling, the ethanol was evaporated and dried in an oven at 90°C. After cooling to room temperature, the raw material was sieved using a 100-mesh sieve.

[0137] (3) The obtained raw materials were placed in a muffle furnace in an air atmosphere and calcined at 320°C for 2 h, then calcined at 800°C for 4 h (heating rate of 5°C / min), and then cooled to room temperature to obtain a precursor.

[0138] (4) The obtained precursor was ground evenly, weighed at a liquid-to-solid ratio of 80:1, placed in a 0.3M sulfuric acid solution and acid-washed at 30°C for 24 hours, filtered, and dried to obtain a titanium-based lithium ion sieve adsorbent.

[0139] (5) 0.2 g of titanium-based lithium ion sieve adsorbent was added to 200 ml of simulated sodium aluminate solution and adsorbed at 90 °C for 4 h. The adsorbed liquid was sampled and the Li in the solution was tested using an inductively coupled plasma emission spectrometer. + and Ti 4+ concentration.

[0140] (6) The lithium absorbing residue was dried in an oven at 60°C, and then acid-washed in a 0.3M sulfuric acid solution at 30°C with a liquid-to-solid ratio of 80:1 for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent having been recycled once was obtained. Based on the above acid washing and adsorption conditions, 10 adsorption / desorption cycles were completed.

[0141] The results showed that Mg 2+ 、Fe 3+ The co-doped titanium lithium ion sieve adsorbent reached adsorption equilibrium in the simulated sodium aluminate solution after 36 minutes of adsorption, with a saturated adsorption capacity of 74 mg / g and an adsorption rate of 90%. 4+ The dissolution loss rate is 0.07%, the capacity retention rate after 10 cycles is 73%, and the Ti 4+ The dissolution loss rate was 0.12%, showing excellent adsorption performance.

[0142] Example 9

[0143] (1) Weigh 4.0911 g of lithium hydroxide monohydrate and 3.8336 g of titanium dioxide in a molar ratio of 1.95:0.96, add 0.6162 g of magnesium sulfate heptahydrate and 0.562 g of ferric sulfate, place the mixture in a ball mill, add 9.1 ml of ethanol solution, and ball mill at 450 rpm for 4 h (ball-to-material ratio is 20:1).

[0144] (2) After ball milling, the ethanol was evaporated and dried in an oven at 90°C. After cooling to room temperature, the raw material was sieved using a 100-mesh sieve.

[0145] (3) The obtained raw materials were placed in a muffle furnace in an air atmosphere and calcined at 420°C for 2 h, then calcined at 800°C for 4 h (heating rate of 5°C / min), and then cooled to room temperature to obtain a precursor.

[0146] (4) The obtained precursor was ground evenly, and the precursor was weighed at a liquid-to-solid ratio of 80:1, placed in a 0.25M sulfuric acid solution, and acid-washed at 25°C for 24 hours. After filtering and drying, a titanium-based lithium ion sieve adsorbent was obtained.

[0147] (5) 0.2 g of titanium-based lithium ion sieve adsorbent was added to 200 ml of simulated sodium aluminate solution and adsorbed at 95 °C for 4 h. The adsorbed liquid was sampled and the Li in the solution was tested using an inductively coupled plasma emission spectrometer. + and Ti 4+ concentration.

[0148] (6) The lithium absorbing residue was dried in an oven at 60°C, and then acid-washed in a 0.25M sulfuric acid solution at a liquid-to-solid ratio of 80:1 at 25°C for 24 hours. After filtration and drying, a titanium-based lithium ion sieve adsorbent was obtained. Based on the above acid washing and adsorption conditions, 10 adsorption / desorption cycles were completed.

[0149] The results showed that Mg 2+ 、Fe 3+ The co-doped titanium lithium ion sieve adsorbent reached adsorption equilibrium in the simulated sodium aluminate solution after 35 minutes of adsorption, with a saturated adsorption capacity of 76 mg / g and an adsorption rate of 94%. 4+ The dissolution loss rate is 0.05%, the capacity retention rate after 10 cycles is 80%, and the Ti 4+ The dissolution loss rate was 0.09%, showing excellent adsorption performance.

[0150] Table 1 shows the adsorption of Li2+ by the titanium-based lithium ion sieve adsorbents obtained in various embodiments and comparative examples of the present invention in sodium aluminate solution. + Equilibrium adsorption time, saturated adsorption capacity, adsorption rate, Ti 4+ Dissolution loss rate and capacity retention after 10 adsorption / desorption cycles and Ti 4+ Dissolution rate.

[0151] Table 1 Composition of titanium-based lithium ion sieve adsorbent precursors obtained in various embodiments of the present invention and comparative examples and the equilibrium adsorption time, saturated adsorption capacity, adsorption rate, Ti4+ dissolution loss rate of the corresponding adsorbents for adsorbing Li+ in sodium aluminate solution, as well as capacity retention rate and Ti4+ dissolution loss rate after 10 cycles

[0152]

[0153]

[0154]

[0155]

[0156] As can be seen from Table 1, the composition of the dual-site doped titanium-based lithium ion sieve adsorbent precursor obtained in Example 1 is Li 1.95 Zn 0.05 Ti 0.95 Zr 0.05 O 3.025 The dual-site doped titanium-based lithium ion sieve adsorbent obtained after acid washing was used to adsorb Li + When the adsorption is carried out, the adsorption equilibrium is reached in 25 minutes, which has a fast kinetics. The saturated adsorption capacity is 80 mg / g and the adsorption rate is 95%.4+ The dissolution loss rate is 0.04%, which has high adsorption capacity and low titanium dissolution loss. The capacity retention rate of the adsorbent after 10 cycles is 80%. 4+ The dissolution loss rate is 0.08%, which has excellent cycle stability. Therefore, the dual-site doped titanium-based lithium ion sieve adsorbent prepared in Example 1 exhibits good adsorption performance.

[0157] In Examples 2 to 3, the addition amounts of the dopants zinc acetate dihydrate and zirconium nitrate pentahydrate were adjusted and appropriate process conditions were matched. In Examples 4 to 5, lithium carbonate was used as the lithium source, nickel acetate tetrahydrate and niobium oxalate were selected as dopants and appropriate process conditions were matched. In Examples 6 to 7, lithium sulfate was used as the lithium source, cobalt sulfate heptahydrate and ferric sulfate were selected as dopants and appropriate process conditions were matched. In Examples 8 to 9, lithium hydroxide was used as the lithium source, magnesium sulfate heptahydrate and ferric sulfate were selected as dopants, sulfuric acid was used as the eluent and appropriate process conditions were matched. The obtained dual-site doped titanium-based lithium ion sieve adsorbents all exhibited good adsorption performance.

[0158] Comparative Example 1: No dopant zinc acetate dihydrate and zirconium nitrate pentahydrate were added during the precursor preparation process. After acid washing and transformation, a pure phase H2TiO3 titanium-based lithium ion sieve adsorbent was obtained. The adsorbent required 120 minutes to reach equilibrium in the sodium aluminate solution. Its saturated adsorption capacity was 28 mg / g, and the adsorption rate was 60%. 4+ The dissolution loss rate is 0.5%, and the capacity retention rate of the adsorbent after 10 cycles is only 30%. 4+ The dissolution loss rate was 1.2%, which was due to the alternation of acidic and alkaline environments during the adsorption / desorption cycle, which destroyed the [TiO6] octahedral structure, resulting in a decrease in the structural stability of the material and a subsequent decrease in the adsorption capacity.

[0159] Comparative Example 2 did not add the dopant zinc acetate dihydrate, and Comparative Example 3 did not add the dopant zirconium nitrate pentahydrate, so both were single-site doping. Compared with pure phase materials, the adsorption performance of the single-site doped adsorbent was improved, but the effect was not significant.

[0160] In Comparative Example 4, a precursor was prepared by calcining at 1000° C. for 4 h in an air atmosphere using a one-step calcination method. The adsorption performance of the adsorbent obtained after acid washing and transformation was reduced.

[0161] In Comparative Example 5, the second step calcination temperature is 1200° C. Since the calcination temperature is too high, the precursor primary particles melt, and the various properties of the adsorbent obtained after acid washing and transformation are reduced.

[0162] The hydrochloric acid concentration in Comparative Example 6 was 2M. Since the acidity of the pickling solution was too strong, the concentration of H + He Li +The purpose of exchange is to replace the solid-state adsorbent with the solid-state adsorbent. However, this strongly acidic environment destroys the layered structure of the precursor. Therefore, the performance of the adsorbent obtained after acid washing and transformation is significantly reduced, and the adsorbent cannot be recycled.

[0163] The concentration of hydrochloric acid in Comparative Example 7 is 0.001M. Since the acidity of the pickling solution is too weak, + Unable to replace Li + , which results in the inability of the precursor to be successfully acid-washed and transformed, and therefore it is impossible to obtain a dual-site doped adsorbent.

[0164] In comparative example 8, the pickling time was 80 h. Due to the long pickling transformation step, the long soaking in acid resulted in the Ti 4+ The large dissolution loss worsens the structural stability of the material, so the adsorbent cannot be recycled.

[0165] In Comparative Example 9, the pickling time was 15 min. Since the pickling time was too short, H + He Li + Complete exchange is impossible, and the resulting adsorbent is mixed with a large amount of precursor phase, so the adsorption performance of the adsorbent is poor.

[0166] In Comparative Example 10, the adsorption temperature is 25°C. Since the temperature range in which industrial sodium aluminate solution exists stably is 55°C to 95°C, a lower adsorption temperature will cause aluminum hydroxide in the sodium aluminate solution to precipitate, forming a coating layer on the surface of the adsorbent, reducing the active adsorption sites of the adsorbent and reducing its adsorption performance.

[0167] In Comparative Example 11, the adsorption temperature is 150°C. Since the temperature range for the stable existence of industrial sodium aluminate solution is 55°C to 95°C, a higher adsorption temperature will cause the sodium aluminate solution to be unstable, hydrolyze to produce aluminum hydroxide precipitation, and cause changes in the composition and properties of the solution, thereby affecting the adsorption performance.

[0168] In Comparative Example 12, the adsorption time was 10 min. Since the adsorption time was short, the adsorbent had not yet reached saturated adsorption, and thus the adsorption performance was poor.

[0169] In Comparative Example 13, the adsorption time was 48 h. Due to the long adsorption time, the long-term adsorption caused the sodium aluminate solution to be unstable and decomposed to produce aluminum hydroxide, which masked the adsorption sites of the adsorbent and deteriorated its adsorption performance.

[0170] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

[0171] In summary, the present invention performs dual-site doping of the precursor of the titanium-based lithium ion sieve adsorbent at the Li and Ti sites, obtains a dual-site doped titanium-based lithium ion sieve adsorbent after acid washing and transformation, and applies the adsorbent to the sodium aluminate solution after high-pressure dissolution purification in the Bayer process of producing alumina to adsorb and extract lithium, and the adsorbent exhibits excellent adsorption performance.

Claims

1. A dual-site doped titanium-based lithium ion sieve adsorbent, characterized in that: The dual-site doped titanium-based lithium ion sieve adsorbent is a delithiation product of a dual-site doped titanium-based lithium ion sieve adsorbent precursor; the general chemical formula of the dual-site doped titanium-based lithium ion sieve adsorbent precursor is Li 2-x M x Ti 1-y N y O z , where M is Na + , K + 、Zn 2+ 、Co 2+ 、Ni 2+ Mg 2+ 、Al 3+ At least one of them occupies the Li position, and N is Cr 3+ 、Fe 3+ 、Zr 4+ 、Nb 5+ 、Ta 5+ 、V 5+ 、Mo 6+ 、W 6+ At least one of them occupies the Ti position, 0.001≤x≤0.5, 0.001≤y≤0.

5.

2. The dual-site doped titanium-based lithium ion sieve adsorbent according to claim 1, characterized in that: The precursor of the dual-site doped titanium-based lithium ion sieve adsorbent is a layered structure; the crystal framework of the dual-site doped titanium-based lithium ion sieve adsorbent precursor is inherited from pure phase Li2TiO3; pure phase Li2TiO3 is composed of alternating pure Li layers and LiTi2 layers; the LiTi2 layers are formed by edge-shared [TiO6] octahedra arranged in a three-dimensional network; The preparation method of the dual-site doped titanium-based lithium ion sieve adsorbent precursor is specifically as follows: The Li and Ti sites in pure Li2TiO3 are doped at two sites, where M ions replace the Li sites in the pure Li layer, expand the interlayer spacing and serve as interlayer pillars of the Li layer; N ions replace the Ti sites in the [TiO6] octahedron, regulate the electron distribution around Ti and strengthen the Ti-O bond, forming a defect-rich modified Li layer and a modified LiTi2 layer, thereby obtaining a two-site doped titanium-based lithium ion sieve adsorbent precursor; the layered structure of the two-site doped titanium-based lithium ion sieve adsorbent precursor is a plurality of modified Li layers and modified LiTi2 layers arranged alternately.

3. A method for preparing the dual-site doped titanium-based lithium ion sieve adsorbent according to any one of claims 1 or 2, characterized in that: The following steps are involved: S1. The lithium source, titanium source, dopant ion source M, dopant ion source N are mixed in a preset ratio to obtain a mixed raw material; S2. The mixed raw materials are ball-milled and dried to obtain a pretreated material; S3. The pretreated material is calcined in two steps to obtain a precursor material; S4. Grinding the precursor material, acid washing, filtering and drying to obtain the titanium-based lithium ion sieve adsorbent.

4. The preparation method according to claim 3, characterized in that In step S1, the lithium source is at least one of lithium carbonate, lithium acetate dihydrate, lithium chloride, lithium nitrate, lithium oxalate, lithium sulfate, lithium fluoride, lithium hydroxide monohydrate, lithium dihydrogen phosphate, lithium hexafluorophosphate and lithium trifluoromethanesulfonyl imide; The titanium source is at least one of titanium dioxide, titanium sulfate, ilmenite, titanium foil, tetrabutyl titanate, titanium tetrachloride, and isopropyl titanate; The dopant ion M source includes Na + , K + 、Zn 2+ 、Co 2+ 、Ni 2+ Mg 2+ 、Al 3+ at least one of the corresponding nitrates, sulfates, oxalates, acetates, and acetylacetonates; The dopant ion N source includes Zr 4+ 、Nb 5+ 、Ta 5+ 、V 5+ 、Mo 6+ 、W 6+ At least one of the corresponding nitrates, sulfates, oxalates, acetates and acetylacetonates.

5. The preparation method according to claim 3, characterized in that The molar ratio of the lithium source and the titanium source is (1.5-2.5): (0.8-1); the molar ratio of the doping ion M source and the lithium source is (0.001-0.5): 1; and the molar ratio of the doping ion N source and the titanium source is (0.001-0.5):

1.

6. The preparation method according to claim 3, characterized in that In step S2, the ball milling time is 1 to 20 hours, the ball milling speed is 100 to 1000 rpm, and the ball-to-material ratio is (5 to 50):

1.

7. The preparation method according to claim 3, characterized in that In step S3, the two-step calcination includes low-temperature calcination and high-temperature calcination; the conditions for the low-temperature calcination are: temperature of 100-400°C, time of 1-8 hours, and atmosphere of air or oxygen; the conditions for the high-temperature calcination are: temperature of 500-1000°C, time of 1-8 hours, and atmosphere of air or oxygen.

8. The preparation method according to claim 3, characterized in that In step S4, the pickling solution used in the pickling is at least one of hydrochloric acid, sulfuric acid, nitric acid, citric acid, and persulfate; the persulfate is at least one of (NH4)2S2O8, K2S2O8, and Na2S2O8; the acid concentration of the pickling solution is 0.02-1.0 mol / L; the pickling temperature is 10-90°C, and the time is 1-48h.

9. Use of the dual-site doped titanium-based lithium ion sieve adsorbent according to any one of claims 1 to 2 or the dual-site doped titanium-based lithium ion sieve adsorbent prepared by the preparation method according to any one of claims 3 to 8 for adsorbing lithium in a liquid lithium solution, characterized in that: The liquid lithium solution is a sodium aluminate solution purified by high-pressure dissolution during the Bayer process for producing alumina.

10. The use according to claim 9, characterized in that The sodium aluminate solution contains Li + The content of the titanium-based lithium ion sieve adsorbent is 20 mg / L to 200 mg / L, the adsorption temperature of the titanium-based lithium ion sieve adsorbent in the sodium aluminate solution is 55° C. to 95° C., the adsorption time of the titanium-based lithium ion sieve adsorbent in the sodium aluminate solution is 1 h to 24 h, and the solid-liquid ratio of the titanium-based lithium ion sieve adsorbent to the sodium aluminate solution is 0.5-10 g / L.

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