Titanium lithium adsorbent and preparation method thereof

Abstract

The invention discloses a titanium lithium adsorbent and a preparation method thereof.The preparation method is characterized by comprising the steps that S100, lithium titanate powder is provided and put into a sulfuric acid solution for a lithium removal reaction, and a first solid and a first liquid are obtained; s200, performing wet mixing on the first liquid, lithium hydroxide and niobium pentoxide, and performing grinding treatment, drying treatment and calcining treatment to obtain a first solid; s300, dispersing the first solid into a solution containing a two-dimensional transition metal carbide or a two-dimensional transition metal nitride, and coating the surface of the first solid with the two-dimensional transition metal carbide or the two-dimensional transition metal nitride under a vacuum condition to form a second solid; and S400, the second solid is placed in an acid solution to be subjected to protonation treatment, and after washing and drying, the titanium-series lithium adsorbent is obtained. According to the titanium-based lithium adsorbent and the preparation method thereof provided by the invention, the recovery treatment of retired lithium titanate battery wastes is optimized, the recovery use of lithium metal is optimized, the recovery cost is reduced, and the recovery treatment efficiency is improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium extraction by adsorption, and in particular to a titanium-based lithium adsorbent and a preparation method thereof. Background Art

[0002] As the negative electrode material in lithium-ion batteries, spinel lithium titanate (Li4Ti5O 12 ), with its face-centered cubic lattice, diamond-type slip plane and crystal structure with specific symmetry elements, that is, the space group Fd-3m structure of the oxygen atom close-packed framework, the volume change of the lattice is less than 0.3% during the lithium ion insertion and extraction process, and the zero strain effect shows that the structure is not damaged during the charge and discharge process of the electrode material, which greatly improves the cycle stability of the battery. However, due to the Li4Ti5O 12 During the lithium insertion or removal process, the potential platform range corresponding to the electrochemical reaction is relatively large relative to the standard lithium electrode (Li + / Li) is only 1.55 volts. On the other hand, the maximum amount of electricity that the electrode material can provide per unit mass in the fully lithiated or delithiated state is low, only 175 mAh / g. 12 The energy density of Li4Ti5O is difficult to meet the increasing demand for high-energy batteries, leading to large-scale retirement. 12 How to recycle materials has become a major difficulty. Summary of the invention

[0003] One purpose of the present application is to provide a titanium-based lithium adsorbent and a preparation method thereof, which is beneficial to optimizing the adsorption activity and usage stability of the lithium adsorbent for lithium and increasing the recovery and processing efficiency.

[0004] Another object of the present application is to provide a titanium-based lithium adsorbent and a preparation method thereof, which is conducive to optimizing the recycling and treatment of retired lithium titanate battery waste, reducing recycling costs and increasing economic benefits.

[0005] Another object of the present application is to provide a titanium-based lithium adsorbent and a preparation method thereof, which has a simple preparation process, is easy to operate, and has the potential to be put into large-scale production.

[0006] To achieve the above objectives, the technical solution adopted in this application is: a method for preparing a titanium-based lithium adsorbent, comprising the steps of: S100, providing lithium titanate powder, and placing it into a sulfuric acid solution for delithiation reaction to obtain a first liquid; S200, wet-mixing the first liquid, lithium hydroxide and niobium pentoxide, and obtaining a first solid through grinding, drying and calcining; S300. Disperse the first solid into a solution containing two-dimensional transition metal carbides or two-dimensional transition metal nitrides. Under vacuum conditions, the two-dimensional transition metal carbides or two-dimensional transition metal nitrides are coated on the surface of the first solid to form a second solid. S400. Place the second solid in an acid solution for protonation treatment, and obtain a titanium-based lithium adsorbent after washing and drying.

[0007] In some embodiments, the structural general formula of the two-dimensional transition metal carbides or the two-dimensional transition metal nitrides is M n+1 X n T x , where M is a transition metal layer, X is a carbon layer or a nitrogen layer, T x is a surface functional group, and n is the number of adjacent transition metal layers. The value of n is 1, or 2, or 3.

[0008] In some embodiments, the two-dimensional transition metal carbide is Ti3C2T x , and the T x includes one or more of hydroxyl groups and oxygen groups.

[0009] In some embodiments, in the step S100, the lithium titanate is spinel-type lithium titanate, the molar concentration of the sulfuric acid solution is 1.0 mol / L to 4.0 mol / L, the reaction time of the delithiation reaction is 2 h to 12 h, and the reaction temperature is 45°C to 95°C.

[0010] In some embodiments, in the step S200, the molar ratio of titanium element to lithium element in the first solid is 1:(2.00 to 2.10), and the mass fraction of niobium pentoxide is 0.2 wt.% to 1 wt.%.

[0011] In some embodiments, in the step S200, the particle size distribution range after the grinding treatment is 0.3 μm to 0.6 μm; the median particle size range of the product after the drying treatment is 20 μm to 40 μm, and the drying treatment is spray drying treatment; the treatment temperature of the calcination treatment is 600°C to 800°C, and the treatment time is 4 h to 16 h.

[0012] In some embodiments, in the step S300, the mass concentration of the two-dimensional transition metal carbides or the two-dimensional transition metal nitrides solution is 5 g / L to 10 g / L, and the mass fraction of the two-dimensional transition metal carbides or the two-dimensional transition metal nitrides coated on the surface of the first solid is 2 wt.% to 5 wt.%; the temperature of the vacuum treatment is 45°C to 65°C, and the time of the vacuum treatment is 4 h to 10 h.

[0013] In some embodiments, in the step S400, the molar concentration of the acid solution is 0.2 mol / L to 2 mol / L, and the acid solution is one of hydrochloric acid, sulfuric acid, and nitric acid; the temperature of the protonation treatment is 35°C to 60°C, and the time of the protonation treatment is 6 h to 10 h.

[0014] In some embodiments, in the step S400, the number of times of the washing treatment is not less than 3 times; the temperature of the drying treatment is 45°C to 60°C, and the time of the drying treatment is 6 h to 10 h.

[0015] To achieve the above object, the technical solution adopted by the present application is: a titanium-based lithium adsorbent prepared by the preparation method described in any one of the above.

[0016] Compared with the prior art, the beneficial effects of the present application are as follows: (1) The present application uses low-cost titanium acid lithium battery waste as raw materials, and prepares a porous titanium-based lithium adsorbent matrix with a high specific surface area through niobium doping technology. Further, a two-dimensional material is coated on the matrix to form a core-shell titanium-based lithium adsorbent with a chemically bonded protective layer, which has both use stability and excellent lithium adsorption performance. While reducing the recovery cost and increasing economic benefits, the recovery processing efficiency is increased.

[0017] (2) The preparation method of the titanium-based lithium adsorbent provided by the present application has the advantages of simple preparation process, easy operation, and the potential for large-scale production. Specific Embodiments

[0018] Next, in combination with specific embodiments, the present application will be further described. It should be noted that on the premise of no conflict, the following-described embodiments or technical features can be combined with each other arbitrarily to form new embodiments.

[0019] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence.

[0020] The terms "comprising" and "having" in the description and claims of the present application and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0021] To achieve the above object, the technical solution adopted by the present application is: a preparation method of a titanium-based lithium adsorbent, comprising the steps of: S100. Provide lithium titanate powder and place it into a sulfuric acid solution for delithiation reaction to obtain a first liquid; S200. Wet-mix the first liquid, lithium hydroxide, and niobium pentoxide, and obtain a first solid after grinding treatment, drying treatment, and calcination treatment; S300. Disperse the first solid into a solution with two-dimensional transition metal carbide or two-dimensional transition metal nitride. Under vacuum conditions, the two-dimensional transition metal carbide or two-dimensional transition metal nitride is coated on the surface of the first solid to form a second solid; S400. Place the second solid into an acid solution for protonation treatment, and obtain a titanium-based lithium adsorbent after washing and drying.

[0022] Through the preparation method of the titanium-based lithium adsorbent provided by this application, using low-cost titanium-lithium battery waste as raw materials, a titanium-based lithium adsorbent precursor is prepared through niobium doping technology, and further a two-dimensional material is coated on the matrix to form a core-shell titanium-based lithium adsorbent with a chemically bonded protective layer, which has both use stability and excellent lithium adsorption properties. While reducing the recovery cost and increasing economic benefits, the recovery treatment efficiency is increased.

[0023] In some embodiments, the structural general formula of the two-dimensional transition metal carbide or two-dimensional transition metal nitride is M n+ 1X n T x , where M is a transition metal layer, X is a carbon layer or a nitrogen layer, and T x is the functional group on the surface, and n is the number of adjacent transition metal layers. The value of n is 1, or 2, or 3. It can be understood that the material conforming to the structural general formula M n+1 X n T x is an MXene material. When the MXene material is coated on the surface of the titanium-based lithium adsorbent precursor, a core-shell structure can be formed, further enhancing the use stability of the titanium-based lithium adsorbent in various use environments, such as acidic environments, and reducing the dissolution loss phenomenon of the titanium-based lithium adsorbent during cyclic use.

[0024] In some embodiments, the two-dimensional transition metal carbide is Ti3C2T x , and T x includes one or more of hydroxyl and oxy groups. It is worth mentioning that when an MXene material containing hydroxyl or oxy groups on the surface is selected as the shell material, the hydroxyl or oxy group can form a chemical bridge with lithium titanate, such as forming a Ti-O-Ti or Ti-O-C covalent bond with the oxygen atoms on the surface of lithium titanate. While further increasing the interfacial transfer rate of lithium ions, the binding force between the core-shell structures is enhanced, which is beneficial to inhibiting the dissolution loss phenomenon of the titanium-based lithium adsorbent in acidic environments and increasing the service life.

[0025] It is understandable that for the currently used lithium ion sieve, such as spinel-type LiMn2O4, when used in an acidic environment with a pH value ≤ 1, Mn 3+ reacts under acidic conditions to form Mn 2+ , and at this time, Mn 2+ rapidly dissociates from the lattice, resulting in the Jahn-Teller distortion phenomenon, which destroys the spinel framework and further damages the lithium ion diffusion channels. Further, after multiple cycles of use, the internal structure degradation of the lithium ion sieve is more serious, the dissolution loss rate of Mn > 12 wt.%, and the capacity attenuation rate exceeds 40%. Therefore, the use of the existing lithium ion sieve in an acidic environment is severely restricted.

[0026] However, through the preparation method of the titanium-based lithium adsorbent with a core-shell structure provided by this application, it has good use stability in acidic environments and various application scenarios, so it has broad application potential in fields such as salt lake brine and waste battery recycling.

[0027] In some embodiments, in step S100, the lithium titanate is spinel-type lithium titanate, and the molar concentration of the sulfuric acid solution is 1.0 mol / L to 4.0 mol / L. Specifically, the molar concentration of the sulfuric acid solution is 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L. It is worth mentioning that spinel-type lithium titanate can use low-cost waste titanium acid lithium batteries, which is beneficial to reducing production costs and increasing economic benefits. On the other hand, using sulfuric acid for the delithiation reaction can undergo a displacement reaction with the lithium in lithium titanate, and can also form hydroxyl groups on the surface of lithium titanate. Moreover, as a strong acid, sulfuric acid can significantly shorten the delithiation time and improve production efficiency on an industrial scale.

[0028] In some embodiments, the reaction time of the delithiation reaction is 2 h to 12 h. Specifically, the reaction time of the delithiation reaction is 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h. Further preferably, the reaction time of the delithiation reaction is 4 h to 8 h, and the reaction temperature is 45 °C to 95 °C. Specifically, the reaction temperature is 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C. Further preferably, the reaction temperature is 60 °C to 85 °C. It is worth mentioning that the delithiation reaction can remove some lithium ions from the spinel-type lithium titanate, resulting in lattice expansion or contraction, thereby forming rich pores and channels. This porous structure can significantly increase the specific surface area of the material, further provide more adsorption active sites for lithium ions, and increase the reaction activity. That is to say, selecting appropriate delithiation reaction conditions is beneficial to form a stable porous structure and increase the adsorption effect on lithium. Among them, the first liquid is a mixed solution of lithium sulfate and titanyl sulfate.

[0029] In some embodiments, in step S200, the molar ratio of titanium element to lithium element in the first solid is 1:(2.00 to 2.10). Specifically, the molar ratio of titanium element to lithium element in the first solid is 1:2.00, 1:2.01, 1:2.02, 1:2.03, 1:2.04, 1:2.05, 1:2.06, 1:2.07, 1:2.08, 1:2.09, 1:2.10. Further preferably, the molar ratio of titanium element to lithium element in the first solid is 1:(2.03 to 2.05). It can be understood that selecting an appropriate molar ratio of titanium element to lithium element in the first solid is beneficial to control the degree of the delithiation reaction. Further, the added lithium hydroxide can regulate the pH value while introducing the lithium source.

[0030] In some embodiments, the mass fraction of niobium pentoxide is 0.2 wt.% to 1 wt.%. Specifically, the mass fraction of niobium pentoxide is 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1 wt.%. Further preferably, the mass fraction of niobium pentoxide is 0.4 wt.% to 0.8 wt.%. It can be understood that since the ionic radius of Nb 5+ is slightly larger than that of Ti 4+ its doping can partially occupy the lattice sites of titanium, relieve the volume change during lithium ion insertion or extraction, and reduce the structural stress. Therefore, the lattice structure can be stabilized by the niobium doping effect, and the structural collapse phenomenon during subsequent processing of the material can be inhibited. On the other hand, the doping of Nb 5+ can induce the formation of active Nb-O-Ti bonding sites on the surface, which is for Li +Its coordination ability is superior to that of the original Ti-O sites, which is beneficial to enhancing the lithium adsorption capacity and adsorption activity.

[0031] It is worth mentioning that in the existing aluminum-based layered double hydroxide (LDHs) lithium ion sieves, the hydroxyl groups present between the layers have an adsorption free energy of reaction intermediates (ΔGads) with divalent cations such as Mg 2+ or Ca 2+ greater than -15 kJ / mol, while the ΔGads with Li + is approximately equal to -8 kJ / mol. Therefore, the coordination affinity between the hydroxyl group and Mg 2+ or Ca 2+ is higher than that with Li + . Therefore, in brines where the mass concentration of Mg 2+ is much higher than that of Li + , for example, when the ratio of the mass of magnesium ions in the brine (m(Mg 2+ )) to the mass of lithium ions in the brine (m(Li + )) is greater than 500, the distribution coefficient (Kd) between LDHs and Li + is relatively low, where Kd < 10 L / g, indicating that its adsorption capacity for Li + is poor and it cannot effectively extract lithium from high-magnesium brines. That is to say, the selective adsorption of LDHs for Li + is poor.

[0032] In some embodiments, in step S200, the particle size distribution range after grinding treatment is 0.3 μm to 0.6 μm. Specifically, the particle size after grinding treatment is 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm; the median particle size range of the product after drying treatment is 20 μm to 40 μm. Specifically, the median particle size of the product after drying treatment is 20 μm, 25 μm, 30 μm, 35 μm, 40 μm. It can be understood that through sufficient grinding treatment, it is beneficial to increase the contact area and mixing uniformity between components, thereby improving the efficiency of subsequent reactions; the reactants after drying treatment are converted into a dry state, which is convenient for subsequent calcination treatment.

[0033] In some embodiments, the equipment used for grinding treatment is a sand mill, and the type of the sand mill is one of a turbine type or a rod pin type; the diameter of the grinding balls used in the grinding treatment is 0.1 mm to 1 mm, and further preferably, the diameter of the grinding balls is 0.15 mm to 0.3 mm. The linear velocity of the sand mill during use is ≥12 m / s, and the grinding time is 2 h to 4 h. Through sufficient grinding treatment, it is beneficial to increase the contact area and mixing uniformity between components, thereby improving the efficiency of subsequent reactions.

[0034] In some embodiments, the drying treatment is spray drying. Among them, the reactants after the drying treatment are converted into a dry state, facilitating the subsequent calcination treatment. It is worth mentioning that after spray drying, powders with uniform particle sizes can be formed, and during the drying process, the solvent evaporates rapidly, and the obtained powder particles have a complete morphology, further reducing the agglomeration phenomenon, which is beneficial to subsequent reactions and processing.

[0035] In some embodiments, the treatment temperature of the calcination treatment is 600 °C to 800 °C. Specifically, the treatment temperature of the calcination treatment is 600 °C, 650 °C, 700 °C, 750 °C, 800 °C. Further preferably, the treatment temperature of the calcination treatment is 650 °C to 750 °C; the treatment time is 4 h to 16 h. Specifically, the treatment time of the calcination treatment is 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h. Further preferably, the treatment time is 8 h to 12 h. It is worth mentioning that the first solid formed after calcination is Nb 5+ doped layered Li2TiO3 (Nb-LTO) material. Among them, impurities in the material can be removed through the calcination treatment, further improving the purity of the material. On the one hand, when the dried product is sintered at a high temperature, a porous structure will be formed, and this structure increases the specific surface area of the material, providing more active adsorption sites for adsorbing lithium ions; on the other hand, the crystal structure of the material after calcination is more stable, which is beneficial to improving the use stability and mechanical strength.

[0036] In some embodiments, in step S300, the mass concentration of the two-dimensional transition metal carbide or two-dimensional transition metal nitride solution is 5 g / L to 10 g / L. Specifically, the mass concentration of the two-dimensional transition metal carbide or two-dimensional transition metal nitride solution is 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L. The mass fraction of the two-dimensional transition metal carbide or two-dimensional transition metal nitride coated on the surface of the first solid is 2 wt.% to 5 wt.%. Specifically, the mass fraction of the two-dimensional transition metal carbide or two-dimensional transition metal nitride coated on the surface of the first solid is 2 wt.%, 2.5 wt.%, 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%. It is worth mentioning that selecting appropriate reaction concentrations and coating amounts of the coating material is beneficial to improving the bonding strength of the core-shell structure and the adsorption effect on lithium.

[0037] In some embodiments, in step S300, the temperature of the vacuum treatment is 45°C to 65°C. Specifically, the temperature of the vacuum treatment is 45°C, 50°C, 55°C, 60°C, 65°C, and the time of the vacuum treatment is 4 h to 10 h. Specifically, the time of the vacuum treatment is 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h. It can be understood that the niobium-doped hierarchical porous Li2TiO3@MXene (Nb-LTO@MX) heterogeneous adsorbent powder precursor is formed by vacuum-assisted self-assembly. It is worth mentioning that the niobium-doped porous Li2TiO3 is used as the core layer material, and there are many lithium-ion adsorption active sites distributed in the core layer, which can rapidly adsorb lithium ions; while the MXene material is used as the shell layer material. On the one hand, its surface terminal functional groups (-O, -OH) can form chemical bridges with lithium titanate to accelerate the + interface transfer rate of Li, and the strong binding energy of the Ti-O-C bond effectively inhibits the dissolution loss of lithium titanate in acidic media; on the other hand, the MXene material has a two-dimensional layered structure, and the + hydration radius of Li is relatively small, and it can smoothly pass through the interlayer channels of MXene to achieve rapid transmission, while the 2+ hydration radius of Mg and 2+ that of Ca is relatively large and cannot pass through the interlayer channels of MXene, so they are effectively blocked. That is to say, through the porous core-shell structure Nb-LTO@MX material, magnesium, calcium and other impurity ions are screened and blocked in the shell layer, and the adsorption sites on the internal porous core layer can rapidly adsorb lithium ions, further increasing the selectivity, adsorption capacity and adsorption efficiency of lithium ion adsorption.

[0038] Among them, the existing traditional hydrometallurgical recovery uses concentrated hydrochloric acid (hydrochloric acid concentration ≥ 6 mol / L) to intensively leach lithium and titanium components. However, the strong protonation effect generated by concentrated acid easily causes topological condensation phenomena in the spinel skeleton, such as the recombination of Ti-O-Ti bonds, resulting in products mostly being anatase / rutile mixed-phase titanium sources with a low specific surface area (BET < 50 m² / g), which cannot meet the requirements of the adsorbent for mesoporous structure and adsorption activity.

[0039] In some embodiments, in step S400, the molar concentration of the acid solution is 0.2 mol / L to 2 mol / L. Specifically, the molar concentration of the acid solution is 0.2 mol / L, 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, and the acid solution is one of hydrochloric acid, sulfuric acid and nitric acid. Protonation treatment can make the surface of the adsorbent positively charged, which can effectively repel other positively charged impurity ions in the solution, such as Mg 2+ and Ca 2+, reducing the interference with lithium ion adsorption; on the other hand, since the protonation treatment makes the chemical bonds on the adsorbent surface more stable, further improving the chemical stability of the adsorbent when used in acidic or neutral environments.

[0040] In some embodiments, the temperature of the protonation treatment is 35°C to 60°C. Specifically, the temperature of the protonation treatment is 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, and the time of the protonation treatment is 6h to 10h. Specifically, the time of the protonation treatment is 6h, 7h, 8h, 9h, 10h. By selecting appropriate treatment conditions for the protonation treatment, the surface electrical properties of the material are effectively changed, making it more suitable for adsorbing lithium ions, while reducing the interference of other impurities and improving the adsorption efficiency and selectivity of lithium ions.

[0041] In some embodiments, in step S400, the number of washing treatments is not less than 3 times, so as to fully wash away the impurities on the surface of the adsorbent.

[0042] In some embodiments, the temperature of the drying treatment is 45°C to 60°C. Specifically, the temperature of the drying treatment is 45°C, 50°C, 55°C, 60°C; the time of the drying treatment is 6h to 10h. Specifically, the time of the drying treatment is 6h, 7h, 8h, 9h, 10h. Through appropriate drying treatment conditions, the residual moisture on the surface of the adsorbent is removed.

[0043] To achieve the above object, the technical solution adopted in this application is: a titanium-based lithium adsorbent prepared by the preparation method as described above.

[0044] It is worth mentioning that the existing titanium-based adsorbents (such as H2TiO3) prepared by the sol-gel method require high-purity titanium sources (purity ≥ 99.9%) as raw materials, and the proportion of raw material consumption cost is greater than 70%, with poor industrial economy and being not conducive to large-scale production and use. In contrast, through the preparation method of the titanium-based lithium adsorbent provided in this application, the waste recycling and the production of the adsorbent are integrated into a continuous preparation process, and the reaction conditions of each step are intelligently regulated to further achieve the efficient synthesis of the adsorbent, which has the advantages of simple preparation process, easy operation and less cost consumption, thus having the potential for large-scale production.

[0045] Example 1 A preparation method of a titanium-based lithium adsorbent, comprising the steps: S100. Provide 1000g of crushed lithium titanate Li4Ti5O 12The powder was placed in a 3L sulfuric acid solution with a concentration of 2mol / L for delithiation reaction. After stirring at 80°C for 4h, a mixed solution of titanium oxysulfate and lithium sulfate was obtained. After testing the lithium ion adsorption amount, the content of Li was 5.62% and the content of Ti was 50.74%. After calculation, the molar ratio of Li / Ti in the lithium titanate powder was 3.82:5; S200: 572.0g of lithium hydroxide monohydrate and 7.86g of niobium pentoxide were dispersed in the mixed solution of titanium oxysulfate and lithium sulfate. The mixed material was ground using a sand mill at a linear speed of not less than 12m / s for 2h. The D50 of the slurry was 0.412μm. Then the slurry was spray-dried. The inlet temperature was 245°C and the outlet temperature was 110°C. The spray particle size D50 was 28.3μm. Then the spray powder was sintered in a muffle furnace at a sintering temperature of 750°C for 10h of heat preservation. After cooling to room temperature, Nb 5+ doped layered Li2TiO3 (Nb-LTO) powder; S300: 500.0g of Nb-LTO powder was dispersed in 2000mL of Ti3C2T x MXene solution with a concentration of 8g / L. After ultrasonic dispersion for 2h, it was filtered, washed, and vacuum-dried. The vacuum drying temperature was 55°C and the time was 8h to obtain the niobium-doped hierarchical porous Li2TiO3@MXene (Nb-LTO@MX) heterogeneous adsorbent powder precursor; S400: 200.0g of the Nb-LTO@MX heterogeneous adsorbent powder precursor was dispersed in 500L of a dilute hydrochloric acid solution with a concentration of 0.1mol / L. It was mechanically stirred at a constant temperature of 50°C for 6h at a rotation speed of 300rpm. Subsequently, the slurry was filtered, washed 3 times, and then dried in a blast dryer at 60°C for 10h to obtain the Nb-LTO@MX titanium-based lithium adsorbent.

[0046] Example 2 The difference between Example 2 and Example 1 is that the concentration of the Ti3C2T x MXene solution used in step S300 was 5g / L.

[0047] Example 3 The difference between Example 3 and Example 1 is that the concentration of the Ti3C2T x MXene solution used in step S300 was 10g / L.

[0048] Example 4 The difference between Example 4 and Example 1 is that the mass fraction of the niobium pentoxide solution used in step S200 was 0.2wt.%.

[0049] Example 5 Example 5 is different from Example 1 in that the mass fraction of the niobium pentoxide solution used in step S200 is 1 wt.%.

[0050] Example 6 Example 6 is different from Example 1 in that Ti3C2T x MXene solution is used in step S300.

[0051] Example 7 Example 7 is different from Example 1 in that yttrium trioxide is used in step S200.

[0052] Example 8 Example 8 is different from Example 1 in that a titanium carbide nanosheet solution is used in step S300.

[0053] Example 9 Example 9 is different from Example 1 in that a titanium nitride nanosheet solution is used in step S300.

[0054] Example 10 Example 10 is different from Example 1 in that the Li / Ti molar ratio in the lithium titanate powder in step S100 is 3:5.

[0055] Example 11 Example 11 is different from Example 1 in that the Li / Ti molar ratio in the lithium titanate powder in step S100 is 4:5.

[0056] Comparative Example 1 Comparative Example 1 is different from Example 1 in that Ti3C2T x MXene solution is not used in step S300.

[0057] Comparative Example 2 Comparative Example 2 is different from Example 1 in that niobium pentoxide is not used in step S200.

[0058] Comparative Example 3 Comparative Example 3 is different from Example 1 in that the protonation treatment in step S400 is not used.

[0059] Performance Evaluation The lithium ion adsorption capacity of the titanium-based lithium adsorbents in Examples 1 to 10 and Comparative Examples 1 to 4 was tested. The specific steps were as follows: Weigh 50.0 g of the titanium-based lithium adsorbent and soak it in 2 L of lithium hydroxide solution with a lithium content of 2000 mg / L. Samples were taken every 1 h, and the lithium content was tested by inductively coupled plasma mass spectrometry. When there was no difference in the lithium content of the samples taken twice in succession, it was considered that the adsorption saturation state was reached. The adsorption capacity was calculated based on the decrease in lithium in the water sample, and the saturated adsorption capacity of the corresponding titanium-based lithium adsorbent was calculated based on the lithium ion content.

[0060] Table 1: Performance Test of Titanium-Based Lithium Adsorbent

[0061] The basic principles, main features, and advantages of the present application have been described above. Those skilled in the art should understand that the present application is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present application. Without departing from the spirit and scope of the present application, various changes and improvements will occur to the present application, and these changes and improvements all fall within the scope of the present application claimed. The scope of protection required by the present application is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a titanium-based lithium adsorbent, characterized in that, Including the steps: S100. Provide lithium titanate powder, place it into a sulfuric acid solution for delithiation reaction to obtain a first liquid; S200. Wet-mix the first liquid, lithium hydroxide, and niobium pentoxide, and obtain a first solid after grinding treatment, drying treatment, and calcination treatment; S300. Disperse the first solid into a solution with two-dimensional transition metal carbide or two-dimensional transition metal nitride. Under vacuum conditions, the two-dimensional transition metal carbide or two-dimensional transition metal nitride is coated on the surface of the first solid to form a second solid; S400. Place the second solid into an acid solution for protonation treatment, and obtain a titanium-based lithium adsorbent after washing and drying.

2. The preparation method according to claim 1, characterized in that, The structural general formula of the two-dimensional transition metal carbide or the two-dimensional transition metal nitride is M n+1 X n T x , where M is the transition metal layer, X is the carbon layer or the nitrogen layer, and T x is the functional group on the surface, and n is the number of adjacent transition metal layers, and the value of n is 1, or 2, or 3.

3. The preparation method according to claim 2, characterized in that, The two-dimensional transition metal carbide is Ti3C2T x , and the T x includes one or more of hydroxyl groups and oxygen groups.

4. The preparation method according to claim 1, characterized in that, In the step S100, the lithium titanate is spinel-type lithium titanate, the molar concentration of the sulfuric acid solution is 1.0 mol / L to 4.0 mol / L, the reaction time of the delithiation reaction is 2 h to 12 h, and the reaction temperature is 45°C to 95°C.

5. The preparation method according to claim 1, characterized in that, In the step S200, the molar ratio of titanium element to lithium element in the first solid is 1:(2.00 to 2.10), and the mass fraction of niobium pentoxide is 0.2 wt.% to 1 wt.%.

6. The preparation method according to claim 1, characterized in that, In the step S200, the particle size distribution range after the grinding treatment is 0.3 μm to 0.6 μm; the median particle size range of the product after the drying treatment is 20 μm to 40 μm, and the drying treatment is spray drying treatment; the treatment temperature of the calcination treatment is 600°C to 800°C, and the treatment time is 4 h to 16 h.

7. The preparation method according to claim 3, characterized in that, In the step S300, the mass concentration of the two-dimensional transition metal carbide or the two-dimensional transition metal nitride solution is 5 g / L to 10 g / L, and the mass fraction of the two-dimensional transition metal carbide or the two-dimensional transition metal nitride coated on the surface of the first solid is 2 wt.% to 5 wt.%; the temperature of the vacuum treatment is 45°C to 65°C, and the time of the vacuum treatment is 4 h to 10 h.

8. The preparation method according to claim 1, characterized in that, In the step S400, the molar concentration of the acid solution is 0.2 mol / L to 2 mol / L, and the acid solution is one of hydrochloric acid, sulfuric acid, and nitric acid; the temperature of the protonation treatment is 35°C to 60°C, and the time of the protonation treatment is 6 h to 10 h.

9. The preparation method according to claim 1, characterized in that, In the step S400, the number of times of the washing treatment is not less than 3 times; the temperature of the drying treatment is 45°C to 60°C, and the time of the drying treatment is 6 h to 10 h.

10. A titanium-based lithium adsorbent, characterized in that, Prepared by the preparation method according to any one of claims 1-9.

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