A multi-ion doped manganese-based lithium ion sieve adsorbent and a preparation method and application thereof

Abstract

The application discloses a kind of multi-ion doped manganese-based lithium ion sieve adsorbents and its preparation method and application, it is related to lithium ion sieve adsorbent preparation technical field.The present application provides two kinds of process routes of hydrothermal synthesis method and sol-gel method, can realize the one-step synthesis of multi-ion doped manganese-based lithium ion sieve precursor under mild conditions, simple operation, raw material cost is low, without complex equipment, easy to scale up.The problems such as high manganese dissolution loss, poor cycle stability and limited adsorption capacity of existing lithium ion sieve are solved, the target ion sieve is obtained by preparing precursor by the above method and being treated by acid immersion, the crystal structure of the obtained material is stable, the manganese dissolution loss is significantly reduced, the adsorption performance is excellent, especially suitable for high magnesium-lithium ratio system;The adsorbent has high selectivity to lithium in complex ion environment, and its distribution coefficient is much better than that of other ions, and has good practical application prospect.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion sieve adsorbent preparation technology, specifically to a multi-ion doped manganese-based lithium-ion sieve adsorbent, its preparation method, and its application. Background Technology

[0002] Lithium-ion sieve adsorption is an effective method for extracting lithium ions from salt lake brine and seawater. This method utilizes the memory effect of lithium-ion sieve materials to directly and selectively adsorb and extract lithium ions from solutions with complex compositions, thereby eliminating multiple chemical pretreatment steps and significantly simplifying the process.

[0003] Lithium-ion sieve materials mainly fall into three categories: manganese-based, titanium-based, and aluminum-based. Among them, manganese-based lithium-ion sieves, due to the ion-sieving effect imparted by their spinel structure, exhibit excellent selectivity for lithium ions, making them ideal materials for lithium extraction. However, the core technical challenge faced by manganese-based lithium-ion sieves in practical applications lies in the manganese dissolution problem during the acid leaching and delithiation regeneration process.

[0004] During the pickling process, trivalent manganese ions in the spinel structure are prone to disproportionation reactions, generating soluble divalent and tetravalent manganese ions. This causes manganese to dissolve from the crystal lattice, leading to crystal structure collapse and adsorption capacity decay, resulting in a significant decrease in the material's cycle stability.

[0005] To address the manganese dissolution problem, ion doping is considered one of the most effective modification strategies. By introducing foreign ions to partially replace the unstable trivalent manganese ions in the spinel lattice, Jahn-Teller distortion is suppressed at the atomic level, the structural rigidity of the crystal framework is enhanced, and thus the manganese dissolution rate is reduced.

[0006] However, existing ion doping strategies are mostly limited to doping at a single cation site, suppressing manganese dissolution solely by substituting trivalent manganese ions, making it difficult to achieve a good balance between stability and adsorption capacity. Enhancing framework rigidity often comes at the cost of sacrificing lithium adsorption capacity and adsorption kinetics. Furthermore, the radius difference between the dopant ions and native trivalent manganese ions can lead to lattice contraction, shrinking the lithium ion transport channels in the octahedral structure, resulting in a decrease in saturated adsorption capacity and a significant slowdown in adsorption rate.

[0007] In addition, the substitution coverage of single cation doping is limited, and the unprotected trivalent manganese ions in the deep framework will continue to dissolve under long-term cyclic pickling. The rebound of manganese dissolution in the later stage of the cycle is difficult to avoid, and the long-term cyclic stability of the material still cannot meet the requirements of industrial applications.

[0008] Therefore, there is an urgent need to develop a manganese-based lithium ion sieve adsorbent that can balance high structural stability and high adsorption capacity, in order to solve the technical problem that single cation doping in the existing technology cannot simultaneously improve stability and adsorption capacity.

[0009] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0010] To address the aforementioned technical problems, embodiments of the present invention provide a multi-ion-doped manganese-based lithium ion sieve adsorbent, its preparation method, and its application, thereby resolving the issues raised in the background section.

[0011] A multi-ion-doped manganese-based lithium-ion sieve adsorbent, with the general chemical formula: Li 1.6 A x Mn 1.6-x B y O 4-y ; Wherein, A is at least one of Mg, Fe, Co, W, Ni, B, Ti, and Al, occupying the Mn site, and B is at least one of F and S, occupying the O site.

[0012] Preferably, the chemical formula Li 1.6 A x Mn 1.6-x B y O 4-y In the equation, A is Ni, B is F, x = 0.01, and y = 0.02.

[0013] Preferably, the adsorbent has a cubic spinel crystal structure, in which element A uniformly replaces Mn atoms at the octahedral sites in the spinel lattice, and element B uniformly replaces O atoms at the vertex sites in the spinel lattice.

[0014] A method for preparing a multi-ion-doped manganese-based lithium-ion sieve adsorbent according to the above-described method includes the following steps: Step 1: Mix lithium hydroxide monohydrate, manganese trioxide, dopant ion source A, and dopant ion source B in a preset ratio to obtain a mixed raw material; Step 2: Place the mixed raw materials in a hydrothermal reactor for hydrothermal synthesis, and then dry them to obtain the pretreated material; Step 3: Calcine the pretreated material to obtain the precursor material; Step 4: Grind, acid wash, separate, and dry the precursor material to obtain a multi-ion doped manganese-based lithium ion sieve adsorbent.

[0015] Preferably, the molar ratio of lithium hydroxide monohydrate to manganese trioxide is 2:0.9-1; The molar ratio of dopant in the dopant source A and the dopant source B is 0.005-0.2; The hydrothermal synthesis temperature is 100-140℃, and the hydrothermal time is 12-36 h.

[0016] Preferably, the calcination temperature is 100-700℃ and the calcination time is 1-6 h; The pickling solution used is 0.05-0.5 M in concentration, the mass-to-volume ratio of the multi-ion doped manganese-based lithium ion sieve precursor to the pickling solution is 1:100-200 g / mL, and the pickling time is 10-28 h.

[0017] A method for preparing a multi-ion-doped manganese-based lithium-ion sieve adsorbent according to the above-described method includes the following steps: Step 1: Mix lithium chloride, manganese acetate, dopant ion source A, and dopant ion source B in water according to a preset ratio; Step 2: The mixed raw materials are continuously heated and stirred to form a uniform mixed solution, and the solution is dried to obtain the pretreated material; Step 3: Calcine the pretreated material to obtain the precursor material; Step 4: Grind, acid wash, separate, and dry the precursor material to obtain a multi-ion doped manganese-based lithium ion sieve adsorbent.

[0018] Preferably, the molar ratio of lithium chloride to manganese acetate is 2:0.9-1; The molar ratio of dopant in the dopant source A and the dopant source B is 0.005-0.2; The heating and stirring temperature is 20-60℃, and the stirring time is 10-60 min.

[0019] Preferably, the calcination temperature is 100-700℃ and the calcination time is 1-6 h; The pickling solution used is 0.05-0.5 M in concentration, the mass-to-volume ratio of the multi-ion doped manganese-based lithium ion sieve precursor to the pickling solution is 1:100-200 g / mL, and the pickling time is 10-28 h.

[0020] An application of the multi-ion-doped manganese-based lithium ion sieve adsorbent described above in the extraction of lithium ions from seawater or salt lake brine.

[0021] The present invention provides a multi-ion-doped manganese-based lithium ion sieve adsorbent, its preparation method, and its application, which have the following beneficial effects: (1) This invention constructs a dual-site synergistic doping system of cations and anions by simultaneously introducing high-valence cations (A-site doping) and highly electronegative anions (B-site doping) into the spinel lattice. The A-site cation replaces the trivalent manganese ion at the octahedral site, reducing the average valence state of manganese through charge compensation and suppressing the electronic driving force of Jahn-Teller distortion; the B-site anion replaces the oxygen ion at the vertex site, utilizing its strong bond energy effect to enhance the binding energy of the octahedron and stabilize the crystal configuration.

[0022] (2) This invention achieves stable framework structure through dual-site synergistic doping, while ensuring full exposure of active sites, thus overcoming the bottleneck of sacrificial capacity improvement achieved by traditional cation single-doping. The lithium adsorption capacity of the multi-ion co-doped adsorbent is significantly better than that of undoped and single-doped samples, demonstrating significant technical effectiveness. XPS analysis shows that ion doping effectively reduces the relative content of trivalent manganese ions and increases the average valence state of manganese, confirming the effective suppression of the Jahn-Teller effect. At the same time, the exposure of the hierarchical porous structure ensures a rapid lithium ion transport channel.

[0023] (3) The adsorbent of the present invention exhibits excellent recognition selectivity for lithium ions in simulated mixed solutions. The partition coefficient of lithium ions is much higher than that of sodium ions, potassium ions, calcium ions and magnesium ions. The selectivity coefficient for magnesium ions reaches a high level, proving that it can still accurately identify and efficiently capture lithium ions in complex salt lake brine systems where multiple ions such as magnesium, calcium and sodium coexist.

[0024] (4) The adsorbent of the present invention exhibits good capacity retention and structural stability in multiple adsorption-desorption cycles. After multiple cycles, the adsorption capacity remains at a high level, and the manganese dissolution rate is effectively controlled, indicating that it has good cycle stability and resistance to acid washing and dissolution, which meets the requirements of industrial long-term operation for material durability. Attached Figure Description Figure 1 This is a process flow diagram of the preparation method of multi-ion doped manganese-based lithium ion sieve adsorbent provided in the embodiments of the present invention; Figure 2 This is a comparison of the X-ray diffraction patterns of undoped ion sieves and ion sieves with different doping ratios before and after acid washing. Figure 3 This is a comparison of scanning electron microscope images of undoped ion sieves and ion sieves with different doping ratios; Figure 3 (a) is a SEM microstructure image of HT-undoped-LMO; Figure 3 (b) is a SEM microstructure image of 1% W-LMO; Figure 3 (c) is a SEM microstructure image of 1%W10%F-LMO; Figure 3 (d) is the EDS elemental mapping of 1% W-LMO; Figure 3 (e) is the EDS element mapping diagram of 1%W10%F-LMO; Figure 4 These are high-resolution TEM micrographs of undoped ion sieves and ion sieves with different doping ratios, as well as interplanar spacing. Figure 4 (a) is a high-resolution TEM micrograph of HT-undoped-LMO and its interplanar spacing; Figure 4 (b) is a high-resolution TEM micrograph of 1%W-LMO and its interplanar spacing; Figure 4 (c) is a high-resolution TEM micrograph of 1%W10%F-LMO and its interplanar spacing; Figure 4 (d) is a high-resolution TEM micrograph of SG-undoped-LMO and its interplanar spacing; Figure 4 (e) is a high-resolution TEM micrograph of 1%Ni2%F-LMO and its interplanar spacing; Figure 5 It is an X-ray photoelectron spectrum; Figure 6 The graphs show the changes in lithium-ion adsorption capacity over time for undoped ion sieves, single-doped ion sieves, and multi-doped ion sieves. Figure 7 This is a bar chart comparing the adsorption capacity of various metal ions by multi-ion doped manganese-based lithium ion sieve adsorbents in a simulated mixed solution. Figure 8 This is a graph showing the cyclic adsorption capacity and manganese dissolution rate of the 1%Ni2%F-HMO adsorbent as a function of the number of cycles. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] To address the aforementioned technical problems, embodiments of the present invention provide a multi-ion-doped manganese-based lithium ion sieve adsorbent, its preparation method, and its application, thereby resolving the issues raised in the background section.

[0027] I. Specific Implementation Cases Example 1: 1%W5%F-HMO This embodiment provides a multi-ion-doped manganese-based lithium-ion sieve adsorbent, its preparation method, and its application. The preparation and application process is as follows: Figure 1 As shown, the preparation method includes the following steps: (1) 0.8392g lithium hydroxide monohydrate, 0.7815g manganese trioxide, 0.0232g tungsten trioxide and 0.0130g lithium fluoride were mixed to prepare a blend, and then transferred to a polytetrafluoroethylene liner for hydrothermal reaction. (2) The solid product after hydrothermal reaction is collected by centrifugation, washed and dried to obtain a black solid product; (3) The obtained black solid was calcined in a muffle furnace at 600°C for 6 h to obtain a lithium ion sieve precursor; (4) The lithium ion sieve precursor was acid-washed in 0.5M pickling solution for 24 h, and then centrifuged, washed and dried to obtain lithium ion sieve adsorbent 1%W5%F-HMO.

[0028] Example 2: 1%Ni2%F-HMO This embodiment provides another multi-ion-doped manganese-based lithium-ion sieve adsorbent, its preparation method, and its application. The preparation and application process is as follows: Figure 1 As shown, the preparation method includes the following steps: (1) Mix 1.6956g lithium chloride, 4.8528g manganese acetate and 0.0338g nickel fluoride tetrahydrate in water and heat and stir continuously in a beaker until dissolved; (2) The dissolved mixed solution is dried to obtain a yellow solid product; (3) The obtained yellow solid was calcined in a muffle furnace at 450°C for 6 h to obtain a lithium ion sieve precursor; (4) The lithium ion sieve precursor was acid-washed in 0.5M pickling solution for 24 h, and then centrifuged, washed and dried to obtain lithium ion sieve adsorbent 1%Ni2%F-HMO.

[0029] Example 3: 1%W 10%F-HMO The only difference between this embodiment and Example 1 is that in step (1), the amount of lithium fluoride used is 0.0259g, and lithium ion sieve adsorbent 1%W10%F-HMO is obtained. All other conditions are the same as in Example 1.

[0030] Example 4: 1% W 15% F-HMO The only difference between this embodiment and Example 1 is that in step (1), the amount of lithium fluoride used is 0.0389g, and lithium ion sieve adsorbent 1%W15%F-HMO is obtained. All other conditions are the same as in Example 1.

[0031] Example 5: 1%W 20%F-HMO The only difference between this embodiment and Example 1 is that in step (1), the amount of lithium fluoride used is 0.05188g, and lithium ion sieve adsorbent 1%W20%F-HMO is obtained. All other conditions are the same as in Example 1.

[0032] Example 6: 2%Ni4%F-HMO The only difference between this embodiment and embodiment 2 is that the amount of nickel tetrahydrate used in step (1) is 0.0675g, and the lithium ion sieve adsorbent 2%Ni4%F-HMO is obtained. All other conditions are the same as in embodiment 2.

[0033] Example 7: 3%Ni6%F-HMO The only difference between this embodiment and embodiment 2 is that the amount of nickel tetrahydrate used in step (1) is 0.1013g, and the lithium ion sieve adsorbent 3%Ni6%F-HMO is obtained. All other conditions are the same as in embodiment 2.

[0034] Example 8: 0.5%Ni1%F-HMO The only difference between this embodiment and embodiment 2 is that the amount of nickel tetrahydrate used in step (1) is 0.01688g, and lithium ion sieve adsorbent 0.5%Ni1%F-HMO is obtained. All other conditions are the same as in embodiment 2.

[0035] Example 9: 1.5%Ni3%F-HMO The only difference between this embodiment and embodiment 2 is that the amount of nickel tetrahydrate used in step (1) is 0.0506g, and lithium ion sieve adsorbent 1.5%Ni3%F-HMO is obtained. All other conditions are the same as in embodiment 2.

[0036] Comparative Example 1: HT-undoped-HMO The only difference between this comparative example and Example 1 is that in step (1), the amount of tungsten trioxide and lithium fluoride used is 0g, and undoped lithium ion sieve adsorbent HT-undoped-HMO is obtained. All other conditions are the same as in Example 1.

[0037] Comparative Example 2: 1% W-HMO The only difference between this comparative example and Example 1 is that in step (1), the amount of tungsten trioxide is 0.0232g and the amount of lithium fluoride is 0g, resulting in tungsten-doped lithium ion sieve adsorbent 1%W-HMO. All other conditions are the same as in Example 1.

[0038] Comparative Example 3: SG-undoped-HMO The only difference between this comparative example and Example 2 is that the amount of nickel tetrahydrate used in step (1) is 0g, and undoped lithium ion sieve adsorbent SG-undoped-HMO is obtained. All other conditions are the same as in Example 2.

[0039] II. Performance Testing Experiment The lithium adsorption capacity and manganese dissolution rate in Examples 1-9 and Comparative Examples 1-3 are shown in Table 1. Among them, the data in Table 1 show that Example 2 has the highest lithium adsorption capacity, reaching 54.48 mg / g, while the manganese dissolution rate is only 2.27%, and its overall performance is better than other examples and comparative examples.

[0040] Table 1 refer to Figure 2 XRD characterization was performed on undoped and ion sieves with different doping ratios. The results showed that the diffraction peaks of undoped and ion sieves with different doping ratios were similar to those of Li. 1.6 Mn 1.6 The O4 standard card comparison is good, indicating that the spinel structure of the manganese-based lithium ion sieve has been successfully prepared, and that appropriate ion doping does not change the spinel structure of the ion sieve.

[0041] When the doping ions are excessive, the intensity of the diffraction peaks weakens or even disappears, indicating that excessive ion doping may lead to a decrease in crystallinity and the generation of other impurities. After acid washing, it can be observed that the diffraction peaks of the undoped ion sieve basically disappear, while the doped ion sieve still maintains good crystallinity. The diffraction peaks show good contrast with the standard card, indicating that an appropriate amount of doping is beneficial to maintaining the stability of the crystal structure.

[0042] refer to Figure 3-4 The microstructure of undoped and ion sieves with different doping ratios was characterized. The results showed that appropriate ion doping does not change the material morphology of the ion sieve. EDS characterization results showed that the dopant elements were uniformly distributed, proving that the ions were successfully doped into the ion sieve.

[0043] refer to Figure 5 X-ray photoelectron spectroscopy (XPS) was used to analyze the structural changes and stabilization mechanism of the samples before and after doping. In the full XPS spectrum of the tungsten-fluorine co-doped sample, characteristic peaks of W 4f and F 1s were observed at 36 eV and 686.2 eV, respectively, confirming that tungsten and fluorine had been successfully incorporated into the ion sieve lattice. Peak fitting of the Mn 2p orbitals showed that Mn³ in the undoped sample… + and Mn 4+ The contents were 57.52% and 42.48%, respectively; after single-doping with tungsten, Mn³ + The content decreased to 42.71%, Mn 4+ The content increased to 57.29%; after further tungsten-fluorine co-doping, Mn³ + The content continued to decrease to 38.70%, Mn 4+The content increased to 61.30%. Similarly, the XPS spectra of the nickel-fluorine co-doped samples showed characteristic peaks for Ni 2p and F 1s, while Mn³⁺… + The content decreased from 60.06% in the undoped state to 50.19%, Mn 4+ The content increased from 39.94% to 49.81%. These results indicate that ion doping effectively reduced Mn³⁺. + The relative content of [a certain element] increased the average valence state of manganese, thereby inhibiting its interaction with Mn³ [a certain element] to some extent. + The associated Jahn-Teller effect enhances the stability of the spinel structure.

[0044] refer to Figure 6 Li was adsorbed by ion sieve. + Experiment. 0.1 g of the examples and comparative examples were added to 50 ml of 300 mg / L lithium solution, stirred at 30 °C, and samples were taken at different times. The ion concentration was tested using ICP-OES, and the adsorption capacity was calculated. It can be seen that the adsorption capacity of the multi-ion-doped ion sieve is significantly better than that of the undoped and single-doped ion sieves.

[0045] refer to Figure 7 As shown in Table 2, selective adsorption experiments were conducted. 0.1 g of Example 3 was added to 50 ml of a simulated mixed solution, stirred at 30°C, and the ion concentration was measured using ICP-OES to calculate the adsorption capacity. It can be seen that it maintains excellent lithium adsorption capacity and anti-interference ability even in complex ionic environments, exhibiting good selectivity for lithium ions.

[0046] Table 21%W10%F-HMO Adsorption Selectivity refer to Figure 8 Adsorption-desorption cycle performance experiments were conducted, and it can be seen that the initial lithium adsorption capacity of F-HNMO-1% is [value missing]. After 8 cycles, its adsorption capacity can still be maintained at 80%. After 8 cycles, the dissolution rate of Mn decreased from 3.89% to 2.27%, a decrease of 41.65%. This indicates that the lithium adsorption capacity and manganese dissolution rate of F-HNMO-1% after ion doping are improved compared with the undoped form, and it has good cycle stability.

[0047] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A multi-ion-doped manganese-based lithium-ion sieve adsorbent, characterized in that, The chemical formula is: Li 1.6 A x Mn 1.6- x B y O 4-y ; Wherein, A is at least one of Mg, Fe, Co, W, Ni, B, Ti, and Al, occupying the Mn site, and B is at least one of F and S, occupying the O site.

2. The multi-ion-doped manganese-based lithium-ion sieve adsorbent according to claim 1, characterized in that, The chemical formula Li 1.6 A x Mn 1.6-x B y O 4-y In the equation, A is Ni, B is F, x = 0.01, and y = 0.

02.

3. The multi-ion-doped manganese-based lithium-ion sieve adsorbent according to claim 1, characterized in that, The adsorbent has a cubic spinel crystal structure, in which element A uniformly replaces Mn atoms at the octahedral sites in the spinel lattice, and element B uniformly replaces O atoms at the vertex sites in the spinel lattice.

4. A method for preparing a multi-ion-doped manganese-based lithium-ion sieve adsorbent according to claim 1, characterized in that, Includes the following steps: Step 1: Mix lithium hydroxide monohydrate, manganese trioxide, dopant ion source A, and dopant ion source B in a preset ratio to obtain a mixed raw material; Step 2: Place the mixed raw materials in a hydrothermal reactor for hydrothermal synthesis, and then dry them to obtain the pretreated material; Step 3: Calcine the pretreated material to obtain the precursor material; Step 4: Grind, acid wash, separate, and dry the precursor material to obtain a multi-ion doped manganese-based lithium ion sieve adsorbent.

5. The preparation method of the multi-ion doped manganese-based lithium ion sieve adsorbent according to claim 4, characterized in that, The molar ratio of lithium hydroxide monohydrate to manganese trioxide is 2:0.9-1; The molar ratio of dopant in the dopant source A and the dopant source B is 0.005-0.2; The hydrothermal synthesis temperature is 100-140℃, and the hydrothermal time is 12-36 h.

6. The preparation method of the multi-ion doped manganese-based lithium ion sieve adsorbent according to claim 4, characterized in that, The calcination temperature is 100-700℃, and the calcination time is 1-6 h; The pickling solution used is 0.05-0.5 M in concentration, the mass-to-volume ratio of the multi-ion doped manganese-based lithium ion sieve precursor to the pickling solution is 1:100-200 g / mL, and the pickling time is 10-28 h.

7. A method for preparing a multi-ion-doped manganese-based lithium-ion sieve adsorbent according to claim 1, characterized in that, Includes the following steps: Step 1: Mix lithium chloride, manganese acetate, dopant ion source A, and dopant ion source B in water according to a preset ratio; Step 2: The mixed raw materials are continuously heated and stirred to form a uniform mixed solution, and the solution is dried to obtain the pretreated material; Step 3: Calcine the pretreated material to obtain the precursor material; Step 4: Grind, acid wash, separate, and dry the precursor material to obtain a multi-ion doped manganese-based lithium ion sieve adsorbent.

8. The preparation method of the multi-ion doped manganese-based lithium ion sieve adsorbent according to claim 7, characterized in that, The molar ratio of lithium chloride to manganese acetate is 2:0.9-1; The molar ratio of dopant in the dopant source A and the dopant source B is 0.005-0.2; The heating and stirring temperature is 20-60℃, and the stirring time is 10-60 min.

9. The preparation method of the multi-ion doped manganese-based lithium ion sieve adsorbent according to claim 7, characterized in that, The calcination temperature is 100-700℃, and the calcination time is 1-6 h; The pickling solution used is 0.05-0.5 M in concentration, the mass-to-volume ratio of the multi-ion doped manganese-based lithium ion sieve precursor to the pickling solution is 1:100-200 g / mL, and the pickling time is 10-28 h.

10. The application of the multi-ion doped manganese-based lithium ion sieve adsorbent according to claim 1 in the extraction of lithium ions from seawater or salt lake brine.

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