Preparation method of chromium-doped manganese lithium ion sieve and application of chromium-doped manganese lithium ion sieve in lithium extraction

Abstract

The invention belongs to the field of hydrometallurgy, and particularly relates to a preparation method of a chromium-doped manganese lithium ion sieve and application of the chromium-doped manganese lithium ion sieve in lithium extraction. The preparation method comprises the following steps: by taking a lithium source, a manganese source and a chromium source as raw materials, synthesizing a chromium-doped spinel type lithium ion sieve precursor through a high-temperature solid-phase method, and further performing acid leaching treatment, thereby obtaining the ion sieve with high adsorption selectivity and low manganese solution loss. The method is simple in process and low in cost, and the prepared chromium-doped manganese lithium ion sieve is stable in crystal structure and low in manganese solution loss rate. The developed chromium-doped manganese lithium ion sieve is suitable for efficient extraction of lithium resources of salt lake brine, and a low-cost solution is provided for efficient extraction of the lithium resources of the salt lake.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy, specifically relating to a method for preparing a chromium-doped manganese lithium-ion sieve and its application in lithium extraction. Background Technology

[0002] Lithium, as a core resource in the new energy field, is irreplaceable in areas such as lithium-ion batteries, special alloys, and the nuclear industry. Approximately 72.3% of global lithium resources are found in salt lake brines, with my country's salt lake lithium reserves accounting for 79% of the national total. However, Chinese salt lake brines generally exhibit high magnesium-to-lithium ratios (Mg²⁺ / Li⁺ mass ratio 500-1900) and low lithium concentrations, resulting in low efficiency and high costs for traditional precipitation and solvent extraction methods. In recent years, adsorption methods have become the mainstream technology for lithium extraction from salt lakes due to their high selectivity and low energy consumption. Among these, manganese-based lithium ion sieves (LiMn₂O₄) have attracted significant attention due to their high theoretical adsorption capacity and excellent Li⁺ / Mg²⁺ selectivity.

[0003] However, manganese-based ion sieves are prone to manganese disproportionation during acid leaching and desorption, resulting in a manganese loss rate exceeding 20%, severely limiting their cycle life and industrial applications. Existing technologies utilize elemental doping (such as Fe, Co, Na, and Mg) to partially suppress manganese loss. While these methods improve stability, they suffer from insufficient bonding strength between the dopant element and manganese, and a tendency for crystal structure collapse. Furthermore, they struggle to simultaneously meet the dual requirements of high adsorption capacity and low loss rate. In addition, traditional preparation processes (such as hydrothermal methods and co-precipitation methods) suffer from harsh reaction conditions and poor product uniformity, further limiting the potential for optimizing material properties.

[0004] Therefore, developing a simple, low-cost method for preparing lithium-ion sieves that simultaneously achieves high adsorption capacity and low manganese loss is crucial for technological innovation in lithium extraction from salt lake brine. To address this issue, this invention aims to provide a method for preparing a chromium-doped manganese-based lithium-ion sieve. Summary of the Invention

[0005] This invention proposes a method for preparing manganese-based lithium-ion sieves based on chromium doping and high-temperature solid-state method. By optimizing the crystal structure and bonding strength, a synergistic improvement in high adsorption capacity and low manganese dissolution loss is achieved, thereby addressing the problems of high acid leaching dissolution rate, poor cycle stability, and complex preparation process of existing manganese-based lithium-ion sieves.

[0006] The technical solution adopted in this invention is:

[0007] A chromium-doped manganese-based lithium-ion sieve, the preparation method of which includes the following steps:

[0008] 1) Preparation of precursor: Lithium source, manganese source and chromium source are mixed, dissolved in deionized water, stirred and evaporated to dry, to obtain mixed powder. The mixed powder is placed in an atmosphere furnace for calcination and cooled to obtain spinel type chromium doped lithium manganese oxide precursor.

[0009] 2) Preparation of chromium-doped manganese lithium-ion sieve: The precursor obtained in step 1) was added to a dilute hydrochloric acid solution for acid leaching, stirred at room temperature, and then centrifuged, washed and dried to obtain chromium-doped manganese lithium-ion sieve CLMO.

[0010] Furthermore, in the above-mentioned chromium-doped manganese lithium-ion sieve, in step 1), the lithium source is lithium hydroxide monohydrate (LiOH·H2O), the manganese source is manganese carbonate (MnCO3) or manganese oxide (MnO), and the chromium source is chromium trioxide (Cr2O3).

[0011] Furthermore, in the above-mentioned chromium-doped manganese lithium-ion sieve, in step 1), the molar ratio of the lithium source and the manganese source is Li:Mn = 7:10, and the molar ratio of the manganese source and the chromium source is Mn:Cr = 10:1 to 10:3.

[0012] Furthermore, in the aforementioned chromium-doped manganese lithium-ion sieve, in step 1), the evaporation drying temperature is 70–80 °C, and the vacuum degree is -0.08–-0.1 MPa.

[0013] Furthermore, in the aforementioned chromium-doped manganese lithium-ion sieve, step 1) involves introducing one of air, nitrogen, and helium into the atmosphere furnace.

[0014] Furthermore, in the aforementioned chromium-doped manganese lithium-ion sieve, step 1) involves heating to 500–800 °C at a heating rate of 10–15 °C / min for 8–10 hours.

[0015] Furthermore, in the aforementioned chromium-doped manganese-based lithium-ion sieve, in step 2), the concentration of the dilute hydrochloric acid solution is 2.5 wt.% to 5.0 wt.%, and the acid leaching time is 2 to 5 hours.

[0016] Furthermore, in step 2) of the aforementioned chromium-doped manganese lithium-ion sieve, the washing solvent is a mixture of deionized water and anhydrous ethanol in a volume ratio of 1:1 to 1:2.

[0017] Furthermore, in the aforementioned chromium-doped manganese lithium-ion sieve, step 2) involves drying at a temperature of 80–100°C for 8–12 hours.

[0018] The application of any of the above-mentioned chromium-doped manganese lithium-ion sieves in brine lithium extraction.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention addresses the problems of high acid leaching loss rate, poor cycle stability, and complex preparation process of existing manganese-based lithium ion sieves. It proposes a method for preparing manganese-based lithium ion sieves based on chromium doping and high-temperature solid-state method. By optimizing the crystal structure and bonding strength, a synergistic improvement in high adsorption capacity and low manganese loss is achieved.

[0021] 2. The process of this invention is simple and easy to produce, without the need for complex doping post-processing. Compared with traditional manganese-based lithium ion sieves, it has the advantages of high adsorption capacity retention, excellent cycle stability, and strong process compatibility. Moreover, it has no harmful by-products, is environmentally friendly, and has significant social and economic benefits. Attached Figure Description

[0022] Figure 1 Scanning electron microscope image of the chromium-doped manganese lithium-ion sieve (CLMO-2) prepared in Example 2.

[0023] Figure 2 The precursors (LiCr) prepared in Examples 1, 2, and 3 0.25 Mn 1.75 X-ray diffraction analysis spectrum of O4.

[0024] Figure 3 The precursors (LiCr) prepared in Examples 1, 2, and 3 0.25 Mn 1.75 Fourier transform infrared spectrum of O4.

[0025] Figure 4 The curve showing the relationship between adsorption capacity and adsorption time for the chromium-doped manganese lithium-ion sieve (CLMO) in Example 4 is shown. Detailed Implementation

[0026] The following specific embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and substance of the present invention should be covered within the scope of the claims of the present invention.

[0027] Example 1

[0028] 1) Preparation of precursors

[0029] LiOH·H2O, MnCO3, and Cr2O3 were mixed in a molar ratio of Li:Mn:Cr = 7:10:1, dissolved in 200 mL of deionized water, stirred for 60 min, and then transferred to a rotary evaporator. The mixture was evaporated and dried at 70 °C under a vacuum of -0.08 MPa to obtain a mixed powder. This powder was then placed in an atmosphere furnace and calcined at 10 °C / min to 500 °C for 10 hours under air atmosphere. After cooling, a spinel-type chromium-doped lithium manganese oxide precursor (LiCr) was obtained. 0.25 Mn 1.75 O4);

[0030] Its X-ray diffraction analysis spectrum is as follows Figure 2 As shown in the figure, the chromium-doped manganese lithium-ion sieve conforms to the LiCr standard. 0.25 Mn 1.75 The standard card for O4 (JCPDS 88-0597), belonging to the Fd-3m space group, has a cell parameter a = 8.226 Å, proving that the precursor (LiCr) 0.25 Mn 1.75 Successful preparation of O4.

[0031] Its Fourier transform infrared spectrum is as follows Figure 3 As shown in the figure, at 630 cm -1 A distinctive vibrational peak of the Mn-O bond exists at 520 cm⁻¹. -1 There is a special vibrational peak of the Li-O bond at 700 cm⁻¹. -1 up to 200 cm -1 The presence of low vibrational frequencies and a broad spectral band of Cr-O bonds at this location confirms the successful preparation of the precursor (LiCr). 0.25 Mn 1.75 O4).

[0032] 2) Preparation of chromium-doped manganese-based lithium-ion sieves

[0033] 10 g of precursor was added to 100 mL of 2.5 wt.% dilute hydrochloric acid solution and stirred at room temperature for 2 hours. After centrifugation, the precipitate was washed three times with a mixed solution of deionized water and anhydrous ethanol (volume ratio of deionized water to anhydrous ethanol = 1:1) and dried under vacuum at 80 °C for 12 hours to obtain chromium-doped manganese lithium ion sieve (CLMO-1).

[0034] Example 2

[0035] 1) Preparation of precursors

[0036] LiOH·H2O, MnO, and Cr2O3 were mixed in a molar ratio of Li:Mn:Cr = 7:10:2, dissolved in 200 mL of deionized water, stirred for 60 min, and then transferred to a rotary evaporator. The mixture was evaporated and dried at 75 °C under a vacuum of -0.09 MPa to obtain a mixed powder. This powder was then placed in an atmosphere furnace and calcined at 650 °C at a rate of 15 °C / min under a nitrogen atmosphere for 9 hours. After cooling, a spinel-type chromium-doped lithium manganese oxide precursor (LiCr) was obtained. 0.25 Mn 1.75 O4);

[0037] Its X-ray diffraction analysis spectrum is as follows Figure 2 As shown in the figure, the chromium-doped manganese lithium-ion sieve conforms to the LiCr standard. 0.25 Mn 1.75 The standard card for O4 (JCPDS 88-0597), belonging to the Fd-3m space group, has a cell parameter a = 8.226 Å, proving that the precursor (LiCr) 0.25 Mn 1.75 Successful preparation of O4.

[0038] Its Fourier transform infrared spectrum is as follows Figure 3 As shown in the figure, at 630 cm -1 A distinctive vibrational peak of the Mn-O bond exists at 520 cm⁻¹. -1 There is a special vibrational peak of the Li-O bond at 700 cm⁻¹. -1 up to 200 cm -1 The presence of low vibrational frequencies and a broad spectral band of Cr-O bonds at this location confirms the successful preparation of the precursor (LiCr). 0.25 Mn 1.75 O4).

[0039] 2) Preparation of chromium-doped manganese-based lithium-ion sieves

[0040] 10 g of precursor was added to 100 mL of 3.5 wt.% dilute hydrochloric acid solution and stirred at room temperature for 3.5 hours. After centrifugation, the precipitate was washed three times with a mixed solution of deionized water and anhydrous ethanol (volume ratio of deionized water to anhydrous ethanol = 1:2). The precipitate was then dried under vacuum at 90 °C for 10 hours to obtain a chromium-doped manganese lithium ion sieve (CLMO-2).

[0041] The scanning electron microscope results are as follows: Figure 1 As shown in the image, the product has high crystallinity, a dense crystal surface, and a large number of grooves and gaps between the crystals. The crystal size is about 70 nm.

[0042] Example 3

[0043] 1) Preparation of precursors

[0044] LiOH·H2O, MnO, and Cr2O3 were mixed in a molar ratio of Li:Mn:Cr = 7:10:3, dissolved in 200 mL of deionized water, stirred for 60 min, and then transferred to a rotary evaporator. The mixture was evaporated and dried under a vacuum of -0.1 MPa at 80 °C to obtain a mixed powder. This powder was then placed in an atmosphere furnace and calcined at 800 °C at a rate of 15 °C / min for 8 hours under a helium atmosphere. After cooling, a spinel-type chromium-doped lithium manganese oxide precursor (LiCr) was obtained. 0.25 Mn 1.75 O4);

[0045] Its X-ray diffraction analysis spectrum is as follows Figure 2 As shown in the figure, the chromium-doped manganese lithium-ion sieve conforms to the LiCr standard. 0.25 Mn 1.75 The standard card for O4 (JCPDS 88-0597), belonging to the Fd-3m space group, has a cell parameter a = 8.226 Å, proving that the precursor (LiCr) 0.25 Mn 1.75 Successful preparation of O4.

[0046] Its Fourier transform infrared spectrum is as follows Figure 3 As shown in the figure, at 630 cm -1 A distinctive vibrational peak of the Mn-O bond exists at 520 cm⁻¹. -1 There is a special vibrational peak of the Li-O bond at 700 cm⁻¹. -1 up to 200 cm -1 The presence of low vibrational frequencies and a broad spectral band of Cr-O bonds at this location confirms the successful preparation of the precursor (LiCr). 0.25 Mn 1.75 O4).

[0047] 2) Preparation of chromium-doped manganese-based lithium-ion sieves

[0048] 10 g of precursor was added to 100 mL of 5 wt.% dilute hydrochloric acid solution and stirred at room temperature for 5 hours. After centrifugation, the precipitate was washed three times with a mixed solution of deionized water and anhydrous ethanol (volume ratio: deionized water: anhydrous ethanol = 1:2). The precipitate was then dried under vacuum at 100℃ for 8 hours to obtain chromium-doped manganese lithium ion sieve (CLMO-3).

[0049] Comparative Example 1

[0050] 1) Preparation of precursors

[0051] LiOH·H2O and MnCO3 were mixed in a molar ratio of Li:Mn=7:10, dissolved in 200 mL of deionized water, stirred for 60 min, and then transferred to a rotary evaporator. The mixture was evaporated and dried at 75 °C under a vacuum of -0.09 MPa to obtain a mixed powder. The mixed powder was placed in an atmosphere furnace and heated to 650 °C at a rate of 15 °C / min under a nitrogen atmosphere. After calcination for 9 hours and cooling, a manganese-based lithium ion sieve precursor was obtained.

[0052] 2) Preparation of manganese-based lithium-ion sieves

[0053] 10 g of precursor was added to 100 mL of 3.5 wt.% dilute hydrochloric acid solution and stirred at room temperature for 3.5 hours. After centrifugation, the precipitate was washed three times with a mixed solution of deionized water and anhydrous ethanol (volume ratio of deionized water to anhydrous ethanol = 1:2) and dried under vacuum at 90 °C for 10 hours to obtain manganese-based lithium ion sieve (LMO).

[0054] Example 4: Application of Chromium-Doped Manganese Lithium-Ion Sieve (CLMO) in Lithium Extraction from Brine

[0055] Experimental methods:

[0056] 1) Adsorption: Take 1.0 g of adsorbent and 100 mL of salt lake water. After filtering to remove suspended solids without adjusting the pH, adsorption is performed. A sample is taken at the experimental endpoint, and the Li content is measured using an atomic absorption spectrometer. + The content of.

[0057] 2) Desorption: The saturated adsorbed CLMO was transferred to the desorption cell, and 3.5 wt.% dilute hydrochloric acid (solid-liquid ratio 1:10) was added. The mixture was stirred at room temperature for 3 hours. After centrifugation, the lithium-containing solution was collected, and the Li⁺ recovery rate and manganese dissolution rate were determined.

[0058] 1. Effect of adsorption time on adsorption capacity

[0059] The relationship between its adsorption capacity and adsorption time is shown in the curve. Figure 4 As shown in the figure, the adsorption rate of manganese-based lithium ion sieves is relatively high from 0 to 15 h, and gradually decreases from 15 to 48 h. All three manganese-based lithium ion sieves with different Cr doping ratios reach dynamic adsorption equilibrium at 24 h. At adsorption dynamic equilibrium, the adsorption capacity of the three lithium ion sieves is in the order CLMO-2 > CLMO-3 > CLMO-1. The lithium adsorption capacity at adsorption equilibrium for CLMO-1, CLMO-2, and CLMO-3 is 21.01 mg·g⁻¹, respectively. -1 23.57 mg·g -1 22.49 mg·g -1 .

[0060] 2. Performance comparison with undoped manganese-based ion sieves

[0061] Table 1. Performance comparison of CLMO-2 in Example 2 and LMO in Comparative Example 1

[0062] sample <![CDATA[Dynamic adsorption capacity (mg·g -1 )]]> Li recovery rate (%) Single manganese dissolution loss rate (%) Capacity retention rate after 5 cycles (%) CLMO-2 23.57 89.7 5.95 91.3 LMO 23.10 85.2 21.05 66.8

[0063] Compared to LMO, CLMO-2 has a higher Li recovery rate (89.7%) and a lower single manganese loss rate (5.95%). After 5 cycles, the manganese loss rate of CLMO-2 is only 8.32%, and the capacity retention rate is >90%, which greatly reduces the cost of adsorbent replacement and is suitable for continuous lithium extraction lines from salt lakes.

Claims

1. A chromium-doped manganese-based lithium-ion sieve, characterized in that, Its preparation method includes the following steps: 1) Preparation of precursor: Lithium source, manganese source and chromium source are mixed, dissolved in deionized water, stirred and evaporated to dry, to obtain mixed powder. The mixed powder is placed in an atmosphere furnace for calcination and cooled to obtain spinel type chromium doped lithium manganese oxide precursor. 2) Preparation of chromium-doped manganese lithium-ion sieve: The precursor obtained in step 1) was added to a dilute hydrochloric acid solution for acid leaching, stirred at room temperature, and then centrifuged, washed and dried to obtain chromium-doped manganese lithium-ion sieve CLMO.

2. The chromium-doped manganese-based lithium-ion sieve according to claim 1, characterized in that, In step 1), the lithium source is lithium hydroxide monohydrate LiOH·H2O, the manganese source is manganese carbonate MnCO3 or manganese oxide MnO, and the chromium source is chromium trioxide Cr2O3.

3. The chromium-doped manganese-based lithium-ion sieve according to claim 1, characterized in that, In step 1), the lithium source and manganese source are in a molar ratio of Li:Mn = 7:10, and the manganese source and chromium source are in a molar ratio of Mn:Cr = 10:1 to 10:

3.

4. The chromium-doped manganese-based lithium-ion sieve according to claim 1, characterized in that, In step 1), the evaporation drying temperature is 70-80 °C and the vacuum degree is -0.08 to -0.1 MPa.

5. The chromium-doped manganese-based lithium-ion sieve according to claim 1, characterized in that, In step 1), one of air, nitrogen, and helium is introduced into the atmosphere furnace.

6. The chromium-doped manganese-based lithium-ion sieve according to claim 1, characterized in that, In step 1), the calcination is carried out by heating to 500-800 ℃ at a heating rate of 10-15 ℃ / min and calcining for 8-10 hours.

7. The chromium-doped manganese-based lithium-ion sieve according to claim 1, characterized in that, In step 2), the concentration of the dilute hydrochloric acid solution is 2.5 wt.% to 5.0 wt.%, and the acid leaching time is 2 to 5 hours.

8. The chromium-doped manganese-based lithium-ion sieve according to claim 1, characterized in that, In step 2), the washing solvent is a mixture of deionized water and anhydrous ethanol in a volume ratio of 1:1 to 1:

2.

9. A chromium-doped manganese-based lithium-ion sieve according to claim 1, characterized in that, In step 2), the drying temperature is 80-100 ℃ and the time is 8-12 hours.

10. The application of the chromium-doped manganese lithium-ion sieve according to any one of claims 1 to 9 in lithium extraction from brine.

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