A method for preparing an aluminum-based lithium adsorbent based on DFT screening and application thereof

Abstract

The application discloses a method for preparing an aluminum-based lithium adsorbent based on DFT screening and application thereof. The aluminum-based lithium adsorbent is Li-Al-CO3-Cl LDH, interlayer anions of which include Cl ‑ and interlayer intercalated anions, the interlayer intercalated anions being CO3 2‑ . The preparation method comprises the following steps: (1) screening interlayer intercalated anions from alternative interlayer anions by using DFT, the interlayer intercalated anions being CO3 2‑ ; (2) selecting CO3 2‑ intercalated in step (1) as interlayer intercalated anions to synthesize the aluminum-based lithium adsorbent with CO3 2‑ intercalation. The application performs efficient screening on interlayer intercalated anions of the aluminum-based lithium adsorbent by DFT calculation, determines that the interlayer intercalated anions are CO3 2‑ , and further, the aluminum-based lithium adsorbent with interlayer intercalated anions prepared by the application has high adsorption capacity, good stability and lithium ion selectivity, and can be used for lithium extraction adsorbent for salt lake brine.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of theoretical calculation of aluminum-based lithium adsorbent and lithium extraction from brine, and in particular to a method for preparing aluminum-based lithium adsorbent based on DFT screening and application thereof. BACKGROUND

[0002] The rapid development of lithium battery new energy vehicles is an important measure for implementing the national double carbon strategic goal of automobile industry structure adjustment. By 2030, China's lithium battery new energy vehicle production capacity is expected to reach 20 million vehicles / year, and the demand for lithium will reach 1.5 million tons / year. Lithium extraction from salt lake brine is a good choice for the development of China's new energy vehicles due to its reserves and cost advantages. At present, aluminum-based lithium adsorbent has a wide application prospect due to its high selectivity and environmentally friendly adsorption and desorption process, and is suitable for the fragile ecological environment of salt lake. However, the development of aluminum-based adsorbent is restricted by the bottleneck problems of low adsorption capacity and unstable structure.

[0003] The adsorption capacity and structural stability of aluminum-based lithium adsorbent are a contradiction: high adsorption capacity requires more lithium ion adsorption sites; more lithium ion adsorption sites can easily lead to the transformation of the adsorbent structure to gibbsite, thereby losing the lithium extraction activity. Therefore, under the premise of more lithium ion adsorption sites, inhibiting the transformation of the adsorbent is the key to solving the problem.

[0004] Therefore, there is a dilemma between the adsorption capacity and structural stability of aluminum-based lithium adsorbent. In order to solve this problem, the present application is proposed. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a preparation and application of aluminum-based lithium adsorbent based on DFT (density functional theory) calculation screening high lithium extraction stability and high adsorption selectivity. Based on the advantages of DFT calculation, the present application efficiently screens different interlayer insertion structures of aluminum-based lithium adsorbent, avoiding the drawbacks of long cycle, high cost and blindness in direct experimental test screening. The adsorbent with interlayer insertion anions is prepared through experimental design, and its lithium extraction performance from brine is tested. The synthesized aluminum-based lithium adsorbent with interlayer insertion anions has high adsorption capacity, good stability and lithium ion selectivity, and can be used for lithium extraction from salt lake brine.

[0006] The present application efficiently screens the interlayer insertion anions of aluminum-based lithium adsorbent through DFT calculation, determines the mechanism of the interlayer anions improving the stability of aluminum-based lithium adsorbent, and determines that the interlayer insertion anion is CO3 2-Further, the aluminum-based lithium adsorbent prepared by the method has high adsorption capacity, good stability and lithium ion selectivity, and can be used for lithium extraction adsorbent for salt lake brine. The method uses the advantages of DFT simulation calculation to efficiently screen the interlayer intercalation modification of the aluminum-based lithium adsorbent, accurately predicts the lithium extraction performance of the modified aluminum-based lithium adsorbent, and provides a new method for modification of the aluminum-based lithium adsorbent.

[0007] The technical scheme for solving the above problems is as follows:

[0008] The first aspect of the present application provides a method for preparing an aluminum-based lithium adsorbent based on DFT screening, wherein the aluminum-based lithium adsorbent is Li-Al-CO3-Cl LDH, the interlayer anions thereof include Cl- and interlayer intercalation anions, and the interlayer intercalation anions are CO3 2- ;

[0009] The preparation method comprises the following steps:

[0010] (1) screening interlayer intercalation anions from alternative interlayer anions by DFT, wherein the interlayer intercalation anions are CO3 2- ;

[0011] (2) selecting CO3 2- as the interlayer intercalation anion, and synthesizing the aluminum-based lithium adsorbent intercalated with CO3 2- .

[0012] Preferably, the alternative interlayer anions in step (1) include but are not limited to: PO4 3- , CO3 2- , SO4 2- , F - , OH - , Cl - , Br - , I - , NO3 - , ClO4 - .

[0013] Preferably, step (1) comprises the following steps:

[0014] (11) selecting a calculation method based on DFT to calculate the desorption energy of the alternative interlayer anion, wherein the alternative interlayer anion with a desorption energy greater than that of Cl - is selected as the interlayer intercalation anion. The interlayer anion of the unmodified aluminum-based lithium adsorbent is Cl - , and by screening by DFT and comparative analysis with the desorption energy of Cl - , a more stable interlayer intercalation anion can be obtained.

[0015] (12) selecting a DFT-based calculation method to perform configuration optimization on the model of the candidate interlayer anion, and calculating the interlayer spacing of the candidate interlayer anion according to the result of the configuration optimization, wherein the interlayer spacing is close to that of Cl - The candidate interlayer anion with a similar interlayer spacing is selected as the interlayer intercalation anion when intercalation. The interlayer spacing is close to that of Cl - When the interlayer spacing is similar, it can ensure the high adsorption selectivity of lithium ions.

[0016] The interlayer intercalation anion needs to meet the conditions in steps (11) and (12) at the same time.

[0017] Preferably, step (2) comprises the following steps:

[0018] (21) Dissolve the aluminum salt and the lithium salt in deionized water respectively, mix them in a certain molar ratio to obtain solution A; add urea to solution A and magnetically stir to dissolve to obtain solution B; add solution B and a certain volume of ethanol and water into a polytetrafluoroethylene hydrothermal reactor and react at a certain temperature;

[0019] (22) Washing, centrifugal separation and freeze-drying the mixture after reaction in (1) to obtain the Li-Al-CO3 LDH aluminum-based lithium adsorbent;

[0020] (23) Adding the Li-Al-CO3 LDH into deionized water, adding a certain volume of hydrochloric acid and lithium chloride solution to react to obtain the Li-Al-CO3-Cl LDH aluminum-based lithium adsorbent.

[0021] Preferably, in step (21), the molar ratio of lithium to aluminum is 0.5:1 to 4:1, the volume ratio of ethanol to water in the reactor is 0:60 to 48:12, the reaction temperature is 100°C to 130°C, and the reaction time is 3 to 20 hours.

[0022] In step (22), the freeze-drying conditions are: the freezing temperature is -40°C to -60°C, and the freezing time is 12 to 30 hours, more preferably, the freezing temperature is -50°C, and the freezing time is 24 hours.

[0023] Preferably, in step (23), the amount-of-substance ratio of hydrochloric acid to adsorbent is 0.2 to 0.8, and the concentration of hydrochloric acid is 0.5 mol / L; the hydrochloric acid needs to be added slowly, and the pH of the mixed solution is controlled to be greater than or equal to 5.

[0024] Preferably, it further comprises step (3) of testing the lithium ion selectivity, lithium ion adsorption capacity and cycle stability of the aluminum-based lithium adsorbent in step (2).

[0025] Step (3) comprises the following steps:

[0026] (31) Put the Li-Al-CO3-Cl LDH aluminum-based lithium adsorbent into deionized water for desorption to generate lithium ion adsorption vacancies;

[0027] (32) Put the aluminum-based lithium adsorbent after desorption in step (31) into brine for lithium ion adsorption, and calculate the adsorption capacity and adsorption selectivity according to formula (1) and formula (2), respectively;

[0028]

[0029] In the formula, Q at is the adsorption amount at time t, mg / g; C at is the concentration of Li + at time t, mg / L; C0 is the concentration of Li + in the initial solution, mg / L; and V is the volume of the adsorption solution, L.

[0030]

[0031] In the formula, K d is the distribution coefficient of each metal cation; C0 is the initial concentration, mg / L; C e is the concentration after adsorption equilibrium, mg / L; m is the mass of the adsorbent, g; and V is the volume of the solution, L.

[0032] (33) Test the adsorption stability of the adsorbent after 30 desorption-adsorption cycles.

[0033] Preferably, in step (31), the desorption process temperature is 40℃; and in step (32), the adsorption process temperature is 50℃.

[0034] The second aspect of the present application provides an application of the aluminum-based lithium adsorbent described in the first aspect of the present application, which is used for lithium extraction from salt lake brine, and the aluminum-based lithium adsorbent has high lithium extraction stability and high adsorption selectivity.

[0035] The present application has the following beneficial effects:

[0036] (1) Based on the advantages of DFT calculation, the present application efficiently screens different interlayer intercalated anions of the aluminum-based lithium adsorbent, avoiding the drawbacks of long cycle, high cost and blindness in direct experimental test screening.

[0037] (2) The present application prepares an aluminum-based lithium adsorbent containing interlayer intercalated anion CO3 2- according to the screening results, tests its lithium extraction performance from brine, and verifies that the aluminum-based lithium adsorbent prepared by the present application containing interlayer intercalated anion CO3 2- has high adsorption capacity, good stability and lithium ion selectivity, and can be used for lithium extraction from salt lake brine. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 Unit cell model of Li-Al LDH intercalated with different interlayer anions

[0039] Figure 2 Effect of cycle number on Li + adsorption capacity of Li-Al-CO3-Cl LDH and Li-Al-Cl LDH. DETAILED DESCRIPTION

[0040] The present patent application is further illustrated below in conjunction with examples.

[0041] The present detailed description is merely an explanation of the present application, and is not a limitation of the present application. Any change made by those skilled in the art after reading the present specification will be within the scope of protection of the patent law, as long as it is within the scope of the claims.

[0042] S1. DFT calculation screening of interlayer anion intercalation of aluminum-based lithium adsorbent layers

[0043] (1) Model establishment: based on the crystal data in The Materials Project database, the calculation model molecular formulas of Li-Al-F LDH, Li-Al-Cl LDH, Li-Al-Br LDH, Li-Al-I LDH, Li-Al-OH LDH, Li-Al-NO3 LDH, Li-Al-CO3 LDH, Li-Al-SO4 LDH, Li-Al-PO4 LDH and Li-Al-ClO4 LDH were established by ion substitution, as shown in Table 1.

[0044] Table 1 Molecular formulas of calculation models intercalated with different anions

[0045]

[0046] (2) Calculation method: the energy of the calculation model was calculated using spin-polarized generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof gradient correction functional (PBE) calculation system. The judgment threshold for convergence of configuration optimization was set as: the cutoff energy of plane wave was 400 eV, EDIFF = 1.0*10 -5 eV; Monkhorst-Pack K-point grid sampling was set as 8x8x3.

[0047] (3) Configuration optimization

[0048] Figure 1 The unit cell structures of aluminum-based lithium adsorbents intercalated with different anions are shown, in which the anions are located between two layers of host slabs, and Al3+ , Li + , OH - constitute the host layer. For halogen ion intercalated aluminum-based lithium adsorbents, the halogen ion and lithium ion occupy positions perpendicularly, and the halogen ion is located in the middle of the two layers of host layers. OH - and NO3 - The occupied positions of O and N are the same as those of halogen ions. CO3 2- The molecular plane of CO3 - , PO4 3- and SO4 2- are tetrahedral.

[0049] (4) Calculation of intercalation energy of different interlayer anions

[0050] The interaction energy of ions and host layers represents the difficulty of ion desorption from the adsorbent. The interaction energy of different anions and Li + and host layers is shown in Table 2. It can be found that the interaction energy of aluminum-based lithium adsorbents intercalated with different anions and Li + is concentrated in the range of 246.4-256.2 kJ / mol, while the desorption energy of anions and Li i X y The desorption energy of anions from large to small is: PO4 3- > CO3 2- > SO4 2- > F - > OH - > Cl - > Br - > I - > NO3 - > ClO4 - , which increases with the increase of the charge of anions and the decrease of the radius of anions.

[0051] Table 2. Lithium ion desorption energy, anion desorption energy and LiX desorption energy of adsorbents intercalated with different interlayer anions

[0052]

[0053] (5) Calculation of interlayer spacing of adsorbents intercalated with different anions

[0054] The interlayer spacing of adsorbents affects the diffusion rate of metal hydrate ions in the interlayer, and has an important influence on the selectivity of metal ions, so the model interlayer spacing calculation and analysis are carried out. The optimized parameters and interlayer spacing of Li-Al-X LDH models intercalated with different interlayer anions are shown in Table 3. The interlayer spacing of aluminum-based lithium adsorbents is affected by the radius of anions, the arrangement of anions and the charge of ions. The anions in tetrahedral configuration: ClO4- PO4 3- and SO4 2- The interlayer spacing of intercalated aluminum-based lithium adsorbent is larger than that of planar and single-atom ions such as CO3 2- F - Cl - Br - I - OH - NO3 - The more the charge of the ion, the stronger the electrostatic interaction with the host layer, and the smaller the interlayer spacing, such as CO3 2- than NO3 - The interlayer spacing of the adsorbent of the poor layer is small. The order of the interlayer spacing of the aluminum-based lithium adsorbent intercalated by different anions from large to small is: ClO4 - > SO4 2- > PO4 3- > NO3 - > I - > Br - > OH - > CO3 2- > Cl - > F - .

[0055] Table 3. Model optimization parameters and interlayer spacing of Li-Al-X LDH intercalated by different interlayer anions

[0056]

[0057] S2. Li-Al-CO3-Cl LDH experimental design synthesis

[0058] Mix 4 mL of 2 mol / L lithium chloride and 4 mL of 1 mol / L aluminum chloride solution uniformly to obtain solution A, then add 2.36 g of urea to dissolve thoroughly to obtain solution B, mix 42 mL of ethanol, 10 mL of deionized water and the solution uniformly, and then add it into a hydrothermal reaction kettle, react at 120 degrees for 12 hours, wash, centrifuge, freeze-dry the mixture to obtain Li-Al-CO3 LDH aluminum-based lithium adsorbent, the freezing temperature is-50℃, and the freezing time is 24 h. Add 1 g of Li-Al-CO3 LDH aluminum-based lithium adsorbent to 50 mL of deionized water, add 30 mL of 2 mol / L lithium chloride to the mixture, then slowly add 4.5 mL of 0.5 mol / L hydrochloric acid, control the pH of the mixed liquid system to be greater than or equal to 5, and dry after solid-liquid separation to obtain Li-Al-CO3-Cl LDH.

[0059] S3. Li-Al-CO3-Cl LDH lithium extraction performance test

[0060] (1) Adsorption selectivity test

[0061] Li + In addition, there are many competing ions, such as Mg 2+ Ca 2+ K + Na + etc. To study the effect of Li-Al-CO3-Cl LDH on Li + To assess the adsorption selectivity, simulated brine containing LiCl, MgCl2, CaCl2, KCl, and NaCl was prepared, and the partition coefficient K was calculated. d and separation factor The calculation results are shown in Table 4. It can be seen that K... d (Li + The concentration of Li ions is much higher than that of other metal ions, indicating that the adsorbent has a high affinity for Li ions. + It exhibits excellent selectivity. The adsorption selectivity of Li-Al-CO3-Cl LDH for each ion is in the order of Li... + >>Mg 2+ Na + >K + >Ca 2+ .

[0062] Table 4. Metal ion adsorption selectivity of the adsorbent

[0063]

[0064] (2) Lithium extraction cycle stability of Li-Al-CO3-Cl LDH

[0065] The lithium-ion adsorption-desorption cycle stability of Li-Al-CO3-Cl LDH was studied and compared with that of Li-Al-Cl LDH. The test results are as follows: Figure 2 As shown, after 30 adsorption-desorption cycles, the lithium-ion adsorption capacity of the Li-Al-Cl LDH system decreased from 10.4 mg / g to 7.5 mg / g. In the Li-Al-CO3-Cl LDH system, the lithium-ion adsorption capacity decreased from 18.3 mg / g to 17.5 mg / g, a decrease of only 4.4%, far lower than the 27.9% decrease of the Li-Al-Cl LDH system. Clearly, the reusable stability of the Li-Al-CO3-Cl LDH system is significantly higher than that of the Li-Al-Cl LDH system. Furthermore, the adsorption capacity of Li-Al-CO3-ClLDH reached 18.3 mg / g, an increase of 76.0% compared to the unmodified state.

[0066] The above has made the exemplary description to the present application, should indicate that, in not departing from the core of the present application, any simple variation, modification or other field technicians can not spend the equivalent replacement of creative labor falls into the protection scope of the present application.

Claims

1. A method for preparing aluminum-based lithium adsorbents based on DFT screening, characterized in that, The aluminum-based lithium adsorbent is Li-Al-CO3-ClLDH, and its interlayer anions include Cl. - and intercalation anions, wherein the intercalation anions are CO3. 2- ; The preparation method includes the following steps: (1) Intercalation anions are selected from candidate intercalation anions using DFT, wherein the intercalation anion is CO3. 2- ; (2) Select the CO3 screened in step (1) 2- As an intercalation anion, it is used to synthesize CO3. 2- Intercalated aluminum-based lithium adsorbent; The candidate interlayer anions mentioned in step (1) include: PO4 3- CO3 2- SO4 2- F - OH - Cl - ,Br - I - NO3 - ClO4 - ; Step (1) includes the following steps: (11) The extraction energy of the candidate interlayer anions is calculated using a DFT-based calculation method, wherein the extraction energy is greater than that of Cl. - The candidate interlayer anions with extraction energy are used as interlayer intercalation anions; (12) The DFT-based calculation method is used to optimize the configuration of the model of the candidate interlayer anions. The interlayer spacing of the candidate interlayer anions is calculated based on the configuration optimization results, wherein the interlayer spacing is related to Cl. - During intercalation, candidate interlayer anions with similar interlayer spacing are used as interlayer intercalation anions; The intercalation anions must simultaneously meet the conditions in steps (11) and (12).

2. The preparation method according to claim 1, characterized in that, Step (2) includes the following steps: (21) Dissolve aluminum salt and lithium salt separately in deionized water, and mix them in a certain molar ratio to obtain solution A; add urea to solution A and stir magnetically to dissolve it to obtain solution B; add solution B and a certain volume of ethanol and water to a polytetrafluoroethylene hydrothermal reactor and react at a certain temperature. (22) The mixture after the reaction in (1) was washed, centrifuged, and freeze-dried to obtain Li-Al-CO3 LDH aluminum-based lithium adsorbent; (23) Li-Al-CO3 LDH was added to deionized water, and a certain volume of hydrochloric acid and lithium chloride solution were added to react and obtain Li-Al-CO3-Cl LDH aluminum-based lithium adsorbent.

3. The preparation method according to claim 2, characterized in that, In step (21), the molar ratio of lithium to aluminum is 0.5:1 to 4:1, the volume ratio of ethanol to water in the reactor is 0:60 to 48:12, the reaction temperature is 100℃ to 130℃, and the reaction time is 3 to 20h.

4. The preparation method according to claim 2, characterized in that, In step (22), the freeze-drying conditions are: freezing temperature of -40℃ to -60℃ and freezing time of 12 h to 30 h.

5. The preparation method according to claim 2, characterized in that, In step (23), the ratio of the amount of hydrochloric acid to the amount of adsorbent is 0.2 to 0.8, and the concentration of hydrochloric acid is 0.5 mol / L; the pH of the mixture is controlled to be greater than or equal to 5.

6. The preparation method according to claim 1, characterized in that, It also includes step (3), testing the lithium-ion selectivity, lithium-ion adsorption capacity and cycle stability of the aluminum-based lithium adsorbent in step (2); Step (3) includes the following steps: (31) The Li-Al-CO3-Cl LDH aluminum-based lithium adsorbent was placed in deionized water for desorption, generating lithium ion adsorption vacancies; (32) The aluminum-based lithium adsorbent after desorption in step (31) is placed in brine to adsorb lithium ions, and the adsorption capacity and adsorption selectivity are calculated according to formula (1) and formula (2), respectively. Equation (1) In the formula, Q at The adsorption amount at time t, in mg / g; C at Let Li be at time t + The concentration of Li in the initial solution is mg / L; C0 is the initial concentration of Li in the initial solution. + The concentration of is mg / L; V is the volume of the adsorption solution, L; Equation (2) In the formula, K d C represents the partition coefficient of each metal cation; C0 is the initial concentration, mg / L; C e The concentration after adsorption equilibrium is mg / L; m is the adsorbent mass in g; V is the solution volume in L. (33) The adsorbent was subjected to 30 desorption-adsorption cycles to test its adsorption stability.

7. The preparation method according to claim 6, characterized in that, In step (31), the desorption process temperature is 40°C; in step (32), the adsorption process temperature is 50°C.

8. The application of an aluminum-based lithium adsorbent obtained by the preparation method according to any one of claims 1-7, characterized in that, As an adsorbent for lithium extraction from salt lake brine, the aluminum-based lithium adsorbent has high adsorption capacity, high lithium extraction stability, and high adsorption selectivity.

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