Preparation method and application of composite membrane for extracting lithium from brine

Abstract

The invention relates to a preparation method and application of an MXene / H2TiO3 composite membrane for extracting lithium from brine. The preparation method comprises the following steps: preparation of stripped MXene, preparation of H2TiO3, preparation of the MXene / H2TiO3 composite membrane, and application of the MXene / H2TiO3 composite membrane in adsorbing lithium. The method can eliminate the adverse effect of a common granulation mode on the lithium extraction ion sieve, so that the adsorption performance of the ion sieve is improved.

Description

Technical Field

[0001] The present invention belongs to the field of ion sieve materials, and in particular relates to a preparation method and application of a MXene@H2TiO3 composite membrane for lithium extraction from brine. Background Art

[0002] With the shortage of oil resources and the increasing prominence of environmental protection issues, the lithium battery industry has achieved rapid development. Lithium batteries have the advantages of high output power, high voltage, fast charge and discharge speed, good cycle performance, long life and high charging efficiency, and have shown huge economic benefits and application prospects in the fields of electronic equipment, automobiles, etc. With the rapid development of the above-mentioned lithium multi-industry, lithium and its compounds will become very important metal materials in industrial production. Lithium resources in nature mainly exist in salt lake brine, granite pegmatite deposits and seawater. Due to the successive development or exploration of super-large salt lake brine resources in South America and China, brine lithium resources have occupied a major position in the world's lithium resources, and salt lake brine has become the focus of lithium resource development.

[0003] Traditional precipitation, solvent extraction and impregnation methods are not suitable for extracting lithium from salt lake brine with low lithium concentration. Lithium ion sieve (LIS) is an effective adsorbent for extracting lithium ions from salt lake brine. It has attracted widespread attention from researchers due to its significant advantages such as large adsorption capacity, good economic benefits and low pollution. The lithium ion sieve adsorbent materials currently studied mainly include manganese lithium oxide and titanium lithium oxide. Manganese-based adsorbents have the advantages of large adsorption capacity and high adsorption efficiency, but this type of adsorbent material has poor acid and alkali resistance and high dissolution rate, and is not suitable for lithium extraction from alkaline brine. Titanium-based adsorbents have the advantages of large adsorption capacity, good acid and alkali resistance, and high lithium adsorption selectivity, and are particularly suitable for lithium extraction from alkaline brine.

[0004] Powdered lithium ion sieve adsorbents have many problems in the actual adsorption process, such as easy agglomeration, difficult flow, large pressure drop and powder loss, which leads to poor fluidity and permeability of ion sieves in actual industrial applications, which in turn affects the diffusion rate of ion sieve adsorbents in salt lake brine and seawater and the actual adsorption capacity. In order to improve the industrial practicality of lithium ion sieves, researchers choose to mix lithium ion sieves with other molding materials to form lithium ion sieve composite materials with specific forms. At present, the commonly used molding method of lithium ion sieve composite materials is mainly granulation. The polymer or blended material used in granulation will cover some of the adsorption sites of the ion sieve, resulting in a reduction in the effective area of ​​the lithium ion sieve, resulting in a reduction in the adsorption capacity of the lithium ion sieve. Summary of the invention

[0005] The technical problem to be solved by the present invention is that during the molding process of the existing lithium ion sieve adsorbent, there are problems of adsorbent loss and effective adsorption area loss.

[0006] The present invention provides a method for preparing a MXene@H2TiO3 composite film to eliminate the adverse effects of conventional granulation methods on the extraction of lithium ion sieves, thereby improving the adsorption performance of the ion sieve.

[0007] A composite membrane for extracting lithium from brine, which is in sheet form and contains a titanium-based adsorbent and MXene nanosheets.

[0008] The weight proportion of the titanium-based adsorbent is 10-30%.

[0009] The titanium-based adsorbent is H2TiO3.

[0010] The method for preparing the composite membrane comprises the following steps:

[0011] Step 1, obtaining a titanium-based adsorbent and MXene nanosheets;

[0012] Step 2: Mix the titanium-based adsorbent and MXene nanosheets in water, load them on the surface of the carrier to obtain a wet film, and dry them; then sinter and solidify them to obtain a composite film.

[0013] In the step 2, the material is loaded onto the surface of the carrier by filtering.

[0014] During sintering and solidification, negative pressure or vacuum conditions are used, and the sintering temperature is 300-500° C.; the sintering and solidification process adopts spark plasma sintering.

[0015] The conditions of spark plasma sintering are: applying an axial pressure of 1-10 MPa, sintering under vacuum conditions, heating at a rate of 100-150°C / min, sintering temperature of 300-500°C, keeping warm for 5-10 minutes, and cooling to room temperature with the furnace.

[0016] The preparation method of the titanium-based adsorbent comprises the following steps:

[0017] Step a1, dispersing TiO2 and Li2CO3 in a solvent, mixing them evenly, and calcining them to obtain a metatitanate type lithium adsorbent precursor Li2TiO3;

[0018] Step a2, adding the precursor of lithium titanate adsorbent Li2TiO3 into the acidic solution to extract lithium ions, and then filtering, washing and drying to obtain lithium titanate adsorbent H2TiO3.

[0019] In the step a1, the molar ratio of TiO2 to Li2CO3 is 1:0.8-1.2; the solvent is anhydrous ethanol, and the calcination treatment time is 5-20 hours.

[0020] In the step a2, the acidic solution is hydrochloric acid, the concentration of the hydrochloric acid is 0.1-0.3 mol / L, and the stirring temperature is 40-60°C.

[0021] The method for preparing the MXene nanosheets comprises the following steps:

[0022] Step b1, reacting Ti3AlC2 with HF to perform etching;

[0023] Step b2, washing and centrifuging the product obtained in step b1, taking the centrifugal precipitate, and drying it to obtain the exfoliated Mxene.

[0024] In the step 1, the usage ratio of Ti3AlC2 and HF is 3-5g:50-100ml, and the volume percentage concentration of HF is 20-60wt%.

[0025] In the step 1, the reaction temperature is 30-40° C. and the reaction time is 24-48 hours.

[0026] In the step 2, the centrifugal speed is 5000-7000 rpm, and the centrifugal time is 5-10 min.

[0027] Beneficial Effects

[0028] Compared with the existing granulation technology, the H2TiO3@MXene composite film of the present invention has a better adsorption capacity, a simple preparation process and good mechanical properties. The two-dimensional composite film prepared by the present invention solves both the problem of adsorption capacity and the problem that the powder is not easy to recycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 : Photos of composite films, wherein (a) is a photo of the MXene@H2TiO3 composite film prepared in Example 1 of the present invention; (b) is a SEM image of the surface of the MXene@H2TiO3 composite film prepared in Example 1 of the present invention; (c) is a SEM image of the corresponding Figure 1 (b) is the Ti element distribution diagram; (d) is the SEM image of the cross section of the MXene@H2TiO3 composite film prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The preparation method of the MXene@H2TiO3 composite film provided by the present invention can exemplarily adopt the following process:

[0031] Pour a certain amount of 3-5g Ti3AlC2 into a polytetrafluoroethylene beaker, slowly drip 50-100ml HF (40wt.%) into the beaker, and stir while dripping. After the HF is added, put the beaker into a constant temperature water bath at 30-40℃ and stir magnetically for 24-48h;

[0032] After the magnetic stirring is completed, the reaction solution in step (2) is centrifuged at a speed of 5000-7000 rpm for 5-10 minutes with pure water to wash and remove the HF and by-products remaining in the upper layer of the centrifuge, and the centrifuge is repeated until the pH reaches about 5, and the precipitate in the lower layer of the centrifuge is vacuum dried at 60°C for 24 hours to obtain the exfoliated MXene;

[0033] TiO2 and Li2CO3 were mixed evenly in a molar ratio of 1:1 with anhydrous ethanol as a medium, dried in an oven at 80°C, and then calcined at a high temperature of 700-900°C for 12h to obtain a metatitanate lithium adsorbent precursor Li2TiO3;

[0034] The lithium adsorbent precursor Li2TiO3 is placed in hydrochloric acid with a concentration of 0.1-0.3 mol / L, placed in a constant temperature magnetic stirrer, and stirred at a temperature of 40-60°C until the extraction of lithium ions in Li2TiO3 reaches equilibrium, and then filtered, washed, and dried to obtain a metatitanate lithium adsorbent H2TiO3;

[0035] Take an appropriate amount of exfoliated MXene and dissolve it in pure water, disperse it ultrasonically, take an appropriate amount of metatitanate lithium adsorbent H2TiO3 powder and mix it with the MXene dispersion solution by magnetic stirring;

[0036] The mixed liquid was filtered into a Mxene@H2TiO3 composite membrane using a suction filtration device and then dried in a vacuum environment at 60°C;

[0037] The Mxene@H2TiO3 composite film is sintered and solidified in a spark plasma sintering furnace under a uniaxial pressure of 5 to 10 MPa in a vacuum atmosphere at a sintering temperature of 300 to 500°C.

[0038] In the following examples, the chemical composition of the salt lake brine used is shown in Table 1:

[0039] Table 1 Chemical composition of salt lake brine

[0040]

[0041] Example 1

[0042] (1) A preparation method and application of a MXene@H2TiO3 composite membrane for lithium extraction from brine in the present invention specifically comprises the following steps:

[0043] (2) Pour a certain amount of 3g Ti3AlC2 into a polytetrafluoroethylene beaker, slowly drip 50ml HF (40wt.%) into the beaker, and stir while dripping. After the HF is added, place the beaker in a constant temperature water bath at 40°C and stir magnetically for 24h;

[0044] (3) After the magnetic stirring is completed, the reaction solution in step (2) is centrifuged at a speed of 5000 rpm for 10 min with pure water to wash and remove the HF and by-products remaining in the upper layer of the centrifuge, and the mixture is centrifuged several times until the pH reaches about 5. The precipitate in the lower layer of the centrifuge is vacuum dried at 60° C. for 24 h to obtain the exfoliated MXene;

[0045] (4) TiO2 and Li2CO3 are mixed evenly in a molar ratio of 1:1 with anhydrous ethanol as a medium, placed in an oven at 80°C for drying, and then calcined at a high temperature of 700°C for 12h to obtain a metatitanate-type lithium adsorbent precursor Li2TiO3;

[0046] (5) placing the lithium adsorbent precursor Li2TiO3 in hydrochloric acid with a concentration of 0.1 mol / L, placing it in a constant temperature magnetic stirrer, stirring at a temperature of 40° C. until the extraction of lithium ions in Li2TiO3 reaches equilibrium, filtering, washing, and drying to obtain a metatitanate lithium adsorbent H2TiO3;

[0047] (6) taking an appropriate amount of the MXene stripped in step (5) and dissolving it in pure water, ultrasonically dispersing it, taking an appropriate amount of lithium titanate adsorbent H2TiO3 powder and magnetically stirring and mixing it with the MXene dispersion solution in step (6), so that the weight ratio between the stripped MXene and H2TiO3 powder is 7:3;

[0048] (7) filtering the mixed liquid in step (7) into a Mxene@H2TiO3 composite membrane using a suction filtration device, and then drying it under a vacuum environment at 60° C.;

[0049] (8) using a spark plasma sintering furnace, sintering and curing the Mxene@H2TiO3 composite film in a vacuum atmosphere under a uniaxial pressure of 5 MPa, and the sintering temperature is 300°C;

[0050] (9) Take 1000 mL of brine with the composition shown in Table 1, immerse 50 g of Mxene@H2TiO3 composite membrane, stir while immersing, and filter after 60 min to obtain the adsorption tail A. Determine the content of each ion in A. Loaded with Li + The Mxene@H2TiO3 composite membrane was immersed in 1.0 mol / L hydrochloric acid, stirred while soaking, and filtered after 60 min to obtain the desorption solution B. The content of each ion in B was determined. + The Mxene@H2TiO3 composite membrane can be recycled after desorption.

[0051] Example 2

[0052] (1) A preparation method and application of a MXene@H2TiO3 composite membrane for lithium extraction from brine in the present invention specifically comprises the following steps:

[0053] (2) Pour a certain amount of 5g Ti3AlC2 into a polytetrafluoroethylene beaker, slowly drip 100ml HF (40wt.%) into the beaker, and stir while dripping. After the HF is added, place the beaker in a constant temperature water bath at 40°C and stir magnetically for 48h;

[0054] (3) After the magnetic stirring is completed, the reaction solution in step (2) is centrifuged at a speed of 7000 rpm for 10 min with pure water to wash and remove the HF and by-products remaining in the upper layer of the centrifuge, and the mixture is centrifuged several times until the pH reaches about 5. The precipitate in the lower layer of the centrifuge is vacuum dried at 60° C. for 24 h to obtain the exfoliated MXene;

[0055] (4) TiO2 and Li2CO3 were mixed evenly in a molar ratio of 1:1 with anhydrous ethanol as a medium, dried in an oven at 80°C, and then calcined at a high temperature of 900°C for 12h to obtain a metatitanate-type lithium adsorbent precursor Li2TiO3;

[0056] (5) placing the lithium adsorbent precursor Li2TiO3 in hydrochloric acid with a concentration of 0.3 mol / L, placing it in a constant temperature magnetic stirrer, stirring at a temperature of 60° C. until the extraction of lithium ions in Li2TiO3 reaches equilibrium, filtering, washing, and drying to obtain a metatitanate lithium adsorbent H2TiO3;

[0057] (6) taking an appropriate amount of the MXene stripped in step (5) and dissolving it in pure water, ultrasonically dispersing it, taking an appropriate amount of lithium titanate adsorbent H2TiO3 powder and magnetically stirring and mixing it with the MXene dispersion solution in step (6), so that the weight ratio between the stripped MXene and the H2TiO3 powder is 8:2;

[0058] (7) filtering the mixed liquid in step (7) into a Mxene@H2TiO3 composite membrane using a suction filtration device, and then drying it under a vacuum environment at 60° C.;

[0059] (8) using a spark plasma sintering furnace, sintering and curing the Mxene@H2TiO3 composite film in a vacuum atmosphere under a uniaxial pressure of 10 MPa, and the sintering temperature is 500°C;

[0060] (9) Take 1000 mL of brine with the composition shown in Table 1, immerse 50 g of Mxene@H2TiO3 composite membrane, stir while immersing, and filter after 60 min to obtain the adsorption tail A. Determine the content of each ion in A. Loaded with Li + The Mxene@H2TiO3 composite membrane was immersed in 1.0 mol / L hydrochloric acid, stirred while soaking, and filtered after 60 min to obtain the desorption solution B. The content of each ion in B was determined. +The Mxene@H2TiO3 composite membrane can be recycled after desorption.

[0061] Example 3

[0062] (1) A preparation method and application of a MXene@H2TiO3 composite membrane for lithium extraction from brine in the present invention specifically comprises the following steps:

[0063] (2) Pour a certain amount of 4g Ti3AlC2 into a polytetrafluoroethylene beaker, slowly drip 80ml HF (40wt.%) into the beaker, and stir while dripping. After the HF is added, place the beaker in a constant temperature water bath at 35°C and stir magnetically for 36h;

[0064] (3) After the magnetic stirring is completed, the reaction solution in step (2) is centrifuged at a speed of 6000 rpm for 8 min with pure water to wash and remove the HF and by-products remaining in the upper layer of the centrifuge, and the mixture is centrifuged several times until the pH reaches about 5. The precipitate in the lower layer of the centrifuge is vacuum dried at 60° C. for 24 h to obtain the exfoliated MXene;

[0065] (4) TiO2 and Li2CO3 are mixed evenly in a molar ratio of 1:1 with anhydrous ethanol as a medium, placed in an oven at 80°C for drying, and then calcined at a high temperature of 800°C for 12 hours to obtain a metatitanate lithium adsorbent precursor Li2TiO3;

[0066] (5) placing the lithium adsorbent precursor Li2TiO3 in hydrochloric acid with a concentration of 0.2 mol / L, placing it in a constant temperature magnetic stirrer, stirring at a temperature of 50° C. until the extraction of lithium ions in Li2TiO3 reaches equilibrium, filtering, washing, and drying to obtain a metatitanate lithium adsorbent H2TiO3;

[0067] (6) taking an appropriate amount of the MXene stripped in step (5) and dissolving it in pure water, ultrasonically dispersing it, taking an appropriate amount of lithium titanate adsorbent H2TiO3 powder and magnetically stirring and mixing it with the MXene dispersion solution in step (6), so that the weight ratio between the stripped MXene and H2TiO3 powder is 7.5:2.5;

[0068] (7) filtering the mixed liquid in step (7) into a Mxene@H2TiO3 composite membrane using a suction filtration device, and then drying it under a vacuum environment at 60° C.;

[0069] (8) using a spark plasma sintering furnace, sintering and curing the Mxene@H2TiO3 composite film under a uniaxial pressure of 8 MPa in a vacuum atmosphere, and the sintering temperature is 400°C;

[0070] (9) Take 1000 mL of brine with the composition shown in Table 1, immerse 10 g of Mxene@H2TiO3 composite membrane, stir while immersing, and filter after 60 min to obtain the adsorption tail A. Determine the content of each ion in A. The content of Li + The Mxene@H2TiO3 composite membrane was immersed in 1.0 mol / L hydrochloric acid, stirred while soaking, and filtered after 60 min to obtain the desorption solution B, Li + The Mxene@H2TiO3 composite membrane can be recycled after desorption.

[0071] Comparative Example 1

[0072] The difference from Example 1 is that the H2TiO3 adsorbent is made of polymer materials such as PVA and granulated into a traditional spherical shape, and then used for adsorption of brine. The saturated exchange capacity of the adsorbent is:

[0073]

[0074] Where Q is the saturated exchange capacity (mg / g); C0 is the Li + concentration (mg / L); C is the Li in the exchange solution + where V is the volume of the solution (L); W is the mass of the exchanger (g).

[0075] The distribution coefficient Kd is used to describe the ratio of the concentration of the component in the stationary phase to the concentration in the liquid phase, and then reflects the migration ability of the solute in the two phases and the separation efficiency:

[0076]

[0077] Where Kd is Li + The distribution coefficient at room temperature (mL / g); C0 is the concentration of metal ions in the initial solution (mg / L); C is the concentration of metal ions in the adsorption tail liquid (mg / L); V is the volume of the solution (mL); W is the mass of the adsorbent (g).

[0078] The separation factor reflects the difficulty of separating two components:

[0079]

[0080] Among them, Kd Li It's Li + The partition coefficient at room temperature, Kd Me is the distribution coefficient of each metal ion at room temperature, It's Li + Separation coefficients for various metal ions.

[0081] Example 1

[0082]

[0083] Example 2

[0084]

[0085] Example 3

[0086]

[0087]

[0088] Comparative Example 1

[0089]

[0090] From the above tests, it can be seen that in this patent, the H2TiO3 adsorbent is loaded on the surface of Mxene and subjected to film-forming treatment, so that the adsorption amount is increased. On the one hand, the dispersibility of the H2TiO3 adsorbent is improved, and at the same time, the adsorbent can be molded, which is convenient for practical industrial use.

Claims

1. A composite membrane for extracting lithium from brine, characterized in that: The whole material is in sheet form and contains titanium-based adsorbent and MXene nanosheets.

2. The composite membrane for extracting lithium from brine according to claim 1, characterized in that: The weight of the titanium-based adsorbent is 10-30%.

3. The composite membrane for extracting lithium from brine according to claim 1, characterized in that: The titanium-based adsorbent is H2TiO3.

4. The method for preparing a composite membrane for extracting lithium from brine according to claim 1, characterized in that: The method for preparing the composite membrane comprises the following steps: Step 1, obtaining a titanium-based adsorbent and MXene nanosheets; Step 2, mixing the titanium adsorbent and the MXene nanosheets in water, loading them on the surface of the carrier to obtain a wet film, and performing a drying process; After sintering and solidification, a composite membrane is obtained.

5. The method for preparing a composite membrane for extracting lithium from brine according to claim 1, characterized in that: In the step 2, the material is loaded onto the surface of the carrier by filtering.

6. The method for preparing a composite membrane for extracting lithium from brine according to claim 1, characterized in that: During sintering and solidification, negative pressure or vacuum conditions are used, and the sintering temperature is 300-500° C.; the sintering and solidification process adopts spark plasma sintering.

7. The method for preparing a composite membrane for extracting lithium from brine according to claim 1, characterized in that: The conditions of spark plasma sintering are: applying an axial pressure of 1-10 MPa, sintering under vacuum conditions, heating at a rate of 100-150°C / min, sintering temperature of 300-500°C, keeping warm for 5-10 minutes, and cooling to room temperature with the furnace.

8. The method for preparing a composite membrane for extracting lithium from brine according to claim 1, characterized in that: The preparation method of the titanium-based adsorbent comprises the following steps: Step a1, dispersing TiO2 and Li2CO3 in a solvent, mixing them evenly, and calcining them to obtain a metatitanate type lithium adsorbent precursor Li2TiO3; Step a2, adding the precursor of lithium titanate adsorbent Li2TiO3 into the acidic solution to extract lithium ions, and then filtering, washing and drying to obtain lithium titanate adsorbent H2TiO3. In the step a1, the molar ratio of TiO2 to Li2CO3 is 1:0.8-1.2; the solvent is anhydrous ethanol, and the calcination treatment time is 5-20 hours.

9. The method for preparing a composite membrane for extracting lithium from brine according to claim 1, characterized in that: The method for preparing the MXene nanosheets comprises the following steps: Step b1, reacting Ti3AlC2 with HF to perform etching; Step b2, washing and centrifuging the product obtained in step b1, taking the centrifugal precipitate, and drying it to obtain the exfoliated Mxene.

10. Use of the composite membrane for extracting lithium from brine according to claim 1 in extracting lithium from a lithium-containing solution.

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