Titanium-based MXenes recycling method

Abstract

The application discloses a titanium-based MXenes recycling and regenerating method, and the method comprises the following steps: (1) adding failed MXenes into an alkali solution to form an A solution; (2) hydrothermally treating the A solution at a specific temperature for a certain time; (3) centrifuging the solution after reaction to collect, and adding an acid solution into the collected sludge to form a B solution; and (4) stirring the B solution under ambient conditions for a certain time, and then centrifugally washing and collecting the solution by using deionized water to obtain regenerated MXenes. The application removes failed titanium-based MXenes derived oxide nanoparticles through alkali hydrothermal treatment and subsequent acid etching, and realizes MXenes recycling and regeneration. The strategy utilizes cheap and environment-friendly alkali and acid for step-by-step etching, and has the advantages of simple operation, environmental friendliness, low cost and easy industrialization scale application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material recycling, in particular to a method for recycling and regenerating failed titanium-based MXenes, and the present application aims at solving the problem of performance degradation of titanium-based MXenes caused by oxidation during storage, transportation and use, and proposes a safe and environmentally friendly method for recycling and regenerating titanium-based MXenes. BACKGROUND

[0002] In recent years, a new type of two-dimensional transition metal carbide (or nitride) - MXenes has shown wide application prospects in many fields due to its ultra-high conductivity (20000 S cm -1 ), rich and tunable termination groups on the surface, excellent hydrophilicity and super flexibility, and its tunable element composition and ratio make it the fastest growing family of two-dimensional materials in recent years. Titanium-based MXenes have become the most promising MXenes material due to their early advantages and relatively environmentally friendly and high-yield preparation methods. However, titanium-based MXenes are easily oxidized by oxygen and water molecules in the environment and solution during storage, transportation and use, and are converted into low-conductivity and non-electrochemical active titanium dioxide, which greatly reduces their performance in electromagnetic shielding, electrochemical energy storage and other fields. This oxidation is a stable thermodynamic process and is completely unavoidable. Therefore, how to realize the recycling and regeneration of titanium-based MXenes is crucial for their industrial application and development. SUMMARY

[0003] The present application aims to provide a safe and environmentally friendly method for recycling and regenerating titanium-based MXenes, which solves the problem of recycling and regeneration of failed MXenes caused by oxidation during storage, transportation and use.

[0004] To solve the above technical problems, the present application adopts the following technical solution: a safe and environmentally friendly method for recycling and regenerating titanium-based MXenes, comprising the following steps:

[0005] (1) introducing an appropriate amount of failed MXenes into an alkaline solution to form a mixed solution A;

[0006] (2) hydrothermally treating the mixed solution A at a specific temperature for a certain period of time;

[0007] (3) centrifuging the reaction solution to collect it;

[0008] (4) adding an appropriate amount of acid solution to the collected slurry to obtain solution B;

[0009] (5) stirring solution B for a certain period of time, then repeatedly centrifuging and washing it with deionized water to collect the recycled MXenes;

[0010] Preferably, the failed titanium-based MXenes in (1) include tunable different proportions of carbon or nitrogen elements, including but not limited to Ti3C2T x , Ti3CNT x , Ti2CT x , Ti4N3T x , etc.

[0011] The alkali solution in step (1) can be selected from sodium hydroxide solution, potassium hydroxide solution or a mixture of the two.

[0012] The introduction of the alkali solution in step (1) can be from 5 mol L -1 to saturation.

[0013] The hydrothermal temperature in step (1) can be from 120℃ to 180℃, and the holding time range is 2h to 12h.

[0014] Preferably, the acid solution in step (2) can be selected from one or more acids mixed solution of hydrochloric acid, sulfuric acid, acetic acid.

[0015] The acid solution concentration in step (2) is 2mol L -1 or more.

[0016] Titanium dioxide has extremely high stability and does not react with most acids and bases under environmental conditions. The existing reports on the recovery of failed MXenes are mainly through hydrofluoric acid etching, but it is well known that hydrofluoric acid has high toxicity and corrosivity, and there is a potential environmental pollution and production safety risk. The present application ingeniously uses the step-by-step reaction etching to remove the titanium-based MXenes derived titanium dioxide under alkaline and acidic conditions. During the process, titanium dioxide reacts with alkali solution under hydrothermal conditions to form titanate, which is then dissolved and removed under acidic conditions, finally realizing the separation and recovery of MXenes and derived titanium dioxide.

[0017] In summary, the preparation method of the present application has the following beneficial effects:

[0018] 1. The method uses conventional and easily available alkali / acid etching to realize the recovery of failed titanium-based MXenes, which has the advantages of wide source, simple operation, low cost and environmental friendliness.

[0019] 2. The method is suitable for various types of titanium-based MXenes with tunable element types and proportions.

[0020] 3. The method can simultaneously modify the surface groups of MXenes during the recovery process, which can further release the electrochemical energy storage potential of MXenes. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The present application is aimed at a concentration of 2mg ml-1 Ti3C2T x Aqueous solution 25℃ placed for 30 days failure and recovery XRD results;

[0022] Figure 2 For the present invention for the concentration 2mg ml -1 Ti3C2T x Aqueous solution 25℃ placed for 30 days failure and recovery SEM morphology. DETAILED DESCRIPTION

[0023] The above summary of the application will be further described in conjunction with the specific embodiments of the application. However, it should not be understood as limiting the scope of the above subject matter of the application to only the following examples. According to ordinary technical knowledge and conventional means in the art, various substitutions, changes and improvements, etc. made without departing from the above technical idea of the application should be included in the scope of the application.

[0024] The present application provides a safe and environmentally friendly titanium-based MXenes recycling method, which utilizes the reaction of lye and failed titanium-based MXenes-derived titanium dioxide under hydrothermal conditions to generate titanate, and then utilizes acid dissolution to dissolve and separate the titanate, finally realizing the recycling of MXenes. The present application utilizes conventional alkali and acid as the raw materials for recycling reaction, and has the advantages of simple operation, low cost, wide source and environmental friendliness, etc.

[0025] Example 1

[0026] Take 500mg of waste MXene (Ti3C2T x ) and add 70ml of 10mol / L -1 NaOH solution, stir and mix uniformly to obtain solution A, transfer solution A to a 100ml hydrothermal kettle, hydrothermal at 120℃ for 4h, then centrifugal collection, add 40ml of concentrated hydrochloric acid (12mol / L) to the collected sludge, stir for 20min to obtain solution B. Centrifugal washing of solution B with deionized water until pH>6, then dry the centrifugal collected product to obtain recycled MXene.

[0027] Example 2

[0028] Take 500mg of waste MXene (Ti3C2T x ) and add 70ml of 5mol / L -1 NaOH solution, stir and mix uniformly to obtain solution A, transfer solution A to a 100ml hydrothermal kettle, hydrothermal at 120℃ for 4h, then centrifugal collection, add 40ml of concentrated hydrochloric acid (12mol / L) to the collected sludge, stir for 20min to obtain solution B. Centrifugal washing of solution B with deionized water until pH>6, then dry the centrifugal collected product to obtain recycled MXene.

[0029] Example 3

[0030] Take 500 mg of waste MXene (Ti3C2T x ) into 70 ml of 10 mol / L -1 potassium hydroxide solution, stir and mix uniformly to obtain solution A, transfer solution A to a 100 ml hydrothermal kettle, hydrothermal at 120°C for 4 h, then centrifugal collection, add 40 ml of concentrated hydrochloric acid (12 mol / L) to the collected sludge, stir for 20 min to obtain solution B. Centrifugal wash solution B with deionized water until pH is greater than 6, then dry the centrifugal collected product to obtain recovered and regenerated MXene.

[0031] Example 4

[0032] Take 500 mg of waste MXene (Ti3C2T x ) into 70 ml of 10 mol / L -1 sodium hydroxide solution, stir and mix uniformly to obtain solution A, transfer solution A to a 100 ml hydrothermal kettle, hydrothermal at 180°C for 4 h, then centrifugal collection, add 40 ml of concentrated hydrochloric acid (12 mol / L) to the collected sludge, stir for 20 min to obtain solution B. Centrifugal wash solution B with deionized water until pH is greater than 6, then dry the centrifugal collected product to obtain recovered and regenerated MXene.

[0033] Example 5

[0034] Take 500 mg of waste MXene (Ti2CT x ) into 70 ml of 10 mol / L -1 sodium hydroxide solution, stir and mix uniformly to obtain solution A, transfer solution A to a 100 ml hydrothermal kettle, hydrothermal at 120°C for 4 h, then centrifugal collection, add 40 ml of concentrated hydrochloric acid (12 mol / L) to the collected sludge, stir for 20 min to obtain solution B. Centrifugal wash solution B with deionized water until pH is greater than 6, then dry the centrifugal collected product to obtain recovered and regenerated MXene.

[0035] Example 6

[0036] Take 500 mg of waste MXene (Ti3CNT x ) into 70 ml of 10 mol / L -1A solution A was obtained by stirring and mixing uniformly in a sodium hydroxide solution, the solution A was transferred to a 100 ml hydrothermal kettle, and after hydrothermal treatment at 120 DEG C for 4 h, centrifugal collection was performed, 40 ml of concentrated hydrochloric acid (12 mol / L) was added to the collected sludge, and stirring reaction was performed for 20 min to obtain a solution B. The solution B was washed by centrifugal washing with deionized water until the pH was greater than 6, and then the centrifugal collected product was dried to obtain the recovered and regenerated MXene.

[0037] Example 7

[0038] 500 mg of waste MXene (Ti3C2T x ) was added to 70 ml of a sodium hydroxide solution with a concentration of 10 mol / L -1 A solution A was obtained by stirring and mixing uniformly in a sodium hydroxide solution, the solution A was transferred to a 100 ml hydrothermal kettle, and after hydrothermal treatment at 120 DEG C for 4 h, centrifugal collection was performed, 40 ml of concentrated hydrochloric acid (12 mol / L) was added to the collected sludge, and stirring reaction was performed for 20 min to obtain a solution B. The solution B was washed by centrifugal washing with deionized water until the pH was greater than 6, and then the centrifugal collected product was dried to obtain the recovered and regenerated MXene. -1 A solution A was obtained by stirring and mixing uniformly in a sodium hydroxide solution, the solution A was transferred to a 100 ml hydrothermal kettle, and after hydrothermal treatment at 120 DEG C for 4 h, centrifugal collection was performed, 40 ml of concentrated hydrochloric acid (12 mol / L) was added to the collected sludge, and stirring reaction was performed for 20 min to obtain a solution B. The solution B was washed by centrifugal washing with deionized water until the pH was greater than 6, and then the centrifugal collected product was dried to obtain the recovered and regenerated MXene.

[0039] Example 8

[0040] 500 mg of waste MXene (Ti3C2T x ) was added to 70 ml of a sodium hydroxide solution with a concentration of 10 mol / L -1 A solution A was obtained by stirring and mixing uniformly in a sodium hydroxide solution, the solution A was transferred to a 100 ml hydrothermal kettle, and after hydrothermal treatment at 120 DEG C for 4 h, centrifugal collection was performed, 40 ml of concentrated hydrochloric acid (12 mol / L) was added to the collected sludge, and stirring reaction was performed for 20 min to obtain a solution B. The solution B was washed by centrifugal washing with deionized water until the pH was greater than 6, and then the centrifugal collected product was dried to obtain the recovered and regenerated MXene. -1 A solution A was obtained by stirring and mixing uniformly in a sodium hydroxide solution, the solution A was transferred to a 100 ml hydrothermal kettle, and after hydrothermal treatment at 120 DEG C for 4 h, centrifugal collection was performed, 40 ml of concentrated hydrochloric acid (12 mol / L) was added to the collected sludge, and stirring reaction was performed for 20 min to obtain a solution B. The solution B was washed by centrifugal washing with deionized water until the pH was greater than 6, and then the centrifugal collected product was dried to obtain the recovered and regenerated MXene.

[0041] The corresponding microstructure analysis and test of the safe and environmentally friendly titanium-based MXenes recycling method of the present application are as follows.

[0042] 1. XRD analysis

[0043] Figure 1 The concentration of the 2 mg / ml -1 Ti3C2T x aqueous solution was 25 DEG C for 30 days, and the XRD results of the recovery were obtained. It can be seen that after 25 days, the diffraction pattern around 27 DEG appeared obvious anatase structure titanium dioxide diffraction peak, which proved the generation of MXenes derived titanium dioxide during the placement process. After etching by the method of example 2 of the present application, the diffraction peak disappeared, and the single-phase Ti3C2T x diffraction peak was reconverted.

[0044] 2. SEM analysis

[0045] Figure 2 For the present application, the concentration of 2 mg / ml -1 Ti3C2T x The SEM morphology of the water solution placed at 25℃ for 30 days and recovered. It can be seen that after 30 days, Ti3C2T x A large number of titanium dioxide particles are dispersed on the surface of the nanosheet Figure 2 a), and after etching by the method of Example 2 of the present application, the oxide particles disappear, and the surface of the nanosheet becomes smooth and flat again Figure 2 b).

[0046] 3. EDS analysis

[0047] Table 1 is the concentration of 2 mg / ml -1 Ti3C2T x The EDS element content change of the water solution placed at 25℃ for 30 days and recovered. It can be seen that the invalid MXenes have a high O element content of 32.2% due to the generation of oxides, and after etching by the method of Example 2 of the present application, i.e. after removing the titanium dioxide, the O element content is reduced to 23.6%.

[0048] Table 1

[0049]

[0050] The above is the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements are also considered to be within the scope of protection of the present application.

Claims

1. A method of etching removal of titanium-based MXenes failure-derived titania, characterized by, The method comprises the following steps: (1) introducing a proper amount of failed MXenes into an alkali solution to configure a mixed solution A; (2) hydrothermally preserving the mixed solution A at a certain temperature for a certain time; (3) centrifuging and collecting the solution after reaction; (4) adding a proper amount of acid solution to the collected slurry to obtain solution B; (5) after stirring solution B for a certain time, repeatedly centrifuging and collecting the solution to obtain recovered MXenes.

2. The method of claim 1, wherein the method is characterized by: The failed MXenes in step (1) comprise Ti-based tunable different proportions of carbon or nitrogen elements.

3. The method of claim 2, wherein the method is characterized by: The failed MXenes include one or more of Ti3C2T x , Ti3CNT x , Ti2CT x , Ti4N3T x .

4. The method of claim 1, wherein the method is characterized by: The alkali solution in step (1) is selected from a sodium hydroxide solution, a potassium hydroxide solution or a mixture of the two.

5. The method of claim 4, wherein the method is characterized by: The alkali solution concentration is selected from 5 mol L -1 to saturation.

6. The method of claim 1, wherein the method is characterized by: The hydrothermal temperature in step (1) is 120-180 DEG C.

7. The method of claim 6, wherein the method is characterized by: The preservation time in step (1) is 2-24 h.

8. The method of claim 1, wherein the method is characterized by: The acid solution in step (2) is selected from one or more of a mixture of hydrochloric acid, sulfuric acid and acetic acid.

9. The method of claim 8, wherein the method is characterized by: The acid solution concentration in step (2) is 2 mol L -1 The above.

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