A lipoic acid-modified titanium nanotube adsorption material, preparation method and application

Abstract

The present invention discloses a lipoic acid modified titanic acid nanotube adsorbent material, a preparation method and an application thereof, belonging to the technical field of nanotube materials. Aiming at the problem of low adsorption efficiency of traditional adsorbents due to the complex composition, high chroma, difficult degradation, and many harmful chemical substances of dye wastewater pollutants, the present invention uses lipoic acid to modify titanic acid nanotubes to prepare a lipoic acid modified titanic acid nanotube modified material (TNTs-LA). The microscopic morphology, crystal structure and elemental composition of TNTs-LA are analyzed, and the adsorption performance of TNTs-LA for methylene blue is studied using methylene blue (MB) as a model compound. Compared with other traditional adsorbents, the lipoic acid modified titanic acid nanotube adsorbent material prepared by the present invention has a unique one-dimensional nanotube structure with a hollow middle, a multi-layer outer wall, and one or both ends open. This structure is conducive to the adsorption of reactants, has good adsorption performance, and has a simple process and convenient operation, and has potential application prospects in the field of sewage treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of nanotube materials, and specifically relates to a lipoic acid modified titanate nanotube adsorption material and a preparation method and application thereof. Background Art

[0002] Dye wastewater is still a major topic in the research of industrial wastewater treatment and utilization due to its complex composition, high chromaticity, difficulty in degradation, and many harmful chemicals. At present, the removal of dye wastewater includes chemical coagulation, biochemical method, adsorption method and advanced oxidation method. With the advantages of simple operation, low energy consumption, high removal efficiency, large removal volume, short reaction time and no formation of toxic components, the adsorption method has shown significant advantages in treating wastewater.

[0003] Titanate nanotubes (TNTs) are typical one-dimensional tubular nanomaterials with unique microscopic morphology, hollow and multi-layered outer walls, large specific surface area, high porosity, and good ion exchange performance. They have received extensive attention in the adsorption of cationic dyes, anionic dyes, heavy metals, radionuclides, and methylene blue. In addition, the presence of a large number of oxygen-containing functional groups (such as Ti-OH) in titanate nanotubes makes them easy to modify. Zhang Xingtang et al. used hexadecanol and Ti-OH to dehydrate titanate nanotubes to make them soluble in organic solvents. In addition, researchers also used hydroxyapatite, thioacetic acid, polyvinyl alcohol, and polypyridine to modify and modify them to further improve their adsorption performance.

[0004] Lipoic acid (LA), C8H 14 O2S2 is an amphiphilic compound with a hydrophobic five-membered disulfide ring and a hydrophilic carboxyl group connected by a methylene chain. The disulfide bond in the five-membered disulfide ring is easily opened in water to form two sulfhydryl groups (—SH), which are very easy to coordinate with metals to form a stable covalent chelation reaction, thereby giving lipoic acid-modified titanate nanotubes the ability to adsorb metals. The terminal carboxyl group can be deprotonated to form a hydrophilic carboxylic acid group and stably exist in aqueous solution. It is also easy to combine with cations, making it of great research value in the field of adsorption to increase the adsorption amount. Summary of the invention

[0005] In view of the problem that traditional adsorbents have low adsorption efficiency due to the complex composition of dye wastewater pollutants, high chroma, difficulty in degradation, and many harmful chemicals, the present invention provides a lipoic acid modified titanate nanotube adsorption material and a preparation method and application thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a lipoic acid-modified titanate nanotube material comprises the following steps:

[0008] Step 1: Thoroughly mix titanium dioxide P25 and NaOH solution for hydrothermal reaction; after completing the reaction, take the precipitate for centrifugation, wash with deionized water, then disperse in ethanol, and dry to obtain titanate nanotubes (TNTs).

[0009] Step 2: Mix the titanate nanotubes with lipoic acid solution, and then stir magnetically until the color turns light yellow, then perform suction filtration and drying to obtain TNTs-LA, which is the lipoic acid-modified titanate nanotube material.

[0010] Furthermore, the mass ratio of titanate nanotubes to lipoic acid is 1:1.

[0011] Furthermore, the dosage ratio of titanium dioxide P25 to NaOH is 1:22.

[0012] Furthermore, the concentration of the NaOH solution is 10 mol / L; the concentration of lipoic acid is 0.1 mol / L.

[0013] Furthermore, in Step 1, the temperature of the hydrothermal reaction needs to be controlled at 130 °C for 72 h.

[0014] Furthermore, the conditions for centrifugation in Step 1 are centrifugation at 8000 r / min for 5 min.

[0015] Furthermore, the drying temperature in Step 1 is 80 °C for 8 h.

[0016] Furthermore, in Step 2, a stirring operation needs to be performed before suction filtration and drying, and stir for 24 h.

[0017] A lipoic acid-modified titanate nanotube material prepared by the preparation method of the lipoic acid-modified titanate nanotube material as described above, the lipoic acid-modified titanate nanotubes are randomly wound and interlaced in a disordered state, the nanotubes are hollow with a multi-layer outer wall structure, and one or both ends of the nanotubes are open. The diameter is about 9 nm and the length is about two hundred nanometers.

[0018] An application of the lipoic acid-modified titanate nanotube material prepared by the preparation method of the lipoic acid-modified titanate nanotube material as described above in adsorbing methylene blue.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] The lipoic acid-modified titanate nanotube adsorbent prepared by the present invention, compared with other traditional adsorbents, has a unique one-dimensional nanotube structure with a hollow middle, multi-layer outer walls, and one or both ends open. This structure is conducive to adsorbing reactants, has good adsorption performance, and the process is simple and the operation is convenient, and has potential application prospects in the field of sewage treatment. Description of the Drawings

[0021] Figure 1 Flow chart of the lipoic acid modified titanate nanotube adsorbent prepared in Example 1;

[0022] Figure 2 SEM image of the lipoic acid modified titanate nanotube adsorbent prepared in Example 1;

[0023] Figure 3 TEM image of the lipoic acid modified titanate nanotube adsorbent prepared in Example 1;

[0024] Figure 4 XRD pattern of the lipoic acid modified titanate nanotube adsorbent prepared in Example 1;

[0025] Figure 5 Adsorption performance graph of the lipoic acid modified titanate nanotube adsorbent on methylene blue at different dosages in Experimental Example 1;

[0026] Figure 6 Adsorption performance graph of the lipoic acid modified titanate nanotube adsorbent at different pH values in Experimental Example 2;

[0027] Figure 7 Adsorption performance graph of the lipoic acid modified titanate nanotube adsorbent on methylene blue at different times in Experimental Example 3;

[0028] Figure 8 Adsorption performance graph of the lipoic acid modified titanate nanotube adsorbent on methylene blue at different concentrations in Experimental Example 4. Detailed implementation method

[0029] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. The examples are only for illustrating the present invention and do not limit the scope of application of the present invention.

[0030] Example 1

[0031] Step 1: Disperse 1.2 g of TiO2 in 66 mL of a 10 mol / L NaOH solution and stir magnetically for 24 h. Then pour the mixture into a reaction kettle, control the temperature at 130 °C, and carry out a hydrothermal reaction for 72 h. After the reaction is completed, centrifuge at 8000 r / min for 5 min to obtain the precipitate, wash it with deionized water until the pH = 7, then disperse it in ethanol and dry it at 80 °C to obtain titanate nanotubes (TNTs).

[0032] Step 2: Take 1 g of the TNTs obtained in step (1) and mix it with an equal mass of 0.1 mol / L lipoic acid solution, then stir magnetically for 24 h until the color turns light yellow, filter by suction, and dry at 80 °C to obtain lipoic acid modified titanate nanotubes (TNTs-LA).

[0033] Application Example 1

[0034] Adsorption performance of lipoic acid-modified titanate nanotube adsorbent for methylene blue at different dosages. Methylene blue was 50 mg / L. 100 mL of the solution was placed in a 250 mL conical flask, and HCl or NaOH was used to adjust the pH to 6.

[0035] 0.1, 0.2, 0.4, 0.6, 0.8, and 1 g / L of the lipoic acid-modified titanate nanotube adsorbent prepared by the above preparation method were added respectively. After mixing evenly, it was placed in a constant temperature shaker and shaken. The reaction temperature was 25 °C, the shaking speed was 200 rpm, and the shaking time was 24 h. After the reaction, the reaction system was separated by centrifugation. The absorbance of the pollutants in the solution was measured using a spectrophotometer, and the adsorption efficiency of the lipoic acid-modified titanate nanotube for methylene blue pollutants at different dosages was calculated according to the standard curve.

[0036] Specifically as Figure 5 shown, it indicates that the removal rate of methylene blue is positively correlated with the dosage of TNTs-LA and then gradually stabilizes; the adsorption amount of methylene blue gradually decreases. When the dosage of the adsorbent increases from 0.1 g / L to 0.4 g / L, the removal rate of MB increases from 59.42% to 99.25%. After that, when the dosage is further increased, the removal rate tends to be stable and reaches the maximum value of 99.66% (dosage 1 g / L). It can be seen that the lipoic acid-modified titanate nanotube adsorbent has excellent removal ability for methylene blue.

[0037] Application Example 2

[0038] Adsorption performance of lipoic acid-modified titanate nanotube adsorbent for methylene blue at different pH values. Methylene blue was 50 mg / L. 100 mL of the solution was placed in a 250 mL conical flask, and 0.3 g / L of the lipoic acid-modified titanate nanotube adsorbent obtained in Example 1 was added. After mixing evenly, HCl or NaOH was used to adjust the pH to 2, 4, 6, 8, 10, and 12. The reactor was placed in a constant temperature shaker and shaken. The reaction temperature was 25 °C, the shaking speed was 200 rpm, and the shaking time was 24 h. After the reaction, the reaction system was separated by centrifugation. The absorbance of the pollutants in the solution was measured using a spectrophotometer, and the adsorption efficiency of pollutants with different initial concentrations was calculated according to the standard curve. As the pH value gradually increased from 2 to 4, the adsorption rate rapidly increased from 33.76% to 95.41%; then during the process of the pH value increasing to 10, the adsorption rate increased slowly; finally, as the pH value increased, the adsorption rate decreased instead. Specifically as Figure 6 shown, it can be seen that the lipoic acid-modified titanate nanotube adsorbent of the present invention is most suitable for the treatment process of sewage and wastewater within the pH range of 4 - 10.

[0039] Application Example 3

[0040] Adsorption performance of lipoic acid-modified titanate nanotube adsorbent for methylene blue at different times (kinetic adsorption experiment). The concentration of methylene blue was 50 mg / L. 200 mL of the solution was placed in a 500 mL conical flask, and 0.6 g / L of the lipoic acid-modified titanate nanotube adsorbent obtained in Example 1 was added. The mixture was stirred evenly, and the pH was adjusted to 6 using HCl or NaOH. The reactor was placed in a constant temperature shaker and shaken. The reaction temperature was 25 °C, the shaking speed was 200 rpm, and the shaking time was 5 h. Samples were taken at intervals using a syringe, and the samples were centrifuged. The absorbance of the pollutants in the solution was measured using a spectrophotometer, and the adsorption efficiency of pollutants with different initial concentrations was calculated according to the standard curve.

[0041] Specifically, as Figure 7 shown, it can be seen that the adsorption process of lipoic acid-modified titanate nanotubes for methylene blue is relatively fast, concentrated in the first 30 min, and the adsorption reaches equilibrium after 60 min. The fitting effect of the pseudo-second-order reaction model is relatively better, and the correlation coefficient is larger (r 2 = 0.9847). At the same time, the experimentally measured equilibrium adsorption capacity q e,cal is more consistent with the adsorption capacity q e,exp obtained by the model. Therefore, the pseudo-second-order adsorption kinetic model better describes the whole process of TNTS-LA adsorbing MB. The pseudo-second-order reaction kinetics is based on the assumption that the rate-limiting step is chemical adsorption or physicochemical adsorption. Therefore, it can be preliminarily judged that the process of TNTS-LA adsorbing MB includes chemical adsorption.

[0042] Application Example 4

[0043] Adsorption performance of lipoic acid-modified titanate nanotube adsorbent for methylene blue with different concentrations (isotherm adsorption experiment). The initial concentrations of methylene blue were 20, 40, 60, 80, and 100 mg / L respectively. 100 mL of the solution was placed in a 250 mL conical flask, and 0.3 g / L of the lipoic acid-modified titanate nanotube adsorbent obtained in Example 1 was added respectively. The mixture was stirred evenly, placed in a constant temperature shaker and shaken. The reaction temperature was 25 °C, the shaking speed was 200 rpm, and the shaking time was 24 h. After the reaction, the reaction system was separated by centrifugation. The absorbance of the pollutants in the solution was measured using a spectrophotometer, and the adsorption efficiency of pollutants with different initial concentrations was calculated according to the standard curve. Specifically, as Figure 8 shown, it can be seen that the lipoic acid-modified titanate nanotubes have excellent adsorption capacity for methylene blue. The maximum adsorption capacity of the lipoic acid-modified titanate nanotube material for methylene blue obtained by fitting the experimental data model is 216.98 mg / g. Therefore, the lipoic acid-modified titanate nanotube material is an adsorbent with broad-spectrum adsorption capacity for organic pollutants, especially cationic dye pollutants.

[0044] The content not described in detail in the specification of the present invention belongs to the prior art well-known to those skilled in the art. Although the illustrative specific embodiments of the present invention are described above for the understanding of those skilled in the art of the present technology, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

Claims

1. A preparation method of a lipoic acid-modified titanium acid nanotube adsorption material, characterized in that: The following steps are involved: Step 1, fully mixing titanium dioxide P25 and NaOH solution to carry out hydrothermal reaction; after the reaction is completed, centrifuging the precipitate, washing with deionized water, then dispersing with ethanol, and drying to obtain titanate nanotubes TNTs; Step 2, mixing titanate nanotubes with lipoic acid solution, stirring magnetically until the color changes to light yellow, filtering, drying, and obtaining TNTs-LA, which is lipoic acid-modified titanate nanotube adsorption material; The mass ratio of the titanate nanotubes to the lipoic acid solution is 1:1; The centrifugal condition in step 1 is 8000r / min for 5min; The drying temperature in step 1 is 80° C. for 8 hours; The magnetic stirring time in step 2 is 24 hours.

2. The preparation method of a lipoic acid modified titanium acid nanotube adsorption material according to claim 1, characterized in that: The mass ratio of titanium dioxide P25 and NaOH solution is 1:

22.

3. The preparation method of a lipoic acid modified titanium acid nanotube adsorption material according to claim 1, characterized in that: The concentration of the NaOH solution is 10 mol / L; the concentration of the lipoic acid solution is 0.1 mol / L.

4. The preparation method of a lipoic acid modified titanic acid nanotube adsorption material according to claim 1, characterized in that: In the step 1, the hydrothermal reaction is carried out at a temperature of 130° C. for 72 hours.

5. The lipoic acid modified titanic acid nanotube adsorbent material prepared by the preparation method of the lipoic acid modified titanic acid nanotube adsorbent material according to claim 1, characterized in that: The lipoic acid-modified titanate nanotubes are randomly wound and intertwined in a disordered state, the nanotubes are hollow in a multi-layer outer wall structure, and one or both ends of the nanotubes are open.

6. Use of the lipoic acid modified titanate nanotube adsorption material obtained by the preparation method of the lipoic acid modified titanate nanotube adsorption material as claimed in claim 1 in adsorbing methylene blue.

Images