Preparation method of polyfunctional group synergistic modified halloysite nanotube-based composite membrane

Abstract

The invention discloses a preparation method of a polyfunctional group synergistic modified halloysite nanotube-based composite membrane, which comprises the following steps: modifying a halloysite nanotube by using a sulfydryl silane coupling agent to obtain a sulfhydrylated halloysite nanotube; the preparation method comprises the following steps: grafting L-cysteine to the surface of a sulfhydrylated halloysite nanotube by utilizing 1, 3-dichloropropanol to obtain a multifunctional group synergistic modified halloysite nanotube; the preparation method comprises the following steps: by taking amino on the surface of a polyfunctional group synergistically modified halloysite nanotube as an anchor point, grafting polyaniline on the surface of the polyfunctional group synergistically modified halloysite nanotube through in-situ cross-linking polymerization, then carrying out suction filtration to form a film, washing and drying to obtain the polyfunctional group synergistically modified halloysite nanotube-based composite film with the gram weight of not more than 15g / m < 2 >. According to the invention, the adsorption capacity of the halloysite nanotube to heavy metal ions is improved, and the problem of separation and recovery of the halloysite nanotube is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane technology for separation and adsorption, and particularly to a preparation method of a multi-functional group synergistically modified halloysite nanotube-based composite membrane. Background Art

[0002] Traditional heavy metal wastewater treatment methods, such as chemical precipitation, ion exchange, electrolysis, and membrane separation, can remove heavy metal ions in wastewater to a certain extent, but they often have problems such as high treatment costs, complex operations, and easy generation of secondary pollution. Halloysite nanotubes (HNTs), as a natural silicate nanomaterial, have certain application potential in the field of heavy metal adsorption due to their unique tubular structure, good chemical stability, and biocompatibility. However, the surface functional groups of halloysite nanotubes are limited and they are prone to agglomeration, resulting in a low adsorption capacity. Moreover, the nano-sized particle size characteristics lead to difficulties in the separation and recovery of halloysite nanotubes. Summary of the Invention

[0003] Aiming at the above-mentioned defects of the prior art, the present invention provides a preparation method of a multi-functional group synergistically modified halloysite nanotube-based composite membrane, which can improve the adsorption capacity of halloysite nanotubes for heavy metal ions and solve the problems of separation and recovery of halloysite nanotubes.

[0004] The technical solution of the present invention is as follows: A preparation method of a multi-functional group synergistically modified halloysite nanotube-based composite membrane includes the following steps: (1) Modify halloysite nanotubes with a mercapto silane coupling agent to obtain mercapto-functionalized halloysite nanotubes; (2) Graft L-cysteine onto the surface of mercapto-functionalized halloysite nanotubes using 1,3-dichloropropanol to obtain multi-functional group synergistically modified halloysite nanotubes; (3) Using the amino group on the surface of the multi-functional group synergistically modified halloysite nanotubes as an anchor point, in-situ cross-linking polymerization and grafting of polyaniline are carried out on the surface of the multi-functional group synergistically modified halloysite nanotubes, and then filtration is carried out to form a membrane. After washing and drying, a multi-functional group synergistically modified halloysite nanotube-based composite membrane with a grammage not greater than 15 g / m 2 is obtained.

[0005] Further, step (1) is specifically to ultrasonically disperse halloysite nanotubes in toluene, then add a mercapto silane coupling agent and stir for reaction. After the reactants are fully washed and dried, mercapto-functionalized halloysite nanotubes are obtained.

[0006] Further, the mass ratio of the halloysite nanotubes to the mercapto silane coupling agent is 1:(0.1 - 0.5), and the mercapto silane coupling agent is one of 3-mercaptopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane.

[0007] Further, in the step (1), the temperature of the stirring reaction is 80-100°C, and the reaction time is 10-15 h.

[0008] Further, in the step (2), specifically, the mercapto-functionalized halloysite nanotubes are added to ethanol, ultrasonically dispersed uniformly, 1,3-dichloropropanol and an acid-binding agent are added, and a stirring reaction is carried out. Then, L-cysteine is added, and the stirring reaction is continued. After the reactants are washed thoroughly and dried, multi-functional group synergistically modified halloysite nanotubes are obtained.

[0009] Further, the mass ratio of the mercapto-functionalized halloysite nanotubes, 1,3-dichloropropanol, the acid-binding agent and L-cysteine is 1:(0.2-0.6):(1-2):(0.3-0.8), and the acid-binding agent is one of triethylamine and pyridine.

[0010] Further, in the step (2), the stirring reaction is a reflux reaction at 80-90°C for 6-8 h.

[0011] Further, in the step (3), specifically, aniline monomer is fully stirred and dissolved in a hydrochloric acid solution in an ice-water bath, then the prepared multi-functional group synergistically modified halloysite nanotubes are added, and after ultrasonic dispersion is uniform, an ammonium persulfate solution that has been precooled is added dropwise, and a stirring reaction is carried out.

[0012] Further, the dosage ratio of the aniline monomer, the multi-functional group synergistically modified halloysite nanotubes and the ammonium persulfate solution is (2-6) mL:1 g:(20-60) mL, the concentration of the hydrochloric acid solution is 1 mol / L - 2 mol / L, and the concentration of the ammonium persulfate solution is 0.2-0.3 mol / L.

[0013] Further, in the step (3), the stirring reaction is carried out in an ice-water bath for 4 h - 6 h.

[0014] The present invention first uses a mercapto coupling agent to treat halloysite nanotubes and introduce mercapto groups on their surfaces. Subsequently, by means of the reaction between mercapto groups and chlorine atoms, with 1,3-dichloropropanol as a "bridge", L-cysteine is grafted onto the surface of halloysite, introducing abundant carboxyl, hydroxyl and amino groups on its surface, that is, realizing multi-functional group synergistic modification. On this basis, further through in-situ polymerization, polyaniline is directly cross-linked and polymerized on the surface of the halloysite nanotubes modified by multi-functional group synergistic effect, realizing cross-linking and composite modification at the same time. This step not only realizes the complementary and synergistic effects of halloysite nanotubes and polyaniline in adsorption performance, but also improves the agglomeration phenomenon of halloysite nanotubes, effectively improving the permeation flux of the membrane. At the same time, it promotes the effective cross-linking between halloysite nanotubes and increases the porosity of the membrane. Finally, with the help of a simple vacuum filtration technique, a multi-functional group synergistic modified halloysite nanotube-based composite membrane with excellent structural stability and adsorption performance is successfully prepared, effectively promoting the application of halloysite nanotubes in the field of water treatment.

[0015] The advantages of the present invention compared with the prior art are as follows: (1) The present invention realizes the carboxyl-rich, hydroxyl-rich and amino-rich modification on the surface of halloysite nanotubes. This multi-functional group synergistic modification not only improves the adsorption performance of the material, but also promotes the in-situ cross-linking polymerization with polyaniline, thus significantly enhancing the structural stability of the composite membrane and facilitating recycling and reuse.

[0016] (2) The composite membrane prepared by the present invention contains rich functional groups, realizes the dual enhancement and synergistic optimization of the adsorption performance of both halloysite nanotubes and polyaniline, and has a rich pore structure and excellent permeation flux at the same time. Therefore, it has excellent adsorption capacity for heavy metal ions. Description of the Drawings

[0017] Figure 1 It is the infrared spectrum diagram of the original halloysite nanotubes and the multi-functional group synergistic modified halloysite nanotubes prepared in Example 1.

[0018] Figure 2 It is the SEM diagram of the composite membrane prepared in Example 1. Detailed Embodiments

[0019] The present invention will be further described below in conjunction with embodiments, but it is not limited to the present invention.

[0020] Example 1 A preparation method of a multi-functional group synergistic modified halloysite nanotube-based composite membrane includes the following steps: (1) 1 g of halloysite nanotubes (Xianfeng Nano, CAS No.: 1332-58-7) was ultrasonically dispersed in toluene, 0.1 g of 3-mercaptopropyltriethoxysilane was added, and the mixture was stirred and reacted at 80 °C for 15 h. After thorough washing with ethanol and drying, mercapto-functionalized halloysite nanotubes were obtained.

[0021] (2) 1 g of the prepared mercapto-functionalized halloysite nanotubes was added to ethanol and ultrasonically dispersed evenly. 0.2 g of 1,3-dichloropropanol and 1 g of triethylamine were added. After reflux reaction at 80 °C for 8 h, 0.3 g of L-cysteine was added, and the reflux reaction was continued at 80 °C for 8 h. After thorough washing and drying, multi-functional group synergistically modified halloysite nanotubes were obtained. The infrared spectrum is as Figure 2 shown. It can be seen that the original halloysite nanotubes showed stretching vibration and deformation vibration absorption peaks of O-H in the Al-OH group at 3695 cm -1 and 3621 cm -1 respectively, a characteristic absorption peak of the Si-O-Si bond at 1031 cm -1 and a bending vibration peak of Al-OH at 912 cm -1 respectively. These are all typical absorption peaks of halloysite. After multi-functional group synergistic modification, most of the Al-OH on the surface of the halloysite nanotubes participated in the reaction, and the absorption peak intensity of the extremely small amount of unreacted Al-OH was weak and was masked by the strong peak caused by the hydroxyl, amino, and carboxyl groups introduced by the modification at 3419 cm -1 . At the same time, some stronger new absorption peaks appeared after modification: the characteristic absorption peaks of -CH2- at 2925 cm -1 and 2856 cm -1 , the absorption peak at 1725 cm -1 was caused by the stretching vibration of C=O in the carboxyl group, the absorption peak at 1602 cm -1 was the N-H bending vibration peak of the amino group, and the absorption peak at 684 cm -1 was the stretching vibration peak of C-S.

[0022] (3) 2 mL of aniline monomer was fully stirred and dissolved in 1 mol / L hydrochloric acid solution (100 mL) in an ice-water bath. Then 1 g of the prepared multi-functional group synergistically modified halloysite nanotubes was added. After ultrasonic dispersion evenly, 20 mL of pre-cooled ammonium persulfate solution (concentration: 0.2 mol / L) was added dropwise. The mixture was stirred and reacted in an ice-water bath for 4 h. After the reaction, solvent (deionized water) was added to make the reaction system reach 3000 mL. 39.3 mL of the reaction solution was taken for suction filtration to form a film. After washing alternately with ethanol and water and drying, a multi-functional group synergistically modified halloysite nanotube-based composite film with a diameter of 10 cm and a grammage of 5 g / m 2 was obtained. The SEM image is as Figure 2 shown. It can be seen that the composite film has a rich pore structure.

[0023] The adsorption performance test experiment of the multi-functional group synergistic modified halloysite nanotube-based composite membrane prepared in Example 1 is as follows: Prepare 100 mL of an aqueous solution with a lead ion (lead nitrate as the reagent) concentration of 100 mg / L in a flask. After adjusting the pH of the solution to 7 with 0.1 M NaOH, add the prepared multi-functional group synergistic modified halloysite nanotube-based composite membrane, and then adsorb for 3 h at 30 °C in a constant temperature shaker at a rotation speed of 200 rpm. After adsorption, take the supernatant and use ICP-OES to measure the concentration of lead ions in the supernatant. Calculate the adsorption capacity of the adsorbent for lead ions through the following formula ( Q , mg / g), and the results are listed in Table 1.

[0024] Q =( C 0 - C t ) V / M Q is the adsorption capacity (mg / g); C 0 is the initial concentration of heavy metal ions (mg / L); C t is the concentration of heavy metal ions after adsorption (mg / L); V is the volume of the solution (L); M is the mass of the adsorbent (g).

[0025] Example 2

[0026] A preparation method of a multi-functional group synergistic modified halloysite nanotube-based composite membrane includes the following steps: (1) Ultrasonically disperse 1 g of halloysite nanotubes (Xianfeng Nano, CAS No.: 1332-58-7) in toluene, add 0.3 g of 3-mercaptopropyltrimethoxysilane, and stir and react at 90 o °C for 12.5 h. Wash thoroughly with ethanol and dry to obtain mercapto-functionalized halloysite nanotubes.

[0027] (2) Add 1 g of the prepared mercapto-functionalized halloysite nanotubes to ethanol, ultrasonically disperse evenly, add 0.4 g of 1,3-dichloropropanol and 1.5 g of pyridine, reflux and react at 85 o °C for 7 h, then add 0.55 g of L-cysteine and continue to reflux and react at 85 o °C for 7 h. Wash thoroughly and dry to obtain multi-functional group synergistic modified halloysite nanotubes.

[0028] (3) Dissolve 4 mL of aniline monomer in 1.5 mol / L hydrochloric acid solution (200 mL) with sufficient stirring in an ice-water bath. Then add 1 g of the prepared multi-functional group synergistically modified halloysite nanotubes. After ultrasonic dispersion to uniformity, gradually dropwise add 40 mL of pre-cooled ammonium persulfate solution (concentration: 0.25 mol / L). Stir and react in the ice-water bath for 5 h. After the reaction, add solvent (deionized water) to make the reaction system reach 3000 mL. Take 47.1 mL of the reaction solution for suction filtration to form a film. After washing alternately with ethanol and water and drying, a composite film of multi-functional group synergistically modified halloysite nanotubes with a diameter of 10 cm and a grammage of 10 g / m 2 is obtained. The adsorption capacity of the composite film for lead ions is determined according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0029] Example 3

[0030] A preparation method of a composite film based on multi-functional group synergistically modified halloysite nanotubes, comprising the following steps: (1) Ultrasonically disperse 1 g of halloysite nanotubes (Xianfeng Nano, CAS No.: 1332-58-7) in toluene, add 0.5 g of 3-mercaptopropyltriethoxysilane, and stir and react at 100 o °C for 10 h. Wash thoroughly with ethanol and dry to obtain mercapto-functionalized halloysite nanotubes.

[0031] (2) Add 1 g of the prepared mercapto-functionalized halloysite nanotubes to ethanol, ultrasonically disperse to uniformity, add 0.6 g of 1,3-dichloropropanol and 2 g of triethylamine, and reflux and react at 90 o °C for 6 h. Then add 0.8 g of L-cysteine and continue to reflux and react at 90 o °C for 6 h. Wash thoroughly and dry to obtain multi-functional group synergistically modified halloysite nanotubes.

[0032] (3) Dissolve 6 mL of aniline monomer in 2 mol / L hydrochloric acid solution (200 mL) with sufficient stirring in an ice-water bath. Then add 1 g of the prepared multi-functional group synergistically modified halloysite nanotubes. After ultrasonic dispersion to uniformity, gradually dropwise add 60 mL of pre-cooled ammonium persulfate solution (concentration: 0.3 mol / L). Stir and react in the ice-water bath for 6 h. After the reaction, add solvent (deionized water) to make the reaction system reach 3000 mL. Take 50.5 mL of the reaction solution for suction filtration to form a film. After washing alternately with ethanol and water and drying, a composite film of multi-functional group synergistically modified halloysite nanotubes with a diameter of 10 cm and a grammage of 15 g / m 2 is obtained. The adsorption capacity of the composite film for lead ions is determined according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0033] Example 4

[0034] A preparation method of a multi-functional group synergistically modified halloysite nanotube-based composite membrane. Steps (1) and (2) are the same as those in Example 1. The difference between this example and Example 1 is that in step (3) of this example, 78.6 ml of the cross-linked polymerization reaction solution is taken for suction filtration to form a membrane, and a multi-functional group synergistically modified halloysite nanotube-based composite membrane with a diameter of 10 cm and a grammage of 10 g / m 2 is obtained. The rest is the same as in Example 1. The adsorption capacity of lead ions is measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0035] Example 5

[0036] A preparation method of a multi-functional group synergistically modified halloysite nanotube-based composite membrane. Steps (1) and (2) are the same as those in Example 1. The difference between this example and Example 1 is that in step (3) of this example, 117.9 ml of the cross-linked polymerization reaction solution is taken for suction filtration to form a membrane, and a multi-functional group synergistically modified halloysite nanotube-based composite membrane with a diameter of 10 cm and a grammage of 15 g / m 2 is obtained. The rest is the same as in Example 1. The adsorption capacity of lead ions is measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0037] Comparative Example 1 1 g of halloysite nanotubes (Xianfeng Nano, CAS No.: 1332-58-7) is ultrasonically dispersed in 3000 mL of 1 mol / L hydrochloric acid solution until evenly dispersed. 117.8 mL of the reaction solution is taken for suction filtration to form a membrane. After washing alternately with ethanol and water and drying, a pure halloysite nanotube membrane with a diameter of 10 cm and a grammage of 5 g / m 2 is obtained. The adsorption capacity of lead ions is measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0038] Comparative Example 2 Prepare mercapto-functionalized halloysite nanotubes according to step (1) in Example 1. Then, 1 g of mercapto-functionalized halloysite nanotubes is added to 3000 mL of 1 mol / L hydrochloric acid solution and ultrasonically dispersed evenly. 117.8 mL of the reaction solution is taken for suction filtration to form a membrane. After washing alternately with ethanol and water and drying, a mercapto-functionalized halloysite nanotube membrane with a diameter of 10 cm and a grammage of 5 g / m 2 is obtained. The adsorption capacity of lead ions is measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0039] Comparative Example 3 Prepare multi-functional synergistic modified halloysite nanotubes according to steps (1) and (2) in Example 1. Then, add 1 g of multi-functional synergistic modified halloysite nanotubes to 3000 mL of 1 mol / L hydrochloric acid solution, disperse evenly by ultrasonic wave, take 117.8 mL of the reaction solution for suction filtration to form a film, wash alternately with ethanol and water, and dry to obtain a multi-functional synergistic modified halloysite nanotube film with a diameter of 10 cm and a grammage of 5 g / m 2 The adsorption capacity of the film for lead ions was determined according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0040] Table 1 Adsorption amount of lead ions by halloysite nanotube-based composite membranes prepared in Examples 1-5 and Comparative Examples 1-3

[0041] It can be seen from the results that the multi-functional synergistic modified halloysite nanotube-based composite membrane prepared by the present invention not only contains rich functional groups, but also realizes the strong combination and synergistic enhancement of the adsorption performance of halloysite nanotubes and polyaniline. In addition, effective cross-linking is achieved between halloysite nanotubes and polyaniline, which not only improves the porosity of the composite membrane, but also promotes the uniform dispersion of halloysite nanotubes. Therefore, the multi-functional synergistic modified halloysite nanotube-based composite membrane prepared in the example has excellent adsorption performance for lead ions, and the adsorption amount can reach 338 mg / g.

[0042] Moreover, the more the number and types of surface functional groups of halloysite nanotubes, the stronger the adsorption amount of the composite membrane for lead ions, as shown by the results of Example 1, Comparative Example 1 and Comparative Example 2. The comparison of the results of Example 1 and Comparative Example 3 fully illustrates the importance of in-situ cross-linking graft polymerization of polyaniline on the surface of halloysite nanotubes for improving the adsorption performance of multi-functional synergistic modified halloysite nanotube-based composite membranes. This is because in-situ cross-linking graft polymerization can not only form good interfacial bonding between halloysite nanotubes and between halloysite nanotubes and polyaniline, promote the uniform dispersion of halloysite nanotubes, increase the permeation flux of the membrane, but also improve the porosity of the membrane, and can more synergistically play the adsorption role of halloysite and polyaniline. In addition, it can be seen from the results of Example 1, Example 4 and Example 5 that when the mass of the multi-functional synergistic modified halloysite nanotube-based composite membrane increases to a certain extent (the diameter remains unchanged and the thickness will increase), it will affect the total adsorption amount of metal ions. This is because the increase in the thickness of the multi-functional synergistic modified halloysite nanotube-based composite membrane will lead to a decrease in permeability.

Claims

1. A method for preparing a multi-functional group synergistically modified halloysite nanotube-based composite membrane, characterized in that: The following steps are involved: (1) using a mercaptosilane coupling agent to modify halloysite nanotubes to obtain mercapto-modified halloysite nanotubes; (2) L-cysteine ​​was grafted onto the surface of thiolated halloysite nanotubes using 1,3-dichloropropanol to obtain multi-functional group synergistically modified halloysite nanotubes; (3) Using the amino groups on the surface of the multi-functional group synergistically modified halloysite nanotubes as anchor points, in-situ cross-linking polymerization and grafting polyaniline on the surface of the multi-functional group synergistically modified halloysite nanotubes, and then filtering to form a membrane, washing and drying to obtain a film with a gram weight of no more than 15 g / m 2 Multi-functional group synergistically modified halloysite nanotube-based composite membranes.

2. The method for preparing a multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 1, wherein the step (1) specifically comprises ultrasonically dispersing the halloysite nanotubes in toluene, then adding a mercaptosilane coupling agent for stirring and reacting, and the reactants are fully washed and dried to obtain mercapto-modified halloysite nanotubes.

3. According to the preparation method of the multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 2, the mass ratio of the halloysite nanotubes to the mercaptosilane coupling agent is 1: (0.1-0.5), and the mercaptosilane coupling agent is one of 3-mercaptopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane.

4. The method for preparing a multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 2, wherein the stirring reaction temperature in step (1) is 80-100°C and the reaction time is 10-15 hours.

5. The method for preparing a multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 1, wherein the step (2) specifically comprises adding thiolated halloysite nanotubes to ethanol, uniformly dispersing them by ultrasonication, adding 1,3-dichloropropanol and an acid binding agent, stirring and reacting, then adding L-cysteine, continuing to stir and react, and fully washing and drying the reactants to obtain multi-functional group synergistically modified halloysite nanotubes.

6. The method for preparing a multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 5, wherein the mass ratio of the thiolated halloysite nanotubes, 1,3-dichloropropanol, acid binding agent and L-cysteine ​​is 1: (0.2-0.6): (1-2): (0.3-0.8), and the acid binding agent is one of triethylamine and pyridine.

7. The method for preparing a multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 5, wherein the stirring reaction in step (2) is a reflux reaction at 80-90°C for 6-8h.

8. The method for preparing a multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 1, wherein in step (3), the aniline monomer is dissolved in a hydrochloric acid solution by fully stirring in an ice-water bath, and then the prepared multi-functional group synergistically modified halloysite nanotubes are added, and after ultrasonic dispersion, a pre-cooled ammonium persulfate solution is added dropwise to carry out a stirring reaction.

9. The method for preparing a multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 8, wherein the usage ratio of the aniline monomer, the multi-functional group synergistically modified halloysite nanotube and the ammonium persulfate solution is (2-6) mL: 1 g: (20-60) ml, the concentration of the hydrochloric acid solution is 1 mol / L-2 mol / L, and the concentration of the ammonium persulfate solution is 0.2-0.3 mol / L.

10. The method for preparing a multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 8, wherein the stirring reaction in step (3) is carried out in an ice-water bath for 4 to 6 hours.

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