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

Abstract

The present invention discloses a preparation method of a multi-functional group synergistic modified halloysite nanotube-based composite membrane, comprising the steps of: modifying halloysite nanotubes with a mercapto silane coupling agent to obtain mercapto-functionalized halloysite nanotubes; grafting L-cysteine onto the surface of the mercapto-functionalized halloysite nanotubes by using 1,3-dichloropropanol to obtain multi-functional group synergistic modified halloysite nanotubes; taking the amino group on the surface of the multi-functional group synergistic modified halloysite nanotubes as an anchor point, in-situ cross-linking and polymerizing to graft polyaniline on the surface of the multi-functional group synergistic modified halloysite nanotubes, and then performing suction filtration to form a membrane, washing and drying to obtain a multi-functional group synergistic modified halloysite nanotube-based composite membrane with a grammage not greater than 15 g / m<supgt;2< / supgt>. The present invention improves the adsorption capacity of halloysite nanotubes for heavy metal ions and solves the problem of separation and recovery of halloysite nanotubes.

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 synergistic 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, although can remove heavy metal ions in wastewater to a certain extent, often have problems such as high treatment cost, complex operation, 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-scale particle size characteristics lead to the problems of 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 synergistic 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 at the same time.

[0004] The technical solution of the present invention is as follows: A preparation method of a multi-functional group synergistic modified halloysite nanotube-based composite membrane, comprising the following steps:

[0005] (1) Modify halloysite nanotubes with a mercapto silane coupling agent to obtain mercapto-functionalized halloysite nanotubes;

[0006] (2) Graft L-cysteine onto the surface of the mercapto-functionalized halloysite nanotubes by using 1,3-dichloropropanol to obtain multi-functional group synergistic modified halloysite nanotubes;

[0007] (3) Using the amino group on the surface of the multi-functional group synergistic modified halloysite nanotubes as an anchor point, in-situ crosslinking polymerization and grafting of polyaniline on the surface of the multi-functional group synergistic modified halloysite nanotubes, and then filtering to form a membrane, washing and drying to obtain a multi-functional group synergistic modified halloysite nanotube-based composite membrane with a grammage not greater than 15 g / m 2 2.

[0008] Further, the specific operation of step (1) is to ultrasonically disperse halloysite nanotubes in toluene, then add a mercapto silane coupling agent for stirring reaction, and the reactants are fully washed and dried to obtain mercapto-functionalized halloysite nanotubes.

[0009] 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.

[0010] Further, in the step (1), the temperature of the stirring reaction is 80-100°C, and the reaction time is 10-15 h.

[0011] Further, the step (2) is specifically adding the mercapto-functionalized halloysite nanotubes into ethanol, ultrasonically dispersing them evenly, adding 1,3-dichloropropanol and an acid-binding agent, carrying out a stirring reaction, then adding L-cysteine, continuing the stirring reaction, and obtaining the multi-functional group synergistically modified halloysite nanotubes after the reactants are fully washed and dried.

[0012] 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.

[0013] Further, the stirring reaction in the step (2) is a reflux reaction at 80-90°C for 6-8 h.

[0014] Further, the step (3) is specifically stirring and dissolving aniline monomer in a hydrochloric acid solution in an ice-water bath, then adding the prepared multi-functional group synergistically modified halloysite nanotubes, ultrasonically dispersing them evenly, and then dropwise adding a pre-cooled ammonium persulfate solution and carrying out a stirring reaction.

[0015] 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.

[0016] Further, the stirring reaction in the step (3) is carried out in an ice-water bath for 4 h - 6 h.

[0017] The present invention first treats halloysite nanotubes with a mercapto coupling agent to introduce mercapto groups onto their surfaces. Subsequently, by means of the reaction between mercapto groups and chlorine atoms, using 1,3-dichloropropanol as a "bridge", L-cysteine is grafted onto the surface of halloysite, introducing abundant carboxyl, hydroxyl, and amino groups onto its surface, namely achieving 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 multi-functional group synergistically modified halloysite nanotubes, simultaneously realizing cross-linking and composite modification. 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 enhancing 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 composite membrane based on multi-functional group synergistically modified halloysite nanotubes with excellent structural stability and adsorption performance is successfully prepared, effectively promoting the application of halloysite in the field of water treatment.

[0018] The advantages of the present invention compared with the prior art are as follows:

[0019] (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.

[0020] (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 at the same time has a rich pore structure and excellent permeation flux, so it has excellent adsorption capacity for heavy metal ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the infrared spectrum diagram of the original halloysite nanotubes and the multi-functional group synergistically modified halloysite nanotubes prepared in Example 1.

[0022] Figure 2 It is the SEM diagram of the composite membrane prepared in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be further described below in conjunction with examples, but it is not limited to the present invention.

[0024] Example 1

[0025] A preparation method of a composite membrane based on multi-functional group synergistically modified halloysite nanotubes, comprising the following steps:

[0026] (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.

[0027] (2) 1 g of the prepared mercapto-functionalized halloysite nanotubes was added to ethanol, 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. Its 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 Al-OH groups at 3695 cm -1 and 3621 cm -1 respectively, a characteristic absorption peak of Si-O-Si bond at 1031 cm -1 and a bending vibration peak of Al-OH at 912 cm -1 . These are all typical absorption peaks of halloysite. After multi-functional group synergistic modification, most of the Al-OH on the surface of 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 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.

[0028] (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 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. Its SEM image is as Figure 2 shown. It can be seen that the composite film has a rich pore structure.

[0029] The adsorption performance test experiment of the multi-functional group synergistic modified halloysite nanotube-based composite membrane prepared in Example 1 is as follows:

[0030] Prepare 100 mL of an aqueous solution with a lead ion (using 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. Then, place it in a constant temperature shaker at 30 °C and adsorb for 3 h 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.

[0031] Q =( C 0 - C t ) V / M

[0032] 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).

[0033] Example 2

[0034] A preparation method of a multi-functional group synergistic modified halloysite nanotube-based composite membrane includes the following steps:

[0035] (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.

[0036] (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.

[0037] (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 synergistic modified halloysite nanotubes. After ultrasonic dispersion until homogeneous, gradually add dropwise 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. Wash alternately with ethanol and water, and dry to obtain a multi-functional synergistic modified halloysite nanotube-based composite film with a diameter of 10 cm and a grammage of 10 g / m 2 The adsorption capacity of the multi-functional synergistic modified halloysite nanotube-based composite film for lead ions was measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0038] Example 3

[0039] A preparation method of a multi-functional synergistic modified halloysite nanotube-based composite film, comprising the following steps:

[0040] (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.

[0041] (2) Add 1 g of the prepared mercapto-functionalized halloysite nanotubes to ethanol, ultrasonically disperse until homogeneous, 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 synergistic modified halloysite nanotubes.

[0042] (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 synergistic modified halloysite nanotubes. After ultrasonic dispersion until homogeneous, gradually add dropwise 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. Wash alternately with ethanol and water, and dry to obtain a multi-functional synergistic modified halloysite nanotube-based composite film with a diameter of 10 cm and a grammage of 15 g / m 2 The adsorption capacity of the multi-functional synergistic modified halloysite nanotube-based composite film for lead ions was measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0043] Example 4

[0044] 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 crosslinked polymerization reaction solution is taken for vacuum filtration to form a membrane, obtaining 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 . The rest is the same as in Example 1. The adsorption capacity for lead ions is measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0045] Example 5

[0046] 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 crosslinked polymerization reaction solution is taken for vacuum filtration to form a membrane, obtaining 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 . The rest is the same as in Example 1. The adsorption capacity for lead ions is measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0047] Comparative Example 1

[0048] 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. Then, 117.8 mL of the reaction solution is taken for vacuum 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 for lead ions is measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0049] Comparative Example 2

[0050] Prepare thiolated halloysite nanotubes according to step (1) in Example 1. Then, 1 g of thiolated halloysite nanotubes is added to 3000 mL of 1 mol / L hydrochloric acid solution and ultrasonically dispersed evenly. Take 117.8 mL of the reaction solution for vacuum filtration to form a membrane. After washing alternately with ethanol and water and drying, a thiolated halloysite nanotube membrane with a diameter of 10 cm and a grammage of 5 g / m 2 is obtained. The adsorption capacity for lead ions is measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0051] Comparative Example 3

[0052] Prepare multi-functional synergistic modified halloysite nanotubes according to steps (1) and (2) in Example 1. Then, add 1 g of the multi-functional synergistic modified halloysite nanotubes to 3000 mL of 1 mol / L hydrochloric acid solution, and disperse them evenly by ultrasonic treatment. Take 117.8 mL of the reaction solution for suction filtration to form a film. After washing alternately with ethanol and water and drying, a halloysite nanotube film with a diameter of 10 cm and a grammage of 5 g / m 2 is obtained. Its adsorption capacity for lead ions is measured according to the adsorption performance experiment of the product in Example 1, and the results are listed in Table 1.

[0053] Table 1 Adsorption amounts of halloysite nanotube-based composite membranes prepared in Examples 1-5 and Comparative Examples 1-3 for lead ions

[0054]

[0055] It can be seen from the results that since the multi-functional synergistic modified halloysite nanotube-based composite membrane prepared in the present invention not only contains abundant functional groups, but also realizes the strong combination and synergistic enhancement of the adsorption properties 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.

[0056] 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 the multi-functional synergistic modified halloysite nanotube-based composite membrane. 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 exert the adsorption effects 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 preparation method of a multi-functional group synergistically modified halloysite nanotube-based composite membrane, characterized in that, It 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 the mercapto-functionalized halloysite nanotubes using 1,3-dichloropropanol to obtain multi-functional group synergistically modified halloysite nanotubes; (3) Using the amino groups on the surface of halloysite nanotubes modified by multi-functional group synergistic effect as the anchor points, in-situ cross-linking polymerization and grafting of polyaniline are carried out on the surface of halloysite nanotubes modified by multi-functional group synergistic effect, and then filtered into a film. After washing and drying, a composite film based on halloysite nanotubes modified by multi-functional group synergistic effect with a grammage not greater than 15 g / m 2 is obtained.

2. The preparation method of the multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 1, wherein in step (1), the halloysite nanotubes are ultrasonically dispersed in toluene, and then a mercapto silane coupling agent is added for stirring reaction. After the reactants are thoroughly washed and dried, mercapto-functionalized halloysite nanotubes are obtained.

3. The preparation method of the multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 2, wherein 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.

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

5. The preparation method of the multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 1, wherein in step (2), the mercapto-functionalized halloysite nanotubes are added to ethanol, ultrasonically dispersed evenly, 1,3-dichloropropanol and an acid-binding agent are added, and stirring reaction is carried out. Then L-cysteine is added, and stirring reaction continues. After the reactants are thoroughly washed and dried, multi-functional group synergistically modified halloysite nanotubes are obtained.

6. The preparation method of the multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 5, wherein 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.

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

8. The preparation method of the multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 1, wherein in step (3), 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, ultrasonically dispersed evenly, and a pre-cooled ammonium persulfate solution is added dropwise, and stirring reaction is carried out.

9. The preparation method of the multi-functional group synergistically modified halloysite nanotube-based composite membrane according to claim 8, wherein 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.

10. The preparation method of the multi-functional group synergistic 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 h to 6 h.

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