Preparation method of cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nano composite aerogel

Abstract

The invention discloses a preparation method of cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nano composite aerogel, which comprises the following steps: adopting mercaptoethylamine as a guest molecule, and carrying out intercalation treatment on alpha-zirconium phosphate to obtain thiolated intercalated zirconium phosphate; modifying the surface and interlayer of the sulfhydrylated intercalated zirconium phosphate with epoxy chloropropane through a substitution reaction of sulfydryl and chlorine atoms to obtain epoxidized intercalated zirconium phosphate; the epoxidized intercalated zirconium phosphate is ultrasonically dispersed in an aqueous solution of polyethyleneimine for cross-linking modification and stripping reaction, the epoxidized intercalated zirconium phosphate is used as a cross-linking agent, and the polyethyleneimine is cross-linked and grafted on the surface and between layers of the zirconium phosphate; finally, the reaction liquid is subjected to freeze drying, and the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nano composite aerogel is obtained. The problems that polyethyleneimine is easy to remain in a solution and the interface compatibility of zirconium phosphate and a resin matrix is poor are solved, and efficient adsorption of heavy metal ions is realized.

Description

Technical Field

[0001] The invention relates to the technical field of aerogels, and in particular to a method for preparing a cross-linked modified peeled zirconium phosphate-polyethyleneimine nanocomposite aerogel. Background Art

[0002] Polyethyleneimine is a heavy metal ion adsorption material. Its molecular chain is rich in various amino functional groups such as primary amine, secondary amine and tertiary amine. These functional groups can specifically adsorb heavy metal ions through electrostatic interaction and coordination binding. However, when polyethyleneimine is used alone as an adsorption material, due to its good water solubility, part of polyethyleneimine will remain in the solution, making it difficult to effectively remove heavy metal ions in water.

[0003] Figure 1 The layered nanomaterial α-zirconium phosphate shown in the figure is often used as a functional additive to enhance the adsorption efficiency of resin-based composites for heavy metals due to its large specific surface area, excellent mechanical properties, good thermal stability and high ion exchange capacity. However, the high crystallinity and small interlayer spacing of α-zirconium phosphate make it difficult to achieve uniform dispersion in the resin matrix. In order to improve its compatibility with the resin matrix and promote its synergistic effect with the matrix, α-zirconium phosphate needs to be surface modified. However, the current modification technology is mainly limited to surface and edge modification, while the interlayers are still in a stacked unmodified state. The adhesion efficiency of the modifier is not high, which limits the improvement of compatibility, resulting in an insignificant improvement in the adsorption of its composite materials. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the present invention provides a method for preparing a cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel, which achieves efficient adsorption of heavy metal ions and solves the problems of polyethyleneimine easily remaining in the solution and poor interface compatibility between zirconium phosphate and the resin matrix.

[0005] The technical solution of the present invention is as follows: A method for preparing a cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel comprises the following steps: (1) Using mercaptoethylamine as a guest molecule, α-zirconium phosphate is intercalated to obtain thiolated intercalated zirconium phosphate; (2) modifying the surface and interlayer of the thiol-intercalated zirconium phosphate with epichlorohydrin through a substitution reaction between thiol groups and chlorine atoms to obtain an epoxy-intercalated zirconium phosphate; (3) Ultrasonic dispersion of the epoxylated intercalated zirconium phosphate in an aqueous solution of polyethyleneimine for crosslinking modification and exfoliation reaction, using the epoxylated intercalated zirconium phosphate as a crosslinking agent to crosslink and graft polyethyleneimine on the surface and between layers of the zirconium phosphate, and finally freeze-drying the reaction solution to obtain a crosslinked, modified, exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel.

[0006] Furthermore, the step (1) specifically comprises ultrasonically dispersing α-zirconium phosphate in deionized water, then slowly dropping an aqueous solution of mercaptoethylamine to carry out an intercalation reaction, filtering, washing and drying.

[0007] Furthermore, the mass ratio of the α-zirconium phosphate to mercaptoethylamine is 1:(0.6-0.8), and the concentration of the mercaptoethylamine aqueous solution is 10-16 mg / mL.

[0008] Furthermore, the intercalation reaction in step (1) is carried out under the action of 40-60 kHz ultrasound for 5-7 hours.

[0009] Furthermore, the step (2) specifically comprises ultrasonically dispersing the thiolated intercalated zirconium phosphate in ethanol, then adding epichlorohydrin and an acid binding agent, stirring to react, filtering, washing and drying.

[0010] Furthermore, the mass ratio of the thiolated intercalated zirconium phosphate, epichlorohydrin and the acid binding agent is 1:(0.5-1):(1-2), and the acid binding agent is one of triethylamine and pyridine.

[0011] Furthermore, the stirring reaction in step (2) is performed under reflux at 80-90° C. for 4-6 hours.

[0012] Furthermore, in step (3), the mass ratio of the epoxy intercalated zirconium phosphate to polyethyleneimine is 1:(8-20).

[0013] Furthermore, the crosslinking modification and stripping reaction in step (3) is carried out by stirring at 50 to 80° C. for 6 to 8 hours.

[0014] Furthermore, the freeze drying in step (3) is to freeze dry the reaction solution at -50 to -40°C for 30 to 50 hours.

[0015] The present invention uses mercaptoethylamine as a guest molecule to perform intercalation treatment on zirconium phosphate, and at the same time provides a possibility for subsequent modification. Subsequently, epichlorohydrin is modified on the surface and interlayer of zirconium phosphate through the substitution reaction of mercapto groups and chlorine atoms, which not only further expands the interlayer spacing, but also provides active sites for subsequent cross-linking and grafting reactions. Then, using epoxy intercalated zirconium phosphate as a cross-linking agent, the reaction between the epoxy group and the amino group of polyethyleneimine is utilized to achieve cross-linking and grafting on the surface and interlayer of zirconium phosphate. This process not only constructs a stable cross-linking network between zirconium phosphate and polyethyleneimine, but also the steric hindrance effect generated by the cross-linking and grafting reaction promotes the effective peeling of the zirconium phosphate interlayer, forming a peeled nano-composite material. Finally, with the help of freeze-drying technology, a nano-composite aerogel with both structural stability and excellent adsorption performance is prepared.

[0016] The advantages of the present invention compared with the prior art are: (1) Through the steric hindrance effect brought about by interlayer grafting modification, the present invention implements efficient exfoliation treatment on intercalated zirconium phosphate. The exfoliated structure not only gives the composite material a larger specific surface area and better performance, but also achieves comprehensive modification of the surface, edge and interlayer of zirconium phosphate, effectively improves the adhesion rate of the modifier, significantly enhances its interfacial compatibility with the matrix, promotes its synergistic effect with the matrix, and thus comprehensively improves the comprehensive performance of the composite material.

[0017] (2) The nanocomposite aerogel prepared by the present invention not only has a rich pore structure, but also combines the excellent structural characteristics of exfoliated zirconium phosphate and the rich active amino groups of polyethyleneimine. Due to the excellent interfacial compatibility, the deep combination and synergistic enhancement of the adsorption performance of the two are achieved, which greatly improves its adsorption performance for heavy metal ions.

[0018] (3) In the nanocomposite aerogel of the present invention, polyethyleneimine is firmly cross-linked into a water-insoluble network structure, which effectively solves the problem of its residue in the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the SEM image of the original α-zirconium phosphate.

[0020] Figure 2 This is the SEM image of the peeled zirconium phosphate with surface cross-linked grafted polyethyleneimine obtained in Example 1.

[0021] Figure 3 This is the SEM image of the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel obtained in Example 1. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the embodiments, but are not intended to limit the present invention.

[0023] Example 1

[0024] A method for preparing a cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel comprises the following steps: (1) 1 g of α-zirconium phosphate (13772-29-7, Shanghai Aladdin Reagent Co., Ltd.) was ultrasonically dispersed in deionized water, and then 60 mL of a 10 mg / mL aqueous solution of mercaptoethylamine was slowly added dropwise. Under the action of 40 kHz ultrasonic waves, the intercalation reaction was carried out for 7 h. The thiolated intercalated zirconium phosphate was filtered, washed, and dried to obtain the thiolated intercalated zirconium phosphate.

[0025] (2) 1 g of the prepared thiolated intercalated zirconium phosphate was ultrasonically dispersed in ethanol, and then 0.5 g of epichlorohydrin and 1 g of triethylamine were added. The mixture was refluxed at 80°C for 6 h, and then filtered, washed, and dried to obtain the epoxy intercalated zirconium phosphate.

[0026] (3) 8 g of polyethyleneimine (molecular weight 600) was fully stirred and dissolved in deionized water, and then 1 g of the epoxy-intercalated zirconium phosphate was added and dispersed evenly by ultrasonication. After stirring and reacting at 50°C for 8 h, the reaction solution was freeze-dried at -40°C for 50 h to obtain a cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel. The SEM image of the exfoliated zirconium phosphate (before freeze-drying treatment) of the surface cross-linked grafted polyethyleneimine is shown in the figure. Figure 2 As shown in the figure, it can be seen that polyethyleneimine is cross-linked and grafted on the surface of the nanosheets, and the scattered thin sheets are connected together to form a large nanofilm. Moreover, due to the effective peeling, the polyethyleneimine cross-linking coverage surface area increases, and the polyethyleneimine grafted on the adjacent thin sheets will connect the nanosheets, resulting in a large number of wrinkles. The SEM image of the prepared cross-linked modified peeled zirconium phosphate-polyethyleneimine nanocomposite aerogel is shown in Figure 3 As shown, it can be seen that the prepared aerogel has a large number of pore structures.

[0027] The adsorption performance experiment of the cross-linked modified peeled zirconium phosphate-polyethyleneimine nanocomposite aerogel prepared in Example 1 is as follows: Prepare 100 mL of an aqueous solution with a lead ion concentration of 100 mg / L (lead nitrate as a reagent) in a flask, adjust the solution pH to 7 with 0.1 M NaOH, add the prepared cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel, and then adsorb for 3 hours at 200 rpm in a constant temperature oscillator at 30 ° C. After adsorption, take the upper clear liquid, determine the concentration of lead ions in the clear liquid by ICP-OES, and calculate the adsorption amount of lead ions by the adsorbent material by the following formula ( Q , mg / g), and the results are listed in Table 1.

[0028] Q =( C 0 - C t ) V / M , in, Q is the adsorption amount (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).

[0029] Example 2

[0030] A method for preparing a cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel comprises the following steps: (1) 1 g of α-zirconium phosphate (13772-29-7, Shanghai Aladdin Reagent Co., Ltd.) was ultrasonically dispersed in deionized water, and then 54 mL of an aqueous solution of 13 mg / mL mercaptoethylamine was slowly added dropwise. Under the action of 50 kHz ultrasonic waves, the intercalation reaction was carried out for 6 h. The thiolated intercalated zirconium phosphate was filtered, washed, and dried to obtain the thiolated intercalated zirconium phosphate.

[0031] (2) 1 g of the prepared thiolated intercalated zirconium phosphate was ultrasonically dispersed in ethanol, and then 0.75 g of epichlorohydrin and 1.5 g of pyridine were added. The mixture was refluxed at 85°C for 5 h, and then filtered, washed, and dried to obtain the epoxy intercalated zirconium phosphate.

[0032] (3) 14 g of polyethyleneimine (molecular weight 600) was fully stirred and dissolved in deionized water, and then 1 g of the prepared epoxy-intercalated zirconium phosphate was added and dispersed evenly by ultrasonication. After stirring and reacting at 65°C for 7 h, the reaction solution was freeze-dried at -45°C for 40 h to obtain a cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel. The adsorption performance of the aerogel was measured according to the adsorption performance experiment of the product in Example 1. The results are listed in Table 1.

[0033] Example 3

[0034] A method for preparing a cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel comprises the following steps: (1) 1 g of α-zirconium phosphate (13772-29-7, Shanghai Aladdin Reagent Co., Ltd.) was ultrasonically dispersed in deionized water, and then 50 mL of an aqueous solution of 16 mg / mL mercaptoethylamine was slowly added dropwise. Under the action of 60 kHz ultrasound, the intercalation reaction was carried out for 5 h. The thiolated intercalated zirconium phosphate was filtered, washed, and dried to obtain the thiolated intercalated zirconium phosphate.

[0035] (2) 1 g of the prepared thiolated intercalated zirconium phosphate was ultrasonically dispersed in ethanol, and then 1 g of epichlorohydrin and 2 g of triethylamine were added. The mixture was refluxed at 90°C for 4 h, and then filtered, washed, and dried to obtain the epoxy intercalated zirconium phosphate.

[0036] (3) 20 g of polyethyleneimine (molecular weight 600) was fully stirred and dissolved in deionized water, and then 1 g of the prepared epoxy-intercalated zirconium phosphate was added and dispersed evenly by ultrasonication. After stirring and reacting at 80°C for 6 h, the reaction solution was freeze-dried at -50°C for 30 h to obtain a cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel. The adsorption performance of the aerogel was measured according to the adsorption performance experiment of the product in Example 1. The results are listed in Table 1.

[0037] Comparative Example 1 8 g of polyethyleneimine (molecular weight 600) was fully stirred and dissolved in deionized water, and then 1 g of untreated zirconium phosphate was added and dispersed evenly by ultrasonication. After stirring and reacting at 50°C for 8 hours, the reaction solution was freeze-dried at -40°C for 50 hours to obtain zirconium phosphate-polyethyleneimine composite aerogel. The adsorption performance of the aerogel was measured according to the adsorption performance experiment of the product in Example 1. The results are listed in Table 1.

[0038] Comparative Example 2 8 g of polyethyleneimine (molecular weight 600) was fully stirred and dissolved in deionized water, and then 1 g of thiolated intercalated zirconium phosphate (prepared according to step (1) in Example 1) was added and dispersed evenly by ultrasonication. After stirring and reacting at 50° C. for 8 h, the reaction solution was freeze-dried at -40° C. for 50 h to obtain a thiolated intercalated zirconium phosphate-polyethyleneimine composite aerogel. The adsorption performance of the aerogel was measured according to the adsorption performance experiment of the product in Example 1. The results are listed in Table 1.

[0039] Comparative Example 3 8 g of polyethyleneimine (molecular weight 600) was fully stirred and dissolved in deionized water, and then 1 g of epoxy intercalated zirconium phosphate (prepared according to steps (1) and (2) in Example 1) was added and dispersed evenly by ultrasonication. After stirring and reacting at 50° C. for 8 h, the reaction solution was freeze-dried at -40° C. for 50 h to obtain epoxy intercalated zirconium phosphate-polyethyleneimine composite aerogel. The adsorption performance of the aerogel was measured according to the adsorption performance experiment of the product in Example 1. The results are listed in Table 1.

[0040] Table 1 Adsorption amount of lead ions by aerogels prepared in Examples 1-3 and Comparative Examples 1-2

[0041] It can be seen from the results that the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel prepared in the embodiment of the present invention has excellent adsorption performance for lead ions due to its rich pore structure, the perfect combination and synergistic enhancement of the excellent structural characteristics of the exfoliated zirconium phosphate and the rich active amino groups contained in polyethyleneimine, and the adsorption amount can reach 349 mg / g.

[0042] In the aerogels prepared in Comparative Examples 1, 2 and 3, the zirconium phosphate layers were not cross-linked and grafted, which not only failed to exert the more excellent performance of the peeled zirconium phosphate, but also the polyethyleneimine matrix only formed a weak hydrogen bond interface binding force with the surface and edge of the zirconium phosphate, resulting in poor interfacial compatibility between the two, and the synergistic adsorption and synergistic effect of the two could not be fully exerted. In addition, a large number of hydroxyl groups with excellent adsorption performance were introduced during the cross-linking process, which can further improve the adsorption performance of the composite aerogel for heavy metal ions. Therefore, the aerogel prepared in the comparative example is far less excellent than the nano-composite aerogel prepared in the example in terms of heavy metal ion adsorption performance.

Claims

1. A method for preparing a cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel, characterized in that: The following steps are involved: (1) Using mercaptoethylamine as a guest molecule, α-zirconium phosphate is intercalated to obtain thiolated intercalated zirconium phosphate; (2) modifying the surface and interlayer of the thiol-intercalated zirconium phosphate with epichlorohydrin through a substitution reaction between thiol groups and chlorine atoms to obtain an epoxy-intercalated zirconium phosphate; (3) Ultrasonic dispersion of the epoxylated intercalated zirconium phosphate in an aqueous solution of polyethyleneimine for crosslinking modification and exfoliation reaction, using the epoxylated intercalated zirconium phosphate as a crosslinking agent to crosslink and graft polyethyleneimine on the surface and between layers of the zirconium phosphate, and finally freeze-drying the reaction solution to obtain a crosslinked, modified, exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel.

2. According to the method for preparing the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel according to claim 1, the step (1) specifically comprises ultrasonically dispersing α-zirconium phosphate in deionized water, then slowly dropping an aqueous solution of mercaptoethylamine to carry out an intercalation reaction, filtering, washing, and drying.

3. The method for preparing the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel according to claim 2, wherein the mass ratio of α-zirconium phosphate to mercaptoethylamine is 1:(0.6-0.8), and the concentration of the mercaptoethylamine aqueous solution is 10-16 mg / mL.

4. The method for preparing the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel according to claim 2, wherein the intercalation reaction in step (1) is carried out under the action of 40-60 kHz ultrasonic waves for 5-7 hours.

5. The method for preparing the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel according to claim 1, wherein the step (2) specifically comprises ultrasonically dispersing the thiolated intercalated zirconium phosphate in ethanol, then adding epichlorohydrin and an acid binding agent, stirring to react, filtering, washing, and drying.

6. The method for preparing the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel according to claim 5, wherein the mass ratio of the thiolated intercalated zirconium phosphate, epichlorohydrin and the acid binding agent is 1:(0.5-1):(1-2), and the acid binding agent is one of triethylamine and pyridine.

7. The method for preparing the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel according to claim 5, wherein the stirring reaction in step (2) is refluxed at 80-90°C for 4-6 hours.

8. The method for preparing the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel according to claim 1, wherein the mass ratio of the epoxy-intercalated zirconium phosphate to the polyethyleneimine in step (3) is 1:(8-20).

9. The method for preparing the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel according to claim 1, wherein the cross-linking modification and exfoliation reaction in step (3) is carried out at 50-80°C with stirring for 6-8 hours.

10. The method for preparing the cross-linked modified exfoliated zirconium phosphate-polyethyleneimine nanocomposite aerogel according to claim 1, wherein the freeze drying in step (3) is to freeze dry the reaction solution at -50 to -40°C for 30 to 50 hours.

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