CN110804204A

CN110804204A - Bacterial cellulose/X-type molecular sieve composite aerogel and preparation method thereof

Info

Publication number: CN110804204A
Application number: CN201810886789.3A
Authority: CN
Inventors: 孙东平; 林建斌; 孙汴京; 石琳; 张威威
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2018-08-06
Filing date: 2018-08-06
Publication date: 2020-02-18

Abstract

The invention discloses a preparation method of bacterial cellulose/X-type molecular sieve composite aerogel. The method comprises the steps of mixing dry bacterial cellulose wadding with a sodium silicate solution, adding a sodium metaaluminate solution, placing the obtained mixed system at 80-120 ℃ for hydrothermal reaction, and carrying out freeze drying to obtain the bacterial cellulose/X-type molecular sieve composite aerogel. The invention prepares the bacterial cellulose/X type molecular sieve composite aerogel by a blending hydrothermal crystallization method. The method is simple to operate, low in cost and environment-friendly in the process, and the bacterial cellulose solution and the molecular sieve are well compounded.

Description

Bacterial cellulose/X-type molecular sieve composite aerogel and preparation method thereof

Technical Field

The invention relates to a bacterial cellulose/X-type molecular sieve composite aerogel and a preparation method thereof, belonging to the technical field of aerogel material preparation.

Background

Bacterial Cellulose (BC) is a high-performance microbial synthetic material produced by certain bacteria. Compared with plant cellulose, the bacterial cellulose has no concomitant substances of lignin and hemicellulose, has higher purity, tensile strength and Young modulus, and has good biocompatibility, degradability and the like, so that the bacterial cellulose is widely applied to the fields of biomedicine, tissue engineering, food, textile and the like. The application field of the bacterial cellulose can be widened by adding the inorganic functional material into the bacterial cellulose.

The zeolite molecular sieve has the advantages of unique framework structure, regular pore canals and cavities, large specific surface area, high ion exchange capacity, good chemical stability, easy regeneration and the like, and has great application potential in the field of dye wastewater adsorption. The types of zeolite molecular sieves are various, and are classified into X type, Y type, A type and the like according to the silica-alumina ratio. Wherein n (SiO)₂)/n(Al₂O₃) 2.2 to 3.0, namely X-type molecular sieve, has a framework structure of natural mineral faujasite, and the unit cell composition of the X-type molecular sieve is Na₈₆[Al₈₆Si₁₀₆O₃₈₄]·264H₂The pore diameter of O is about 0.74nm, the framework contains three-dimensional twelve-membered ring channels, the pore volume is larger (about 50%), the structure can provide faster intracrystalline diffusion advantage for adsorption and catalysis, and the structure has larger application potential and prospect in the fields of dye wastewater adsorption and the like.

In recent years, the method for compounding the organic matrix material and the inorganic functional material comprises doping, surface coating, suction filtration, in-situ growth and the like. Currently, because bacterial cellulose is insoluble in water and common solvents, the compounding of cellulose with certain inorganic materials (such as montmorillonite, graphene, etc.) must be achieved by means of some special solvent systems such as urea/sodium hydroxide systems, ionic liquids, etc. The molecular sieve as an inorganic material is easy to agglomerate when being mixed with a bacterial cellulose solution and cannot be well dispersed. Although the molecular sieve can be dispersed in the aqueous phase solvent, the aqueous phase solvent of the bacterial cellulose contains high-concentration sodium hydroxide and salts, so that the molecular sieve is separated out due to the salt effect, the bacterial cellulose solution and the molecular sieve are difficult to be uniformly mixed, and the composite effect of the two is poor.

Disclosure of Invention

The invention aims to provide a bacterial cellulose/X-type molecular sieve composite aerogel and a preparation method thereof. The molecular sieve in the composite aerogel is used as a functional material, the cellulose is used as a framework of the aerogel, and the molecular sieve is uniformly dispersed in the bacterial cellulose nanofiber matrix.

The technical scheme for realizing the purpose of the invention is as follows:

the preparation method of the bacterial cellulose/X-type molecular sieve composite aerogel comprises the following specific steps:

step 1, carrying out vacuum drying on the bacterial cellulose wadding after impurity removal and decoloration to prepare a bacterial cellulose dry wadding;

step 2, mixing the bacterial cellulose dry floc with a sodium silicate solution, and uniformly stirring and dispersing to obtain a mixed solution of the bacterial cellulose and the sodium silicate;

step 3, according to the mass ratio of the bacterial cellulose to the sodium metaaluminate of 5-10: 1, slowly adding a sodium metaaluminate solution into a mixed solution of bacterial cellulose and sodium silicate, and stirring while adding until the mixture is uniformly mixed;

and 4, performing hydrothermal reaction on the mixed system obtained in the step 3 at 80-120 ℃, filtering after the reaction is finished, washing with water to be neutral, and performing freeze drying to obtain the bacterial cellulose/X-type molecular sieve composite aerogel.

Preferably, in step 2, the molar ratio of sodium silicate to sodium metaaluminate is 1.5: 1.

preferably, in the step 2, the stirring time is 1-2 h.

Preferably, in the step 4, the hydrothermal reaction time is 10-12 h.

Preferably, in the step 4, the freeze-drying time is 12-24 hours.

The invention prepares the bacterial cellulose/X type molecular sieve composite aerogel by a blending hydrothermal crystallization method. Simple operation, low cost and environmental protection in the process. The obtained bacterial cellulose/X-type molecular sieve composite aerogel realizes good compounding of a bacterial cellulose solution and a molecular sieve.

Drawings

FIG. 1 is an infrared image of the bacterial cellulose/X-type molecular sieve composite aerogel obtained in examples 1 and 2 and comparative example 1.

FIG. 2 is an XPS plot of bacterial cellulose/X-type molecular sieve composite aerogels prepared in examples 1 and 2 and comparative example 1.

FIG. 3 is an SEM image of the bacterial cellulose/X-type molecular sieve composite aerogels prepared in examples 1 and 2 and comparative example 1.

Detailed Description

The present invention will be described in further detail with reference to the following examples and the accompanying drawings.

Example 1

Weighing 0.43gNa₂SiO₃·9H₂Adding 20ml of deionized water into the O crystal to prepare a sodium silicate solution, weighing 0.5g of bacterial cellulose, adding 20ml of deionized water solution, and beating into a bacterial cellulose suspension by using a high-speed dispersion homogenizer. Adding the bacterial cellulose suspension into a sodium silicate solution, and magnetically stirring for 1h at room temperature. 0.1g of sodium metaaluminate is weighed and added with 10ml of deionized water to prepare sodium metaaluminate solution. And slowly adding the sodium metaaluminate solution into the mixed solution of the bacterial cellulose and the sodium silicate, stirring while adding, and continuing to stir for 1 hour by magnetic force after adding. Adding the obtained mixed system into a hydrothermal reaction kettle, and performing hydrothermal crystallization for 10 hours at 120 ℃. After the reaction is completed, the system after the reaction is filtered and washed to be neutral by deionized water. And (3) placing the filtered substance obtained after filtering in a six-hole plate for freeze drying to obtain the bacterial cellulose/X-type molecular sieve composite aerogel.

Example 2

Weighing 0.22g Na₂SiO₃·9H₂Adding 20ml of deionized water into the O crystal to prepare a sodium silicate solution, weighing 0.5g of bacterial cellulose, adding 20ml of deionized water solution, and beating into a bacterial cellulose suspension by using a high-speed dispersion homogenizer. Adding the bacterial cellulose suspension into a sodium silicate solution, and magnetically stirring for 1h at room temperature. 0.05g of sodium metaaluminate is weighed and 10ml of deionized water is added to prepare a sodium metaaluminate solution. And slowly adding the sodium aluminate solution into the mixed solution of the bacterial cellulose and the sodium silicate, stirring while adding, and continuing to stir for 1 hour by magnetic force after adding. Adding the obtained mixed system into a hydrothermal reaction kettle, and performing hydrothermal crystallization for 10 hours at 120 ℃. After the reaction is completed, the reaction is carried outThe system after the reaction was completed was filtered and washed to neutrality with deionized water. And (3) placing the filtered substance obtained after filtering in a six-hole plate for freeze drying to obtain the bacterial cellulose/X-type molecular sieve composite aerogel.

Comparative example 1

Weighing 2.6g Na₂SiO₃·9H₂Adding 20ml of deionized water into the O crystal to prepare a sodium silicate solution, weighing 0.5g of bacterial cellulose, adding 20ml of deionized water solution, and beating into a bacterial cellulose suspension by using a high-speed dispersion homogenizer. Adding the bacterial cellulose suspension into a sodium silicate solution, and magnetically stirring for 2 hours at room temperature. 0.5g of sodium metaaluminate is weighed and added with 10ml of deionized water to prepare sodium metaaluminate solution. And slowly adding the sodium aluminate solution into the mixed solution of the bacterial cellulose and the sodium silicate, stirring while adding, and continuing to stir for 2 hours by magnetic force after adding. Adding the obtained mixed system into a hydrothermal reaction kettle, and performing hydrothermal crystallization for 12 hours at the temperature of 100 ℃. After the reaction is completed, the system after the reaction is filtered and washed to be neutral by deionized water. And (3) placing the filtered substance obtained after filtering in a six-hole plate for freeze drying to obtain the bacterial cellulose/X-type molecular sieve composite aerogel.

FIG. 1 is an infrared image of the bacterial cellulose/X-type molecular sieve composite aerogel obtained in example 1, which is 1278-1500cm^-1The peak of the bacterial cellulose/X-type molecular sieve composite aerogel appears at the same position as the bacterial cellulose, which shows that the bacterial cellulose and the X-type molecular sieve are well compounded.

FIG. 2 is an XPS plot of bacterial cellulose/X-type molecular sieve composite aerogels prepared in examples 1 and 2 and comparative example 1. As can be seen from FIG. 2(a), the content of Si in the composite aerogel obtained in example 1 is up to 5.6%, and the content of Al is up to 4.0%, i.e., n (SiO) in the composite material₂)/n(Al₂O₃) 2.80, the composition of the X-type molecular sieve is met, and the X-type molecular sieve can be better compounded with bacterial cellulose. As can be seen from FIG. 2(b), the content of Si in the composite aerogel obtained in example 2 is up to 0.74%, and the content of Al is up to 0.56%, i.e., n (SiO) in the composite material₂)/n(Al₂O₃) 2.64, corresponding to the composition of X-type molecular sieve, the X-type molecular sieve can be seenBetter compound with bacterial cellulose. As can be seen from FIG. 2(c), the content of Si in the composite aerogel obtained in comparative example 1 was 7.9%, and the content of Al in the composite aerogel was 5.8%, i.e., n (SiO) in the composite material₂)/n(Al₂O₃) 2.72, which accords with the composition of the X-type molecular sieve, and shows that the X-type molecular sieve can be well compounded with bacterial cellulose. The results show that the X-type molecular sieve/bacterial cellulose composite aerogel with different loading amounts can be prepared by regulating and controlling the adding amounts of sodium metaaluminate and sodium silicate.

FIG. 3 is an SEM image of the bacterial cellulose/X-type molecular sieve composite aerogel obtained in examples 1 and 2 and comparative example 1. The SEM analysis of the composite aerogels obtained in examples 1 and 2 and comparative example 1 showed that the network structure is bacterial cellulose and the particles covered on the surface are X-type molecular sieves, as shown in fig. 3. As can be seen from the figure, the original three-dimensional structure of the bacterial cellulose is still maintained, and the X-type molecular sieve generated in situ is uniformly loaded on the surface of the bacterial cellulose, which shows that the bacterial cellulose and the X-type molecular sieve are well compounded. And as can be seen from fig. 3(c), when the mass ratio of the bacterial cellulose to the sodium metaaluminate is too large, the molecular sieve is obviously agglomerated on the surface.

Claims

1. The preparation method of the bacterial cellulose/X-type molecular sieve composite aerogel is characterized by comprising the following specific steps of:

2. The method according to claim 1, wherein in step 2, the molar ratio of sodium silicate to sodium metaaluminate is 1.5: 1.

3. the preparation method according to claim 1, wherein in the step 2, the stirring time is 1-2 h.

4. The preparation method according to claim 1, wherein in the step 4, the hydrothermal reaction time is 10-12 h.

5. The preparation method according to claim 1, wherein the freeze-drying time in step 4 is 12-24 hours.

6. The bacterial cellulose/X type molecular sieve composite aerogel prepared by the preparation method according to any one of claims 1 to 5.