Preparation Of Mesoporous Silica And Its Properties As Separation Materials

Due to its ordered mesoporous structure,adjustable pore size,surface functionalization,and good biocompatibility,mesoporous silica has become a hot spot in the design and synthesis of ordered mesoporous silica with fine structures.At present,mesoporous silica has been used in many fields such as energy storage,separation,adsorption,biomedicine,and catalysis.The synthesis methods of mesoporous silica are mainly divided into soft template method,hard template method and template-free method.Among them,the mesoporous silica synthesized by the soft template method has the characteristics of diverse and controllable fine structure,high order,easy control of pore size and high specific surface area,which is the most used method.The key to the synthesis of mesoporous silica by the soft template method is the design of the soft template agent.During the self-assembly process of the template agent and the precursor,the aggregate shape,length,and type of hydrophobic（oleophobic）ends often formed by the soft template agent are often formed.It is the key to the formation of mesoporous silica with fine structure.At the same time,factors such as the addition of different phases in the system,changes in ambient temperature and different stirring rates will affect the self-assembly behavior of the system,thereby affecting its fine structure and ordered structure.In addition,the mesoporous silica synthesized by the soft template method has a large number of silanol groups on the surface,which is a good hydrophilic particle,and can be grafted and modified as a functionalized particle,which has good application value.This article is mainly divided into the following three contents:The synthesized L-16Ala5Py Cl O₄amphiphilic small molecule was used as a soft template,and benzene,cyclohexane,toluene and tetrahydrofuran were used as solvent phases to synthesize ordered mesoporous silica with"two-dimensional hexagonal pores";The synthesized L-16Ala5Py PF₆amphiphilic small molecule was used as a soft templating agent,and TMB was used as a solvent phase to synthesize ordered mesoporous silica with"worm-like";the commercial Cetyltrimethylammonium bromide（CTAB）amphiphilic small molecule was used as a soft templating agent,1,3,5-Trimethylbenzene（TMB）was used as the solvent phase to synthesize ordered mesoporous silica with"radial pores".The microscopic morphology,specific surface area,pore size and order of the mesoporous structure of the samples were tested and characterized by SEM,TEM,BET,SAXRD and other tests.The effect of the structure of the ordered mesoporous silica,the results show that except for tetrahydrofuran as the solvent phase,with the increase of the volume,it has no effect on the synthesis of"two-dimensional hexagonal"ordered mesoporous silica,other mesoporous silica With the increase of the solvent volume,the order of the mesoporous structure of silicon gradually decreased,and even its fine structure also changed.Using ordered mesoporous silica such as"radiating pores","worm-like"and"hollow core-shell"as hydrophilic particles,6 prepared by spraying method combined with PVA-co-PE nanofibrous membrane（PM）.Mesoporous silica/PMs nanofiber composite membrane was used to study the performance of the composite membrane in separating oil-water mixture.In the water contact angle（WCA）test results,the mesoporous silica/PMs nanofiber composite membrane greatly improved the hydrophilicity of PM,from 96 s for water droplet complete infiltration time to the fastest 0.5 s.The six kinds of prepared mesoporous silica/PMs nanocomposite fiber membranes were tested to separate oil-water mixture by gravity-driven method.The results showed that the six kinds of prepared mesoporous silica/PMs nanofiber composite membranes could filter and separate n-hexane/water,silicone oil/water and peanut oil-water mixture,and the separation efficiency is above 98%.Amino-modified mesoporous silica was grafted with 3-aminopropyltriethoxysilane（APTES）,and then grafted with L-Glutamic acid（L-Glu）as a chiral probe to prepare amino acid-functionalized mesoporous silica particles C-Si O₂-2-NH-L-Glu,the adsorption selectivity of this particle as a chiral selector for different amino acid enantiomers was studied.The results showed that the adsorption rate of L-Phenylalanine（L-Phe）AC was 1.27%,and the adsorption rate of L-Phenylalanine（D-Phe）was 1.27%.The adsorption rate AC was 30.95%,and the adsorption selectivity coefficient S_L/D was 0.041,showing good adsorption selectivity for D-Phe;the adsorption rate for L-Tryptophan（L-Trp）was 8.73%,and the adsorption rate for D-Tryptophan（D-Trp）was 0.07%.The selectivity coefficient S_L/D is 130.526,showing excellent adsorption selectivity for L-Trp;the adsorption rate for L-Phenylglycine（L-Phg）is 27.81%,the adsorption rate for D-Phenylglycine（D-Phg）is 9.26%,the adsorption selectivity coefficient S_L/D is 3.003,showed adsorption selectivity for D-Phg.