Rapid Synthesis Of Mesoporous Silica Graphene Aerogel Composite And The Application In VOCs Removal

With the rapid development of modern industry,air pollution is becoming more and more serious,which poses a serious threat to the ecosystem and human health.The emission of volatile organic compounds（VOCs）such as benzene and toluene is the main factor causing air pollution.Mesoporous silicon oxide（MCM-41）has the advantages of high specific surface area,large pore volume,easy adsorption of other substances and good stability,and has greater chemical activity and adsorption capacity than common adsorption materials.However,the nano-sized or micron-sized material properties of MCM-41 make it difficult for gases to pass through tightly packed powders and cannot be used directly as adsorbents in practical applications.Abstract:Using graphene aerogel（GA）as carrier material,an ultra-light mesoporous silica oxide aerogel（MSGA）composite material was prepared by one-step hydrothermal synthesis,which can realize effective adsorption of VOCs（representative substance benzene vapor）.In this paper,MSGA was prepared by hydrothermal reduction method.According to the different raw materials,the composite material obtained by electrolytic oxidation method of graphene oxide（EGO）was named MSEGA,and the composite material obtained by chemical oxidation method of graphene oxide（CGA）was named MSCGA.The composite material synthesized by porous silicon oxide（LPMS）was named LPMSGA.The microstructure,element content and mesoporous structure of the samples were characterized and analyzed by means of SEM,XPF,XRD and N₂adsorption/desorption.The effects of different dosage of MCM-41,different preparation methods of graphene oxide,mesoporous silica particles with different particle sizes and pore sizes on the structure and benzene adsorption properties of the composite were investigated.The benzene adsorption capacity of MSEGA at different temperatures and the influence of water on benzene vapor adsorption properties were explored.The main research work of this paper is as follows:（1）EGO and CGO were used as raw materials and ethylenediamine was used as reducing agent.The hydrogel was synthesized by one-step hydrothermal method in alkaline environment.After freeze drying,GA with low density was prepared.The effect of different EGO concentration on the synthesis of materials was explored,and 8 mg·m L-1 was found to be the best EGO concentration.When the optimal dosage of EDA was added,graphene hydrogels with regular morphology and uniform internal pore structure could be obtained.After freeze-drying,the graphene hydrogels had high mechanical strength.Compared with CGO,EGO has larger lamellations,which is more conducive to synthesizing complete composites.At the same time,the elastic test of GA shows that the pore structure has high stability.GA was characterized by SEM as a honeycomb open-hole structure with well-developed open-hole structure and complete interconnection frame,which was an excellent carrier for MCM-41 load.（2）MCM-41 and reamed silica（LPMS）with different pore sizes and particle sizes were synthesized.On the basis of MCM-41 synthesis method,LPMS with larger particle size and pore diameter can be obtained by using monotrotoluene as pore reamer.MCM-41 is spherical in shape,and the two-dimensional pore structure is orderly arranged.LPMS is elliptical in shape,with highly ordered hexagonal two-dimensional pore structure.The average particle size/pore size is 119/2.73 nm and 201/3.83 nm,and the specific surface areas are 1139.780and 711.789 m²Â·g^-1,respectively.（3）Using GO and MCM-41 as raw materials and ethylenediamine as crosslinking agent,MSGA composites were synthesized by rapid hydrothermal method.Through to the composites microstructure,stability and homogeneity,and pore structure of the material were characterized,graphene oxide can be densely coated silica nanoparticles and composite materials of intermediate water gel can be placed in the container of independence,has a good stability,and after a long time and high temperature of the water thermal response,the mesoporous structure of MSGA in good.When the content of MCM-41 reaches the maximum of 88.2%,the specific surface area reaches 395.5m²Â·g^-1.The results show that MCM-41nanoparticles can be uniformly loaded into the composite materials by measuring the element content distribution at different locations.Using lactose as a crosslinker,LPMSGA not only has a more complete shape and structure,but also has a better silica loading effect according to content analysis.（4）The adsorption performance of MSGA was tested by competitive adsorption apparatus.Will adopt high flux benzene substances,as a representative of the VOCs test conditions(500 m L·min^-1)to study the adsorption of benzene,composite research of mesoporous silica MSEGA addition amount of 74.1%and 88.2%respectively,with the adsorption of benzene on GA,MSEGA and LPMSGA experimental results show that the carrier graphene aerogels adsorption time is shorter,the adsorption performance of composite materials was better than GA,and the adsorption performance is associated with the content and pore size of mesoporous silica.At low temperature,MSEGA is favorable for benzene vapor adsorption.The higher the temperature,the higher the molecular thermal motion increases,and the lower the adsorption amount.Under ambient humidity,the benzene removal performance of MSGA composite material reached 11.07 m L·g^-1.More importantly,the composite material has great application potential in the field of high throughput gas adsorption.