Study On Preparation And Performance Of Nano-silver Modified Cellulose Aerogel

As one of the major hazardous pollutants in industrial wastewater,4-nitrophenol(4-NP)has a very high solubility and stability,therefore,the elimination of 4-NP is an essential part of wastewater purification.Chemical precipitation,physical adsorption and catalytic degradation have been widely used in the purification process of industrial wastewater,among which,the use of metal catalytic reduction technology for 4-NP degradation is not only an efficient method,but also has many advantages such as low energy consumption,high efficiency and universal applicability.Silver nanoparticles(Ag NPs)exhibit high selectivity and fast electron transfer in the catalytic reduction reaction,which can efficiently catalyze the reduction of toxic and hazardous 4-NP to 4-aminophenol(4-AP),an important chemical material.Ag NPs can be combined with various carrier materials such as polymers,clays and carbon-based materials to prepare composites,and the preparation of composites can greatly reduce the self-agglomeration problem of Ag NPs.Nanocellulose aerogel(NCAx)materials have many advantages such as high porosity,large specific surface area,high stability,green and renewable,and excellent mechanical properties,etc.These performance advantages make them an excellent choice as carrier materials for Ag NPs.In order to balance the high specific surface area with the high catalytic efficiency of Ag NPs,this thesis used microcrystalline cellulose as the raw material and ionic liquid as the solvent system to prepare green degradable nanocellulose hydrogel by sol-gel method,and used nanocellulose hydrogel(NCH_x)as the carrier material to generate and load Ag NPs by chemical in situ reduction method to prepare Ag NPs modified cellulose hydrogel catalyst material(NCH_x~a);on the basis of cellulose hydrogel carrier material and Ag NPs-modified cellulose hydrogel catalyst material,cellulose aerogel carrier material(NCA_x)and Ag NPs-modified cellulose aerogel(NCA_x~a)catalyst material were prepared by low-temperature freeze-drying technique using tert-butanol as freeze-drying agent.The molding process,crystal structure and compression strength of NCHx carrier materials were analyzed and studied by means of polarized light microscopy,X-ray diffraction and electron universal tensile tester;the specific surface area test method,electron universal tensile tester,Fourier transform infrared spectroscopy,Raman spectroscopy,wide angle X-ray diffraction and inductively coupled plasma emission spectroscopy were used to analyze and study the specific surface area,pore size,pore size distribution,mechanical and loading properties of NCA_x carrier materials.The specific surface area,pore size,pore size distribution,mechanical and loading properties of the materials were analyzed and studied.The catalytic activity and microstructure of NCH_x~a and NCA_x~a catalysts were analyzed and studied by UV spectrophotometry,field emission scanning electron microscopy and transmission electron microscopy.The experimental results showed that the NCA_x carrier material obtained by the sol-gel method had a large specific surface area and high porosity,and the aerogel had a specific surface area of up to 93.944 m~2/g and porosity of up to 97.05%when the cellulose fraction was 5%.Transmission electron microscopy showed that the Ag NPs were more uniformly distributed on the cellulose and the particle size was around 10 nm,and the NCA_x~a catalyst The material showed high catalytic activity in the catalytic reduction experiments of 4-NP.When the concentration of 4-NP was 0.06 mmol/L,the aerogel with Ag NPs mass fraction of 3.0978%could complete 96.87%of the catalysis in 13 min.In this study,a nanosilver-modified cellulose aerogel catalyst material was successfully prepared.It was not only demonstrated that the ionic liquid[Bmin]Cl/DMF could dissolve microcrystalline cellulose well to prepare cellulose nanomaterials,but also Ag NPs were loaded onto the surface and interior of the cellulose hydrogel by a chemical in situ reductions,and tert-butanol combined with a freeze-drying technique to prepare NCA_x carrier material and NCA_x~a catalyst material with large porosity and specific surface area,and it was demonstrated that the prepared NCA_x~a catalyst material had good catalytic reduction efficiency for the organic aqueous pollutant 4-NP.