Preparation Of Porous Cellulose Composite Aerogel And Its Application In Water Purification

With the progress of global industrialization,a large number of organic pollutants are discharged into water,such as oil pollution and dye pollution.Organic pollutants have the characteristics of high toxicity,low solubility and high persistence,which are harmful to aquatic organisms and human health.Therefore,it is urgent to develop methods and materials that can effectively remove pollutants from water bodies.Porous cellulose aerogel has the advantages of adjustable structure and pore size,large specific surface area and high porosity,which provides the possibility for the removal of pollutants in water.In this thesis,nano-cellulose（CNC）was used as the base material,and chitosan（CS）,sodium alginate（SA）,Konjac glucomannan（KGM）and nano-titanium dioxide（Ti O₂）were combined with it.Through freeze-drying,porous cellulose composite aerogel material was prepared for oil-water separation and catalytic degradation of dyes.Firstly,superhydrophobic CNC/CS composite aerogel was prepared by a two-step method of freeze-thaw impregnation,using CNC and CS as double network units and methyl trimethoxy-silane（MTMS）as modifier.A series of characterization results showed that the composite aerogel showed a three-dimensional interpenetrating porous structure,and the hydrophobic effect was the best when the concentration of MTMS was 1.96 g/μL.The adsorption capacity of isopropyl alcohol remained 92.8%of the initial value after 5regeneration cycles,and the maximum oil absorption was 9.3 g/g.Simultaneously,in order to further improve the mechanical properties of the composite aerogel,a natural polymer material SA with strong viscosity was introduced as the gel network unit,nano titanium dioxide（Ti O₂）was added to increase the roughness of the pore layer,and super hydrophobic CNC/SA/Ti O₂ composite aerogel was prepared.The results showed that the compressive strength and modulus of the aerogel were increased by 169.4%and 312.3%,respectively,compared with CNC/CS aerogel.When the MTMS concentration is 2.20 g/μL,the contact Angle can be up to 155°,and the adsorption capacity of a variety of oil agents can reach 5-10 times of its own mass.It is a benign and renewable biomass based oil absorbing material.In addition,in order to solve the problem of organic dye wastewater pollution,nano Ti O₂ photocatalyst was introduced,which was combined with CNC and KGM to construct CNC/KGM/Ti O₂ composite aerogel.Through SEM observation,Ti O₂ nanoparticles were supported on the pore wall of aerogel,and the aerogel showed good photocatalytic activity under ultraviolet irradiation.The degradation experiment results showed that 10 mg/L methylene blue（MB）solution was used as the simulation dye wastewater.When p H=9 and aerogel dosage was 0.5 g/L,the degradation rate was the best within 120 min.After repeated for 5 times,the degradation rate of MB of composite aerogel was still more than 75%,indicating that the aerogel could be used as a green and renewable biomass catalyst for the removal of organic dyes in water.