Synthesis And Properties Study Of Chitosan-based Gel Materials

With the improvement of human material,spiritual and cultural level,people gradually realize the significance of water pollution treatment for human sustainable development,and the selection of appropriate materials is particularly important to achieve the goal of efficient and low-cost water pollution treatment.Chitosan（CS）is widely used in the field of water treatment because of rich raw materials,biodegradability,and a variety of functional groups（such as amino,hydroxyl）.Supercritical drying or freeze-drying can be used to prepare CS in the aerogel state.CS aerogel not only has a higher specific surface area and more reactive sites,but also CS aerogel has a three-dimensional network skeleton structure,which is conducive to modify its surface by loading its functional material,thereby further improving its water pollution treatment performance.Photocatalytic degradation technology based on semiconductor photocatalysis theory is a green and environmentally friendly water treatment technology.Photocatalytic technology has many advantages:simple device,easy operation,and low energy consumption.However,generally speaking,photocatalyst is usually nano-sized powder,which has the disadvantages of easy agglomeration of particles and difficult recovery of catalyst.These problems can be solved by uniformly loading it on recyclable substrate.Therefore,this thesis takes CS gel as the research material for water pollution treatment and takes Congo red and Rhodamine B as the simulated pollutants to explore the adsorption characteristics of CS aerogel for pollutants.In addition,in combination with the advantages of photocatalytic degradation technology,nano-sized photocatalyst materials were loaded on CS aerogel.CS aerogels were used as the substrate materials of semiconductors,and photocatalysts were used as the functional material of photocatalytic degradation,so as to further modify the removal efficiency of CS aerogel for organic dyes.Therefore,the CS aerogel is used as the substrate material of semiconductor,which makes the semiconductor materials uniformly dispersed,and the CS matrix as the gel material is also better recovered.In this thesis,CS gel spheres were prepared by neutralization precipitation method.CS aerogel spheres were obtained by freeze-drying technology.Then,materials with excellent adsorption properties,photocatalytic properties,and photocatalytic properties were prepared through modification and inorganic material hybridization.The main content can be divided into three aspects:1.CS hydrogel spheres were prepared by neutralization precipitation method.Then,CS aerogel with three-dimensional network structure was obtained by freeze-drying technology.Then,CS-based aerogels with different loading capacities of ZIF-8 were prepared by adjusting the amount of CS aerogel spheres,and the aerogels were applied to adsorb Congo red（CR）dye in water.By exploring a series of factors affecting the adsorption process of adsorbent,found that at 25℃,adding 0.1g/L CS/ZIF-8 adsorbent,p H value of 7,concentration of 200 mg/L CR solution,has the best adsorption performance,the adsorption capacity up to 1085.89 mg/g.In addition,the adsorption mechanism of CS/ZIF-8 composite was investigated by fitting adsorption kinetics model and isothermal adsorption model.2.Chitosan/polyvinyl alcohol（CS/PVA）hydrogel spheres were prepared by neutralization precipitation method,and CS/PVA aerogel spheres were obtained by freeze-drying.Then,CS/PVA/Cd S composite samples were prepared by loading spherical Cd S nanoparticles on the surface of CS/PVA aerogel spheres.The synergistic photocatalytic effect of the composite samples was explored to remove organic dye CR.The results show that the CR removal efficiency of the composite sample is about 60%higher than that of the single adsorption performance under the action of adsorption and photocatalysis.At the same time,the adsorption kinetics model of single adsorption properties was fitted to explore the adsorption mechanism of CR by CS/PVA/Cd S aerogel spheres.The photocatalytic mechanism of the composite samples was studied.It was found that under light,the amino group of CS could attract the photogenerated holes of Cd S and reduce the recombination rate of photogenerated electron holes,which was conducive to the photocatalytic degradation of CR by CS/PVA/Cd S.3.CS/PVA/Fe₂O₃ composite samples were prepared by using hydrothermal method and supported with Alpha phase iron oxide（α-Fe₂O₃）photocatalyst on CS/PVA aerogel spheres.The photocatalytic degradation of Rhodamine B（Rh B）by composite samples was investigated.Among them,α-Fe₂O₃ photocatalyst is magnetic,which is more conducive to the recycling of composite materials.SEM images show that the content of matrix in the composite sample will affect the morphology of the loadedα-Fe₂O₃,and then affect the dye removal performance of the composite.Through a series of tests,it is found that the hydroxyl radical produced byα-Fe₂O₃ under simulated visible light irradiation is the main active substance involved in the photodegradation process.