Preparation Of Starch-based Porous Carbon And Its Photocatalytic Degradation Of Industrial Wastewater

In today’s nature,starchy polysaccharides are the second most important biomass resource in terms of abundance,and the small molecules of starch are easier to utilize resourcefully than cellulose,which ranks first.Therefore,how to utilize starch efficiently is a popular topic of research today.Due to their large specific surface area,rich void structure and in-situ loading of various elements,biomass carbon materials have applications in electrochemical energy storage materials and photocatalytic materials.Therefore,the preparation of biomass carbon materials and their application in these areas are of great significance to solve the problems of energy,environment and resources.In today’s society,environmental problems are becoming more and more serious,and there are a lot of pollutants in life and industry,etc.The problem of how to deal with pollutants has always been concerned and studied by various researchers all over the world.The use of clean and environmentally friendly photocatalytic materials to degrade pollutants in the environment is a popular topic in recent years,but photocatalytic materials often have a small specific surface area and low reaction efficiency,so how to prepare catalytic materials with high specific surface area and efficient photocatalytic degradation ability at the same time becomes the key problem of photodegradation of pollutants.In this thesis,starch was used as the basic raw material to obtain porous carbon materials using molten salt method,and its microscopic morphology was observed and its electrochemical properties were tested.Finally,a high-performance composite photocatalyst was prepared by electrostatic spinning method to study its feasibility as a photocatalytic material,and the main research contents are as follows.（1）Different starch was used as raw materials to prepare biomass carbon materials using molten salt activation method,and the best process conditions were explored as follows:corn starch was used as raw material,ZnCl₂was used as activator using stepwise activation method,activation time was 2 h at 800°C,and the mass ratio of starch to activator was 3:2.The activation effect of ZnCl₂as activator was better than that of other mixed salt or KOH activation methods to prepare biomass carbon materials.The porosity,specific capacitance and cyclic stability of the starch-based biomass porous carbon materials were excellent.The specific capacitance of the prepared porous carbon material can reach 324.7 F/g when tested at a current density of 1 A/g.Moreover,after 5000 cycles of charge/discharge stability test,the electrical properties of the porous carbon material are still good,and the final capacitance value can reach 92.45%of the initial value,which shows that the carbon material prepared in this paper has excellent cycling stability.The specific surface area of the porous carbon material is 2106.62 m²/g and the total pore volume is 1.04 cm³/g.The sample not only has a high specific surface area but also has a large number of pore channels mainly in the form of micropores and mesopores.The prepared starch-based biomass porous carbon is not only a good electrode material for supercapacitors,but also a good carrier for the preparation of catalysts from biomass porous carbon materials,and the starch can be used efficiently,which has good potential for development.（2）Using the prepared starch-based biomass porous carbon,TiO₂and Bi₂O₃were successfully loaded on the porous carbon surface by electrostatic spinning method to prepare TiO₂/porous carbon and Bi₂O₃/porous carbon composite fiber materials,respectively.the photocatalytic effect of TiO₂/porous carbon composite on acrylic acid solution was higher than that of Bi₂O₃/porous carbon,and the degradation rates of acrylic acid after 9 h of reaction were 86.12%and 75%,respectively.The TiO₂/porous carbon composites showed uniform distribution of TiO₂on the surface without agglomeration,while Bi₂O₃/porous carbon composites were prepared with the addition of Bi（NO₃）₃above 1 mmol and obvious agglomeration would occur.The TiO₂/HPC composite with the best photocatalytic performance was prepared by selecting TiO₂/porous carbon nanofiber membrane as the main catalyst and screening the process conditions:the addition amount of PVP was 0.9 g,the addition amount of butyl titanate was 2 ml,the activation temperature was 450°C and the activation time was 2 h.The structural characterization of the samples concluded that the anatase TiO₂was uniformly loaded on the porous carbon fiber and formed Ti-O-C bonding with the carbon material,which resulted in better and more uniform loading effect.The prepared samples of TiO₂-HPC have excellent catalytic ability and research value.（3）The best reaction conditions and the effect of photocatalytic reaction on the structure and chemical properties of the catalyst were explored.The optimal process conditions were:using metal halide lamp as the light source,catalyst concentration of 2 g/L,and optimal reaction time of 6 h.The degradation rate of acrylic acid in the wastewater could reach 98.39%;the COD removal rate of the wastewater was found to be 97.89%by COD detection,and the COD after the reaction was<100 mg/L,which met the national wastewater discharge standard.The structural characterization of the catalysts before and after the reaction concluded that the prepared TiO2/porous carbon catalysts still had photocatalytic activity after the 6h reaction,although their physical structures were changed,the chemical structures on their surfaces were not changed.It was concluded by UV-vis that the catalyst TiO₂-HPC was basically able to achieve complete degradation of acrylic acid.