Study On Photocatalytic Performance Of Semiconductors For Organic Pollutants

With the rapid development of China’s economy and the gradual improvement of the national standard of living,the problem of energy shortage and environment pollution has become increasingly prominent,which has become the two key problem that restricts the further development of China’s social and economic development.Photocatalytic technology can convert low density solar energy into high-density chemical energy,and it can achieve energy conversion and storage simultaneously,besides,photocatlytic technology can degrade organic pollutants into environmentally friendly carbon dioxide and water.Therefore,photocatalytic technology has become one of the most potential solutions to the energy and environmental problems in the.future.China is one of the largest agricultural countries in the world.There are serious environmental pollution problems in the process of agricultural production and storage and transportation of agricultural products in the later stage.For example,a large number of pesticides and herbicides have been used to produce a large amount of pesticide residue and pesticide waste water,causing serious environmental pollution.In the process of storage and transportation of agricultural products and ripe fruits,a lot of decay and waste are caused by the production of ethylene.In order to solve these problems,a large number of studies have been carried out,such as the treatment of sewage by biodegradation,the treatment of pesticide wastewater through advanced oxidation technology,and absorption of gas pollutants through physical adsorption.However,these technologies have innate shortcomings,such as:biotechnology is difficult to apply to high toxicity and high salinity wastewater treatment;advanced oxidation technology is high cost and easy to cause two pollution;activated carbon adsorption technology is difficult to use for a long time,and it is easy to cause two pollution.Among these technologies to solve the pollution of agricultural related environment,photocatalytic technology has unique advantages,such as many advantages,such as wide adaptation,low cost,no secondary pollution and so on.It has become one of the effective ways to solve the above problems.Based on the advantages of photocatalytic technology,we have selected two pollutants-the pesticides or herbicides and the ethylene which have serious harm to the environmental pollution and the storage of agricultural products as the research object.Based on the wide band gap semiconductor photocatalytic material TiO2 and Ga2O3,the photocatalytic degradation of paraquat wastewater and ethylene gas degradation have been carried out.The specific contents are as follows:In the first chapter,the basic principles and development process of nanomaterials,photocatalytic materials and photocatalysis technology are briefly outlined.And then,the research background and significance of this thesis are briefly introduced.Based on the importance of photocatalytic degradation of paraquat wastewater and ethylene,and based on our material design,preparation and characterization,we put forward the main research contents and research ideas in this paper.In the second chapter,photocatalytic degradation of paraquat wastewater was studied.P25,as a photocatalytic material,was chosen to reduce the amount of paraquat sweage by UV irradiation.It was found that NH4+ and Cl-in paraquat polluted water were the main factors affecting the photocatalytic degradation of paraquat wastewater,and the mechanism of photocatalytic degradation of paraquat wastewater was proposed.Based on this principle,a complete set of technological process for degradation of paraquat wastewater is developed.This process is expected to be applied to practical industrial production and to solve the practical problems of environmental pollution of paraquat sewage.On this basis,we chose Ga2O3 with higher oxidation capacity as photocatalytic material to further improve its photocatalytic degradation rate.In the third chapter,four kinds of Ga2O3 with different crystalline polymorphs were prepared,and their crystal structure,morphology and optical absorption properties were studied.Subsequently,four kinds of crystalline Ga2O3 were used to study the photocatalytic degradation of ethylene.The results show that four kinds of crystalline Ga2O3 photocatalytic materials exhibit higher photocatalytic activity than P25 in ethylene degradation.By studying the electronic structure and energy band location,it is found that the photocatalytic activity is mainly determined by the valence band location.Among them,the α-Ga2O3 with the highest valence band location has the highest per unit area photocatalytic activity for ethylene degradation.In addition,the highest photocatalytic degradation activity of the γ-Ga2O3 in the four Ga2O3 polymorphs was observed because of the highest specific surface area.On this basis,four kinds of crystalline Ga2O3 photocatalytic reduction of carbon dioxide were studied.In the fourth chapter,the research content of this paper is summarized and combed,the existing problems and shortcomings are analyzed and discussed,and the research work to be carried out in the next step is prospected,and the related research plans are made.In this paper,the main research objects are paraquat sewage and ethylene,which are seriously harmful to the environmental and physical health and serious effects on the preservation of fruits and vegetables,respectively.The wide band gap semiconductor P25 and Ga2O3 are selected as photocatalytic materials,and the photocatalytic degradation of paraquat and ethene is carried out.In this paper,a photocatalytic degradation process of paraquat wastewater was developed,and a photocatalytic material with high activity for photocatalytic degradation of ethylene was found.They were of potential application value for solving the environmental pollution of paraquat and the preservation of fruits and vegetables.