Research On Photocatalytic Treatment Of Environmental Refractory Pollutants

Since the 21st century,environmental pollution has become an increasingly serious global problem with the increase of the world population and the development of science and technology.Many researchers have tried various to solve or alleviate environmental pollution,but the actual effect has not reached the expectation.Semiconductor photocatalysis is a kind of oxidation technology with friendly environment and mild condition.Free electrons and hole pairs can be generated by illumination excitation,which can be used for mineralization of organic pollutants and disposal of waste solid pollutants,and has a strong application prospect.However,due to the low light utilization rate of photocatalytic materials,the combination of electrons and holes seriously leads to low quantum efficiency,and the position of valence band and conduction band of the material determines its REDOX performance,which leads to the inability of some pollutants to be treated by photocatalytic oxidation,which greatly limits its practical application.Therefore,in addition to improving the efficiency of photocatalysis in the design of photocatalytic materials,we can also add some chemical reagents(such as H₂O₂,PDS,PMS,etc.)and the synergistic effect of photocatalysis to deal with environmental pollutants.This paper aims to treat some environmental pollutants that are difficult to degrade by combining photocatalytic technology and fenton reagents.We mainly explore the following three aspects:First,we prepared a piezoelectric flower-like Mo S₂,deposited Au nanoparticles on the active site at the edge of Mo S₂,and used the plasma effect of gold nanoparticles as a photocatalyst to active PMS molecules to generate a large number of active oxidizing free radicals,which were applied to the degradation of p-chlorophenol.The plasma effect of Au nanoparticles is excited under visible light,which is a kind of visible light catalyst,which can expand the range of light response and increase the light utilization.By means of the heterojunction Structure between Au nanoparticles and Mo S₂,the polarization electric field generated on the surface of Mo S₂under mechanical vibration can promote the charge separation on the surface of Au nanoparticles,so as to improve the quantum efficicency of photocatalysis.Second,we prepared Au,Pt and Pd precious metal nanoparticles supported with Ti O₂by photodeposition method,and explored the activation effect of different metals on PMS,as well as the influence of plasma effect on activation of PMS by adding light conditions on the surface of metal nanoparticles.It is found that Pd nanoparticles have the most obvious activation effect on PMS.Taking Pd/Ti O2 material as the research object,the reaction conditions,the loading amount of Pd,the concentration of PMS ect are adjusted to explore the interaction relationship between the catalyst and PMS molecules,and the mechanism of pollutant degradation.Finally,we use a photocatalysis-thiourea,the dissolution of various metals.Taking Ti O₂as the metal carrier,various metal ions were deposited on the surface of Ti O₂in the form of elemental substance,and Ti O₂was excited by ultraviolet light in the solution of thiourea.It was found that the metals deposited on the face of Ti O₂would be dissolved into the solution.To this phenomenon,the mechanism of the reaction is preliminarily explored.The introduction of photocatalysis as an oxidant to dissolve metals in thiourea gold leaching system is a new idea to dissolve precious metals in thiourea gold leaching system.