A Study On The Preparation Of α-Fe₂O₃/TiO₂HNTAs Catalysts And Photocatalytic Degradation Of Microplastics

The extensive use of plastics since its invention has brought great convenience to people’s daily life.At the same time,however,the problem of plastic pollution has become increasingly serious,which attracts many attentions worldwide.In the context of tighter environmental policies,the voices calling for the removal of harmful substances from the environment are increasingly rising.The utilization of abundant,clean and renewable solar energy to remove microplastics in the environment is of great significance in environmental protection and energy utilization.As a photocatalyst,titanium dioxide（TiO₂）has attracted widespread attention because of its non-toxicity,good stability and excellent photochemical properties.It is also the most widely investigated material in the field of photocatalytic plastic degradation.Therefore,we first study the degradation of microplastics over TiO₂nanotube array thin film under ultraviolet light.Secondly,ultraviolet light only takes4%of solar energy whereas the current photocatalytic systems under visible-light,which takes 43%of solar energy,exhibit low efficiency for microplastics degradation.In order to solve these problems,we focus onα-Fe₂O₃/TiO₂HNTAs thin film photocatalyst and develop a route coupling photocatalytic and photothermal Fenton-like process to achieve efficient degradation of microplastics under visible light.Using polystyrene（PS）plastics as a model,the specific research content of this thesis is as follows:1.Using Ti sheet as raw material,titanium dioxide（TiO₂HNTAs）with photonic-like crystal structure layer/nanotube array hierarchical structure was prepared by two-step anodizing method.The morphology was characterized by SEM.It was found that TiO₂HNTAs exhibited higher activity than the materials prepared via one-step anodic oxidation.Under ultraviolet light irradiation with a light intensity of 150 mw/cm²and 60℃,the particle size of PS plastic sphere gradually decreased until it was completely degraded after 18 h.The effects of temperature,light intensity,acidity,light source and PS film thickness on the degradation of plastics were also investigated.2.By hydrothermal method,α-Fe₂O₃films were deposited on the surface of TiO₂HNTAs via hydrothermal method.The prepared catalysts were characterized by SEM,XRD,UV-VIS,XPS and other techniques.The effects of Fe₂O₃deposition time,TiO₂HNTAs,light intensity,light wavelength and reaction temperature on the degradation of PS plastic spheres were also investigated.The results show thatα-Fe₂O₃is the active center for photocatalysis with visible light and TiO₂HNTAs could promote its photocatalytic activity.Photoexcitation and the coupling of photocatalysis and thermal effect are essential to achieve efficient degradation of plastics.A unique melting phenomenon is observed during the plastics degradation,which is due to the synergistic mode of photothermal process.The degradation rate of PS plastic spheres achieved 100%after 4 h,under visible light irradiation（0.5 W/cm²）and 75℃.Based on above results,we choseα-Fe₂O₃/TiO₂HNTAs as photocatalysts for PS plastic foam degradation.The foam was firstly dissolved with suitable solvent and then sprayed on the surface of the catalyst forming a thin film.The degradation rate of PS plastic film achieved 90%after 12 h under visible light irradiation（0.5 W/cm²）and 75℃.The catalytic system will open a new way for removing（micro）plastics with solar energy.