Preparation Of Separable Titanium-based Composite Photocatalyst And Its Application In Degradation Of Organic Pollutants

The problems of food safety and human health caused by water pollution have gradually attracted people's attention,and the persistent organic pollutants are very stable and difficult to eliminate completely.Therefore,efficient organic pollutant treatment technologies urgently need to be developed.Titanium dioxide?TiO₂?semiconductor photocatalytic technology can convert it into non-polluting small molecules such as carbon dioxide?CO₂?and water?H₂O?,so it has great potential for application.However,in the practical application of nano-TiO₂photocatalysts,there are still some problems such as the difficulty of recycling and reuse and the narrow rang of solar spectral response.In order to solve these problems,the paper synthesized titanium-based composite photocatalysts by introducing magnetic nanomaterials,giving them the ability to separate and recover.Meanwhile,through reasonable structural control and the combination with silver nanoparticles?AgNPs?,carbon nitride?C₃N₄?and upconverting nanomaterials NaYF₄:Yb,Tm?UCNP?,it has better sunlight utilization capabilities.Finally,the representative organic pollutants such as methyl orange?MO?and other dyes were selected as degradation models to study the photocatalytic degradation of the prepared composites.The specific research contents are as follows:1.The synthesis of Fe₃O₄@nanosheet-TiO₂?Fe₃O₄@ns-TiO₂?composite photocatalyst with flower-like core-shell structure and its research on ultraviolet?UV?photocatalytic degradation of organic pollutants.Fe₃O₄ nanoparticles were synthesized by hydrothermal method,and then the sandwich core-shell structure Fe₃O₄@SiO₂@TiO₂ was obtained by the sol-gel method.Magnetic components were successfully introduced.The flower-like core-shell microspheres Fe₃O₄@ns-TiO₂ were prepared by lye hydrothermal etching and assisted by ion exchange and calcination,and then its morphologies and structures were characterized and analyzed.In the photocatalytic degradation of methyl orange,the composite photocatalyst exhibited a higher ultraviolet photocatalytic activity than Fe₃O₄@hollow-TiO₂?Fe₃O₄@h-TiO₂?and its photocatalytic degradation rate constant k is 1.64 times that of the commercial P25.Further experimental studies show that Fe₃O₄@ns-TiO₂ photocatalyst has good recyclability.2.The synthesis of Fe₃O₄@ns-TiO₂/Ag/C₃N₄ composite photocatalyst with visible?VIS?light-enhanced photocatalytic activity and its research on photocatalytic degradation of organic pollutants.5±3 nm AgNPs were deposited on the surface of TiO₂ nanosheets in Fe₃O₄@ns-TiO₂ by chemical reduction method,and then mixed with urea and calcined at high temperature to obtain Fe₃O₄@ns-TiO₂/Ag/C₃N₄.MO photodegradation experiments show that the photocatalyst has visible light-enhanced photocatalytic activity,and at the full wavelength light irradiation experiments its k value is 0.12723 min^-1,2.36 times that of Fe₃O₄@ns-TiO₂and 3.54 times that of P25.The composite photocatalyst still maintains good recycling performance.Finally,the visible light photocatalysis mechanism of Fe₃O₄@ns-TiO₂/Ag/C₃N₄was speculated:under visible light,photogenerated electrons in C₃N₄ were generated,and migrated to TiO₂ or was captured by AgNPs and then transferred to TiO₂,resulting in photocatalytic degradation;The AgNPs deposited on the TiO₂ surface play an important role in the electronic conduction bridge,and its surface plasmon resonance effect can also enhance visible light absorption.3.The synthesis of?Fe₃O₄-UCNP?@TiO₂ composite photocatalyst with near-infrared?NIR?light-enhanced photocatalytic activity and its research on photocatalytic degradation of organic pollutants.Composite photocatalyst?Fe₃O₄-UCNP?@TiO₂ was designed and synthesized by a new method with the combination of electrostatic interaction and sol-gel method.In the full-wavelength photocatalytic degradation experiment,the composite photocatalyst can degrade 71.7%of methylene blue?MB?in solution in 50 min,and the photodegradation rate constant is 1.65 times that of P25.The NIR photocatalytic experimental results and optical properties of the test show that the UCNP part of the composite photocatalyst can convert the near infrared light into UV light to indirectly drive the photocatalytic degradation of TiO₂.The final hysteresis loop characterization and cyclic experimental results show that?Fe₃O₄-UCNP?@TiO₂ photocatalyst also has good recovery and recycling performance.