Preparation Of Photocatalytic Composites With MXene As Co-Catalyst And Their U(Ⅵ) Reduction Immobilization Properties

As a kind of clean energy with high energy density and low carbon dioxide emission,nuclear energy is regarded as one of the energy sources with the greatest development potential in solving the energy crisis.Uranium minerals,as the main raw materials used in the nuclear industry,need to process for later use.But in this stage,it will inevitably release the radioactive water to environment,which is a great threat to the environmental safety and biological health.Uranium has both radiotoxicity and chemical toxicity.If it enters the human body,it will cause irreversible damage to our health.Therefore,it needs to be properly handled.The treatment of radioactive wastewater by photocatalytic reduction method is environmentally friendly and efficient.The specific process is to use semiconductor photocatalyst to reduce soluble U（Ⅵ）to insoluble U（Ⅳ）.Therefore,the development and design of efficient photocatalyst is of great value.Hererin,Ti₃C₂ MXene was used as a co-catalyst to synthesize CeO₂/Ti₃C₂ composites and ZnIn₂S₄/Ti₃C₂ composites,and then their photocatalytic reduction properties of U（Ⅵ）were studied respectively.The main contents are as follows:（1）The in-situ growth of CeO₂ in multilayer Ti₃C₂ was realized by a simple hydrothermal method,and then the obtained CeO₂/Ti₃C₂ composites were characterized,and the possible photocatalytic reduction ability of U（Ⅵ）removal was examined.The photocatalytic results show that the performance of CeO₂/Ti₃C₂ composites in the photocatalytic reduction of U（Ⅵ）is not ideal.For instance,when methanol is used as a sacrificial agent,the removal rate of U（VI）is only～50%after 120 min of full spectrum irradiation.（2）ZnIn₂S₄/Ti₃C₂ composites were prepared by a facile solvothermal approach and then characterized.Subsequently,the effects of different amounts of added MXene on the photocatalytic reduction of U（Ⅵ）were studied.The results show that compared with the pristine ZnIn₂S_4,the visible light response of ZnIn₂S₄/Ti₃C₂ composites is significantly enhanced,and the electron hole separation efficiency is improved,which greatly enhances the photocatalytic reduction performance of U（VI）.With no addition of sacrificant,the removal rate of U（Ⅵ）in solution of ZISTC-3 sample reaches 96.1%under visible light for 120 min.In addition,In³⁺and Zn²⁺were not detected in the solutions in the photocatalytic experiment,indicating that the composites have good stability and still maintains high photocatalytic activity after three cycles of the experiment,which is conducive to subsequent recycling.Finally,the possible photocatalytic mechanism of ZnIn₂S₄/Ti₃C₂ composites is proposed.This thesis has successfully proved that MXene,as an excellent photocatalytic agent,can be used in the construction of photocatalytic composites with enhanced photoelectron-hole separation ability,and the reduction fixation of soluble U（Ⅵ）has been realized.This provides a technical reference for the rapid removal of radioactive pollutants in environmental wastewater and opens new avenues for the design and preparation of efficient photocatalytic materials.