Adsorption Of Eu???,Th??? And U??? On TiO₂/Diatomite Composite From Aqueous Solutions

Radioactive waste is produced in the process of using nuclear energy.These radioactive wastes need to be properly treated before they can be discharged into the environment,which would pose a great threat to environmental safety and public health.In this paper,TiO2/Diatomite composite(referred to as TiO2/Diatomite)was used as adsorbent to study the adsorption of Eu(?),U(?)and Th(?)in aqueous solution.Oxygen vacancies exist on the surface of TiO2,which react with water molecules to produce bridging hydroxyl groups and hydroxyl groups.After hydroxylation of bridge oxygen,some metal ions can be adsorbed by chemical reaction,but,nano-TiO2 will agglomerate in the application.In order to reduce the agglomeration phenomenon and improve the adsorption performance,this paper selects diatomite with unique porous structure as the substrate,and successfully obtains TiO2/Diatomite by sol-gel method.We can obtain the chemical composition,main functional groups and basic structure of samples of TiO2/Diatomite in detail,by the use of X-ray powder diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and N2 adsorption/desorption isotherms technique.It is found that the adsorption performance of U(?)and Th(?)on TiO2/Diatomite in aqueous solution is better than that of diatomite and TiO2,through comparative experiments.The adsorption behaviors of Eu(?),Th(?)and U(?)on TiO2/Diatomite,and the effect of pH,ionic strength,contact time,solid-liquid ratio and temperature on adsorption behaviors were studied by batch experiment.The adsorption process of Eu(?),Th(?)and U(?)on TiO2/Diatomite takes approximately 40 h,24 h and 18 h to reach equilibrium respectively.The kinetics showed that the adsorption of Eu(?),Th(?)and U(?)matched the pseudo-second-order kinetics model,the adsorption rate is mainly affected by the intraparticles diffusion,and the adsorption mechanism is chemical adsorption.Thermodynamics shows that the adsorption of Eu(?),Th(?)and U(?)is spontaneous endothermic under standard conditions.The adsorption of U(?)and Th(?)can be described by Langmuir model while the adsorption of Eu(?)can be described by Freundlich model.The characterization of X-ray photoelectron spectroscopy(XPS),X-ray powder diffraction(XRD)and fluorescence excitation spectroscopy(PL)validate macroscopic results at the molecular level.