Synthesis A Novel Mesoporous Phosphate Materials And Their Performance On Adsorption Of Uranyl And Thorium Ions

In the research of nuclear energy sustainable development,the treatment technology of high-level radionuclide waste has always been a hot spot,and an efficient and convenient treatment technology is urgently needed.In this paper,mesoporous phosphate materials?MZrP,MAlP,MTiSiP?were used to treat radioactive wastewater,and their adsorption behavior for uranium and thorium was explored.MZrP?MAlP?MTiSiP were prepared by non-water solvent evaporation self-assembly and ethanol-hydrothermal method.The structural properties of the materials were characterized by XRD?SEM?FT-IR and nitrogen adsorption desorption.The results show that MZrP and MTiSiP have ordered hexahedral structure and MAlP has layered nanostructures;The materials have larger specific surface area and pore size in mesopores range?2-50 nm?;The surface of the materials has pphosphorus-oxygen groups combined with UO₂²⁺and Th⁴⁺.The results of adsorption of uranium showed that the optimum adsorption conditions for UO₂²⁺on MZrP,MAlP and MTiSiP are C₀=100 mg/L,pH=5.5 and contact reaction time T=6 h,their equilibrium adsorption capacities are respectively 291.37 mg/g?325.56 mg/g,193.85 mg/g,and the adsorption reaction process conforms to the quasi-secondary kinetic model and the Langmuir adsorption isotherm.In addition,Their separation factor constant R_L satisfies the condition of 0<R_L<1and the thermodynamic parameter?G⁰<0,indicating the adsorption of UO₂²⁺on the material is monolayer adsorption,the adsorption reactions tends to be chemical adsorption and belongs to spontaneous process.Similarly,the results of adsorption thorium experiments show that the optimum adsorption conditions for the adsorption of Th⁴⁺on MZrP,MAlP and MTiSiP materials are C₀=100 mg/L,pH=3.5 and contact reaction time T=6 h.Their equilibrium adsorption capacities are respectively 249.81 mg/g,420.39 mg/g,160.20 mg/g,and the adsorption reaction process conforms to the quasi-secondary kinetic model and the Langmuir adsorption isotherm.In addition,their separation factor constant R_L satisfies 0<R_L<1 and thermodynamic parameter?G⁰<0,which show that the adsorption of Th⁴⁺on the material is single-layer adsorption,the adsorption reactions are all chemical adsorption and belong to the spontaneous process.The results of three adsorption-desorption experiments show that the phosphate materials?MZrP,MAlP,MTiSiP?have good chemical stability,although their structures are damaged after acid desorption,they are not completely dissolved,and their equilibrium adsorption capacity is relatively higher.Therefore,the phosphate materials?MZrP,MAlP,MTiSiP?have good recyclability and are suitable as adsorbent materials for UO₂²⁺?Th⁴⁺.