Synthesis Of Protonated Titanate Nanotubes For Adsorption Of U(?)and Cs In Water

With the continuous development of the global nuclear power industry,radionuclides U and Cs have been gradually developed and utilized by people.However,in the process of human peaceful use of nuclear energy and the enrichment of radionuclides,a large amount of radioactive nuclear pollution has also been generated.Among them,²³⁸U,²³⁵U and ¹³⁷Cs have long half-life,strong fluidity and great harm to the environment.With the maturation of material adsorption research,how to prepare high-performance nanomaterials to quickly and efficiently adsorb radionuclide ions in water has become an urgent task for material science.Titanate nanomaterials have been used as adsorbents for radionuclide ions in water due to their large reserves of raw materials,wide range of sources,simpler synthesis methods,and more surface ion exchange sites.In this study,titanate nanotubes were synthesized by hydrothermal reaction and protonated using different concentrations of nitric acid.Four protonated titanate nanotubes with different H⁺/Na⁺ratios were prepared with formulas Na_1.61H_0.39Ti₃O₇·nH₂O,Na_1.26H_0.74Ti₃O₇·nH₂O,Na_0.8H_1.2Ti₃O₇·nH₂O,and Na_0.31H_1.69Ti₃O₇·nH₂O.The materials were characterized by XRD,FT-IR,BET,SEM-EDS and TEM.The microstructure of the material is tubular,the length of the tube is about 50¹50nm,the outer diameter of the tube is about 10nm,the inner diameter is about 5nm,and the titanate nanotubes are still tubular after protonation,and the tube length is shortened to a certain extent.The specific surface areas of the four materials were 203.2678 m²/g,268.7398 m²/g,315.6813 m²/g,and 342.9278m²/g,respectively.The equilibrium adsorption rates of the four materials to 10 mg/L U?VI?were 79%,86%,94%,and 97%,respectively.Adsorption process can well fit the pseudo-second-order kinetics equation,which shows that the adsorption reaction is chemical reaction;the maximum adsorption capacity of U?VI?with different initial concentrations for the four materials is 250.7 mg/g and 217.5 mg/g,190.5mg/g and158.5mg/g.Adsorption process can fit the Langmuir adsorption isotherm model well,indicating that the adsorption reaction process is biased to monolayer uniform adsorption.The equilibrium adsorption rates of the four materials to 10 mg/L Cs were 80%,83%,87%,and 93%,respectively.Adsorption process can better fit the pseudo-second-order kinetics equation,indicating that the adsorption reaction is chemical reaction;the maximum adsorption capacity of four materials for different initial concentrations of Cs is 144.1 mg/g,133.15 mg/g,117.15 mg/g and 99.15 mg/g.The adsorption process can fit the Langmuir adsorption isotherm model well.The adsorption of Cs by Na_0.31H_1.69Ti₃O₇·nH₂O can simultaneously fit the Langmuir and Freundlich adsorption isotherms models.It shows that the adsorption reaction process is a complex adsorption process.The adsorption process of U?VI?and Cs by the four materials is a spontaneous endothermic process.The adsorption rate and adsorption rate of three common seawater temperatures are 35°C>25°C>15°C.The common interference ions Na⁺,K⁺,Ca²⁺and Mg²⁺in seawater have some influence on the adsorption of U?VI?and Cs on protonated titanate nanotubes,and the effect on the adsorption of U?VI?is Ca²⁺>Mg²⁺>K⁺>Na⁺.The effect of adsorption on the Cs of the material is K⁺>Ca²⁺>Na⁺>Mg²⁺.The protonation process has no obvious effect on the anti-interference of the material.