Study On Adsorption Behavior Of Eu(?) And Re(?)on Two-dimensional Transition Metal Carbide

The rapid development of nuclear energy in recent years has led to a significant increase in the production of radioactive nuclear waste.How to safely and properly handle these nuclear wastes in terms of proctection for ecological environment and human health,and is still a key factor affecting the sustainable development of nuclear energy.The development of functional nanomaterials as efficient sorbents for rapid radionuclide removal in water has become an effective means of radioactive pollution prevention and environmental remediation.Two-dimensional transition metal carbide?MXene?is a new type of layered nanomaterial which exhibits high surface area,abundant active sites,high ion exchange capacity,controlled layer spacing and high hydrophilicity,and is expected to play a important role in the treatment of radionuclides from radioactive wastewater.In this thesis,Ti₃C₂T_x and Ti₂CT_x MXenes were selected to prepare alkalized Ti₃C₂T_x?Na-Ti₃C₂T_x?and Ti₂CT_x/PDDA composite materials.The removal behavior of Eu???and Re???in aqueous solution by these novel sorbents was studied,and the corresponding interaction mechanism was clarified.These results provide valuable scientific insights into the applications of cleanup for trivalent actinides and lanthanides,and ⁹⁹Tc radionuclides in environmental waters.?1?An alkalized two-dimensional titanium carbide?Na-Ti₃C₂T_x?was successfully prepared by treating Ti₃C₂T_x MXene with NaOH,and characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?and Zeta potential measurements.The adsorption behavior of Eu???on Na-Ti₃C₂T_x was systematically investigated by batch experiments.The results show that the adsorption process is greatly affected by the pH and ionic strength of the solution.The adsorption equilibrium was reached within 5 minutes.Based on Langmuir model fitting results,the maximum adsorption capacity of Eu???on Na-Ti₃C₂T_x was calculated to be 54.05 mg g^-11 at pH=4.0 and 298 K.The thermodynamic results suggested that the adsorption process was a spontaneous and endothermic reaction.It is concluded that Na⁺ions inside MXene galleries wereexchanged by Eu³⁺ions and outer-sphere surface complexation dominate Eu???adsorption at acidic pH conditions.?2?A novel MXene-polyelectrolyte nanocomposite with three-dimensional networks was prepared by composite of Ti₂CT_x and polydiallyl ammonium chloride?PDDA?,and characterized by XRD,SEM,Zeta potential measurements,Fourier transformed infrared spectroscopy?FT-IR?,Thermal gravimetric analyzer?TGA?,nitrogen adsorption/desorption,X-ray photoelectron spectroscopy?XPS?.The adsorption behavior of Re???on nanocomposite was systematically investigated by batch experiments.Batch adsorption experiment results indicated that the kinetics adsorption of Re???followed the pseudo-second-order model.The adsorption isotherms of Re???on nanocomposite was perfectly fitted by the Langmuir model,and the maximum adsorption capacities of nanocomposite were calculated to be363 mg g^-11 at pH=4.0 and 298K.The immobilization mechanism was confirmed as a sorption-reduction process by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy.