| As nuclear energy industry develops,uranium,thorium and other elements plays an important role as the primary material of nuclear reactor,but it inevitably produces more and more nuclear waste.MXenes are a promising material for the treatment of nuclear waste,but it remains a challenge to address the stacking and oxidability of materials for the treatment of nuclear waste.In this study,Ti3C2Tx,a non-toxic and harmless MXene material,was selected and obtained by mild Li F/HCl etching method in previous studies.The end group on etched MXene was first alkalized and then modified with chloroacetic acid to obtain C-TC material.The carboxyl groups were connected to the surface of Ti3C2Tx,which improved the interlayer distance and adsorption capacity for uranium of the material.Characterization methods including XRD,FT-IR,BET,SEM and TG were used to analyze the material,which confirmed the successful synthesis of the materials.The adsorption of uranium and thorium were investigated by using this material as adsorbent.（1）The effects of solution p H,contact time,initial concentration of uranium-containing solution,temperature and competing ions on the adsorption of uranium and its recycling ability were explored through batch adsorption experiments.The results showed that the adsorption process was more in line with the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model,which was a chemical monolayer adsorption.Under the conditions of p H=5.0,C0=80 mg L-1,and T=308 K,the adsorption quantity of uranium by C-TC material was 165.43 mg g-1.The relevant thermodynamic parameters showed that the adsorption was a spontaneous endothermic process.When the Na Cl concentration reached0.3 M,the adsorption quantity decreased by about 16%.After the introduction of different cations,the adsorption quantity of the C-TC material for uranium was still above 84%.After five cycles,the uranium removal performance remained at about 78%.（2）The effects of different solution p H,contact time,initial concentration of thorium-containing solution,temperature and competing ions on the adsorption of thorium were investigated.According to the fitting analysis,it is determined that the adsorption process was more in line with the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model.It was a chemical monolayer adsorption,and the process also showed a faster adsorption rate（5min to reach balance）.Under the circumstance of p H=3.5,C0=80 mg L-1,and T=308 K,the adsorption ability of thorium by C-TC material was 111.83 mg g-1.The relevant thermodynamic arguments indicated that the adsorption was a spontaneous/endothermal process,and the load ability of C-TC materials for thorium was still above 89%after the introduction of different cations.The above results indicated that this study provided an effective strategy for the modification of MXene nanosheets.The synthesized C-TC can be considered as an efficient adsorbent with good adsorption performance and high selectivity,and has great application prospects in the separation of uranium and thorium from radionuclear wastewater. |
