氮、磷、硫共掺杂石墨烯材料对环境中铀酰去除机理的理论模拟研究

Theoretical study on the removal of uranyl by nitrogen,phosphorus and sulfur doped graphene materials

随着核能的发展,放射性废水的处理成为亟待解决的环境问题之一,是人们广泛关注的焦点.放射性核素铀具有强化学毒性及放射性,从放射性废液中去除铀元素在环境保护方面具有重要的意义.近年来,石墨烯基材料由于其优良的性能被广泛应用于放射性废水的处理中.本文从理论角度构建了12种N、P、S掺杂石墨烯模型,模拟环境中铀酰离子与掺杂石墨烯材料的相互作用,探讨其相互作用的内在机理.基于密度泛函理论,对不同吸附位点(U或铀酰轴向氧原子O_(ax))的24种掺杂石墨烯/铀酰吸附体系进行了几何构型、吸附能、差分电荷密度、振动频率等方面的理论计算和相关分析,探讨了两者的相互作用机制,研究发现:(1)铀酰在N、P、S掺杂石墨烯表面吸附时主要的作用位点为其轴向氧原子(O_(ax));(2)同时,在吸附过程中,铀酰中的配位水分子发挥很重要的作用;(3) P&S共掺杂石墨烯对铀酰的吸附性能最好,最大的吸附能为38.40 kcal/mol;(4)双元素掺杂石墨烯对铀酰的吸附能力明显高于单元素掺杂石墨烯.本文的研究为新型放射性废水处理材料的设计开拓了新的视野,提供了一定的理论依据.

With the development of nuclear energy,the treatment of radioactive waste has become one of the most urgent environmental problems.Radionuclide uranium is chemical toxic and radioactive.The removal of uranium from radioactive waste water is of great significance in environmental protection.In recent years,graphene-based materials had been widely used in the treatment of radioactive waste water due to their excellent properties.12 kinds ofN,P and S doped graphene models were constructed from the theoretical perspective to simulate the interaction between the doped graphene materials and uranyl ions in the aqueous environment.Based on the density functional theory(DFT)method,the geometric configuration,adsorption energy,differential charge density and vibration frequency of 24 doped graphene/uranyl complexes with different adsorption sites(U or were calculated and analyzed.It is found that:(1)the main adsorption site for uranyl ion on the surface of N,P and S doped graphene was the axial oxygen atom(Oax);(2)at the same time,the coordination water molecules of uranyl ion played an important role during the adsorption process;(3)P&S doped graphene displayed the best adsorption capacity towards uranyl and the maximum adsorption energy was 38.40 kcal/mol;(4)the adsorption ability of double element doped graphene materials were obviously higher than that of the single ones.This research provided theoretical basis for broadening the horizon for the design of new radioactive waste water treatment materials.