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结合静态实验和X射线吸收精细结构谱学(EXAFS)技术研究了pH、时间、有机配体等环境因素对放射性核素Eu(III)在钛酸纳米管上的吸附行为和微观机制的影响.宏观实验结果表明:Eu(III)在钛酸纳米管上的吸附在pH<6.0条件下受离子强度影响,而在pH>6.0条件下不受离子强度影响;腐殖酸HA/FA在低pH条件下可以促进Eu(III)在钛酸纳米管上的吸附,而在高pH条件下抑制Eu(III)在钛酸纳米管上的吸附.EXAFS微观分析结果表明:在pH<6.0条件下,吸附属于外层吸附机理;在pH>6.0条件下,吸附属于内层吸附机理.pH<6.0时,中心原子Eu周围只有Eu-O一个配位层,其平均键长为2.40,配位数在9左右;随着pH逐渐升高,第一配位层的配位数下降,表明吸附Eu原子配位的对称性下降.当吸附时间延长或pH升高,吸附原子Eu周围出现了Eu-Eu和Eu-Ti第二配位层,其平均键长分别为3.60和4.40,配位数分别在2或1左右,表明形成了内层吸附产物或表面沉淀或表面多聚体.腐殖酸HA/FA的存在,可以改变Eu(III)在钛酸纳米管表面的吸附形态和微观原子结构,Eu(III)不仅可以与钛酸纳米管的表面羟基直接键合形成二元表面复合物(Eu-TNTs),还可以通过HA/FA的桥连作用形成三元表面复合物(HA/FA-Eu-TNTs).这些研究结果对于评估放射性核素Eu(III)与纳米材料在分子水平上的作用机理及分析Eu(III)在环境中的物理化学行为具有重要的意义.
The effects of pH, time, organic ligand and other environmental factors on the adsorption behavior and microscopic mechanism of radionuclide Eu (III) on titanate nanotubes were investigated by static experiments and X-ray absorption fine structure spectroscopy (EXAFS). The macroscopic experimental results show that the adsorption of Eu (III) on titanate nanotubes is affected by the ionic strength at pH <6.0, but not by the ionic strength at pH> 6.0. The HA / FA of humic acid at low pH , The adsorption of Eu (III) onto titanate nanotubes can be promoted under high pH conditions, while the adsorption of Eu (III) onto titanate nanotubes can be inhibited under high pH conditions. The results of microanalysis by EXAFS show that under the condition of pH <6.0, Adsorption belongs to the adsorption mechanism of the outer layer. Under the condition of pH> 6.0, the adsorption belongs to the inner adsorption mechanism. When pH <6.0, the Eu atom only has a coordinating layer around the central Eu atoms and the average bond length is 2.40. At about 9. With the increase of pH, the coordination number of the first coordination layer decreased, indicating that the coordination symmetry of the adsorbed Eu atoms decreased.When the adsorption time prolonged or pH increased, Eu- Eu and Eu-Ti second coordination layer, the average bond length were 3.60 and 4.40 , respectively, the coordination number of 2 or 1, indicating that the shape The adsorption of the inner layer or the surface precipitates or surface multimers can be achieved by the presence of humic acid HA / FA, which can change the adsorption morphology and microscopic atomic structure of Eu (III) on the surface of titanate nanotubes. Eu (III) The surface hydroxyl groups of titanate nanotubes are directly bonded to form binary surface complexes (Eu-TNTs), and ternary surface composites (HA / FA-Eu-TNTs) can also be formed by bridging HA / FA. The results are of great significance for assessing the molecular mechanism of Eu (III) and nanomaterials at the molecular level and analyzing the physico-chemical behavior of Eu (III) in the environment.