Demnitz M, Hilpmann S, Lösch H, Bok F, Steudtner R, Patzschke M, Stumpf T, Huittinen N
Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden, Germany.
Dalton Trans. 2020 Jun 2;49(21):7109-7122. doi: 10.1039/d0dt00646g.
In the present study we have investigated the complexation of uranyl(vi) with chloride and fluoride using luminescence spectroscopy (TRLFS, time-resolved laser-induced fluorescence spectroscopy). At 25 °C (298.15 K), in the presence of 0-0.175 M fluoride, the first single-component emission spectra for all four uranyl(vi)-fluoride complexes, i.e. UO2F+, UO2F2, UO2F3-, and UO2F42- could be extracted. Based on the aqueous speciation derived from the TRLFS data, log K* values at I = 1 M were calculated for all these complexes and extrapolated to infinite dilution using the SIT approach. In the case of chloride, however, quenching of the uranyl(vi)-luminescence hampered the experiments. Thus, uranyl(vi)-complexation was studied with TRLFS at liquid nitrogen temperatures. Samples were prepared at 25 °C (298.15 K) with chloride concentrations ranging from 0 to 1.0 M followed by instantaneous freezing and subsequent luminescence spectroscopic measurements at -120 °C (153.15 K). This allowed for the determination of the first luminescence spectra for the UO2Cl+ complex with the TRLFS method. The chloride quench reaction was further studied in the temperature range 1-45 °C (274.15-318.15 K) using Stern-Volmer analysis. By applying the Arrhenius and the Eyring equations we obtained the first thermodynamic parameters for the dynamic quench process, i.e. the activation energy (Ea = 55.0 ± 12.9 kJ mol-1), enthalpy (ΔH‡ = 52.5 ± 13.0 kJ mol-1), and entropy (ΔS‡ = 103.9 ± 42.8 J mol-1 K-1).
在本研究中，我们使用发光光谱法（时间分辨激光诱导荧光光谱法，TRLFS）研究了铀酰（VI）与氯离子和氟离子的络合作用。在25°C（298.15K）下，在0 - 0.175M氟离子存在的情况下，可以提取出所有四种铀酰（VI）-氟络合物，即UO2F+、UO2F2、UO2F3-和UO2F42-的首个单组分发射光谱。基于从TRLFS数据得出的水相形态，计算了所有这些络合物在I = 1M时的log K*值，并使用特定离子相互作用理论（SIT）方法外推至无限稀释。然而，对于氯离子，铀酰（VI）发光的猝灭阻碍了实验。因此，在液氮温度下用TRLFS研究了铀酰（VI）的络合作用。样品在25°C（298.15K）下制备，氯离子浓度范围为0至1.0M，随后立即冷冻，然后在-120°C（153.15K）下进行发光光谱测量。这使得能够用TRLFS方法测定UO2Cl+络合物的首个发光光谱。使用Stern-Volmer分析在1 - 45°C（274.15 - 318.15K）温度范围内进一步研究了氯离子猝灭反应。通过应用Arrhenius方程和Eyring方程，我们获得了动态猝灭过程的首个热力学参数，即活化能（Ea = 55.0 ± 12.9 kJ mol-1）、焓（ΔH‡ = 52.5 ± 13.0 kJ mol-1）和熵（ΔS‡ = 103.9 ± 42.8 J mol-1 K-1）。
