Graham Trent R, Kennedy Ashley R, Morton Jacob, Reynolds Jacob G, Pearce Carolyn I
Pacific Northwest National Laboratory, Richland, WA, USA.
Savannah River National Laboratory, Aiken, SC, USA.
Commun Chem. 2025 Jun 7;8(1):180. doi: 10.1038/s42004-025-01546-7.
This study focuses on the transport properties of hexavalent chromium, specifically the chromate anion, to improve predictive models and environmental remediation strategies for Cr(VI) migration. Using Cr Nuclear Magnetic Resonance (NMR) spectroscopy, the research quantifies chromate in multicomponent electrolytes replicating nuclear waste conditions at the Hanford Site in Washington State. The consistency of the Cr NMR signal integral with chromate concentration, despite varying matrix compositions, establishes it as a reliable concentration indicator. The transport properties of chromate in an alkaline solution were assessed using relaxation-based measurements via saturation recovery and Carr-Purcell-Meiboom-Gill experiments, determining spin-lattice and spin-spin relaxation times. These measurements, combined with the Bloembergen-Purcell-Pound equation, helped estimate the rotational correlation time and the Cr self-diffusion coefficient using Stokes-Einstein-Debye and Stokes-Einstein equations. Direct measurements were obtained through pulsed field gradient stimulated echo Cr NMR spectroscopy. Monte Carlo simulations further estimated uncertainty propagation. The results enhance comprehension of chromate transport and highlight prospects for identifying transport properties of NMR-active nuclei, traditionally considered unreachable.
本研究聚焦于六价铬，特别是铬酸根阴离子的传输特性，以改进铬（VI）迁移的预测模型和环境修复策略。利用铬核磁共振（NMR）光谱，该研究对模拟华盛顿州汉福德 Site 核废料条件的多组分电解质中的铬酸盐进行了定量分析。尽管基质成分不同，但铬 NMR 信号积分与铬酸盐浓度的一致性使其成为可靠的浓度指标。通过饱和恢复和 Carr-Purcell-Meiboom-Gill 实验，利用基于弛豫的测量方法评估了碱性溶液中铬酸盐的传输特性，确定了自旋晶格和自旋-自旋弛豫时间。这些测量结果与 Bloembergen-Purcell-Pound 方程相结合，使用 Stokes-Einstein-Debye 和 Stokes-Einstein 方程估算了旋转相关时间和铬的自扩散系数。通过脉冲场梯度激发回波铬 NMR 光谱获得了直接测量结果。蒙特卡罗模拟进一步估计了不确定性传播。研究结果增强了对铬酸盐传输的理解，并突出了识别传统上认为无法实现的 NMR 活性核传输特性的前景。
