Department of Chemical and Biomolecular Engineering, Clemson University, 127 Earle Hall, Clemson, South Carolina 29634, United States.
Department of Environmental Engineering and Earth Sciences, Clemson University, 342 Computer Court, Anderson, South Carolina 29625, United States.
Anal Chem. 2020 Apr 7;92(7):5214-5221. doi: 10.1021/acs.analchem.9b05758. Epub 2020 Mar 24.
The rapid screening of plutonium from aqueous sources remains a critical challenge for nuclear nonproliferation efforts. The determination of trace-level Pu isotopes in water requires offsite sample preparation and analysis; therefore, new methods that combine plutonium purification, concentration, and isotopic screening in a fieldable detection system will provide an invaluable tool for nuclear safeguards. This contribution describes the development and characterization of thin polymer-ligand films for the isolation and concentration of waterborne Pu for direct spectroscopic analyses. Submicron thin films were prepared through spin coating onto Si wafers and consisted of combinations of polystyrene (PS) with dibenzoylmethane, thenoyltrifluoroacetone, and di(2-ethylhexyl)phosphoric acid (HDEHP). Pu uptake studies from solutions at pH from 2.3 to 6.3 indicated that only films containing HDEHP exhibited significant recovery of Pu. High alpha spectroscopy peak energy resolutions were achieved for PS-HDEHP films over a range of film thicknesses from 30 to 250 nm. A separate study was performed to evaluate uptake from a primarily Pu(V) solution where it was observed that doubling the HDEHP loading in the film increased uptake of Pu by an order of magnitude. X-ray photoelectron spectroscopy (XPS) analysis revealed that HDEHP was highly concentrated within the first few nanometers of the film at the higher loading. XPS analysis also revealed that, in the presence of water, HDEHP was stripped from the surface layer of the film at circumneutral pH. While significant losses of ligand were seen in all samples, higher loadings of HDEHP resulted in measurable amounts of ligand retained after a 12-h soak in water. Findings of this study are being used to guide the development of thin-film composite membrane-based detection methods for the rapid, fieldable analysis of Pu in water.
从水相中快速筛选钚仍然是核不扩散努力的一个关键挑战。水中痕量 Pu 同位素的测定需要场外样品制备和分析；因此，将钚纯化、浓缩和同位素筛选结合在一个可现场使用的检测系统中的新方法将为核保障提供宝贵的工具。本贡献描述了用于分离和浓缩水相 Pu 的薄聚合物-配体薄膜的开发和表征，用于直接光谱分析。亚微米薄膜通过旋涂到硅晶片上制备而成，由聚苯乙烯 (PS) 与二苯甲酰甲烷、乙酰丙酮和二(2-乙基己基)磷酸 (HDEHP) 组合而成。从 pH 值为 2.3 至 6.3 的溶液中进行的 Pu 摄取研究表明，只有含有 HDEHP 的薄膜显示出 Pu 的显著回收。在 30 至 250nm 的薄膜厚度范围内，PS-HDEHP 薄膜实现了高阿尔法光谱峰能量分辨率。进行了一项单独的研究来评估主要 Pu(V)溶液中的摄取情况，观察到在薄膜中 HDEHP 负载量增加一倍会使 Pu 的摄取量增加一个数量级。X 射线光电子能谱 (XPS) 分析表明，在较高负载量下，HDEHP 高度集中在薄膜的前几个纳米内。XPS 分析还表明，在中性 pH 值下，HDEHP 从薄膜的表面层中被剥离。虽然所有样品中都观察到配体的大量损失，但较高负载量的 HDEHP 导致在 12 小时的水浸泡后仍能保留可测量量的配体。本研究的结果正在被用于指导基于薄膜复合膜的检测方法的开发，用于快速、现场分析水中的 Pu。
