Bawankule Kaustubh P, Howarter John A
School of Materials Engineering, Purdue University 701 West Stadium Avenue West Lafayette IN 47907-2045 USA.
School of Sustainability Engineering and Environmental Engineering, Purdue University 500 Central Drive West Lafayette IN 47907 USA
RSC Adv. 2025 Sep 11;15(40):33006-33017. doi: 10.1039/d5ra03801d.
: Diglycolamides (DGAs) are widely employed as solvation extractants in industrial lanthanide separations. In solvent extraction, reverse aggregation enables these extractants to form complexation sites that significantly influence extraction yield. Although extraction is parametrically controlled, its efficiency is governed by poorly characterized phenomenological behavior. Therefore, improved control over nanoscale aggregate speciation is expected to enhance extraction efficacy at the macroscale. A multiscale framework can thus be applied to rationalize aggregation phenomena under process-relevant conditions, facilitating development of strategies to modulate solvent-phase structuring and thereby optimize extraction efficacy. : Aggregation tendency of DGAs is enhanced by polar infiltration from aqueous phase. To mechanistically analyze this behavior, a systematic multistage investigation was conducted on the reverse aggregation of ,'-dimethyl-,'-di(-octyl)diglycolamide (DMDODGA), a low-lipophilicity DGA, in -dodecane over a representative experimental range of nitric acid and water concentrations, using molecular dynamics (MD) simulations. : Cluster dynamics exhibit exponential decay, consistent with Smoluchowski's formalism. Aggregates are metastable, with nitric acid acting as a chaotropic agent at low concentrations and shifting to a kosmotropic role at higher levels. Counterions with greater solvating character in the Hofmeister series tend to favor the formation of small to intermediate aggregates. Hydrogen bonding enables water to consistently function as a kosmotropic agent, promoting the formation of larger assemblies. Free energy analysis indicates that systems with narrower cluster distributions and higher nitric acid-to-water ratios exhibit greater aggregate stability.
二甘醇酰胺（DGAs）在工业镧系元素分离中被广泛用作溶剂化萃取剂。在溶剂萃取中，反向聚集使这些萃取剂形成络合位点，显著影响萃取产率。尽管萃取是通过参数控制的，但其效率受表征不佳的现象学行为支配。因此，预计改善对纳米级聚集体形态的控制将提高宏观尺度上的萃取效率。因此，可以应用多尺度框架来合理化与工艺相关条件下的聚集现象，促进开发调节溶剂相结构的策略，从而优化萃取效率。：水相的极性渗透增强了二甘醇酰胺的聚集倾向。为了从机理上分析这种行为，使用分子动力学（MD）模拟，在硝酸和水浓度的代表性实验范围内，对低亲脂性二甘醇酰胺，'-二甲基-,'-二（辛基）二甘醇酰胺（DMDODGA）在正十二烷中的反向聚集进行了系统的多阶段研究。：团簇动力学表现出指数衰减，与斯莫卢霍夫斯基的形式主义一致。聚集体是亚稳态的，硝酸在低浓度时作为离液剂，在较高浓度时转变为促溶剂。霍夫迈斯特序列中具有更强溶剂化特性的抗衡离子倾向于促进小到中等聚集体的形成。氢键使水始终作为促溶剂发挥作用，促进更大聚集体的形成。自由能分析表明，具有更窄团簇分布和更高硝酸与水比例的系统表现出更大的聚集体稳定性。
