Interfacial chemistry in solvent extraction systems. Final report for the period June 1, 1994 - May 31, 1998
The interfacial chemistry that occurs in the liquid/liquid extraction of metals ions still remains very incompletely understood at the molecular level. The objective of this comprehensive research program has been to further the fundamental understanding of this complex chemistry by systematically investigating the interfacial behavior of extraction reagents and their interactions with metal ions at both macroscopic (liquid/liquid) and microscopic (reversed micelles) interfaces. Although the importance of the macroscopic interface is well recognized, it is less appreciated that microscopic interfaces, i.e., association microstructure such as reversed micelles, are often present under practical conditions and play a key role in liquid/liquid extraction. An improved knowledge of the interfacial behavior of extractant molecules is of the utmost importance as it relates to the efficacy (extent, selectivity and rate) of the extraction process. During the recent grant period the authors have more intensively investigated the physicochemical nature of metal-extractant aggregates (or microscopic interfaces) in the organic phase of acidic organophosphorus extraction systems from the perspective of colloid and surface science. Since industrial extraction systems are very complex, the authors emphasized the study of the aggregation behavior in model extraction systems of pure metal salts of bis(2-ethylhexyl)phosphoric acid (HDEHP) (e.g., NaDEHP, Ni(DEHP){sub 2} CO(DEHP){sub 2}) or bis(2-ethylhexyl) sulfosuccinate, whose sodium salt (AOT) is the classical surfactant used often in studies of the structure and properties of reversed micelles, to eliminate any possible uncertainty in the metal-extractant complex composition. This approach evolved into a new initiative that utilized molecular modeling in order to clarify the molecular structure of metal-extractant micellar aggregates for which information is very difficult to obtain from direct experimental measurements. Significantly, they have obtained a number of novel findings that are contrary to conventional views of both the fundamentals of reversed micellar formation and growth as well as liquid/liquid extraction. These findings take on additional importance in view of the general increasing interest in micellar enhanced separation processes. In addition, they have continued to make significant progress in their efforts to develop new methodologies for characterization of the physicochemical nature of the macroscopic liquid/liquid interface by using advanced laser techniques. The research productivity has been nothing short of excellent. This is especially so in view of the very difficult and challenging measurements that they proposed for investigating the structure and dynamics of the liquid/liquid interface, as well as the accomplishments in developing totally new concepts such as the open water-channel model of reversed micelles. Eighteen (18) papers and abstracts have been published since the submittal of the last three-year DOE progress report. Furthermore, several additional papers are in various stages of publication and preparation. In addition, they have given 12 presentations describing various aspects of the liquid/liquid extraction and related research activities.
- Research Organization:
- Auburn University, Auburn, Alabama (US)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- FG05-85ER13357
- OSTI ID:
- 758937
- Report Number(s):
- DOE/ER/13357-29; TRN: AH200029%%149
- Resource Relation:
- Other Information: PBD: 1 Mar 2000
- Country of Publication:
- United States
- Language:
- English
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