• Faculty Directory

Henry Freiser

Education and Appointments

• B.S. 1941, City College of New York
  
• M.S. 1942, Duke University
  
• Ph.D. 1944, Duke University
  

Research Interests

Research Summary

Liquid-liquid separation processes such as solvent extraction, partition chromatography etc. continue to play an exciting and fruitful role in formulating strategic ways of dealing with the many increasingly complex separation problems including: analysis of mixtures at both the trace and macro scales, environmental remediation, and metal value recovery from industrial and environmental wastes. Surfactant-based separation systems such as normal or reversed phase micellar chromatography, micelle-enhanced ultrafiltration, micelle-enhanced capillary zone electrophoresis are growing in importance inasmuch as they are more environmentally friendly'.

The charm and the challenge of solvent extraction arise from the dominant role played by chemistry rather than machinery in defining selectivity and efficiency in a given extraction system. Indeed, the study of solvent extraction processes has provided a fertile approach to the illumination of many interesting areas in separation science as well as in the broader fields of solution chemistry such as the thermodynamics, kinetics and mechanism of metal coordination chemistry.

We are able to interpret kinetics of solvent extraction under high speed stirring conditions in terms of several concurrent chemical reactions taking place in the bulk aqueous phase or at the L-L interface. From our experimental determination of the observed pseudo first order rate constant, we can evaluate the second-order rate constants for the bulk aqueous phase for metal complex formation with the neutral ligand, its anion, as well as for the corresponding interfacial rate constants; similar calculations from experimental chelate dissociation reactions result in relevant dissociation rate constants. Control of factors affecting each of these parameters provides many opportunities for developing dramatic improvements in metal ion separations based on extraction. Hence, understanding the fundamental principles governing the values of these parameters promotes our general ability to make significant progress in this and related separation fields. Of particular interest is the investigation of multistage solvent extraction techniques such as CPC which, in addition to having great practical value, also provide a more critical evaluation of the interplay of the various equilibrium and kinetic parameters in determining selectivity and chemical efficiency of separations.

Our research has improved understanding of the significant role played by the interface in both extraction kinetics and equilibrium. We are one of the few research groups systematically investigating the chemistry of liquid-liquid interfaces. A major focus of the research efforts recently have been to elucidate the various factors affecting the single and multistage extraction and separation of metal ions. The primary goal has remained the role of the liquid- liquid interface in these processes with particular attention being paid to the interfacial activities of the ligands and metal complex The ligand families chosen for study have varying molecular properties, i.e., zwitterion equilibrium (8-mercaptoquinoline), keto-enol equilibrium (acylpyrazolones) and significant dimer formation in the organic phase (alkylphosphinic[CYANEX 272] acids & hydroxyoximes[LIXs]), in order to understand the role of such properties on single and multistage extractions. The metal ions(Ni2+, Cu2+, and Ln3+) represented several charge types as well as both coordinatively -saturated and -unsaturated types. Our findings are directly applicable to other relevant L-L phase transfer processes such as HPLC and micellar chromatography.

Novel approaches to the teaching of chemical concepts involving complex and repetitive calculations have been developed with the help of electronic spreadsheets. Integration of the spreadsheet approach has begun to simplify not only the teaching at both undergraduate and graduate levels, but has also been shown to illuminate and enhance the solutions to many research level problems.

Selected Publications

• E. Ma, S. Muralidharan & H. Freiser, "Kinetic Behavior of Lanthanide Extraction With Acidic Phosphorous Ligands", J. Chem. Techn. Biotechn., 1996, 65, 81.

• S. Muralidharan, Y. Surakitbanharn & H. Freiser, "Centrifugal Partition Chromatographic Separations of Platinum Group Metals by Complexation and Iona Pair Formation", Anal. Chem, 1996, 68, 3934.

• H. Freiser, "New Tools for Old Questions in Solvent Extraction Chemistry", Value Adding Through Solvent Extraction, D.C. Shallcross, R. Paimin & M. Prvcic, Editors, University of Melbourne, Melbourne, 1996, pp11-15.

• S. Muralidharan & H. Freiser, "CPC: Tool for Practical Separation of Metals & Fundamental Investigations of Chemical Mechanisms", Value Adding Through Solvent Extraction, D.C. Shallcross, R. Paimin & M. PRVCIC, Editors, University of Melbourne, Melbourne, 1996, pp427-432.

• S. Muralidharan & H. Freiser, "Selective Separations of Metal Ions Via Centrifugal Paratition Chromatography", Recent Progress in Actinides Separation Chemistry, Z. Yoshida, T. Kimura, & Y. Meguro, Editors, World Scientific, Singapore, 1997, pp191-208.

• R.P. Sperline, Y. Song, & H. Freiser, "Temperature Dependent Structures of Adsorbed Sodium Dodecyl Sulfate at the AIO/Water Interface", Langmuir, 1997, 3727-3732.