Metal extraction by alkyl substituted diphosphonic acids. Part 4, P,P{sup1}-DI(2-ethylhexyl) butanediphosphonic acid.
As part of an ongoing investigation of the properties of dialkyl substituted diphosphonic acids as solvent extraction reagents for metal cations, we have studied the extraction of alkaline earth cations, Fe(III) and representative actinides (Am(III), U(VI) and Th(IV)) at tracer-level concentration by o-xylene solutions of P,P'-di(2-ethylhexyl) butanediphosphonic acid, H{sub 2}DEH[BuDP]. The extractant and acid dependencies of these metal ions exhibited significant differences from those of the previously investigated analogous extractants in which the two phosphonate groups are separated by a methylene or an ethylene bridge. The aggregation of H{sub 2}DEH[BuDP] was investigated in toluene at 25 C by vapor pressure osmometry. H{sub 2}DEH[BuDP] was found to exist predominantly as a trimeric species in the 0.1-0.005 molal concentration range. Osmometric measurements and infrared spectra indicate that Ca(II) is extracted into H{sub 2}DEH[BuDP] solutions with little disruption of the structure of the extractant. Iron(III) causes significant deprotonation of the ligand and dramatically changes the apparent aggregation number. A comparison of the extraction of Ca(II), Am(III) and Fe(III) by H{sub 2}DEH[BuDP] with data obtained using bis(2-ethylhexyl) phosphoric acid (HDEHP) or 2-ethylhexyl 2-ethylhexylphosphonic acid (HEH[EHP]) as the extractant indicates that H{sub 2}DEH[BuDP] has characteristics similar to these monofunctional analogs. Infrared spectra of the Ca(II) and Fe(III) salts of H{sub 2}DEH[BuDP] show a shift of both v{sub asym}(POO-) and v{sub sym}(POO-) to lower frequencies relative to their values in the sodium salt. This indicates a symmetrical interaction between the metal ion and the phosphonate groups through chelate and/or bridging interactions.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- ER
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 938112
- Report Number(s):
- ANL/CHM/JA-27136; SEIEDB; TRN: US200906%%410
- Journal Information:
- Solvent Extr. Ion Exch., Vol. 16, Issue 2 ; 1998; ISSN 0736-6299
- Country of Publication:
- United States
- Language:
- ENGLISH
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