Di-2-ethylhexyl phosphoric acid HDEHP

Dapex [Di-alkylphosphoric acid extraction] A process for the solvent extraction of uranium from sulfuric acid solutions using di-(2-ethylhexyl) phosphoric acid (HDEHP). The HDEHP is dissolved in kerosene containing 4 percent of tributyl phosphate. The uranium is stripped from the organic phase by aqueous sodium carbonate and precipitated as uranyl peroxide (yellow cake). The process was no longer in use in 1988. See also Amex. 

Acidic alkyl esters of phosphoric acid, of which dibutyl-phosphoric acid (HDBP) and di(2-ethylhexyl) phosphoric acid (HDEHP) are typical,... 

A mixture of well-known extractants, di-(2-ethylhexyl)phosphoric acid (HDEHP) and CMPO, in n-paraffin was used for the study of combined extraction of different actinides (americium, plutonium, and uranium) and lanthanides (cerium and europium) and their separation from fission products (cesium, strontium, ruthenium, and zirconium).54 Combined extraction of MAs and lanthanides was studied together with group separation of MAs from lanthanides by selective stripping with a solution of diethylenetriaminepentaacetic acid (DTPA), formic acid, and hydrazine hydrate. This solution strips only MAs, leaving lanthanides in the organic phase. Subsequently, the lanthanides are stripped using a mixture of DTPA and sodium carbonate. 

Di(2-ethylhexyl) phosphoric acid (HDEHP) is an extractant molecule used for An(III)/Ln(III) separation. Used in TALSPEAK-type processes in a mixture with TBP, or in the DIAMEX-SANEX process in a mixture with a malonamide (154-157), it has also been proposed, in a mixture with TBP, to remove strontium from PUREX acid waste solution in the Hanford B plant (158). Therefore, numerous studies have focussed on the radiolytic degradation of HDEHP and its effects on the extraction of Sr(II), lanthanides(III), and actinides(III) (10, 158-163). 

Nd, Tb, Tm (286. 287) Di(2-ethylhexyl) phosphoric acid [HDEHP] in cyclohexane none glycine 3-mercapto-propionic acid < = 2.53b oT 2.85 oT 2.35... 

Extractive Reagent. The extractive reagent is commercial-grade di(2-ethylhexyl) phosphoric acid (HDEHP). Various lots of material obtained from Mobil, from Stauffer, and from Union Carbide, have all appeared equally usable. The commercial material typically contains 1-1.5% of the monoester (which is di-acidic) and a small amount of inert material, probably unreacted 2-ethylhexanol and pyrophosphoric acids. The HDEHP generally titrates about 98% (2.8 M) and is used without treatment other than dilution. 

The aqueous strip solution will form directly the feed solution of the Am, Cm/RE countercurrent separation step, to be performed according to the operating conditions of the TALSPEAK process (15). The presence of a complexing agent like DTPA will prevent the extraction of Am and Cm whereas the RE will be more easily extracted by di(2-ethylhexyl)phosphoric acid (HDEHP) in n-dodecane (pH = 3). 

Chelates of metal ions with alkyl- and arylphosphoric and thiophosphoric acids can be extracted into chloroform and other solvents [25,26]. Such systems enable one to separate, by means of extraction procedures, many metals from strongly acid solutions. Examples of such reagents are di-(2-ethylhexyl)phosphoric acid (HDEHP) and di-n-butyldithiophosphoric acid (formulae 1.9 and 1.10). HDEHP is a viscous liquid (density 0.98), slightly soluble in water, but readily soluble in benzene, hexane, and MIBK. 

Commercial solgel (emulsion) scintillators used were Aquasol II and Biofluor (New England Nuclear), Beckman GP (Beckman Instr.), and PCS (Amersham Corp.). Solvents used were p-xylene (ICN spectral grade) and toluene (Packard "Puresolv") and the scintillators were p-bis-Co-methylstyryl)-benzene (bis-MSB from Eastman Kodak) and 2-(4 -t-butylphenyl)-5-(4"-biphenylyl)-1,3,4-oxadiazole (butyl-PBD from ICN). The chelating agent was di-2-ethylhexyl phosphoric acid (HDEHP) obtained from K K Laboratories and used without further purification. Radionuclide solutions of known radioactivity concentration were supplied by other workers in the NBS Radioactivity Group (Mann, 1979). 

The conventional separation scheme is to leach the primary ore or concentrates and use the resulting solution containing the rare earth mixtures as the feedstock to the solvent extraction plant. Solvent extraction of the rare earth mixture in the leached solution separates them into bulk concentrates of light (La, Ce, Pr, Nd, etc.), middle (Sm, Eu, Gd, etc.) and heavy (Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) rare earths. A typical solvent extraction of rare earths in a HCl medium is with di-2-ethylhexyl phosphoric acid, HDEHP, in a kerosene diluent. The individual rare earth is separated from the bulk light, middle, and heavy rare earth solution mixtures by additional individual rare earth solvent extraction streams. The number of stages for solvent extraction cascades or batteries increases with the increase in purity of each individual rare earth produced. Further purification... 

The primary industrial extractants in use for the separation of rare earths by solvent extraction are di-2-ethylhexyl phosphoric acid (HDEHP), tributyl phosphate (TBP), carboxylic acids, and amines. Many other extractants have been examined and reported in the literature in the search for improving the extraction and separation of individual rare earths. This chapter discusses several of these extractants for their interesting chemistry and potential future development, in addition to the available industrial extractants now in use and proposed for the separation of rare earths. 

Rameback, H., and Skalberg, M. (1998). Waste and fuel cycle applications—Separation of neptunium, plutonium, americium and curium from uranium with di-(2-ethylhexyl)-phosphoric acid (HDEHP) for radiometric and ICP-MS analysis. J. Radioanal. Nucl. Chem. 235(1-2), 229. 

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