Neutral organophosphorus extractants

NeutralExtractants. Many neutral organophosphorus extractants are available phosphate esters, phosphonate esters, phosphinate esters, and phosphine oxides. The most popular neutral extractant is tributylphosphate (I BP), which reacts with RE elements according to a solvation mechanism ... 

Rao, P.R.V., Kolarik, Z. 1996. Areview of third phase formation in extraction of actinides by neutral organophosphorus extractants. Solvent Extr. Ion Exch. 14 (6) 955-993. 

Smirnov I.V. Anomalous effects in extraction of lanthanides and actinides with bidentate neutral organophosphorus extractants. Role of proton hydrate solvates. Radiochemistry (2007), 49 (1), 44-54. 

The stoichiometry shown in Equation (1) is similar to that followed during extraction of trivalent americium by TBP and other monofunctional neutral organophosphorus extractants. Distribution ratio data plotted in Figure 2 show that DBBP extracts Am(III) more strongly than TBP from HNO3 media. The equilibrium constant for Reaction (1) (at zero ionic strength) is 7.4 compared to a value of only 0.4 for the similar reaction with TBP.(5)... 

Tributyl phosphate (TBP) is the traditional and still most widely used neutral organophosphorus extractant . The light trivalent rare earths can be separated in 10-14 extraction stages. Liquid-liquid extraction is used commercially to separate the lanthanoids. ... 

Farbu, L. McKay, H.A.C. Wain, A.G. Transfer of Metal Nitrates Between Aqueous Nitrate Media and Neutral Organophosphorus Extractants. Proc. Int. Solvent Extr. Conf. Soc. Chem. Ind. London, 1974,2427. 

In general, extraction of trivalent lanthanides/actinides by amine extractants suffer from many of the same limitations as the neutral organophosphorus extractants. In fact, they are more severely limited as metal complexes are extracted as anions, analogously with anion exchange resins. Of primary and secondary amine extractants, only Primene JM-T and n-benzyl heptadecyl amine (BzHp-DA) (Weaver 1974) showed any utility in separating lanthanides. 

Recently there has been a renewed interest in the extraction of actinides with various neutral bifunctional organophosphorus extractants (1-9). An excellent review on this subject has been published recently by Schulz and Navratil (9). Interest in neutral bifunctional organophosphorus extractants stems largely from the fact that these compounds have the ability to extract tri-... 

The chemistry of the extraction of UO + by mixtures of organophosphoric acids and neutral organophosphorus compounds has been the subject of many studies, and the available information has been widely discussed.75 118 127 131 134 There is no general agreement on the mechanism of the synergistic effect, although an addition process such as... 

In contrast to the chemistry of extraction of uranium(VI) by organophosphorus acids, that of uranium(IV) has not been widely studied. It is known,135 however, that the extraction of U4+ by mono(2-ethylhexyl)phosphoric acid (2-ethylhexyl dihydrogen phosphate), for example, exceeds that of U022+ by a factor of 105. This clearly provides the basis for the strong extraction of uranium(IV) from phosphoric acid solutions by extractants containing monoalkyl phosphates. The existence of a synergistic effect in the extraction of uranium(IV) by mixtures of mono(2-ethylhexyl)phosphoric acid and neutral organophosphorus compounds was also reported recently.136... 

Modolo, G., Odoj, R. 1999. Synergistic selective extraction of actinides(IH) over lanthanides from nitric acid using new aromatic diorganyldithiophosphinic acids and neutral organophosphorus compounds. Solvent Extr. Ion Exch. 17 (1) 33-53. 

Recently, another class of neutral organophosphorus compounds, namely, N,N-dialkyl carbamoyl methyl phosphonate (CMP) (59) and its phosphine oxide analog (CMPO) have received attention due to their ability to extract even trivalent actinides from acidic solutions along with the hexa- and tetravalent actinide ions. These biden-tate phosphorus-based neutral extractants are reported to be stronger extractants as compared to TOPO (59-62). Pu(IV) and U(VI) are extracted as per the following extraction equilibria ... 

Blake, C.A. Jr. Baes, C.F. Jr. Brown, K.B. Coleman, C.F. White, J.C. Solvent extraction of uranium and other metals by acidic and neutral organophosphorus compounds, In Peaceful Uses of Atomic Energy. Vol. 28, Basic Chemistry in Nuclear Energy, United Nations, Geneva (1958), pp. 289-298. 

There are various types of organic proton exchangers (34, 35, 38). Diesters of phosphoric acid, (RO)2P = 0(0H), phosphonic acids, R(RO)P = 0(0H), and phos-phinic acids, R2P = 0(0H), where R represents linear or branched alkyl or phenyl substituents, are the most common cation exchangers developed in liquid-liquid extraction for the extraction of trivalent 4/and 5/elements. They were initially developed for the American TALSPEAK and the Japanese DIDPA processes and have recently been introduced in the French DIAMEX-SANEX process. As for previously described NOPCs, these organophosphorus acids present oxygen-donor atoms (hard bases) in their structures and therefore will easily coordinate trivalent lanthanide and actinide cations, but they will not allow complete discrimination of the two families of elements. However, contrary to previously described neutral organophosphorus... 

The OOD(iB)CMPO octyl(phcnyl)-A,A-dw so-butylcarbamoylmethyl phosphine oxide] molecule is a neutral bifunctional organophosphorus extractant selected to recover actinides in the TRUEX process. This extractant is mainly used in mixtures with TBP (added to increase solubility and the loading capacity) in diluents like aliphatic hydrocarbons or chlorinated diluents (CC14 or C12C = CC12) (2,177-180). 

The extraction ability of neutral organophosphorus compounds closely related to the charge density of phosphoryl oxygen (qo) and phosphorus atom(qp). It was found that the distribution ratio of cerium enhanced as the qo and qp values was increased. Meanwhile a linear free energy relationship exists between the 2A.i values and the Kabachnik constant for substituents of phosphorus compounds. As estimated by least squares method, an empirical equation v° =-3.84+0.1682Ai was deduced... 

It is generally agreed that the extracted uranium species is U02(N03)2(TBP)2 in which, in contrast to the species extracted into ether, the extractant molecules are directly coordinated to the metal ion. The extraction of uranium(VI) by neutral organophosphorus compounds increases with the number of C—P bonds (as opposed to C—0—P bonds) and with the increased branching of the substituent alkyl groups, as would be expected from the effect of these changes on the electron-donor properties of the phosphoryl group. The extracted thorium(IV) complex has been formulated as Th(N03)4-2S and as Th(N03)4-3S,2 2 and its composition may depend to some extent on the conditions of extraction. The extraction of thorium (like that of... 

---