THE RADIOCHEMISTRY OF PLUTONIUM - Sciencemadness.org

In this equation, HA represents any monoacidic ester of phosphoric acid.
This equation has been shown to be correct for di- and trivalent ions, but tetra-
valent ions in general show a more complex behavior. The extracted complex is some-
times further solvated in the organic phase and nitrate, chloride, and even perchlorate
complexes may be involved in the extraction reaction, depending on the specific aqueous
conditions employed. Thus, no general reaction can be proposed which will account
for all of the observed behavior.
Kosyakov et al. 238 studied the extraction of Pu(IV) and other actinides from
nitric acid solutions by several dialkylphosphoric acids. Their results for Pu(IV) are
shown in Fig. 11. The distribution coefficient increases as the length of the normal
a
4.0
: 3.5
J
3.0
2.5
\
1. Dlbutyl phosphoric acid (HDBP)
2. Dloctylphosphoric acid (HOOP)
3. Dinonylphogpharlc acid (HDNP)
4. Dldecylphosphorlc acid (HDDP)
5. Di-2-ethylhexyl phosphoric (HDEHP)
I I
) o I.0
LOG HN03 CONCENTRATION (~)
Fig. 11. Extraction of Pu(IV) by dialkylphosphoric acids (0.5 ~ in isooctane) from
HN03 solutions’. 238
alkyl chain is increased from butyl to decyl, but that for 2-ethylhexyl is greater than
any of these. The non-linearity of the slope of these extraction curves is ascribed to
nitrate completing in the extracted species. The acid dependency was determined by
extraction into HDEHP from HC 104 solutions at a constant ionic strength of 1.0 and
found to be inverse first power in the region from approximately 0.05 to 1.0 ~ H+.
The Pu is probably extracted as a hydrolyzed species at low acid concentrations. The
distribution coefficient was found to vary directly as the square of the HDEHP con-
centration.
The distribution coefficients for the extraction of Am(III), Pu(IV ), Np(V ) and
U(VI) into HDEHP from nitric acid are ahown in Fig. 12. The discontinuity y in the NP(V )
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