B. Example 2

Extraction of Rare Earths with PC-88A

PC-88A was examined for the extraction of rare-earth metals, such as Pr, N'd, Sm, Gd
Dy, Er, and Y, respectively A metal chloride solution containing hydrochloric acid was
mixed with a PC-88A solution diluted with n-heptane, and the mixture was shaken vigorously
for 20 minutes at 20℃.
The concentration of HCI in the raffinate at every equilibrium was adjusted by addition
of hydrochloric acid to the aqueous phase prior to the extraction. The condition of this
test was as follows:
PC-88A(extractant): 1 mol/g
Diluent: n-heptane
Initial metal concentration: 0.1 mol/l
Initial HCI concentration: 0 - 0.8 mol/g
Volume ratio of organic phase and aqueous phase: 1 to 1
Temperature: 20 +/- 0.3℃
Contacting time: 20 minutes

Fig. 2 shows the distribution equilibria of rare earths with PC-88A used as an extractant
explaining the correlation between the distribution ratio, log D of rare-earth metals, and
the concentration of HCI in the aqueous phase after the extraction.
Fig. 3 shows the plot or Z-curve based on the distribution ratio of rare earths in the
same concentration of HCL in a raffinate, which is derived from Fig. 2, and plotted in
order of the atomic number of each metal.
The extraction behavior of PC-88A in rare earths is shown in Fig. 2 in comparison
with a conventional extractant D2HIPA which is also shown in Fig. 4. These data
shown in Fig. 2 and 4 were obtained under the same conditions.
All the data shown in these figures show that PC-88A, as compare with D2EHPA can
extract rare earths at lower concentration of mineral acid in an aqueous phase at
extraction equilibrium. Therefore, in the stripping stage of metals from an organic phase,
PC-88A can reduce the amount of mineral acid required for stripping.

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