Extraction - Principles of Chemical Separations with Environmental Applications - page 154

Aqueous stream
from wash
V =50

Aqueous
feed
V =100

Extract
V = 300

( N )

( N + 1)

Extraction
section

(1) (0)

Solvent
V = 300

Aqueous
product
V =150
Figure 5.32 Plutonium-recovery extraction process for Problem 5.8.

10 − 3 gmol NaOH/L
and the drag-out with the product wire is at pH 9.0. Two countercurrent rinse stages
are used. Fresh water, pH 7.0, is fed to the rinse operation. The wash-water-to-drag-
out ratio is 16.2 (the drag-out and wash-water flowrates may be assumed constant).
A process change will double the NaOH concentration in the neutralization bath and
will produce drag-out at the same flowrate as before, but containing 5

drag-out solution from the neutralization bath contains 2.78 ×

10 − 3 gmol
NaOH/L. If the same wash-to-drag-out ratio is used as before, how many wash stages
would be needed to achieve:
(a) the same percentage reduction of the NaOH concentration in the drag-out as at
present;
(b) the same NaOH concentration in the drag-out with the product wire as at present?
5.7 An extraction process for separating actinide elements (principally uranium, U, and
plutonium, Pu) from fission products in an aqueous solution of spent fuel rods is
illustrated in Figure 5.31. The extraction solvent is 30% tributyl phosphate (TBP) in
kerosene. The most extractable of the fission products are zirconium, niobium and
ruthenium. Zirconium, Zr, is used herein to represent the fission products. Determine
the number of stages required in the wash section and in the extraction section.
Determine the percentage of the Pu in the feed which is recovered in the extract
product. V denotes the relative volumetric flowrate.
5.8 Consider the plutonium-recovery extraction process shown in Figure 5.32. Determine
the additional number of stages required for each ten-fold reduction in plutonium
concentration, C ,instream 1 (for conditions of high plutonium recovery, i.e., C (1)

. 55 ×

+

C ( N 1)). The plutonium distribution coefficient, K Pu ,is5(ratio of concentration in

organic phase to concentration in aqueous phase). V denotes the relative volumetric
flowrate.