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The influence of uranium and plutonium concentration in the distribution coefficient of Zr(IV)<br />

was tested in the conditions in which the extraction is maximum, TBP 30% and HNO 3 5 M.<br />

The obtained results (Table 3 and Figure 6) show that when uranium concentration increases the<br />

Zr(IV) extraction decreases. The value of the distribution coefficient is very low (0.01) when the<br />

organic phase is 100% saturated with uranium (130 g/L). This effect shows that Zr(IV) is not extracted<br />

in the first cycle of co-extraction of U and Pu in the PUREX process.<br />

Figure 6. Influence of U (g/L) concentration on distribution coefficient of Zr(IV),<br />

TBP-dodecane 30%, HNO 3 5 M<br />

Distribution coefficient (D)<br />

1.0E+00<br />

1.0E-01<br />

1.0E-02<br />

0 50 100 150<br />

[U] or (g/L)<br />

Due to the extraction of Zr(IV) by TBP increases as the nitric acid concentration increases<br />

(Figure 5), it is necessary to study the behaviour of Zr(IV) when the nitric acid concentration, in the<br />

aqueous phase is higher (from 5 M to 8 M) than the range considered in the first studies and within the<br />

maximum extraction conditions TBP 30% and Zr(IV) concentration 1.28 g/L.<br />

H + (M)<br />

Aq. phase<br />

Ratio<br />

Or/Aq<br />

Table 3. Distribution coefficient of Zr(IV) by TBP 30%<br />

in dodecane. Initial Zr(IV) concentration 1.28 g/L<br />

H + M<br />

Aq. phase<br />

U g/L<br />

Aq. phase<br />

Steady state<br />

U g/L<br />

Or. phase<br />

Zr(IV) g/L<br />

Aq. phase<br />

Zr(IV) g/L<br />

Or. phase<br />

Distribution<br />

coefficient<br />

(D)<br />

3.08 3 1.86 0 0 1.31 0.0256 0.0196<br />

3.08 2 2.13 0 0 1.29 0.0395 0.0307<br />

3.08 1 2.49 0 0 1.25 0.0626 0.0203<br />

4.07 3 2.55 0 0 1.14 0.0580 0.0510<br />

4.07 2 2.92 0 0 1.16 0.0951 0.0823<br />

5.06 3 3.20 0 0 0.993 0.119 0.120<br />

4.07 1 3.48 0 0 1.14 0.163 0.144<br />

5.06 2 3.70 0 0 0.935 0.192 0.205<br />

5.06 1 4.39 0 0 0.966 0.362 0.375<br />

5.50 1 4.70 0 0 0.827 0.452 0.547<br />

4.89 1 4.68 < 0.1 52 1.12 0.206 0.183<br />

4.97 1 4.82 < 0.1 97 1.26 0.0762 0.0605<br />

4.88 1 4.88 23 128 1.34 0.0248 0.0185<br />

4.91 1 4.88 76 135 1.34 0.0159 0.0119<br />

4.99 1 4.90 118 138 1.33 0.0150 0.0113<br />

4.89 1 4.90 168 137 1.36 0.0140 0.0103<br />

622

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