Continuous Extraction of Dioxouranium VI in Small Channels

The extraction experiments were carried out in circular channels with different internal diameters, i.e. 0.5, 1, and 2 mm, whilst the lengths varied from 10 to 31.5 cm. Experiments were performed for total volumetric flow rates (Qmix) varying from 7 to 340 cm h and flow rate ratios (Qil/Qhnos) varying from 0.25 to 1. At all experimental conditions plug flow was established with the aqueous phase (HNO3) flowing as non-continuous (dispersed) plugs within the TBP/IL phase (continuous) which was in contact with the channel wall. Extraction experiments were repeated several times with an overall mean relative error of the measurements 

The dioxouranium(Vl) extraction (%E) from the nitric acid solutions into TBP/IL (30 % v/v) in the 0.5 mm ID microchannel is plotted in Fig. 6.4. The total volumetric flow rate was Qnux = 14-6 cm h and the ratio of IL to aqueous phase was 1. The length of the microchannel was 10 cm. As it can be seen, with increasing nitric acid concentration the extraction of dioxouranium(VI) decreases until 1 M and then increases again. The highest conversion ( 64 %) is achieved at the lowest nitric acid concentration, i.e. [HN03]aq,init = 0.01 M. 

6 Liquid-Liquid Mass Transfer Using Ionic Liquids 

A comparison between the three TBP/ionic liquid (30 %, v/v) systems at different nitric acid concentrations is illustrated in Fig. 6.5. As it can be seen, the %E of dioxouranium(VI) follows the same trend as the distribution coefficients (Fig. 6.3) for each TBP/ionic liquid system. However, different trends are found though for the extraction efficiency (%Eeff). 

5 Dioxouranium(VI) extraction (%E) and extraction efficiency (%Ee as a function of initial nitric acid concentration into diffiacnt TBP/IL (30 % v/v) systems in a 10 cm capillary. The lines are used just to aid interpretation 

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