About 40% of the titanium was extracted in the pH range from 5.5to 7.0.
The effect of contact time of the two phases on the extraction efficiency of Al and Cu was examined by changing the flow rates of the water and organic phase. The result is shown in Fig. 3. In this experiment, the pH of the sample solution was adjusted to 7.0 to compare the extraction behavior of Al with Cu. The flow rates of both phases were changed from 20 to 50_lmin−1, which corresponded to the contact time from 0.45 to 0.18 s. As the flow rate increased (the contact time was shorter), the extraction efficiency of Al gradually decreased, on the contrary, that of Cu remained constant at about 90%. Because the complexing rate of Cu with 8-HQ is very fast, there was no difference in the extraction efficiency in the examined time scale (∼0.5 s).