Kinetics of stripping of VO–D2EHPA complex from toluene phase by aqueous sulphate–acetate solution. Comparison of Lewis and Hahn cells

The kinetics of stripping or backward extraction of VO2+ from VOA2 complex existing in di-2-ethylhexylphosphoric acid–toluene phase to the aqueous phase by acidic solutions containing 0.50 M sulphate and 0.25 M acetate has been measured by Lewis and Hahn cell techniques using the pseudo mass transfer coefficient (q) and the flux (F) methods, respectively. In the case of the Lewis cell technique, the stripping mass transfer coefficient (kb) obtained from the (q) method of data treatment has been converted to the (kb) values obtainable from the (F) method of data treatment, and this value has been justified experimentally. In addition, for the Hahn cell, the reverse conversion has been done and justified. The (kb) value obtained from the Lewis cell measurements is about 50 times higher than the Hahn cell (kb) value. The reason for this variation has been discussed. The low activation energy suggests that the diffusion of the species VOA+ to the aqueous film of the interface is the rate controlling. For both cells, the ratio of (kf) to (kb) equals to (Kex) of 10−1.9 obtained from the distribution study.