The extraction rate of copper from acidic solutions with three types of extractants, i.e. Versatic Acid 10, D2EHPA and LIX65N has been studied both theoretically and experimentally. From the viewpoint of the interfacial ion-exchange reaction, two alternative kinetic equations are proposed under the assumption of Langmuir adsorption isotherm for the organic-interface distribution of extractant for the extraction with Versatic Acid 10. In the development of kinetic equation to describe the extraction with D2EHPA or LIX65N, diffusional or mass transfer resistance effect was taken into account. Experimental results obtained by using a Lewis type cell show that the overall reaction of the Cu-Versatic Acid 10 system is controlled by the formation of the second intermediate complex, $CuR_2HR$, and that the forward extraction rate is proportional to the copper concentration in the aqueous phase, inversely proportional to the hydrogen ion concentration and proportional to $[H_2R_2]^{3/2}/(1 + 4.0\sqrt{[H_2R_2]})$ for Versatic Acid 10. The mass transfer resistance was found to give a significant influence to the overall rate of extraction by D2EHPA and LIX65N. However, the second intermediate complex was formed by the reaction of $CuR_i^+$ with extractant in the organic phase and also the intrinsic chemical reaction was controlled by this step. Thus, the mechanism of extraction with D2EHPA was found very similar to that with Versatic Acid 10 in spite of the different type of extractant used.
Furthermore, the study on the prediction of phase disengagement in a continuous settler from the batch settling data has been carried out. The equation to enable the variation of the dispersion band height with dispersion throughput to be predicted has been derived. The batch decay curve showed the typical sigmoidal decay mode, at the first stage of which free sedimentation of drops controlled the overall rate while at the second stage the drop-drop and drop-interface coalescence did. It was concluded that initial drop size and dispersed phase hold-up had to be taken into account in the interpretation of dispersion behavior in a continuous settler. It could be observed that the dispersion band thickness was able to be expressed in terms of parameters proposed here and also that the dispersion elements experienced the identical life course without regard to the surrounding hydrodynamic condition.
