Some interesting findings can be noted from

As the predominant Golvatinib (E7050) are FeL2+ (see section 3.4), the ternary complex FeLαLβ+ would favour the extraction through a better accommodation of the alkyl chains.
3.3.2. Effect of the foaming properties on the extraction coefficient
Regarding foaming properties, foaming formation and foam stability have been considered qualitatively based on empirical observation during flotation experiments. The influence of foaming performances on metal removal during flotation experiments is more evident for some examples shown in Table 4.
Table 4.
Foaming properties of chelating surfactants–metal diades.CompoundFe(III)Cu(II)[Fe(III)]foam[Fe(III)]liquidFoamingStability[Cu(II)]foam[Cu(II)]liquidFoamingStability1a1.2++1.0++++1b0.9−−0.7−−2b3.2++++++++1.6+++7b1.0+−1.1−−8a2.0++++++1.0++Full-size tableTable optionsView in workspaceDownload as CSV
Some surfactants, as compounds 1b and 7b are showed poor foaming properties in presence of either Fe(III) or Cu(II), whereas 2b displayed very good foam formation whatever the metal to be considered. On the other hand, foaming properties of compound 8a changed from good (for Fe(III)) to poor (for Cu(II)), and this behaviour can be correlated with the differences observed in metal recovery. Most of the time, a good extraction coefficient is correlated to good foaming properties. But formation of foam does not necessarily implicate concentration of the metal in the foam as it is shown for the diad 1a-Cu(II). It seems that the metal-surfactant complex has to be adsorbed at the water-air interface to be extracted efficiently.