limited by diffusion into the bulk liquid phase, and the extraction is
enhanced by promoting turbulence within the solvent (Veggi et al.,
2013). The yield decreased markedly when the agitation speed is
increased from 200 to 250 rpm. The reasons for this decrease are
not clear, however it is likely that the hydrodynamic conditions
changed above 200 rpm, i.e. by the creation of vortices and regions
of laminar flow rather than turbulence. This hypothesis is also
supported by the non-linear behaviour with solvent loading shown
in Fig. 5.