To investigate mass transfer into droplets in reactive extraction, a nonint
rusive method for measuring concentration gradients using fluorescent dyes
as sensors was developed. An optical probe is used to focus a laser beam in
to the droplet and to detect the fluorescent light. Scanning the droplet wi
th the probe leads to concentration profiles. The added dyes can either be
indicators to measure gradients of ionic components in the aqueous phase or
be one component of the extraction system. For the description of the syst
em ZnSO4-H2SO4/di(2-ethylhexyl)phosphoric acid in isododecane, experiments
have been carried out in the stagnant as well as in the flowing continuous
phase. To investigate the effects of internal circulation in the droplets,
further mass transfer experiments in a venturi tube have been carried out.
A comparison enables both diffusion and convection inside and outside of a
droplet in a reactive system to be described.