The influence of flow and concentration on the mass transfer mechanism in chelating liquid/liquid-extractions

Abstract Mass transfer of zinc-ions out of water into dithizone-loaded carbon tetrachloride or chloroform was measured in a stirring cell. By the measurements of the dependence of transfer rate on concentration and forced convection, it can be shown that according to the level of concentration, very distinct processes are limiting the transfer rate: at high zinc-ion concentration, the rate is determined by transport processes due to the influence of forced convection, whereas in the range of low metal-ion concentrations, interfacial reactions are rate determining due to their independence of forced convection. Using the conventional concept of mass transfer resistances, the derived general equation is in agreement with the measured influence of forced convection in the whole range of stirring speeds and concentrations.