Membrane concentration test, description

As organic and aqueous phases are macroscopically separated by the membrane, HFM offer several hydrodynamic advantages over other contactors, such as the absence of flooding and entrainment, or the reduction of feed consumption (160, 161). The flowsheets tested in HFM were similar to those developed for centrifugal contactor tests. Computer codes based on equilibrium (162) and kinetics data, diffusion coefficients (in both phases and in the membrane pores), and a hydrodynamic description of the module, were established to calculate transient and steady-state effluent concentrations. It was demonstrated that, by selecting appropriate flow rates (as mass transfer is mainly controlled by diffusion), very high DFs (DI A 11 = 20,000 and DFrm = 830) could be achieved. Am(III) and Cm(III) back-extraction efficiency was up to 99.87%. 

A number of studies have been reported in the literature for the development and testing of mathematical descriptions for solute transport through hquid membranes. The existing models can be broadly classified into (i) the membrane film model in which the entire resistance to mass transfer is assumed to be concentrated in a membrane film of constant thickness and (ii) distributed resistance model which considers the mass transfer resistance to be distributed throughout the emulsion drop. 

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