Hydrodynamics and mass transfer in segmented flow small channel contactors for uranium extraction

Abstract

In this work, the extraction of U(VI) by tributyl phosphate (TBP) is studied in small channels of different sizes, operated in segmented flow. The variables analysed include the channel diameter (1–4 mm I.D.), mixture velocity (1.06 - 4.24 cm s−1), volume fraction of the continuous phase (between 0.200 and 0.500), and concentration of extractant (TBP 30% v/v in kerosene and TBP 100%). The hydrodynamic characteristics of the flow, such as plug and slug lengths, specific interfacial area, and dispersed phase holdup, were obtained experimentally using high-speed imaging, while the pressure drop was measured with a differential pressure transducer. These parameters were correlated to the studied variables. The concentration of uranium in the aqueous phase was measured with UV-vis spectroscopy, and the mass transfer coefficients were compared with the predictions of a numerical model of segmented flow developed in Comsol Multiphysics, with good agreement.