LAUSR

Abstract Mass transfer behavior of extracting La(III), from chloride solution containing complexing agent lactic acid, with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (EHEHPA or P507) has been studied using a rectangular cross-section micro-channel. A liquid-liquid slug flow pattern of dispersed phase (aqueous phase) and continuous phase (organic phase) is observed. The slug size and specific interfacial area are determined using the photographic snapshot method, and affected by flow rate indistinctivly, whistle influenced by channel width significantly. Volumetric mass transfer coefficient (kLa) increases with the increasing of flow rate, but shows a decreasing trend with the increasing of channel width and length, and vary between 0.003 and 0.263 s− 1 which are higher than that obtained in the extraction system using separation funnel (0.03–0.15 s− 1), and at least an order of magnitude higher than that observed in conventional large-scale extractors such as mixer settlers and centrifugal extractor. The information on the mass transfer behavior of liquid-liquid extraction of La(III) in the microchannel can provide reference value for microfluidic extraction of rare earths.