Lanthanides with their strong photoluminescence and magnetic properties are important to many industrial applications.In the field of spent nuclear fuel reprocessing,lanthanides,such as Europium and Yttrium,have been used to regulate nuclear reactors as control rods because they absorb neutrons(Ku?era et al.,2007),and the recovery of the trivalent element is a key step in high-level waste management.The extraction behaviour of Eu(Ⅲ)from nitric acid solutions was studied in intensified small scale separation units using an ionic liquid solution(0.2M n-octyl(phenyl)-N,N-diisobutylcarbamoylmethyphosphine oxide(CMPO)-1.2M Tributylphosphate)(TBP)/1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide([C4min][NTf2])as the extraction phase.The interfacial area in plug flow and the velocity profiles within the plugs were studied with high speed imaging and bright field micro Particle Image Velocimetry(μPIV).Mass transfer coefficients were higher in small channel,where the recirculation within the lugs and interfacial area are large,compared to larger channel for the same mixture velocities and phase flow rates.Within the same channel,mass transfer coefficient decreased with increasing residence time indicating that significant mass transfer takes place at the channel inlet where the two phases come into contact.In order to investigate the significance of channel inlet in mass transfer,Laser induced fluorescence was also conducted by tracking the interphase transfer behaviour of Eu(Ⅲ)between aqueous and ionic liquid phase.The observed Eu(Ⅲ)concentration profile matches well with the extraction study.