Liquid-liquid flow patterns in an impeller-stator spinning disc reactor are qualitatively described. The liquid-liquid flow is studied by contacting water and n-heptane at rotational speeds up to 900 RPM, an axial disc spacing of 1.0 x 10(-3) m, and aqueous volume fractions between 0 and 1 m(AQ)(3) m(L)(-3). The liquid-liquid flow is characterized by six different flow regimes. Each regime is characterized by its continuous liquid phase and the degree of dispersion of the dispersed liquid phase. Regime transitions depend on the formation of boundary layers on the impeller and the stator, the shear stress intensity and the aqueous volume fraction. The impeller is able to selectively pump n-heptane through the reactor, whilst it is intensively mixed with water that remains in the reactor. Combining mixing and separation inane compact reactor is an important step toward a countercurrent operated impeller-based centrifugal extractor. (C) 2013 Elsevier B.V. All rights reserved.