The transient extraction of zinc sulfate with D2EHPA (di-2-ethylhexyl phosphoric acid) in a section of a Kuhni column operated with total recirculation of liquid phases was modeled using the back-mixing and the forward-mixing approaches. The mathematical developments for both models as well as their numerical solutions are given in detail. Operating parameters were calculated using recommended correlations available in the literature and simulations were confronted with experimental data. Both models revealed to describe column operation adequately under evaluated conditions. In addition, as back-mixing and forward-mixing approaches are particularly equivalent in very stirred conditions, the former approach seems to be more advantageous to describe practical situations due to its simplicity in comparison to the later approach. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.