A combined theoretical and experimental approach was undertaken to quantitatively determine the influence of variable solute distribution coefficients on the impurity distribution along multi-pass purification by zone refining. A numerical model capable of predicting the solute redistribution at any stage of a multi-pass zone refining process was used for providing simulations. Experimental work on zone refining was carried out with aluminum samples. Axial impurities profiles have been experimentally determined for eight molten-zone passes. These results have been compared with the theoretical predictions by adopting both variable and constant k values. The comparisons have shown that differences of up to two orders of magnitude can be observed between the simulated profiles and that the variable k approach has matched the experimental impurities profiles. With increasing number of zone passes, the efficiency of purification was shown to be strongly underestimated when a constant value for k is considered. The influence of such approach on the maximum purification is achieved by the zone refining technique, i.e., the ultimate impurity distribution has also been analyzed. (c) 2008 Elsevier B.V. All rights reserved.