In this report the extraction of V(V) and Cr(VI) from a synthetic feed solution and real leaching solution of the chromium-bearing vanadium slag (V-Cr slag) using primary amine LK-N21 was studied. Detailed fundamental research work was conducted to investigate the primary amine extracting V(V) and Cr(VI). The mechanism and the difference between the two metals of extraction were studied and the experimental results were compared with previously published data. The optimum technological parameters for the separation of two metals were determined including: pH value in feed solution, phase ratio, mixing time, as well as others. The results showed that primary amine LK-N21 can extract V(V) selectively by hydrogen bonding association. Cr(VI) competed V(V) to combine with the primary amine, and the concentration of Cr(VI) decided the percentage extraction of V(V) and Cr(VI). Primary amine LK-N21 extracted more than 90% of V(V) which resulted in over 90% of Cr(VI) left in the leaching solution of the V-Cr slag in the optimal conditions. Based on the results of experiments, V(V) and Cr(VI) can be separated with a high degree of selectivity. (C) 2014 Published by Elsevier B.V.