The leach liquor (10 g/L Mo, 27 g/L Al, 2.0 g/L Ni) obtained from the baking and leaching process of spent catalyst was treated using solvent extraction to recover Mo(VI) by LIX 84-I. The influence of various basic variables such as pH, concentration of LIX 84-I, different stripping reagents, phase ratio and diluents, was examined. Using 40% LIX 84-I with the aqueous solution of pH 0.5 and a phase ratio O:A = 1:1, a two-stage McCabe-Thiele plot was constructed which showed 99.9% of Mo extraction with no co-extraction of Ni and Al. This was confirmed by a 6-cycle counter current simulation (CCS) study. The stripping of Mo(VI) was quantitative using a mixture of 1 M NH4OH + 1 M (NH4)(2)CO3. The counter current simulation condition (three stages, phase ratio O:A = 5:1) obtained from the stripping isotherm study further attributes to the enrichment (5 times) of Mo(VI) concentration in the strip solution. The stable complex MoO2R2 formed during extraction which supports the cation exchange mechanism, was confirmed by IR spectral analysis. (C) 2010 Elsevier B.V. All rights reserved.