The separation and recovery of Mo and Co from the synthetic chloride leach liquors of petroleum refining catalyst has been investigated by employing TOPO and Alamine 308 as extractants. The synthetic leach liquor contained Mo 394 mg/L, Al 1782 mg/L. Co 119 mg/L in 3 M HCl. The separation of Mo from Co and Al was achieved with 0.05 M TOPO in Escaid 110 and complete stripping of Mo was attained with combination of 0.1 M NH4OH and 0.05 M (NH4)(2)CO3. After separation of molybdenum, cobalt can be selectively extracted by Alamine 308 from Mo free raffinate after adjusting the concentration of chloride ion to 5 M by adding AlCl3. The back-extraction of cobalt was obtained easily from loaded Alamine 308 with acidified water (pH = 1.0). McCabe-Thiele diagrams were constructed from the extraction and stripping experiments of each element (Mo and Co). From the batch simulation of the counter-current extraction and stripping experiments, it was confirmed that Mo and Co recovery of 99.4% and 99.1% respectively was obtained from the synthetic leach liquor of the chloride solutions. Finally a hydrometallurgical process flow sheet was developed. (C) 2012 Elsevier B.V. All rights reserved.