Selective Extraction of Molybdenum from the spent HDS catalysts using Cyanex272 extractant

Selective extraction of Mo from the spent HDS (Hydrodesulfurization) catalysts was studied using Cyanex272 extractant. The required experiments were designed by RSM (Response Surface Methodology) method according to CCD (Central Composition Design), and four independent parameters were examined, including Cyanex272 concentration, H+ concentration of leach solution, temperature, and Mo concentration in the leach solution. A quadratic equation was derived for the prediction of Mo recovery with R2 equal to 0.98, which verified this equation for fitting the experimental results. The value of Mo recovery in different conditions showed that the effect of the leach solution acidity is insignificant at a low concentration of Cyanex272. The optimum value for Cyanex272 concentration, H+ concentration of leach solution, temperature, and Mo concentration was obtained at 0.27 M, 3.4 M, 30 ˚C, and 279.74 mg/L, respectively. The Mo recovery was 99.05% in these conditions, which had a 0.74 error from the software predicted value.