Optimization of a solvent extraction route for the recovery of Mo from petroleum refinery spent catalyst using Cyphos IL 102

In this study, trihexyl(tetradecyl)phosphonium bromide (Cyphos IL 102) diluted in toluene has been explored for the first time as an organic phase for the extraction, separation, and recovery of Mo(VI) from hydrochloric acid medium. The study focuses on the recovery of metals from spent catalyst, a hazardous solid waste. The metal recovered in the form of metal oxide has further applications in various fields. The widespread use of solvent extraction for metal recovery can be assigned to its economic feasibility and the built-in concentration step thereby providing an appropriate commercial technology for the beneficiation of low-grade sources of metals and recovery of substances from complex matrices. The influence of fundamental extraction variables on Mo(VI) extraction and loading and recycling capacity of the extractant has also been evaluated. Binary separations of Mo(VI) from other associated metal ions have been achieved with high separation factors. Optimized conditions have been employed for the extraction and recovery of Mo(VI) from petroleum refinery spent catalyst leach liquor containing Mo-1141.18 ppm, Al-2158.42 ppm, Ni-270.39 ppm, and Co-61.82 ppm. Quantitative and selective extraction (98.4%) of Mo from spent petroleum refinery catalyst was achieved in two stages at A:O = 3:2 using 2.0 × 10⁻² mol/L Cyphos IL 102. Almost 99% Mo was stripped with 1.0 mol/L (NH₄)₂CO₃ in two stages at O:A = 1:1. MoO₃, obtained from the stripped solution by thermal decomposition was characterized by XRD, FESEM, and EDX techniques. Economical and environmental aspect of present work is supported by high loading capacity and reusability of extractant.