Synergistic extraction of critical metals from the oxalic leachate of spent FCC catalyst

Abstract This study introduces an improved hydrometallurgy process utilizing a synergistic approach to improve metal recovery from secondary sources of critical metals. It provides a more efficient alternative to traditional single‐extractant methods for separating critical metals from spent refinery catalysts. The binary extractant system comprising bis(2‐ethylhexyl)phosphoric acid (D2EHPA/P204) and trioctylamine (Alamine 336) was investigated for its efficacy in the synergistic separation of vanadium (V) from oxalic leachates of spent fluid catalytic cracking (FCC) catalysts, which contain a variety of other metal constituents. Oxalic acid leaching produced competitive results compared to the generally used sulphuric acid, with V and Ni being leached at efficiencies of 93% and 52%, respectively. The synergistic extraction was performed by varying organic to aqueous phases in a screw cap bottle and shaking at 250 rpm at room temperature using Alamine 336 and P204 at the ratio of 1:1. The organic phase contained 20 vol% D2EHPA/Alamine 336 (extractant), 5 vol% TBP (phase modifier), and 75 vol% sulphonated kerosene (diluent). Results showed an extraction efficiency of separating V, Ni, and Mo with high selectivity for V. This confirms that utilizing two types of mixed extractants in equal proportions can enhance the separation efficiency of metal ions through intermolecular interactions, paving the way for tailored solvent formulations for multi‐metal recovery.