Separation and speciation of cobalt, nickel, rhodium, and iridium in non-aqueous solvent extraction systems

Promovendus/a: Vincent Cool

Promotor(en): Prof. dr. Koen Binnemans, Prof. dr. ir. Thomas Van Gerven

The transition to a climate-neutral and environmentally friendly economy depends on reliable access to high-purity metals. These metals are essential for clean technologies such as batteries, renewable energy systems, and advanced electronics. To obtain them in pure form, industry relies on separation techniques that can isolate specific metals from complex mixtures.

One of the most important techniques used is solvent extraction. This process separates metals by allowing them to move between two liquids that do not mix, similar to how oil separates from water. By carefully choosing the liquids, scientists can selectively extract and purify valuable metals.

This PhD project focused on improving solvent extraction systems for critical metals, specifically cobalt, nickel, rhodium, and iridium. The research began by studying how cobalt and nickel can be separated efficiently. To better understand and with the goal of improving their separation, the interaction at the molecular level in the solvent extraction system where investigated.

Later work focused on rhodium, a rare and highly valuable metal used in catalytic converters and clean energy technologies. Using advanced techniques such as nuclear magnetic resonance, its behaviour in non-aqueous solution were revealed and its behaviour towards extraction rationalized. Subsequently, the separation of iridium and rhodium was investigated in depth and several notable behaviours explained.

Finally, the commercial product Cyphos IL 101, often used in studies for as an extractant, was investigated in depth revealing large quantities of impurities in the commercial product. The effect on solvent extraction studies were critically assessed and a purification method was proposed.

Overall, this work provides new insights into how critical metals can be separated more efficiently and selectively. These advances support the goal of producing critical metals in a more sustainable way by investigating two relevant systems and investigating their molecular behaviour in those separation systems. Moreover, this work also warns other researcher for the inconsistencies that can be obtained when using Cyphos IL 101 for solvent extraction purposes.