Case Study
Sustainable Recovery of Critical Minerals: Distillation for Palladium Recycling from Homogeneous Catalyst Systems
Abstract
Distillation is a critical technique for recovering precious metals from homogeneous catalysts in industries such as pharmaceuticals and agrochemicals.
This process separates valuable metal residues from complex mixtures through the following stages:
Solvent Removal: Distillation involves heating the mixture to evaporate lower boiling point solvents, leaving behind a concentrate or tar that contains the precious metals.
Special Conditions: Unlike standard solvent separations, recovering precious metals requires specialised design, operating conditions and additives to optimise recovery.
Concentration: The process concentrates the precious metal residues, making it easier to handle and refine them further.
Situation
Client presented a 100-500ppm Palladium solution containing Water, Ethyl Acetate, Toluene and THF < 5 wt% with particulates present. The feed was variable between IBC’s and contained precipitates from cooled distillation heavies.
Screening Process
Understanding the chemistry of the material using the flow diagram we identified that PGM concentration via distillation was the most effective pre-treatment route:
PGM concentration:
A batch distillation system is used to separate volatile species, creating a non-flammable concentrate that contains valuable metals from low viscosity material.
For materials with high viscosity and solid content, a wiped film evaporator is used. This system involves scraping mechanisms that maintain a thin film of material, improving heat transfer and preventing solid buildup. It efficiently distills off volatile components, collecting enriched solvent waste and directing the remaining heavier materials to collection tanks for refinement.
Both methods elevate the flashpoint of heavies such that they are no longer flammable and therefore non-hazardous.
In this case study as the distillation progressed over a 12 hour period and the colour of the distillation concentrate or residue gets darker and more viscous.
Next Steps
Following distillation, the residue represented ~6 wt% of received material and was then in a suitable form for further processing by Advanced Thermal Treatment at Mastermelt’s Buxton facility.
Whereby a rich Palladium ash was produced which was milled, homogenised, sampled and sub-sampled resulting in a representative sample of the bulk ready for analysis.
Conclusion
In this case study, the client initially deemed £500K worth of palladium as non-recoverable waste due to the perceived complexity of processing. Through Mastermelt’s intervention, £450K of this value was successfully recovered, circumventing additional disposal costs.
Consequently, 16 kg of palladium, classified as a “critical mineral,” was reintroduced into the supply chain, supporting resource conservation and market availability.
To enhance sustainability in processing homogeneous catalysts, distillation plays a critical role by enabling solvent recycling. Pure solvents can be reclaimed and reused as valuable commodity chemicals, reducing the need for new raw materials. Meanwhile, lower-grade solvents, unsuitable for high-purity applications, can be repurposed as fuel, minimizing waste and contributing to overall energy efficiency. This dual-purpose recycling approach not only conserves resources but also supports a circular economy in chemical processes.
To find out more: Homogeneous catalysts Systems Precious Metal Recovery
