Recovering iridium from spent catalyst supports with ALS2
Iridium is one of the rarest and most valuable platinum group metals. Its high melting point, corrosion resistance, and catalytic performance make it useful in demanding industrial applications, including electrochemical systems, chemical processing, pharmaceuticals, and specialty coatings. These same properties, however, make iridium difficult to recover when it is dispersed through a spent catalyst or fixed to a resistant support.
ALS2 offers an acidless route for treating precious-metal-bearing materials. Developed by Ikoi S.p.A. through the ALS2Project, the technology is designed to separate valuable metals from complex secondary resources while reducing dependence on conventional acid-based refining. For spent catalyst supports, this approach can support a more controlled recovery process with a lower chemical burden.
The practical objective is not simply to extract iridium from a single material. A successful process must identify the metal, prepare the support, separate iridium from other valuable elements, manage residues, and produce a recovered fraction suitable for further refining or reuse. ALS2 can become part of that broader circular strategy.
Why spent catalyst supports are difficult to process
Spent catalysts rarely have a uniform composition. Iridium may be present as a coating, finely dispersed active material, an oxide, or part of a mixed-metal formulation. The support can consist of alumina, titania, silica, carbon, ceramic material, or another engineered substrate. Each combination affects particle size, porosity, metal distribution, and separation performance.
The catalyst may also contain residual process chemicals, binders, oils, moisture, and other metals. Depending on its origin, platinum, ruthenium, rhodium, palladium, nickel, cobalt, copper, or iron may be present alongside iridium. These components can influence recovery rates and complicate downstream purification.
Iridium compounds are especially challenging because the metal is chemically stable and can be distributed at relatively low concentrations. A material that appears rich in precious metals may still require accurate sampling and analytical testing before a treatment route is selected. Representative sampling is essential because a small portion of catalyst may contain a disproportionate share of the recoverable metal.
Preparing the feed for acidless separation
Feed preparation determines how effectively the separation stage can access iridium. Spent catalyst supports should be sorted by source and composition before processing. Foreign objects, large debris, packaging, and incompatible materials should be removed. Drying may be required where moisture affects weighing, handling, or process control.
Size reduction can expose active material and improve contact between the feed and the separation system. Milling, screening, or controlled crushing may be appropriate, although the selected method must limit dust generation and avoid contaminating the material. Fine iridium-bearing dust should be managed through suitable containment and collection systems because its value and occupational risks both warrant careful control.
Characterisation should include precious-metal assay, support composition, moisture content, and the presence of hazardous contaminants. Techniques such as X-ray fluorescence, inductively coupled plasma analysis, microscopy, or other laboratory methods can help establish a reliable process baseline. ALS2 treatment conditions should then be confirmed through representative bench-scale trials rather than inferred from a generic catalyst recipe.
How ALS2 can support iridium recovery
ALS2 is based on acidless separation, offering an alternative to process routes that rely heavily on aggressive mineral acids. In a suitable configuration, the technology can help release and separate precious metals from a prepared feed while reducing the need for conventional acidic leaching and associated neutralisation steps.
For iridium-bearing supports, the process concept involves several linked decisions. The support must be opened or conditioned sufficiently for the active metal to become accessible. The valuable fraction then needs to be separated from the bulk support and from coexisting metals. Finally, the iridium-bearing product must be concentrated and characterised so that it can move to an appropriate refining or reuse stage.
The exact treatment sequence depends on the feed. A catalyst containing iridium on an oxide support may behave differently from a carbon-based electrode material or a mixed platinum group metal residue. ALS2 should therefore be viewed as a flexible technology platform rather than a fixed operating recipe. Process development can focus on maximising precious-metal recovery while preserving a manageable residue and limiting secondary waste.
| Process concern | Relevance to iridium-bearing catalysts | ALS2 development focus |
|---|---|---|
| Iridium concentration | Low or uneven loading can make sampling and recovery assessment difficult | Establish representative assays and mass balances |
| Support composition | Alumina, titania, silica, carbon, and ceramics respond differently to treatment | Select conditioning and separation steps for the specific substrate |
| Mixed precious metals | Platinum group metals may require selective downstream separation | Characterise the recovered fraction and define purification needs |
| Catalyst contaminants | Oils, binders, salts, and base metals can affect handling and performance | Include feed preparation and contaminant management |
| Product quality | A high recovery percentage does not guarantee a marketable product | Verify grade, composition, and suitability for further refining |
| Process sustainability | Conventional routes can generate acid consumption and neutralisation residues | Compare chemical use, waste generation, and energy demand |
Measuring performance beyond recovery percentage
Iridium recovery should be evaluated through a complete material balance. The amount entering the process must be compared with the metal retained in the recovered product, intermediate streams, residues, and dust collection systems. This identifies losses that a single headline recovery figure might conceal.
Product grade is equally important. A concentrated iridium fraction may still contain other platinum group metals or support-derived impurities. In some cases, a mixed precious-metal product is appropriate for an external refinery. In others, additional separation may be needed to produce an iridium-rich material for a specific application.
Environmental indicators should be measured alongside technical results. These can include reagent consumption, water demand, energy use, residue volume, emissions controls, and the potential for process-water reuse. An acidless route may reduce certain burdens, but responsible evaluation still requires a site-specific assessment of every input and output.
Safety and operational controls
Replacing mineral acids does not remove the need for rigorous industrial controls. Spent catalysts can contain toxic metals, respirable dust, combustible carbon, or residues from the original manufacturing process. Storage, transfer, crushing, and sampling should be designed around the actual hazard profile of the feed.
Closed handling, local extraction, filtration, spill controls, and appropriate personal protective equipment may be necessary. Operators should receive training in precious-metal-bearing waste, contaminated dust, machinery hazards, and emergency procedures. The process area should also support traceability, since even small losses can have significant economic value when iridium concentrations are high.
Waste classification must be addressed before scale-up. Solid residues, process liquids, filters, and discarded packaging may have different regulatory requirements. ALS2Project’s sustainability focus is relevant here: cleaner separation should be considered as part of an integrated plant design that manages material efficiency, worker protection, and end-of-life residues together.
Integrating the process into a recycling plant
A compact recovery plant needs more than a separation unit. It requires receiving and inspection areas, feed preparation, controlled treatment, solid-liquid or solid-product separation where applicable, product collection, analytical sampling, and secure storage. The plant layout should avoid cross-contamination between high-value fractions and low-value residues.
Iridium recovery can also be integrated with wider WEEE and precious-metal recycling operations. Electronic waste, catalyst materials, and other secondary resources may share preparation, weighing, laboratory, and logistics infrastructure. However, combining streams without adequate characterisation can dilute valuable material or create an unpredictable feed. Separate campaigns and documented batch control are often preferable during initial operation.
Economic assessment should include feed purchasing, transport, labour, maintenance, analytical testing, residue management, and the value of recovered iridium and co-products. Since iridium prices and availability can vary, a robust business case should examine several feed grades and recovery outcomes. The ability to treat difficult or previously uneconomic residues may be as important as the metal yield itself.
Practical recommendations for project development
- Begin with representative sampling and independent assay of iridium, other platinum group metals, support materials, and contaminants.
- Run controlled ALS2 trials on each major catalyst type instead of combining materially different feeds at the start.
- Track complete mass balances for iridium, co-metals, support material, liquids, dust, and final residues.
- Define the required product specification with the intended refinery, manufacturer, or reuse partner before selecting the final separation stages.
- Compare chemical use, energy demand, residue generation, and worker-safety requirements against the existing acid-based route.
The strongest implementation strategy links laboratory evidence to plant decisions. Test work should establish achievable recovery, product quality, operating controls, and residue characteristics. Pilot-scale campaigns can then reveal how feed variability, equipment design, throughput, and maintenance affect the overall result.
For catalyst owners, this creates a route to treat spent material as a secondary resource rather than a disposal problem. For recyclers, it can expand the range of precious-metal-bearing feeds that fit a compact recovery operation. For technology developers, iridium-bearing supports provide a demanding test case for selective, lower-impact separation.
Recovering iridium requires precision from the first sample to the final product. ALS2 provides a foundation for investigating that recovery without relying on a conventional acid-intensive process. Ikoi S.p.A. and the ALS2Project can support the next stage through feed characterisation, process trials, and evaluation of a recovery configuration suited to the material.
Bring your spent catalyst stream into a structured assessment and explore how acidless separation can convert iridium-bearing residues into a controlled, traceable source of precious metals.