Precious metal refining is the process of separating and purifying platinum group metals from mined concentrate or recycled scrap into metal of at least 99.95% purity. Six metals, platinum, palladium, rhodium, ruthenium, iridium and osmium, move through the same chemical separation chain whether they start as mine concentrate or a decanned catalytic converter. The sections below follow that chain from concentration through dissolution, separation, assay and the final refined sponge, plate or grain, then compare the two commercial ways a refiner pays for scrap.
What Is Precious Metal Refining?#
Precious metal refining for the platinum group metals runs through four stages: concentration, smelting, base metal refining and precious metal refining, each stripping away a different set of impurities. Sinisalo and Lundström's 2018 review in Metals traces this chain from milled and floated ore concentrate through electric-furnace smelting and converting to a magnetic PGM alloy fraction, then into a base metal refinery that strips nickel, copper and cobalt, and finally into the precious metal refinery that actually separates platinum from palladium, rhodium and the other platinum group metals. Anyone selling scrap platinum, palladium and rhodium from spent catalytic converters or industrial scrap feeds material into this same four-stage chain, usually entering it partway through rather than at the mine.
This page covers the process itself and is distinct from precious metal refining as a business decision. Refining is also not to be confused with platinum reforming catalysts in petroleum refining, an application that consumes already-refined platinum rather than producing it; that separate use of the word is covered under platinum reforming catalysts in petroleum refining.
The Four-Stage PGM Processing Chain#
The refinery, the last of the four stages, captures 95 to 98% of a metal's refined value for about 2% of the industry's total processing cost, according to Sinisalo and Lundström's PGM value-chain analysis, itself adapted from Ndlovu's earlier work on PGM extraction. Mining, by contrast, surrenders roughly half of a metal's refined value while carrying 67% of total operating cost, because ore grades of only 1 to 5 g/t 4E mean most of the expense sits in moving and crushing rock rather than in final chemistry. The table below sets out the full payability and cost ladder across all four stages.
| Stage | Purchase price paid, as % of refined value | Share of total operating cost |
|---|---|---|
| Mining | 50% | 67% |
| Concentration | 85% | 20% |
| Smelting | 90% | 8% |
| Base metal refining | 90% | 4% |
| Precious metal refining | 95-98% | 2% |
That inverse relationship, the smallest share of cost claiming the largest share of value, is why access to a base metal refinery and precious metal refinery, not access to ore, is the binding constraint on new PGM supply, and why independent scrap sellers without their own refinery capacity settle for a payability discount rather than the full refined-value price.
How Platinum, Palladium and Rhodium Are Separated#
Platinum, palladium, rhodium, ruthenium, iridium and osmium are separated from one another by repeated dissolution, precipitation and, at the largest refiners, solvent extraction or ion exchange. At least eight discrete separations are required to take a mixed PGM solution down to six individually refined metals, and the classical chemistry behind those separations is built on PGM chloride complexes rather than on any single universal solvent.
Dissolution: Why Refiners Use Chlorine and Hydrochloric Acid, Not Aqua Regia#
Industrial PGM refiners dissolve concentrate with chlorine gas sparged into hot hydrochloric acid, not aqua regia, because it is more selective and avoids nitrate contamination downstream. Aqua regia does appear at small scale in secondary refining, but it dissolves only platinum and palladium as chloro-complexes; rhodium, iridium, ruthenium and osmium are largely refractory to it and report instead to the insoluble residue, which is precisely why the classical separation sequence works at all. A refiner that describes aqua regia as dissolving "the platinum group metals" as a class is describing platinum and palladium only.
Precipitation, Solvent Extraction and Ion Exchange#
Three PGM refiners use three different separation technologies: precipitation (the historic Lonmin, now Sibanye-Stillwater, route), solvent extraction (Valterra) and ion exchange (Impala), per Sinisalo and Lundström (2018), citing Crundwell and co-authors as the upstream source for the underlying process comparison. The three flowsheets also run at different feed grades and dissolution conditions, summarized below.
| Refinery | Technology | Feed grade | Dissolution conditions |
|---|---|---|---|
| Sibanye-Stillwater, Brakpan (formerly Lonmin) | Precipitation | 65-75% PGMs | HCl/Cl2, 65°C, atmospheric pressure |
| Valterra Platinum, Rustenburg | Solvent extraction | 30-50% PGMs | HCl/Cl2, 120°C, 4 bar |
| Impala Platinum, Springs | Ion exchange | 60-65% PGMs | HCl/Cl2, 85°C, 1 bar |
The solvent extraction route is also used by Johnson Matthey and Vale. Palladium precipitates with ammonium acetate at Sibanye-Stillwater's Brakpan plant, extracts with a beta-hydroxyl oxime and strips with ammonium hydroxide at Valterra, and exchanges through the resin SuperLig 2 before precipitating with ammonium hydroxide at Impala; the resulting palladium(II) chloride and other chloride intermediates in this circuit sit alongside compounds such as ammonium hexachloroplatinate, the classical platinum precipitation product reduced to sponge later in the chain. Rhodium (Rh, atomic number 45, CAS 7440-16-6) follows a separate precipitation route of its own, covered next.
Ruthenium, Osmium, Rhodium and Iridium: The Volatile and the Last-Out Metals#
Ruthenium and osmium are recovered by exploiting the fact that both form volatile tetroxides; rhodium and iridium are recovered last of all six metals, after ruthenium is distilled off. That distillation step is deliberately engineered as an early, closed, dedicated stage, because the volatile ruthenium tetroxide can cause explosions and the volatile osmium tetroxide is highly toxic. Each of the four remaining metals then follows its own separation route.
- Ruthenium is oxidized to ruthenium tetroxide with sodium chlorate and bromate, distilled off, and separated from osmium in the distillate by precipitating ammonium chlororuthenate.
- Osmium travels with ruthenium as its own volatile tetroxide, then is reduced from ammonium hexachloroosmate to metal powder or sponge under hydrogen.
- Rhodium precipitates through the pentammine complex Rh(NH3)5Cl3, chloropentamminerhodium(III) chloride, then redissolves and reprecipitates with ammonium chloride.
- Iridium precipitates as ammonium hexachloroiridate, (NH4)2IrCl6, or, at Rustenburg, extracts from solution with the organic amine n-iso-tridecyl tridecanamide.
How Refiners Assay PGM Concentrate and Scrap#
Assay is the measurement that every custody transfer in the refining chain is settled on, from concentrate sale to Good Delivery bar issue. Whichever method a refiner uses, fineness is reported by difference, calculated by subtracting the sum of measured impurities from 100%, rather than measured directly for the target metal itself.
The full six-metal PGE suite is best determined by nickel sulphide fire assay; XRF is used for fast, non-destructive screening of scrap but is not accepted as a settlement assay. Classical lead-collection fire assay, the definitive technique for gold, also determines platinum and palladium, but it does not reliably collect rhodium, iridium, ruthenium or osmium. The table below sets the five methods against their role and their practical limit in a PGM refinery.
| Method | Role | Limit |
|---|---|---|
| Lead fire assay | Definitive for gold; also determines platinum and palladium | Does not reliably collect rhodium, iridium, ruthenium or osmium |
| Nickel sulphide (NiS) fire assay | Collects the full six-element PGE suite for settlement-grade assay | Detection limits from 0.07 ppb (iridium) to 0.7 ppb (gold), per Savard et al. (2010) |
| ICP-OES | Concentrate, matte and refined-metal impurity determination | Detection limits roughly one to two orders worse than ICP-MS; severe spectral overlaps among the PGMs |
| ICP-MS | Trace and ultra-trace PGE determination | Severe isobaric interferences; osmium is lost as volatile OsO4 |
| XRF | Rapid, non-destructive screening of scrap and converter feed | Not accepted as a settlement assay for refined metal |
The assay ton, the standard fire-assay sample weight, is fixed at 29.167 grams, the historical basis that lets an assayer read milligrams of button weight directly as ounces per ton of ore. Independent PGM assay coverage of these five methods, including the specific detection limits commercial labs publish, sits on its own page, and the same nickel sulphide method underpins catalytic converter assay once a converter's ceramic substrate has been milled to a homogeneous sample.
Refined Product Forms and Purity Grades#
The standard output of a precious metal refinery is sponge, a porous metal powder produced by hydrogen reduction, at a minimum purity of 99.95% for platinum, palladium, rhodium, iridium and ruthenium. Sponge purity is not measured on the target metal directly; it is what remains once the other platinum group metals, the contaminants nearest and hardest to separate chemically, and base-metal impurities such as lead, iron and copper are subtracted out. The forms and grades a refiner actually sells are set out below.
| Form | Typical purity | Use |
|---|---|---|
| Sponge | Min. 99.95% (Pt, Pd, Rh, Ir, Ru) | Default primary refinery output |
| Powder | ASTM 99.80-99.95% (Rh); 99.80-99.90% (Ir) | Fabrication feed for rhodium, iridium, ruthenium, osmium |
| Plate or ingot | Min. 99.95% | LPPM Good Delivery wholesale trading bars (Pt, Pd) |
| Grain or shot | Typically 99.95%+ | Jewelers and fabricators, priced at a premium to cover conversion |
| Salts and solutions | Specified by metal content (for example Pt 40%) | Catalyst, plating and chemical customers |
Sponge, Powder, Plate and Grain#
Refiners sell PGMs in five primary forms: sponge, powder, plate or ingot, grain or shot, and salts or solutions. Sponge and powder differ mainly in density and particle size rather than in chemistry, plate and ingot are the cast wholesale-trading shapes, grain and shot are free-flowing cast granules sold to fabricators and jewelers, and salts and solutions are specified on metal content rather than on fineness because chemical customers buy contained metal, not a bar.
LPPM Good Delivery: The Wholesale Standard for Platinum and Palladium#
LPPM Good Delivery is the wholesale trading specification for platinum and palladium plate and ingot, requiring a minimum fineness of 99.95% and a weight between 1 and 6 kilograms. Gold and silver Good Delivery is a separate LBMA standard; there is no "LBMA platinum bar," because platinum and palladium sit under the London Platinum and Palladium Market, a sister organization to the LBMA rather than the same body. A refiner applying for LPPM listing must show at least 5 years of operating history, at least 3 years of refining experience, minimum annual production of 500 kg of refined platinum or palladium, and tangible net worth of at least £15 million, then pass an independent spectrographic assay test set by referees whose identities it is never told.
Toll Refining vs Outright Purchase#
Refiners offer scrap sellers two commercial models: outright purchase, where the refiner buys the material and takes the price risk, and toll refining, where the seller keeps title and pays a processing charge. Under outright purchase the refiner strikes a price on assayed contained metal, usually against an agreed reference price, and takes ownership immediately; under toll refining the supplier keeps legal title to the metal throughout and pays a treatment charge plus a refining charge to get refined metal, or a metal-account credit, back. Sellers running material through catalytic converter recycling, from decanning through milling to a homogeneous sample, choose between these two models at the point of settlement, after assay but before payment.
Payability, Refining Charges and Settlement Time#
Typical toll-refining terms pay 96-98% of contained platinum and palladium but only 88-93% of contained rhodium, according to Ecotrade Group, because rhodium is the hardest of the three to refine cleanly. Recohub, a second industry source, gives a narrower but directionally identical gap: 98% for platinum and palladium against 94-95% for rhodium. Both sources agree on the direction even where the exact percentages differ, which is why rhodium scrap settlements need their own dedicated payability discussion separate from platinum and palladium.
| Metal | Payable %, Ecotrade | Payable %, Recohub |
|---|---|---|
| Platinum | 96-98% | 98% |
| Palladium | 96-98% | 98% |
| Rhodium | 88-93% | 94-95% |
On top of the payability discount, Ecotrade documents a fixed treatment charge of US$200 to US$500 per lot plus a variable refining charge of US$5 to US$25 per troy ounce, equal to roughly US$161 to US$805 per kilogram. Small-lot refiners commonly settle platinum, palladium and rhodium within 3 to 12 business days of receipt, according to platinumrefineries.com, once preliminary XRF and final ICP assay results are both approved.
Choosing a Refiner#
An accredited PGM refiner is one that has passed an independent assay test and meets minimum operating-history and net-worth thresholds set by an industry body such as the LPPM. DailyPlatinum's list of accredited PGM refiners covers the full roster worldwide, while sellers holding platinum or palladium specifically can go straight to scrap platinum price or scrap palladium price for metal-specific settlement guidance.
The process covered on this page explains how refined metal is made; the separate question of choosing a PGM refiner, including counterparty risk, settlement speed and lot minimums, is covered on its own page for sellers ready to act.
Accredited PGM Refiners#
Accredited refiner lists exist for platinum and palladium Good Delivery (LPPM) and, uniquely among the minor PGMs, rhodium sponge (LPPM); no exchange contract and no accreditation regime of any kind exists for iridium, ruthenium or osmium. DailyPlatinum profiles individual refiners on their own pages, including Asahi Refining, Johnson Matthey and Rand Refinery, each detailing that company's specific accreditations, product forms and history.
Refining FAQ#
What is precious metal refining?#
Precious metal refining is the industrial process of purifying platinum (Pt, atomic number 78, CAS 7440-06-4) and the other platinum group metals to a saleable metal grade. It runs on the same dissolution, precipitation and separation chemistry described above, whether the feed is mine concentrate or catalytic converter scrap, and ends in sponge, powder, plate or another refined form at 99.95% purity or better.
How is precious metal refining different from recycling?#
Recycling is collecting and preparing scrap; refining is the chemical separation and purification step that follows it, and the two are usually done by different companies. A recycler decans, mills and homogenizes a converter or industrial scrap stream into a sampled, assayable lot; a refiner then dissolves that lot and runs it through the separation chemistry that yields refined platinum, palladium and rhodium.
How much do precious metal refiners make?#
Refiners earn a margin on the 2 to 12 percentage points of contained metal they retain as payability, plus a fixed treatment charge and a per-ounce refining charge. That margin is why the refinery captures a small share of total processing cost yet a large share of total metal value, and small-lot platinum, palladium and rhodium settlements complete in roughly 3 to 12 business days once assay results are approved.
Who is the largest precious metal refinery in the US?#
No sourced, dated ranking of the largest precious metal refinery in the United States exists in DailyPlatinum's records. Several large refiners, including Asahi Refining, Elemetal and United PMR, operate in the US market, and each markets itself with its own scale claims rather than an independently ranked figure.
Can I sell scrap directly to a refinery?#
Most refiners buy scrap outright at a lot minimum of about 1 tonne, though some, such as Ecotrade, accept smaller lots from 500 kilograms under a toll or fast-settlement service. A seller below even that reduced threshold typically goes through an aggregator or a recycler first rather than shipping directly to a refinery's own intake.