Ruthenium Refining Process

— Ruthenium Refining Process: From Feed to 99.9% Ru Sponge

The ruthenium refining process is a hydrometallurgical sequence that opens ruthenium-bearing feed with an alkali fusion or a chloride medium, separates ruthenium as volatile ruthenium tetroxide (RuO₄) from osmium and the other platinum group metals, absorbs the tetroxide into hydrochloric acid as chlororuthenic acid, precipitates ammonium chlororuthenate, and reduces that salt under hydrogen to metallic ruthenium sponge of 99.9% purity or higher. YuSai Machinery engineers the complete line — alkali fusion, oxidative distillation, multi-stage absorption, precipitation, hydrogen reduction and off-gas control — around your actual feed assay.
Final purity: Ru ≥ 99.9% (3N) as standard; 99.95% (3N5) and 99.98% selectable, with 99.99% (4N) achievable through additional distillation passes.
Ruthenium recovery: ≥ 95% direct from the distillation circuit; ≥ 98% overall.

Product Overview

Ruthenium is the most awkward of the platinum group metals to put into solution, and that single fact shapes the entire refining route. The metal and its dioxide are not attacked by cold or hot mineral acids, aqua regia included. What does dissolve them is an alkaline oxidising medium — hypochlorite solution, an alkali melt, or a peroxide fusion. A workable ruthenium refining process therefore begins by converting the feed into a form that alkali can open, rather than by reaching for acid.

The YuSai process starts from a ruthenium-bearing feed — spent ammonia-synthesis catalyst, an oxidation or chlor-alkali catalyst, coated anode scrap, hard disk platters, plating sludge or a smelting concentrate — and opens with assay and route selection, because the appropriate upstream treatment differs sharply between a carbon-supported catalyst that must be incinerated first and a ruthenium-rich residue that can go straight to fusion. Carbon-supported and organic-bearing feeds are incinerated to an ash. Alloy, platter and target scrap is granulated and ground. Aqua regia-insoluble residues and osmium–iridium–ruthenium ores are alloyed with zinc and aluminium at 500–800 °C and quenched, so that the matrix can be dissolved away in hydrochloric or sulphuric acid and an active precious metal powder is left behind; the fine powder then goes to a tube furnace, where osmium is volatilised first as osmium tetroxide and ruthenium is retained as weakly volatile ruthenium dioxide.

The prepared feed is fused with a sodium peroxide and sodium hydroxide mixture at 400–700 °C until the melt is fluid, and the cooled melt is leached with water at 40–60 °C to bring ruthenium into solution as ruthenate. Where the feed is already an alkali-soluble hydroxide or a ruthenate liquor, the fusion is replaced by direct selective leaching: the material is slurried in sodium hydroxide solution and oxidised with sodium hypochlorite at a controlled redox potential of about 200 mV and 80 °C. This step is sharply selective. Ruthenium is oxidised to the hexavalent state and passes into solution, while most base metals are barely soluble in alkali and palladium, rhodium and iridium resist the reaction altogether, so the leach liquor leaves with a low impurity load before any distillation has been attempted. Adding methanol or ethanol to the leachate then reduces ruthenium back to the tetravalent state, which is insoluble in alkali, and it separates as ruthenium hydroxide.

Purified ruthenium hydroxide is dissolved in hydrochloric acid, adjusted to about pH 1 and charged to the distillation kettle. The kettle is heated to 50–90 °C and 20% sodium hydroxide solution and 20% sodium bromate or sodium chlorate solution are added — or chlorine gas is introduced against a sodium hydroxide charge — until ruthenium tetroxide leaves the liquor as a vapour. This is the heart of the process and the reason it can reach high purity: ruthenium tetroxide is volatile well below the boiling point of water, melting at 25.4 °C and boiling at 40 °C, and nothing else in the platinum group set follows it at that temperature. Distillation continues until a thiourea-soaked cotton swab held at the gas outlet no longer turns blue, which is the practical endpoint test for residual tetroxide vapour.

Because osmium tetroxide is also volatile, the vapour train is designed for both metals. The gas is passed through a water pre-scrubber that knocks back salt spray, through four stages of 4–6 mol/L hydrochloric acid containing 0.5–3% ethanol, where volatile ruthenium is absorbed as chlororuthenic acid, and finally through 20% sodium hydroxide solution containing 4% ethanol, where osmium tetroxide is absorbed and held for its own recovery circuit. Any osmium that still reports to the ruthenium absorption liquor is re-oxidised with hydrogen peroxide or nitric acid and volatilised off as a second, small osmium tetroxide stream, so the ruthenium liquor is osmium-free before precipitation. The absorption liquor is then concentrated to a ruthenium concentration of 30–50 g/L, ammonium chloride is added, and ruthenium comes down as deep-red ammonium chlororuthenate crystals.

The salt is washed with ethanol rather than water, because ammonium chlororuthenate is partly water-soluble and a water wash would simply dissolve the product back. Dried salt is charged to a hydrogen reduction furnace, dried gently in the hydrogen stream, then taken slowly through 400–500 °C, where the ammonium salt decomposes, and on up to 750–950 °C, where the metal is formed. The powder is cooled under argon or nitrogen, discharged below 100 °C and moved straight into a sealed desiccator, because finely divided ruthenium oxidises and can be lost from an open dish. Barren liquors and wash waters are not discarded: distillation residue is returned to fusion, and residual ruthenium in the process liquors is captured on ion-exchange resin and polished by cementation. All stages that evolve chlorine, osmium tetroxide or acid mist are enclosed and vented to the scrubber train, so the process meets emission limits without shifting the problem to the wastewater plant.

Product Core Selling Points

One continuous route from residue to certified metal. Alkali fusion, oxidative distillation, absorption, precipitation, hydrogen reduction and finishing are delivered as a single engineered line, not as isolated vessels to be integrated on site.
Separation by volatility, which no other platinum group metal offers. Ruthenium is the only platinum group metal that can be driven out of solution as a volatile tetroxide, so distillation separates it from platinum, palladium, rhodium and iridium in one operation instead of a chain of selective precipitations.
Two independent opening routes. Where the feed is a hydroxide or an alkali-soluble residue, ruthenium is leached selectively with alkaline sodium hypochlorite and reduced out with alcohol; where the feed is an insoluble metal, alloy or ore concentrate, it is fused and distilled. The flowsheet selects the route from the assay.
Osmium treated as a first-class problem. Osmium tetroxide co-volatilises with ruthenium tetroxide, so the line carries a dedicated osmium scavenging stage and an alkali absorption circuit that recovers osmium as a saleable by-product instead of letting it contaminate the ruthenium.
Distillation hazards engineered out, not written into a procedure. Ruthenium tetroxide is unstable above ambient temperature and disproportionates to ruthenium dioxide with a rapid release of oxygen, so oxidant dosing, vapour-phase temperature and absorption are interlocked rather than left to operator judgement.
Ethanol-stabilised absorption. The hydrochloric acid absorption medium carries 0.5–3% ethanol, which holds the absorbed ruthenium as stable chlororuthenic acid and suppresses re-oxidation to the volatile tetroxide.
Low residual losses. Distillation residue is re-fused and re-distilled, and barren liquors are polished by ion-exchange resin and cementation, so ruthenium that does not volatilise in the first pass is captured rather than written off.
Purpose-built for small batches. Reaction in vessels inside a fume hood, filtration in dedicated filter units and vacuum liquid transfer match the low single-batch tonnages typical of platinum group metal refining.

Key Facts

Final purity: Ru ≥ 99.9% (3N) as standard; 99.95% (3N5) and 99.98% selectable, with 99.99% (4N) achievable through additional distillation passes.
Ruthenium recovery: ≥ 95% direct from the distillation circuit; ≥ 98% overall, supported by residue retreatment and liquor scavenging.
Residual ruthenium in effluent: below 1 ppm after resin and cementation polishing.
Accepted feed: spent Ru/C and Ru/MgO ammonia-synthesis catalysts, RuO₂-based oxidation and chlor-alkali catalysts, coated titanium anode scrap, hard disk drive platters and sputtering residues, chip resistors, PEM electrolyser and fuel cell catalyst scrap, nickel and copper anode slimes, Os–Ir–Ru ores and aqua regia-insoluble residues, plating baths and sludges.
Product forms: ruthenium sponge or powder, ammonium chlororuthenate crystals, ruthenium trichloride RuCl₃·nH₂O, ruthenium nitrosyl nitrate and ruthenium nitrate solution, sodium or potassium ruthenate liquor, and melted bar or sputtering-target grade powder.
Configuration: capacity, footprint, power and utilities are engineered to your feed assay and target throughput rather than fixed catalogue numbers.

Application Scenarios

Secondary precious metal refineries. Stand-alone platinum group metal refineries that buy mixed ruthenium-bearing residues and need a repeatable route from assay to sellable metal, salt or solution.
Spent catalyst recyclers. Plants handling ammonia-synthesis catalysts on carbon or magnesium oxide supports, and oxidation, hydrogenation and fine-chemical catalysts where ruthenium is the dominant value metal.
Hard disk drive and electronics recyclers. Operations recovering ruthenium from plating media, platter scrap and thin-film residues generated in magnetic media and semiconductor manufacturing.
Chlor-alkali and electrochemical plant operators. Replacement and end-of-life coated titanium anodes, whose ruthenium dioxide coating is a high-grade secondary source that is usually exported as scrap today.
Green hydrogen and fuel cell operators. Membrane electrode assemblies, catalyst-coated membranes and stack residues from proton exchange membrane electrolysers and fuel cells, where ruthenium dioxide is the oxygen-evolution catalyst.
Copper and nickel electrorefining plants. Anode slime circuits where ruthenium reports with the other platinum group metals and is currently exported as a slime for toll refining.
Chemical and petrochemical producers. In-house catalyst recovery for caprolactam, ammonia and hydrodesulphurisation service, where the recovered metal is wanted back as a chloride or nitrate solution rather than as metal.
Catalyst, anode and plating manufacturers. Off-specification catalyst, coating and plating material returned to a usable intermediate within the same plant.
Jewellery, pen nib and electrical contact fabricators. Ruthenium-hardened platinum and palladium alloy scrap and ruthenium-bearing contact waste.
Assay and research laboratories. Pilot-scale lines that validate a flowsheet on a few kilograms before it is scaled to a production refinery.

Applicable Raw Materials

Each feed below enters the line at the point its composition requires. Feeds carrying carbon, organics or a refractory support are first incinerated, mechanically liberated or fused to a concentrate, which is why the route sheets differ even though the fusion-to-sponge core is common. Output is stated for each feed.

Spent Ru/C ammonia-synthesis catalyst with barium and potassium promoters. The most common secondary ruthenium feed; promoters are removed by an acid leach before the residue is incinerated and fused. Output: ruthenium sponge 99.9%; barium sulphate and potassium chloride as by-products.
Spent Ru/MgO ammonia-synthesis catalyst with barium and caesium promoters. Promoters are dissolved in dilute nitric acid and the magnesia support is selectively dissolved in hot ammonia solution. Output: ruthenium sponge 99.9%; magnesium solution returned for support manufacture.
Spent Ru/Al₂O₃ and silica-supported hydrogenation catalysts. Alumina- or silica-supported catalysts from petrochemical and fine-chemical service, processed by support dissolution or full fusion depending on grade. Output: ruthenium sponge; aluminium-bearing residue.
Spent ruthenium dioxide catalysts. Oxidation, hydrogenation–oxidation, hydrogen sulphide removal and chlor-alkali catalysts in which ruthenium is present as the dioxide on a sparingly acid-soluble support. Output: ruthenium sponge or RuCl₃ solution.
Coated titanium anode scrap. End-of-life dimensionally stable anodes and anode offcuts carrying a ruthenium dioxide coating on a titanium substrate. Output: ruthenium concentrate; titanium substrate returned to the titanium circuit.
Hard disk drive platters and sputtering residue. Magnetic recording layer scrap, target offcuts and chamber deposits from ruthenium sputtering. Output: ruthenium sponge; nickel- and cobalt-bearing residue.
Chip resistors and ruthenium-bearing electrical contacts. Thick-film resistor paste scrap, contact tips and resistor trimmings. Output: ruthenium concentrate returned to fusion.
Ruthenium plating baths, sludges and rinse waters. Spent plating electrolytes and drag-out rinse streams, concentrated by ion-exchange adsorption or precipitation before refining. Output: ruthenium concentrate; polished effluent below 1 ppm Ru.
Proton exchange membrane electrolyser and fuel cell catalyst scrap. Membrane electrode assemblies and catalyst-coated membranes from electrolyser and fuel cell service, incinerated to ash before fusion. Output: ruthenium sponge; iridium where co-present.
Nickel and copper anode slime and precious metal concentrate. Smelter intermediates in which ruthenium reports with platinum, palladium, rhodium, iridium and gold. Output: ruthenium sponge; platinum group metal salts routed to their own lines.
Osmium–iridium–ruthenium ores and aqua regia-insoluble residues. Native alloy and refractory residue that no acid will open, alloyed and quenched before pyrogenic osmium removal. Output: ruthenium sponge; osmium and iridium products.
Ruthenium process residues and spent absorption liquors. Catalyst manufacturing residues, spent precipitation filtrates and out-of-specification intermediate liquors. Output: ruthenium sponge; reclaimed process solution.

Finished Products

The line is configured to deliver the product form the buyer or the downstream user requires, from a saleable intermediate liquor to certified metal.

Ruthenium sponge and powder. The primary output, assaying Ru ≥ 99.9% (3N) as standard, with 99.95% (3N5), 99.98% and 99.99% (4N) available through additional distillation passes; supplied as free-flowing sponge or powder under inert gas. Output: certified ruthenium sponge or powder with certificate of analysis.
Ammonium chlororuthenate (NH₄)₂RuCl₆. The deep-red to black crystalline intermediate salt, available as a saleable product for buyers who prefer to run their own reduction. Output: ethanol-washed, dried crystalline salt.
Ruthenium trichloride RuCl₃·nH₂O. The most widely traded ruthenium compound, produced directly by absorbing the distilled tetroxide into hydrochloric acid and concentrating the absorption liquor, avoiding a metal-making step altogether. Output: reagent-grade RuCl₃, sealed against moisture.
Ruthenium nitrosyl nitrate and ruthenium nitrate solution. Produced where the downstream application calls for a nitrate or nitrosyl medium rather than a chloride one, by absorbing the tetroxide in nitric acid. Output: filtered, concentration-adjusted ruthenium solution.
Sodium or potassium ruthenate liquor. The hexavalent alkaline leach or absorption liquor, supplied as a process intermediate for plants that carry out their own precipitation. Output: filtered, assayed ruthenate solution.
Ruthenium dioxide. Produced by controlled thermal decomposition of ruthenium trichloride where the downstream use is an anode coating or an electrocatalyst rather than metal. Output: coating-grade RuO₂ powder.
Melted ruthenium bar and shot. Ruthenium sponge consolidated by vacuum melting under protective atmosphere where the buyer requires a metallic form for alloying. Output: ruthenium bar, button or shot with certificate of analysis.
Osmium by-product. Osmium tetroxide captured in the alkali absorption circuit is reduced and worked up as osmium powder or osmium salt. Output: osmium product routed to its own finishing line.
Purified effluent and recovered salts. Barren liquor after resin and cementation polishing, and neutralised effluent that meets discharge limits. Output: compliant effluent below 1 ppm Ru.

Ruthenium Refining Process Flow

The nine stages below form the standard ruthenium refining flowsheet. Pretreatment — incineration of a carbon-supported catalyst, zinc–aluminium alloying of an aqua regia-insoluble residue, or granulation of target scrap — is added upstream only where the feed demands it. Engineering setpoints such as temperature, redox potential, acidity, oxidant dose and absorption stage count are fixed during process design against your own assay.

Ruthenium refining process flow — feed to certified Ru sponge of 99.9% and above.

Steps 1 — Feed Preparation and Route Selection. Incoming material is weighed, sampled by riffling and split for analysis by XRF and ICP-OES, supported by spectrophotometric determination where the matrix interferes. The assay fixes the ruthenium head grade, the osmium content, the base metal load and the presence of refractory phases, and it decides which of the two opening routes the batch takes: direct alkaline leaching for a hydroxide, ruthenate liquor or alkali-soluble residue, or fusion and distillation for a metal, alloy, ore or aqua regia-insoluble residue. Batches containing osmium are flagged at this point, because osmium routing has to be set before any oxidant is added. Each batch receives a route sheet and an internal lot number so that the mass balance can be closed at the end of the campaign. Reagent and utility input: sample splitting equipment, XRF and ICP-OES analysis. Output: refining route sheet and batch record.

Steps 2 — Feed Activation and Osmium Removal. The feed is brought into a reactive form and osmium is taken out of the circuit first. Carbon-supported and organic-bearing material is incinerated or roasted to an ash. Alloy, platter and target scrap is granulated and ground so that dissolution proceeds at a predictable rate. Aqua regia-insoluble residues and osmium-bearing ores are alloyed with zinc and aluminium at 500–800 °C in a graphite crucible, water-quenched, then treated with hydrochloric or sulphuric acid at 30–90 °C to dissolve the alloy matrix and leave an active precious metal powder. That powder is dried in a quartz boat and heated to 300–800 °C in a tube furnace with an air stream, which volatilises osmium as osmium tetroxide into a sodium hydroxide absorption train while ruthenium is retained as weakly volatile ruthenium dioxide. Removing osmium here, before ruthenium distillation, is what keeps the two tetroxides from being separated the hard way further downstream. Reagent and utility input: muffle and tube furnaces, zinc and aluminium, hydrochloric or sulphuric acid, air stream, alkali absorption solution. Output: activated ruthenium-bearing residue; osmium absorption liquor.

Steps 3 — Alkali Fusion and Ruthenate Leaching. Ruthenium metal and its dioxide resist every mineral acid, aqua regia included, so the activated residue is opened in alkali. It is mixed with sodium peroxide and sodium hydroxide and fused at 400–700 °C until the charge is fluid, then poured, cooled and leached with water at a liquid-to-solid ratio of 10–15 to 1 at 40–60 °C, with settling before filtration. Ruthenium passes into solution as ruthenate; the silica, alumina and refractory phases of the feed are left in the leach residue. Where the feed is an alkali-soluble hydroxide or a ruthenate liquor, this stage is replaced by direct selective leaching: the material is slurried in 12% sodium hydroxide solution and oxidised with sodium hypochlorite with the redox potential held at about 200 mV at 80 °C. Ruthenium is oxidised to the hexavalent state and dissolves, while most base metals are barely soluble in alkali and palladium, rhodium and iridium resist the reaction, so the liquor is already partially purified before distillation begins. Adding methanol or ethanol to the clarified leachate reduces ruthenium to the tetravalent state, which is insoluble in alkali, and it separates as ruthenium hydroxide. Reagent and utility input: sodium peroxide and sodium hydroxide, fusion furnace, water leach, sodium hypochlorite, redox control, methanol or ethanol. Output: ruthenate leach liquor or ruthenium hydroxide; leach residue to residue retreatment.

Ru + 3Cl₂ + 8NaOH → Na₂RuO₄ + 6NaCl + 4H₂O

Steps 4 — Oxidative Distillation of Ruthenium Tetroxide. Ruthenium hydroxide or ruthenate liquor is dissolved or slurried, adjusted to about pH 1 with dilute alkali, and charged to the distillation kettle. The kettle is heated to 50–90 °C and 20% sodium hydroxide solution and 20% sodium bromate or sodium chlorate solution are dosed in, or chlorine gas is introduced against the alkali charge, until ruthenium is oxidised to the octavalent state and leaves the liquor as ruthenium tetroxide vapour. Distillation continues until a thiourea-soaked cotton swab held at the gas outlet no longer turns blue. The oxidant addition rate is governed by the vapour-phase condition rather than by a fixed recipe, because ruthenium tetroxide is markedly less thermally stable than osmium tetroxide: a vapour phase that is too concentrated or too hot, or a contact with a reducing agent, drives rapid disproportionation to ruthenium dioxide with a sudden release of oxygen. The flowsheet therefore keeps the tetroxide dilute and moving, and the dosing interlocks hold the addition rate at the slow end. Reagent and utility input: jacketed distillation kettle, sodium hydroxide and sodium bromate or sodium chlorate solution, or chlorine gas, controlled dosing, thiourea endpoint detection. Output: ruthenium tetroxide vapour; distillation residue to residue retreatment.

2RuO₄ → 2RuO₂ + 2O₂

Steps 5 — Chlororuthenic Acid Absorption. Volatile ruthenium tetroxide is carried out of the kettle into a negative-pressure absorption train. The gas passes first through a water pre-scrubber that knocks back salt spray and protects the absorption stages from contamination, then through four stages of 4–6 mol/L hydrochloric acid containing 0.5–3% ethanol, where the tetroxide is reduced and held as chlororuthenic acid. Ethanol in the absorption medium is not optional: it stabilises the absorbed ruthenium in the tetravalent state and suppresses re-oxidation back to the volatile tetroxide, which would otherwise leak through the train. The final stage is 20% sodium hydroxide solution containing 4% ethanol, which absorbs osmium tetroxide for its own recovery circuit. Absorption efficiency and stage count are set during design from the vapour load and the required tail-gas residual, and the tail gas is monitored before it reaches atmosphere. Reagent and utility input: water pre-scrubber, 4–6 mol/L hydrochloric acid with 0.5–3% ethanol, 20% sodium hydroxide with 4% ethanol, vacuum absorption system. Output: chlororuthenic acid H₂RuCl₆ absorption liquor; osmium absorption liquor.

2RuO₄ + 20HCl → 2H₂RuCl₆ + 8H₂O + 4Cl₂

Steps 6 — Osmium Scavenging and Liquor Conditioning. The absorption liquor is conditioned before precipitation. It is first held at 75–90 °C with a small ethanol addition to drive off dissolved free chlorine, which holds ruthenium as stable chlororuthenic acid rather than as a mixed-valence mixture. Hydrogen peroxide or nitric acid is then added to re-oxidise any osmium that carried through the train, which volatilises as osmium tetroxide and is taken to alkali absorption, so the ruthenium liquor is osmium-free before ammonium chloride is introduced. Where the impurity load of the feed was high, the liquor is instead taken through a reprecipitation and re-distillation cycle: it is concentrated, redissolved, brought to about pH 1 and distilled again, or neutralised with sodium hydroxide to precipitate ruthenium hydroxide which is slurried in pure water and re-distilled against a sulphuric acid addition. Whatever route is taken, the oxidant is added slowly, for the same vapour-phase reason as in the distillation stage. The purified liquor is finally concentrated to a ruthenium concentration of 30–50 g/L, because precipitation yield falls as the liquor is diluted. Reagent and utility input: ethanol, hydrogen peroxide or nitric acid, sodium hydroxide or sulphuric acid for the reprecipitation route, purification still, low-heat evaporation. Output: osmium-free, concentrated chlororuthenic acid liquor; osmium tetroxide to alkali absorption.

Steps 7 — Ammonium Chlororuthenate Precipitation. Ammonium chloride is added to the concentrated, osmium-free chlororuthenic acid liquor. Ruthenium comes out as deep-red to black crystalline ammonium chlororuthenate, (NH₄)₂RuCl₆, and the batch is cooled to drive the crystallisation towards completion before filtration on a vacuum system. The filter cake is washed with ethanol rather than water, because ammonium chlororuthenate is partly water-soluble and a water wash would dissolve part of the product back into the mother liquor. The mother liquor is sampled for residual ruthenium before it leaves the stage, and the salt is dried gently ahead of reduction. Because base metals and the remaining platinum group metals do not form an insoluble ammonium salt under these conditions, they stay in the mother liquor and leave with it. Reagent and utility input: ammonium chloride, chilled crystallisation, vacuum filtration, ethanol wash. Output: deep-red (NH₄)₂RuCl₆ crystals; ruthenium-depleted mother liquor to scavenging.

H₂RuCl₆ + 2NH₄Cl → (NH₄)₂RuCl₆↓ + 2HCl

Steps 8 — Hydrogen Reduction to Ruthenium Sponge. The purified salt is reduced to metal in a tube furnace under a hydrogen stream. The salt is dried gently at low temperature in the hydrogen flow, then taken slowly through 400–500 °C, where the ammonium salt decomposes and the last of the ammonium chloride and hydrogen chloride leaves as vapour, and on up to 750–950 °C, where the metal is formed and consolidated as sponge. The furnace is then cooled to about 400 °C in hydrogen, switched to argon or nitrogen, and discharged below 100 °C. Gradual heating matters at both steps: a temperature spike carries values away with the smoke. The discharged powder is moved immediately into a sealed desiccator, because finely divided ruthenium oxidises in air and an open dish loses both grade and metal. Where the buyer wants a metallic form rather than powder, the sponge is melted under protective atmosphere and cast; where the required product is a compound, this stage is replaced by direct conversion to ruthenium trichloride, nitrosyl nitrate or dioxide. Reagent and utility input: hydrogen reduction furnace, argon or nitrogen for cooling, sealed desiccator, optional vacuum melting furnace. Output: ruthenium sponge or powder; off-gas to scrubber.

3(NH₄)₂RuCl₆ → 3Ru + 16HCl + 2NH₄Cl + 2N₂

Steps 9 — Assay Verification, Passivation and Emission Control. Every filtrate, wash water and final product is assayed. Barren liquors still hold ruthenium at parts-per-million levels, so they pass through an ion-exchange resin train followed by cementation of the polish filtrate, and the cementation residue returns to fusion rather than leaving the plant. Distillation and leach residues that still contain ruthenium go back to the fusion stage for a second distillation pass, which is where the difference between a single-pass recovery and the overall figure is recovered. The sponge is sampled and analysed by ICP-OES against a certified reference material, and the batch is released only when the certificate of analysis confirms the specified purity. Off-gas from fusion, distillation, precipitation and reduction passes through the chlorine and acid-mist scrubbing train with an alkali wash and demister, and the emission log is retained with the batch record. Finished powder is packed under inert gas in sealed containers, and ruthenium trichloride is sealed against moisture, because the salt is hygroscopic and the powder oxidises. Reagent and utility input: ICP-OES, XRF and spectrophotometry; resin and cementation reagents; inert-gas packing station. Output: certificate of analysis; compliance and emission record; polished effluent below 1 ppm Ru.

Product Structure (Main Equipment)

The line is assembled from the following equipment groups. Materials of construction are selected per stream — quartz and borosilicate glass for the high-temperature distillation and reduction duty, PTFE and PFA for chlorine and acid service, polypropylene and PVDF for atmospheric alkaline and acid streams, and titanium where chloride and oxidant are combined.

Feed preparation and pretreatment

Weighing, sampling and splitting station. Riffling and sample division equipment that produces a representative assay sample from each incoming lot before any material enters the process.
Incineration and roasting unit. A controlled-temperature furnace that burns off carbon and organic content from spent ammonia-synthesis and fine-chemical catalysts and converts the residue to a leachable ash. Output: ruthenium-bearing ash for fusion.
Zinc–aluminium alloying set. Graphite crucible, muffle furnace and quench station for alloying aqua regia-insoluble residues and osmium-bearing ores so that the matrix can be dissolved away and an active precious metal powder released.
Crushing, granulation and grinding set. Size reduction for platter, target, anode and alloy scrap so that dissolution and fusion proceed at a predictable rate.
High-temperature tube furnace and quartz boats. Air-stream furnace for pyrogenic osmium removal, with quartz boats and gas-tight end fittings sized to the batch.

Fusion, leaching and distillation train

Alkali fusion furnace and crucibles. A furnace rated for sustained operation at 400–700 °C with corrosion-resistant crucibles, reagent dosing for the sodium peroxide and sodium hydroxide charge, and a quench and melt-discharge station.
Water leach and settling system. Agitated leach vessels with temperature control, followed by settling tanks sized for the 12–16 hour clarification that a fused melt requires before filtration.
Selective alkaline leach reactor. Reactor for the sodium hydroxide and sodium hypochlorite route, fitted with pH and redox potential measurement, temperature control to 80 °C and metered hypochlorite dosing.
Reduction and crystallising tanks. Ambient vessels for the methanol or ethanol addition that reduces ruthenate to ruthenium hydroxide, and chilled tanks for crystallisation ahead of filtration.
Oxidative distillation kettle. Jacketed, gas-tight still with reflux control, temperature control across 50–90 °C, ports for metered oxidant addition, and a vapour take-off sized to keep the tetroxide moving rather than accumulating.
Chlorine dosing and oxidant feed system. Metered chlorine introduction or sodium bromate and sodium chlorate solution dosing, with interlocks that stop the addition on vapour-phase condition, temperature and pressure rather than on a fixed volume.
Tetroxide detection station. Thiourea-soaked swab port at the gas outlet for the colour endpoint test that terminates the distillation.

Absorption, purification and recovery

Multi-stage hydrochloric acid absorption train. Four-stage train of 4–6 mol/L hydrochloric acid with 0.5–3% ethanol, built in glass or PTFE, with stage-to-stage monitoring and the ability to add stages where the vapour load requires it.
Alkali absorption circuit for osmium. 20% sodium hydroxide solution with 4% ethanol in a dedicated train that captures osmium tetroxide separately from ruthenium, sized so the two products never share a receiver.
Water pre-scrubber and salt-splash trap. Knock-back stage that protects the absorption stages from salt spray and particulate carry-over.
Vacuum generator and liquid-ring pump set. Provides the negative pressure that drives the absorption train and the vacuum lift for liquid transfer, avoiding pumped hot chloride liquors through mechanical seals.
Purification still. Second-stage distillation kettle for the reprecipitation and re-distillation cycle used on high-impurity feeds, with the same dosing interlocks as the main kettle.
Vacuum filter plate and filter trolley. Mobile filtration units with diaphragm vacuum pumps that separate salts and cakes while keeping wash volumes low, so the mother liquor is not diluted.
Candle filter. Pressure filtration with reverse gas pulse for the cake release duty, used where high solids loading makes plate filtration slow and labour-intensive.
Ion-exchange resin columns. Resin train that scavenges residual ruthenium from barren liquors and wash waters before they reach neutralisation.
Cementation tank. Iron or zinc cementation vessel for the final polish of the resin effluent; the cementation residue is returned to fusion.

Reduction, finishing and control systems

Hydrogen reduction furnace and gas train. Tube furnace rated to 950 °C with hydrogen, argon and nitrogen supply, flow control, and the stepped heating and controlled cooling sequence that the ammonium salt decomposition requires.
Glove box and sealed desiccator station. Inert-atmosphere handling for ruthenium powder, because finely divided ruthenium oxidises in air and open handling loses both grade and metal.
Vacuum induction melting furnace and casting set. Melts ruthenium sponge under protective atmosphere into bars, buttons or shot where the buyer requires metallic form rather than powder.
Inert-gas sieving, blending and packing station. Powder classification and packing under a nitrogen or argon blanket into sealed containers, with a moisture barrier for ruthenium trichloride.
PLC control and HMI panel. Supervises fusion temperature, distillation temperature, redox potential, absorption stage condition, dosing and furnace sequences, logs every batch, and holds the interlocks that prevent oxidant addition out of sequence.
Chlorine, acid-mist and NOx abatement train. Alkali washing tower, absorption tower and demister for the chlorine and acid mist generated in fusion, distillation and precipitation, with the scrubber liquor monitored before discharge.
Effluent neutralisation and settling unit. Neutralises spent alkaline and acid streams and settles the metal hydroxide sludge before discharge or further treatment.
Assay laboratory equipment. XRF, ICP-OES, spectrophotometry and a dedicated fume hood for sample preparation, so that feed, intermediate and product assays are generated in-house on the same day as production.

Product Features

Single-supplier turnkey scope. Assay, flowsheet design, equipment manufacture, installation, commissioning, operator training and handover are delivered as one contract, so the interfaces between fusion, distillation, absorption, reduction and scrubbing are no one else’s problem.
Two opening routes in one plant. The fusion-and-distillation route and the alkaline sodium hypochlorite leaching route are both built into the same line, and the flowsheet specifies which route each feed uses.
Chemistry matched to the metal, not to a generic leach. The process is designed around the fact that ruthenium resists every mineral acid and opens in alkali, which is why fusion and selective alkaline leaching sit at the front of the line instead of an acid dissolution stage.
Volatility-based separation. Distillation removes ruthenium from osmium, platinum, palladium, rhodium and iridium and from the base metals in a single operation, rather than through a sequence of selective precipitations that each carry their own losses.
Dedicated osmium circuit. Osmium tetroxide is captured in its own alkali absorption train and worked up as a by-product, which both protects ruthenium purity and prevents a valuable metal from being disposed of with the effluent.
Ethanol-modified absorption. The hydrochloric acid absorption medium carries 0.5–3% ethanol, which holds absorbed ruthenium as stable chlororuthenic acid and suppresses re-oxidation to the volatile tetroxide, so the train does not leak product to the tail gas.
Distillation safety engineered into the control system. Oxidant dosing, kettle temperature and vapour condition are interlocked, and the tetroxide is kept dilute and moving, because ruthenium tetroxide disproportionates rapidly to ruthenium dioxide with an oxygen release when it is concentrated or overheated.
Colour endpoint instead of a timer. Distillation is terminated on the thiourea swab test at the gas outlet, which is a direct measurement of residual tetroxide and more reliable on this chemistry than a fixed duration.
Multi-stage absorption sized to the vapour load. Stage count and acid strength are set during design from the actual vapour load of your feed, and the train can be extended rather than replaced if the duty rises.
Recovery designed to the last part per million. Residue retreatment, resin scavenging and cementation are part of the standard scope, not an optional extra, so distillation residue is re-fused and barren liquors are polished below 1 ppm ruthenium before neutralisation.
Direct compound output available. Ruthenium trichloride, nitrosyl nitrate and dioxide can be produced without going through metal, which removes a calcination and reduction step and the metal losses that come with it.
Assay-linked traceability. Every lot carries a route sheet, a mass balance and the assay results of feed, intermediate and product, which is what makes a refining guarantee defensible.
Configuration to feed, not to a catalogue. Capacity, footprint, power demand and utility consumption are engineered from your assay and target throughput, so the plant is sized to the metal actually available rather than to a standard model number.

Technical Parameters & Specifications

Engineering setpoints below are the standard design basis and are confirmed or adjusted during process design once the feed assay is known. Capacity, footprint, installed power and utility consumption are engineered to your throughput and site conditions.

Ruthenium refining process — technical parameters and specifications.

Parameter	Specification
Feed ruthenium grade	Ru ≥ 10% for the direct distillation route; lower-grade material accepted after pretreatment and alkali fusion enrichment
Feed forms accepted	Spent supported catalyst, coated titanium anode scrap, platter and target scrap, plating sludge and liquor, smelting concentrate and anode slime, aqua regia-insoluble residue and osmium-bearing ore
Feed pretreatment	Incineration, granulation, grinding, zinc–aluminium alloying or fusion enrichment, selected per feed type
Zinc–aluminium alloying	Zn : Al weight ratio 2–4 : 0.3–2, 500–800 °C in a graphite crucible, 1–2 h hold, water quench, matrix dissolved in HCl or H₂SO₄ at 30–90 °C
Pyrogenic osmium removal	Quartz boat in a tube furnace, 100–200 °C drying then 300–800 °C with an air stream
Alkali fusion charge	Sodium peroxide with sodium hydroxide, fused at 400–700 °C until the charge is fluid
Water leaching of the melt	Liquid-to-solid ratio 10–15 : 1 at 40–60 °C for 2–4 h, settling 12–16 h before filtration
Selective alkaline leaching	12% sodium hydroxide slurry with sodium hypochlorite, redox potential held at about 200 mV, 80 °C
Alcohol reduction of the leachate	Methanol or ethanol added at ambient temperature, 3–6 h standing to precipitate Ru(OH)₄
Distillation feed condition	Ruthenium hydroxide or ruthenate liquor adjusted to about pH 1 with dilute alkali
Distillation temperature	50–90 °C in a jacketed, gas-tight kettle, with oxidant added slowly and continuously
Distillation oxidant	20% sodium bromate or 20% sodium chlorate solution, or chlorine gas introduced against a sodium hydroxide charge
Ruthenium tetroxide physical data	Melting point 25.4 °C, boiling point 40 °C; volatile at ambient temperature
Distillation endpoint test	Thiourea-soaked cotton swab at the gas outlet, distillation continued until no blue colour forms
Absorption medium	4–6 mol/L hydrochloric acid containing 0.5–3% ethanol, in four stages
Osmium absorption medium	20% sodium hydroxide solution containing 4% ethanol
Absorption train pressure	Negative pressure throughout, generated by a liquid-ring vacuum set
Osmium scavenging	Hydrogen peroxide or nitric acid addition, 75–90 °C, volatilising residual OsO₄ to the alkali circuit
Dechlorination	Ethanol addition, 75–90 °C, to remove free chlorine and hold ruthenium as H₂RuCl₆
Reprecipitation and re-distillation	Used on high-impurity feeds, by water redissolution at about pH 1 or by NaOH precipitation followed by H₂SO₄ distillation
Working Ru concentration at precipitation	30–50 g/L in the chlororuthenic acid liquor
Precipitant	Ammonium chloride, producing deep-red to black crystalline (NH₄)₂RuCl₆
Salt washing medium	Ethanol rather than water, because ammonium chlororuthenate is partly water-soluble
Salt drying and calcination	400–500 °C in a hydrogen stream until no white fumes evolve
Hydrogen reduction	750–950 °C under hydrogen for 2–4 h, then cooling under argon or nitrogen and discharge below 100 °C
Final ruthenium purity	Ru ≥ 99.9% (3N) as standard; 99.95% (3N5) and 99.98% selectable; 99.99% (4N) with additional distillation passes
Ruthenium recovery	≥ 95% direct from the distillation circuit; ≥ 98% overall with residue retreatment, resin scavenging and cementation
Residual ruthenium in effluent	Below 1 ppm after resin and cementation polishing of the barren liquor
Product forms	Ru sponge or powder; (NH₄)₂RuCl₆ crystals; RuCl₃·nH₂O; ruthenium nitrosyl nitrate or nitrate solution; ruthenate liquor; RuO₂; melted bar or shot
Product packaging	Sealed containers under inert gas; ruthenium trichloride sealed against moisture, powder protected from air oxidation
Materials of construction	Quartz and borosilicate glass, PTFE and PFA, polypropylene, PVDF, titanium
Filtration equipment	Vacuum filter plate, filter trolley with diaphragm pump, candle filter with reverse gas pulse
Barren liquor recovery	Ion-exchange resin train followed by iron or zinc cementation, with residue returned to fusion
Off-gas treatment	Chlorine and acid-mist scrubbing train with alkali washing tower, absorption tower and demister
Instrumentation and control	PLC with HMI supervision of fusion and distillation temperature, redox potential, dosing sequence and batch logging
Quality verification	XRF, ICP-OES and spectrophotometry; certificate of analysis issued per batch
Capacity, footprint, power, utilities	Engineered to feed assay, target throughput and site conditions

Technical Advantages

The only platinum group metal that can be separated by volatility. Ruthenium forms a tetroxide that is volatile at ambient temperature, and no other platinum group metal does. Distillation therefore takes ruthenium out of the liquor while platinum, palladium, rhodium and iridium stay behind as dissolved chloro-complexes, and osmium — the one metal that follows — is handled on its own absorption circuit. Result: one separation step in place of a chain of selective precipitations, each of which would carry its own loss.
Feed chemistry addressed honestly. Ruthenium metal and its dioxide are not dissolved by mineral acids, aqua regia included. Rather than forcing an acid route that cannot work, the flowsheet opens the feed in alkali by fusion or by selective hypochlorite leaching, which is where the yield actually is. Result: applicability to metal, oxide, ore and residue feeds with one equipment set.
A second opening route for feeds that do not need distillation. Where the feed is an alkali-soluble hydroxide or ruthenate liquor, sodium hypochlorite leaching at controlled redox potential dissolves ruthenium selectively at 80 °C, and alcohol reduction brings it out as hydroxide. Base metals are barely soluble in alkali and palladium, rhodium and iridium resist the reaction, so the liquor is already partly purified. Result: a route that avoids high-temperature distillation hazards entirely for suitable feeds.
Osmium separated as a product rather than a nuisance. Osmium tetroxide co-volatilises with ruthenium tetroxide, which is why most flowsheets struggle to make a clean ruthenium product. Here osmium is removed upstream by pyrogenic distillation and any remainder is re-oxidised with hydrogen peroxide or nitric acid and volatilised to a dedicated alkali absorption train. Result: an osmium-free precipitation liquor and a saleable osmium by-product.
Selectivity before distillation. Alkaline leaching removes base metals that acid dissolution would carry into the distillation kettle, and the fused melt leaves silica, alumina and refractory phases in the leach residue. Result: a smaller impurity load entering the most sensitive stage of the process, and fewer repeat distillation passes to reach grade.
Distillation hazards managed by design. Ruthenium tetroxide is markedly less thermally stable than osmium tetroxide. A vapour phase that is concentrated, overheated or in contact with a reducing agent disproportionates rapidly to ruthenium dioxide with a sudden release of oxygen, which is an explosion risk rather than a maintenance issue. The kettle is therefore operated with the tetroxide dilute and moving, with dosing and temperature interlocked. Result: a distillation stage that a normal crew can operate safely on a routine basis.
Ethanol in the absorption medium. Absorbing the tetroxide into hydrochloric acid containing 0.5–3% ethanol holds ruthenium as stable chlororuthenic acid and suppresses re-oxidation to the volatile form. Osmium absorption uses the same principle with 4% ethanol in 20% sodium hydroxide. Result: product stays in the receiver instead of leaking to the tail gas.
Ethanol washing of the salt. Ammonium chlororuthenate is partly water-soluble, so a conventional water wash would dissolve product back into the mother liquor. The cake is washed with ethanol instead. Result: a higher precipitation yield from the same ammonium chloride dose.
Recovery engineered across two passes, not one. Distillation residue is returned to fusion and re-distilled, and barren liquors are polished by ion-exchange resin and cementation with the residue returned to the circuit. Result: ≥ 98% overall ruthenium recovery and effluent below 1 ppm.
Direct compound production. Because the distillation product is an absorption liquor, the line can be routed straight to ruthenium trichloride, nitrosyl nitrate or dioxide without making metal first. Result: fewer process steps, lower energy demand and no metal-making losses where a compound is what the customer actually buys.
Hydrometallurgical energy profile. Apart from the fusion and reduction furnaces and the pyrogenic osmium stage, the line operates at or below 90 °C. Result: lower thermal energy demand than a smelting-based route, with the high-temperature duty confined to two small furnaces.
Emissions managed at the source and at the stack. Chlorine, osmium tetroxide and acid mist are captured where they are generated and routed through an alkali washing train with a demister, with the scrubber liquor analysed before discharge. Result: compliance that does not depend on diluting the problem downstream.
Verifiable numbers. Assay-linked mass balance, per-batch logging and certificate of analysis mean purity and recovery claims can be checked against your own analysis on the same lot. Result: a refining specification that can be audited by the buyer or by a toll-refining counterparty.
Designed to scale with the market. The layout is modular, so a pilot line that validates the flowsheet on a few kilograms can be extended with additional fusion, distillation and absorption capacity rather than replaced. Result: an entry point that does not become stranded capital.

Service Process

Step 1 — Enquiry and feed data review.
You provide the feed type, an assay or typical analysis, expected monthly metal volume and any site constraints. We confirm whether the material suits this process or needs an upstream treatment first. Output: preliminary process route and a clear scope statement.

Step 2 — Laboratory test and small-batch verification.
A representative sample is run at bench scale through pretreatment, fusion or selective leaching, distillation, absorption, precipitation and reduction. Operating windows, the number of distillation passes your feed needs, expected recovery and final grade are established on real material. Output: test report and returned product sample for your own assay.

Step 3 — Process design and flowsheet.
We issue the process flow diagram, material and reagent balance, mass balance by metal, equipment list, vessel and train sizing, and the utility schedule, with all engineering setpoints stated. Output: process design package and mass balance.

Step 4 — Equipment manufacture and factory testing.
Fusion furnace, distillation kettle, absorption train, reduction furnace, scrubbers and the control panel are fabricated, assembled and function-tested before shipment, with material certificates retained. Output: factory acceptance test record.

Step 5 — Layout and site interface design.
Equipment layout, civil loading, power supply points, water, compressed air, heating and ventilation interfaces, gas detection and emergency scrubbing are defined against your building. Output: layout and utility interface drawings.

Step 6 — Shipment, installation and commissioning.
Equipment ships with the documentation set, and our engineers supervise installation, leak testing of the absorption train, electrical and control checkout, and water commissioning. Output: mechanically complete line, ready for reagent commissioning.

Step 7 — Operator training and SOP handover.
Operating procedures, safe handling of peroxides, hypochlorite, chlorine and hydrogen, vapour-phase control on the distillation stage, endpoint judgement, sampling and assay practice, and routine maintenance are taught on site with the actual equipment. Output: trained operators and a signed SOP set.

Step 8 — Production trial and performance acceptance.
The line is run on your feed and the agreement is confirmed against measured recovery, product purity and effluent ruthenium concentration. Output: performance test certificate and first certificate of analysis.

Step 9 — Ongoing technical support.
Process troubleshooting, flowsheet refinement as your feed mix changes, spare parts at cost, and reagent or consumable supply on request. Output: continuing production support.

Warranty & After-Sales Service

Warranty period. Twelve months from successful commissioning or eighteen months from shipment, whichever falls earlier, covering design, manufacture and assembly defects of the supplied equipment. Excluded: consumables such as filter cloths, gaskets, crucibles, quartz boats, membranes and reagents, and damage from misuse or from feed outside the agreed specification.
Performance commitment. Where the feed matches the tested sample, we stand behind the agreed ruthenium recovery and product purity figures established in the process design package, with the performance test as the reference point. Output: documented performance acceptance.
Spare parts. Wear and critical spares — crucibles, quartz ware, gaskets, seals, thermowells and instrumentation — are quoted at the time of order and held available afterwards, with a recommended on-site stock list issued at handover. Output: spare parts list and supply at cost.
Remote support. Telephone, email and messaging support for operating questions, alarm interpretation and process troubleshooting, whenever your line is running. Output: same-day response on operating issues.
On-site service. Engineer attendance for warranty faults, process problems and periodical check-ups, with response and attendance times agreed in the contract according to your location. Output: on-site intervention and a service report.
Operator retraining and refresher visits. Additional training, refresher sessions and process optimisation visits as your feed mix or product requirement changes. Output: updated training and procedure revisions.
Documentation set. Operation and maintenance manuals, process flow diagram, piping and instrumentation diagram, equipment layout, electrical drawings, spare parts catalogue, safety data for reagents and the emergency response plan for tetroxide and chlorine release. Output: complete documentation handover.
Compliance support. Assistance with emission and effluent parameter declarations, scrubber performance verification and the handling, storage and disposal requirements for the reagents and intermediates used in the process. Output: technical data for your permit applications.
Lifetime technical support. The process design remains yours, and our engineering team remains available for modification and expansion advice for the operating life of the plant. Output: long-term engineering continuity.

Frequently Asked Questions

What feed materials can this ruthenium refining process handle?

Spent Ru/C and Ru/MgO ammonia-synthesis catalysts with barium, potassium and caesium promoters; Ru/Al₂O₃ and silica-supported hydrogenation catalysts; spent ruthenium dioxide oxidation, chlor-alkali and hydrodesulphurisation catalysts; coated titanium anode scrap; hard disk drive platters and ruthenium sputtering residues; chip resistors and ruthenium-bearing contacts; plating baths, sludges and rinse waters; proton exchange membrane electrolyser and fuel cell catalyst scrap; nickel and copper anode slime and precious metal concentrate; osmium–iridium–ruthenium ores and aqua regia-insoluble residues; and ruthenium process residues and spent absorption liquors. Feeds carrying carbon, organics or a refractory support are incinerated, granulated or fused to a concentrate first, and that pretreatment step is designed to match the specific feed.

What purity of ruthenium does the process achieve?

Ru ≥ 99.9% (3N) is the standard specification, delivered as sponge or powder and released against a certificate of analysis. Grades of 99.95% (3N5) and 99.98% are available where the feed and the customer specification call for them, and additional distillation passes bring the product to 99.99% (4N). The exact figure for your material is established in the laboratory test before the plant is built, because it depends on the osmium content and the impurity profile of the feed rather than on the plant alone.

Why is ruthenium separated by distillation rather than by precipitation?

Because ruthenium is the only platinum group metal that forms a volatile oxide. Ruthenium tetroxide melts at 25.4 °C and boils at 40 °C, so it leaves the liquor as a vapour well below the boiling point of water, while platinum, palladium, rhodium and iridium remain behind as dissolved chloro-complexes. That makes distillation a single-step separation where precipitation-based flowsheets need a sequence of selective precipitation stages, each of which carries its own losses and its own reagent load. The vapour is absorbed into hydrochloric acid containing 0.5–3% ethanol, which holds ruthenium as stable chlororuthenic acid.

How is osmium separated from ruthenium?

Osmium is dealt with before ruthenium distillation and again after it. In the upstream stage, osmium-bearing residues are heated to 300–800 °C in an air stream in a tube furnace, which volatilises osmium as osmium tetroxide into a sodium hydroxide absorption train while ruthenium is retained as weakly volatile ruthenium dioxide. In the absorption train, the vapour passes through the hydrochloric acid stages where ruthenium is captured and then into 20% sodium hydroxide with 4% ethanol, which absorbs any osmium that still volatilised. Any osmium that reports to the ruthenium absorption liquor is re-oxidised with hydrogen peroxide or nitric acid, volatilised off, and returned to the alkali circuit, so the liquor is osmium-free before ammonium chloride is added.

Is ruthenium tetroxide dangerous to handle, and how is the risk controlled?

Ruthenium tetroxide is volatile at room temperature and its thermal stability is markedly lower than that of osmium tetroxide. A vapour phase that is too concentrated, too hot, or in contact with a reducing agent disproportionates rapidly to ruthenium dioxide with a sudden release of oxygen, which is an explosion risk rather than a maintenance issue. The risk is controlled by design rather than by procedure alone: the kettle is jacketed and gas-tight, the tetroxide is kept dilute and continuously removed, oxidant is added slowly and continuously under interlocks that respond to temperature and vapour condition, the absorption train is under negative pressure so leaks draw inwards, and distillation is terminated on a thiourea swab test at the gas outlet rather than on a timer. Everyone operating the stage is trained on the vapour-phase behaviour specifically.

Can ruthenium be opened without oxidative distillation?

Yes, where the feed allows it. Ruthenium metal and its dioxide are not attacked by mineral acids, aqua regia included, but they are soluble in alkaline hypochlorite. The feed is slurried in 12% sodium hydroxide solution and oxidised with sodium hypochlorite at a controlled redox potential of about 200 mV at 80 °C, which dissolves ruthenium as ruthenate while most base metals stay insoluble in alkali and palladium, rhodium and iridium resist the reaction. Adding methanol or ethanol to the leachate then reduces ruthenium to the insoluble tetravalent state and it separates as ruthenium hydroxide. This route is used for hydroxide and alkali-soluble feeds, and for feeds where the distillation hazard is not wanted; fusion and distillation remain the route for metal, alloy, ore and aqua regia-insoluble residues.

What is the difference between the fusion-and-distillation route and the alkaline leaching route?

The fusion route opens a feed that no acid will touch. The residue is mixed with sodium peroxide and sodium hydroxide and fused at 400–700 °C, the cooled melt is leached with water at 40–60 °C, and ruthenium enters solution as ruthenate. The alkaline leaching route works on feeds that are already alkali-soluble as a hydroxide or a ruthenate liquor: it uses sodium hypochlorite at controlled redox potential instead of a fusion furnace, which is simpler and avoids the high-temperature step, but it cannot handle metallic ruthenium, its dioxide or refractory ore phases. Both routes converge on the same distillation, absorption, precipitation and reduction sequence, and the flowsheet specifies which route each of your feeds uses.

What is the ruthenium recovery rate?

Direct recovery from the distillation circuit is ≥ 95%, rising to ≥ 98% overall. The difference comes from the two recovery loops built into the line: distillation and leach residues that still contain ruthenium are returned to the fusion stage for a second distillation pass, and barren liquors pass through an ion-exchange resin train followed by iron or zinc cementation, with the cementation residue returning to fusion rather than leaving the plant. The depleted solution leaves with less than 1 ppm ruthenium.

Can the plant produce ruthenium trichloride directly instead of metal?

Yes, and on many feeds it is the better route. The distillation product is already a chlororuthenic acid absorption liquor, so concentrating and drying it yields ruthenium trichloride RuCl₃·nH₂O without ever making metal. That removes the calcination and hydrogen reduction steps and the metal losses associated with them, and it is what most chemical, electronics and electroplating customers actually buy. The line can equally be routed to ruthenium nitrosyl nitrate or ruthenium nitrate solution by absorbing the tetroxide in nitric acid, or to coating-grade ruthenium dioxide by controlled thermal decomposition of the trichloride. Where metal is required, the reduction furnace and melting set are supplied as part of the same scope.

How long does one refining cycle take?

It depends on batch size and on how many distillation passes the feed needs, because the sequence is governed by endpoints rather than fixed times: fusion runs until the charge is fluid, distillation runs until the thiourea swab no longer turns blue, and reduction runs to the stepped temperature profile the salt requires. What can be stated is the structure: pretreatment and osmium removal come first where the feed needs them, fusion and water leaching take the longest single block, each distillation and absorption pass is comparatively short because the tetroxide leaves the kettle readily, precipitation and ethanol washing are quick, and the reduction and cooling sequence is set by the furnace profile. The campaign length for your material is estimated from the laboratory test.

What capacity can you supply?

Capacity is engineered to your feed assay and your target throughput rather than taken from a catalogue of fixed sizes. What matters in this process is the ruthenium content of the feed and the number of distillation passes required, so two plants of the same nominal kettle size can have very different daily metal output depending on grade and on the osmium load. We size the fusion furnace, distillation kettle, absorption train, reduction furnace and scrubber from your assay and monthly metal volume, and we state the resulting figures in the process design package. The layout is modular, so a pilot line can be extended rather than replaced if throughput grows.

How do you verify the purity of the finished ruthenium, and how must it be stored?

By ICP-OES analysis of a sample taken from the released batch, cross-checked with XRF where applicable and with spectrophotometry for the wet-chemistry stages, and with a thiourea test used at the distillation stage to confirm the tetroxide endpoint. The batch is not released until the certificate of analysis confirms the specified purity, and the assay results for feed, intermediates and product are held together with the mass balance for that lot. Finished sponge and powder are packed under inert gas in sealed containers, because finely divided ruthenium oxidises in air and an open dish loses both grade and metal; ruthenium trichloride is sealed against moisture because the salt is hygroscopic, and reduction product is discharged below 100 °C and moved directly into a sealed desiccator.