Platinum Refining Process

— Turnkey Platinum Refining Process

The platinum refining process delivered by YuSai Machinery is a turnkey circuit that takes crude platinum, PGM concentrate and secondary feed through aqua regia dissolution, ammonium chloride precipitation, oxidative hydrolysis and 800 °C calcination to 99.95% and 99.99% sponge platinum, and 99.999% on request. Platinum is not refined by electrorefining, so the line runs the two routes that work — ammonium chloride precipitation to sparingly soluble (NH₄)₂PtCl₆ while base metals and gold, palladium and iridium stay in solution, and oxidative hydrolysis to soluble NaPt(OH)₆ while the rest hydrolyse out. Precipitation runs at 50–80 g/L Pt with free ammonium chloride at 5–10%; three dissolution–precipitation cycles take 90% crude platinum to the salt calcined into 99.99% sponge. Recovery is 98–99%.

Product Overview

A platinum refining process is the sequence of chemical operations that raises platinum from a concentrated but impure form to a specification form — sponge, powder or ingot that a trading market, a catalyst maker or a glassworks will accept. The feed to it is never ore. Ore contains 2–6 g/t platinum; a flotation concentrate carries 85–850 g/t of PGMs; a smelter matte carries roughly 1.4 kg of PGMs per tonne; and the residue left after base-metal removal carries 15–20% PGMs. By the time platinum reaches a refinery it is already the rich fraction of a long chain, and refining is the last step that converts that concentration into a number a buyer will pay for: 99.95%, 99.99% or 99.999%. In plant terms the refining circuit is the wet-chemistry half of a platinum refinery plant — dissolution and reaction vessels, filtration and hydrolysis units, precipitation and reduction vessels, the fume hoods and ductwork that make aqua regia chemistry operable indoors, and the absorption train that keeps the whole circuit legal. Specified as one supply, those units make up a single platinum refining system engineered around one feed and one required daily output — and the same platinum purification equipment serves a customer who wants platinum salts or solutions rather than metal, because the circuit branches after purification instead of always running to the casting floor.

The process begins upstream of the refinery and the page therefore follows the whole chain, because platinum is the clearest case in precious-metals metallurgy of a metal whose chemistry is set by where it came from. On the primary route, ore is blasted, crushed and milled, and the platinum-bearing minerals are floated into a concentrate with collectors and frothers; the concentrate is smelted in an electric or reverberatory furnace above 1,200 °C with flux to bind the gangue into a removable slag, matte smelting runs at roughly 1,350 °C and up to 1,600 °C when the concentrate carries chromite, and the molten matte is then converted by blowing air or oxygen through it to strip iron and sulphur, leaving a base-metal/platinum bullion. That bullion goes to base-metal removal by pressure leaching with sulphuric acid, which dissolves copper, nickel and iron and leaves a PGM-rich residue. On the secondary route the same step is reached from spent automotive and petrochemical catalysts, fuel-cell membrane electrode assemblies, glass-industry refractory scrap, plating liquors and electronic scrap, where the metal is pre-concentrated by incineration, roasting, smelting or aqueous chlorination before it reaches the refinery. Both routes converge on the same problem: a mixture of precious metals in chloride solution, from which platinum must be taken out selectively and economically.

What happens next is where platinum differs from gold, and the difference is chemistry rather than preference. Platinum in chloride medium forms hexachloroplatinic acid, H₂PtCl₆, and that compound has two properties that the whole industrial process is built on. First, in acidic medium, adding ammonium chloride precipitates ammonium chloroplatinate, (NH₄)₂PtCl₆, a yellow sparingly-soluble salt, while base-metal chlorides and the low-valent chloroammonium salts of gold, palladium and iridium remain in solution — a clean split between platinum and almost everything else. Second, in alkaline medium, platinum forms a soluble hydroxo complex, NaPt(OH)₆, while the other precious metals and the base metals hydrolyse into insoluble hydroxides — a second clean split, this time between platinum and the metals that would not separate by precipitation alone. A refinery that owns both properties can therefore move platinum between a soluble state and a solid state repeatedly, and every repetition raises purity, because each precipitate carries a smaller fraction of the original impurities into the next dissolution. Oxidative hydrolysis and repeated ammonium chloride precipitation are the two industrial expressions of that idea, and solvent extraction is used to prepare or polish a stream rather than as a stand-alone route to specification platinum.

The circuit is run at the concentrations and temperatures the chemistry demands rather than at the largest scale the vessels allow. Precipitation is carried out on a solution adjusted to 50–80 g/L Pt, hot and stirred, with ammonium chloride added until the free ammonium chloride concentration is 5–10% — enough excess to drive the precipitation towards completion, since the salt has a measurable solubility and the platinum that stays in solution is platinum that has to be recovered in the next cycle. The precipitate is cooled, filtered and washed with 5% ammonium chloride acidified with hydrochloric acid to pH 1, which is the wash that removes occluded base-metal liquor without redissolving the platinum salt. A small sample of each batch is calcined to sponge platinum and sent for spectrographic analysis, so that the decision to proceed is made on an assay rather than on a colour. When a batch is off specification the material is not scrapped: it is calcined back to crude platinum and redissolved, or reduced at room temperature with hydrazine hydrate to platinum black, redissolved in hydrochloric acid with hydrogen peroxide and precipitated again with ammonium chloride — the short rework loop that keeps an off-spec batch inside the circuit instead of costing a full cycle. In normal operation, 90% crude platinum goes through three dissolution–precipitation cycles to reach (NH₄)₂PtCl₆ pure enough for the 800 °C calcination that produces 99.99% sponge platinum.

The reason a platinum refinery is bought as an engineered package rather than assembled from vessels is that the dissolution chemistry is the most aggressive chemistry in precious-metal processing. Aqua regia on platinum feed releases nitrogen oxides at roughly 30,000 mg/m³ at the reactor outlet, which is an order of magnitude above a jewellery gold line, and every one of those gas streams carries metal. The design answer is not a bigger scrubber at the end of the ductwork but a sealed reactor head with a condenser and a gas–liquid separator, so that the vapour which leaves the dissolving vessel is condensed and the condensate — which contains dissolved precious metal — is returned to the reactor instead of being vented. Reaction is carried out inside a reaction fume hood, in vessels that can be opened and observed, so that an operator can follow a dissolution that behaves differently every time the feed changes; the residual nitrogen oxides pass into a multi-stage jet absorption train with 99.5% or better absorption, reducing the inlet load to below 150 ppm at the stack, and the acid effluent is neutralised to a controlled pH before discharge or reuse. Platinum-group metal separation is a low-tonnage, high-value operation by nature, and the plant is built to that scale: batch sizes are small, vessels are transparent where transparency helps the operator judge a reaction, filtration and liquid transfer are closed and assisted by vacuum rather than by pouring, and the metal that is held up on vessel walls, in filter media and in ductwork is a design variable rather than an accepted loss.

What the operator ends up with is a circuit that produces sponge platinum at 99.95% or 99.99%, and 99.999% on request, from a feed range that spans crude platinum above 90% Pt, PGM concentrate, leach liquor, solvent-extraction strip liquor, spent catalyst residue and anode slime, with 98–99% recovery on a closed metal balance, 1–4 days for a platinum or palladium cycle, and the gold, palladium and iridium fractions that are deliberately kept out of the platinum precipitate recovered as separate streams rather than lost. Wetted parts are selected against the duty from titanium, glass, enamel-lined steel and PPH, the reactor and filtration drain lines are laid out so that no solution is poured by hand, and the whole train can be laid into an existing refinery building or supplied as a compact, containerised unit for a greenfield site.

Application Scenarios

A platinum refining process is installed wherever platinum arrives as a rich but unsellable fraction, and wherever the operator wants to own the step that converts metal at a discount into metal at the market price instead of paying a third-party refiner’s deduction. The following are the situations in which this line is built.

Primary PGM producers and mine-site refineries — refine the PGM residue that follows base-metal removal from converter matte into specification platinum, and route the palladium, rhodium, iridium and ruthenium fractions onward as separate streams. Output: 99.95%–99.99% sponge platinum with the co-metals separated rather than lost.
Copper and nickel electrorefineries — treat the platinum fraction of anode slime, where platinum arrives as a rich residue after silver and gold have been taken out. Output: sponge platinum plus a gold and palladium stream recovered from the same liquor.
Spent automotive catalyst recyclers — refine platinum recovered from three-way catalyst monoliths and washcoat concentrate, where the metal is pre-concentrated by incineration, grinding and leaching. Output: 99.95% platinum for catalyst, chemical and investment markets.
Petrochemical and refinery catalyst operators — refine platinum from reforming, isomerisation and oxidation catalysts on alumina or carbon carriers, in-house rather than through a toll refiner. Output: sponge platinum returned to catalyst manufacture.
Fuel-cell and hydrogen-industry processors — refine platinum from membrane electrode assemblies, gas diffusion layers and catalyst ink production scrap, and close the loop back into catalyst manufacture. Output: high-purity platinum for new electrode and catalyst batches.
Glass, fibreglass and optical-fibre manufacturers — refine the platinum and platinum-rhodium fraction recovered from bushing scrap, stirrer scrap and refractory brick, where the metal is the consumable that defines the process economics. Output: specification platinum plus a platinum-rhodium stream routed to alloy make-up.
Nitric acid and caprolactam producers — refine the platinum-rhodium and platinum-palladium gauze recovered from ammonia oxidation campaigns. Output: sponge platinum with the rhodium fraction recovered separately.
Chemical and pharmaceutical catalyst users — refine platinum from spent hydrogenation, dehydrogenation and platinum-carbon catalysts. Output: refined platinum with a documented batch metal balance.
Precious-metal recyclers and urban-mining operators — finish the platinum fraction produced by e-waste, PCB, plating-sludge and MLCC recovery circuits on the same site as the gold and silver circuits. Output: 99.95%–99.99% platinum alongside the gold and silver products.
Semiconductor, PCB and electronics manufacturers — recover platinum from sputtering targets, evaporated-film scrap, plating baths and process residue. Output: platinum for target or chemical manufacture.
Jewellery and watch manufacturers — refine platinum alloy scrap, swarf, polishing dust and sweeps, including platinum-cobalt and platinum-ruthenium alloys where the alloying metal has to be taken out. Output: assay-certified platinum for alloy make-up.
Dental and medical device makers — refine platinum and platinum-alloy scrap, crucible residue and bench sweeps in-house. Output: high-fineness platinum for alloy production.
Precious-metal refineries and assay houses — add a dedicated platinum finishing circuit behind an existing gold or silver refinery and take on platinum-bearing toll material. Output: a standalone platinum refinery route with auditable metal balance.
National programmes and greenfield refining projects — build domestic platinum refining capacity with a single supplier for dissolution, separation, reduction, calcination and emissions control. Output: a complete platinum refining circuit from concentrate to specification metal.
Pilot, laboratory and teaching facilities — small-batch refining and process development on the same flow sheet as a production refinery. Output: analytical-grade platinum for development work.

Applicable Raw Materials

Platinum refining accepts a wider range of feed than gold refining does, because the metal arrives at a refinery in more different chemical forms — as crude metal, as a chloride solution, as a strip liquor, as a residue on a carrier, and as an alloy with other platinum-group metals. The route is not fixed by the material’s name but by two questions answered in the laboratory: how much platinum is in it, and what is the platinum with. Material assaying above about 90% Pt can go straight into aqua regia dissolution and ammonium chloride precipitation; material carrying gold, palladium or iridium as a significant fraction needs the mother liquor stripped and the co-metals separated rather than precipitated with the platinum; and material that is lean, carried on an organic substrate or locked in a refractory oxide needs pre-concentration before any of the platinum chemistry can start. Every feed is sampled, homogenised and assayed first, because a platinum refining batch runs on chemistry that has to be set from numbers.

Crude platinum and platinum sponge — the intermediate metal produced by an upstream separation circuit, typically above 90% Pt with base metals and the other PGMs as the balance; dissolved directly in aqua regia. Output: (NH₄)₂PtCl₆ and, after calcination, 99.99% sponge platinum.
PGM concentrate and smelter matte residue — the PGM-rich fraction produced by flotation, matte smelting, converting and base-metal removal, carrying 15–20% PGMs together with the other platinum-group metals; dissolved in aqua regia after a nitric pre-treatment where silver or palladium content demands it. Output: platinum as refined metal with palladium, gold and iridium separated into their own streams.
Platinum-bearing leach liquor and chloride solutions — chloride leach liquor, ion-exchange eluate and precipitation mother liquor produced elsewhere in the plant; adjusted to the precipitation concentration before ammonium chloride is added. Output: precipitated ammonium chloroplatinate from a solution that would otherwise be a bleed stream.
Solvent-extraction strip liquor — the concentrated platinum solution produced by stripping a loaded organic phase in a solvent-extraction circuit; fed to precipitation directly. Output: sponge platinum from a solution the extraction circuit has already upgraded.
Spent automotive three-way catalysts — platinum with palladium and rhodium on a cordierite monolith and alumina washcoat; incinerated or roasted to remove carbon and hydrocarbons, milled, sampled and leached. Output: refined platinum plus separate palladium and rhodium fractions.
Spent petrochemical and chemical catalysts — platinum on alumina or on activated carbon, from reforming, isomerisation, hydrogenation and oxidation duties; carbon-supported material is roasted first, alumina-supported material goes to dissolution after a carrier-removal step. Output: sponge platinum at 99.95% or above.
Fuel-cell membrane electrode assemblies and catalyst scrap — platinum on carbon in membrane form; mechanically separated from the membrane and ionomer, ashed and leached. Output: platinum returned to electrode or catalyst manufacture.
Platinum-rhodium and platinum-iridium gauzes — ammonia oxidation gauze, spinneret and bushing alloy recovered as worn metal; dissolved and separated rather than re-alloyed, because the rhodium and iridium fractions are worth more separated than diluted. Output: platinum metal plus rhodium and iridium routes.
Glass-industry refractory brick and bushing scrap — platinum and platinum-rhodium locked in alumina-silica-zircon refractory; sintered or slagged with flux before leaching. Output: a platinum fraction concentrated for the refining circuit.
Copper and nickel anode slime — the platinum-bearing residue left after copper, silver and gold have been taken out; nitric acid is used to remove silver and palladium ahead of the platinum dissolution. Output: platinum as refined metal with the gold and palladium fractions recovered separately.
Platinum-cobalt, platinum-ruthenium and platinum-tungsten alloys — jewellery, watch and industrial alloy scrap where the alloying metal has to be removed before specification platinum can be produced. Output: assay-certified platinum for re-alloying.
Plating liquors, plating sludge and spent electrolytes — platinum from electroplating and anodising baths, and from the sludges and filter cartridges those baths produce; concentrated by ion exchange, precipitation or evaporation before refining. Output: platinum recovered from a stream that is otherwise a disposal cost.
Semiconductor and electronics process residue — sputtering targets, evaporation boat residue, thick-film paste scrap and bond-wire production waste; mechanically and thermally pre-treated, then leached. Output: platinum for target or chemical manufacture.
Platinum-rhenium and platinum-nickel process scrap — high-temperature alloy scrap from thermocouples, turbine and catalyst duties, where the alloying elements must be taken out. Output: refined platinum with the alloying metal routed as a by-product.
Returned, off-spec and contaminated platinum material — customer returns, mixed-grade stock, contaminated sponge and legacy inventory; blended and assayed before a route is fixed. Output: specification platinum with a documented traceability record.

Output Products

The circuit is designed around one primary product — specification platinum — and a set of by-products that come out of the same vessels and are sold or recycled rather than discarded. The product forms and grades below are the ones the line is engineered to deliver.

Sponge platinum, 99.99% — the standard product of the ammonium chloride route, produced by calcining purified (NH₄)₂PtCl₆ at 800 °C; the form most catalyst and chemical customers buy. Output: 99.99% platinum sponge, released against a Certificate of Analysis.
Sponge platinum, 99.95% — the grade traded as good-delivery platinum and the most widely traded specification; produced on a shorter precipitation schedule where the feed allows. Output: 99.95% platinum sponge with a per-batch assay.
Platinum at 99.9% (2N9) to 99.999% (5N) — the full purity band the process can hold, from a single precipitation pass at the lower end to a fully repeated dissolution–precipitation schedule at the top end. Output: platinum powder or sponge graded to the purity the customer nominates.
Platinum ingots and bars to the LPPM Good Delivery specification — melted and cast as 1–6 kg bars at a minimum purity of 99.95%, the weight and purity range the London Platinum and Palladium Market recognises for good delivery. Output: cast platinum bars with stamped weight and purity.
Platinum granules and shot — melted and granulated for customers who want a free-flowing, easily weighed form for alloy make-up or for dissolution in their own process. Output: free-flowing platinum granules or shot.
Platinum target and evaporation material — platinum melted and cast or rolled for sputtering targets and evaporation sources. Output: platinum target blanks or evaporation material.
Platinum salt products — chloroplatinic acid (H₂PtCl₆) solution or crystals, ammonium chloroplatinate, and platinum chloride compounds produced from the purified intermediate rather than from a fresh dissolution. Output: platinum chemicals at reagent specification.
Platinum-carbon and platinum-alumina catalyst intermediates — purified platinum solution delivered as the impregnation feed for catalyst manufacture. Output: platinum solution or support-loaded platinum for the customer’s own catalyst line.
A separated palladium stream — palladium kept out of the platinum precipitate and recovered from the mother liquor by its own precipitation and reduction route. Output: palladium salt, sponge or solution handed to the palladium circuit.
A separated gold stream — gold retained in solution during platinum precipitation and recovered before the mother liquor is bled. Output: a gold-bearing liquor or gold powder routed to the gold circuit.
A platinum-group-metal residue — the iridium, rhodium and ruthenium fraction that does not follow platinum through precipitation or hydrolysis; washed, dried, bagged and assayed. Output: an assayed PGM residue for onward separation.
An assayed and traceable batch metal balance — feed weight and assay in, product weight and assay out, and every residue, filter cake, mother liquor and clean-up stream weighed and assayed, issued with the batch. Output: a per-batch metal balance report and a Certificate of Analysis for the product.

Platinum Refining Process Flow

The platinum refining process runs in eleven stages, arranged in the order the chemistry requires: the feed is characterised and a route is chosen, primary-route feed is concentrated from ore into a PGM-rich residue, that residue is dissolved into chloride solution, platinum is taken out of solution as a sparingly soluble salt, the salt is broken and reformed to raise its purity, and the purified salt is calcined into metal — with the gas, effluent and metal-bearing residues produced along the way treated inside the same package. Steps 2 to 4 are the concentration half of the chain and apply only to primary-route feed; steps 5 to 10 are the refining half and apply to every feed, including the PGM concentrate, the leach liquor, the strip liquor and the secondary material that arrives at the refinery gate already concentrated. Step 11 closes the loop on the streams that would otherwise leave as emission, effluent or unaccounted metal.

Steps 1 — Feed Assay and Route Selection. Feed is weighed, sampled, homogenised and assayed before any chemistry is set, because a platinum batch runs on numbers rather than on judgement: the platinum content fixes the precipitation charge, the palladium and gold content fixes how long the mother liquor has to be stripped, the iridium content fixes how many precipitation cycles are needed, and the form of the platinum — metal, salt, solution, or metal locked in a refractory or on a carbon carrier — fixes whether the material can be dissolved directly or has to be pre-treated first. The laboratory returns a route decision, an expected recovery, the reagent charge and the achievable purity band for that specific material, and the batch is released to the plant only after that decision is recorded. Output: an assayed, homogenised feed lot with a recorded starting weight, a route decision and a target purity band.

Steps 2 — Crushing, Milling and Froth Flotation. On the primary route, ore is drilled and blasted from the reef, hoisted, crushed and milled to liberate the platinum-bearing minerals from the silicate gangue, and the valuable minerals are floated into a concentrate using collectors to render the mineral surfaces hydrophobic and frothers to stabilise the bubble layer that carries them. Air is pumped through the pulp, platinum-bearing particles report to the froth, and the froth is skimmed off while the waste rock leaves as tailings. The reason this stage exists is the concentration ratio: ore carries roughly 2–6 g/t of platinum and a flotation concentrate carries 85–850 g/t of platinum-group metals, so a smelter can only be fed economically after flotation has done that work. Output: a dried flotation concentrate carrying 85–850 g/t of platinum-group metals, plus tailings.

Steps 3 — Smelting and Converting to PGM Matte. Concentrate is melted in an electric or reverberatory furnace at above 1,200 °C, with flux added to bind the remaining non-metallic impurities into a slag that can be tapped off and discarded; matte smelting runs at approximately 1,350 °C, and higher — up to about 1,600 °C — when the concentrate carries chromite, which is why furnace selection is a feed-dependent decision rather than a catalogue choice. Air or oxygen is then blown through the molten matte in the converting step to oxidise and strip iron and sulphur, leaving a base-metal/platinum bullion that carries roughly 1.4 kg of platinum-group metals per tonne. The purpose of this half of the chain is to collect every precious metal into a small, dense, sulphur-bearing phase that can be leached, which is the most reliable way to recover platinum from a silicate matrix. Output: converter matte and PGM-bearing bullion at approximately 1.4 kg/t PGM, plus a discard slag.

Steps 4 — Base-Metal Removal by Pressure Leaching. The bullion or matte is leached under pressure with sulphuric acid, which dissolves copper, nickel and iron and leaves the platinum-group metals behind as a concentrated insoluble residue carrying 15–20% PGMs. Pressure leaching is used rather than atmospheric leaching because the base-metal sulphides that carry the PGMs dissolve slowly and incompletely at ambient pressure, and because the precious metals must be kept in the residue rather than taken into solution, where they would have to be recovered twice. The residue is filtered, washed and dried — and that dried residue, together with the PGM concentrate and the secondary material that arrives by another route, is the true feed to the refining circuit. Output: a washed, dried PGM residue at 15–20% PGM, and a base-metal sulphate liquor routed to copper and nickel recovery.

Steps 5 — Dissolution to Chloroplatinic Acid Solution. The PGM residue or crude platinum is charged to a titanium or glass-lined reaction vessel and dissolved in aqua regia — approximately one part concentrated nitric acid to three parts concentrated hydrochloric acid — added in portions at a controlled rate under heating to 80–90 °C, converting metallic platinum to chloroplatinic acid, H₂PtCl₆. The reaction is Pt + 4HNO₃ + 6HCl → H₂PtCl₆ + 4NO₂ + 4H₂O; where the material resists aqua regia, sodium chlorate is used as the oxidant instead, by 3Pt + 2NaClO₃ + 18HCl → 3H₂PtCl₆ + 2NaCl + 6H₂O. The reactor head is sealed and the vapour is drawn through a condenser and gas–liquid separator so that the evaporated acid and the metal-bearing mist condense and return to the vessel rather than leaving as loss. Where the feed carries significant silver or palladium — anode slime and ore-derived residue usually do — a nitric acid parting step at 80–90 °C for around three hours is run first, which takes silver and palladium into solution and leaves a nitric residue for the aqua regia stage; that residue is subsequently dissolved in aqua regia at approximately 80 °C, and the material that resists both acids is the iridium fraction and is routed to its own circuit. The solution is then cooled, filtered and clarified, and any insoluble residue is washed and assayed. Output: clarified chloroplatinic acid liquor plus a washed insoluble residue routed to the iridium and rhodium circuit.

Steps 6 — Platinum Precipitation as Ammonium Chloroplatinate. The clarified liquor is adjusted to 50–80 g/L Pt and heated, and ammonium chloride is added with agitation to precipitate ammonium chloroplatinate, (NH₄)₂PtCl₆, the yellow sparingly soluble salt that carries platinum out of solution: H₂PtCl₆ + 2NH₄Cl → (NH₄)₂PtCl₆↓ + 2HCl. Ammonium chloride is added in excess, so that the free ammonium chloride concentration in the mother liquor is held at 5–10% — the excess is what drives the precipitation towards completion, because the salt has a measurable solubility and platinum left in solution is platinum that must be recovered in the next cycle. Base-metal chlorides and the low-valent chloroammonium salts of gold, palladium and iridium stay in solution, which is the whole point of the step: the acid-medium behaviour of the platinum salt performs the primary separation. The batch is cooled, the salt is filtered off and washed with 5% ammonium chloride acidified with hydrochloric acid to pH 1, which removes occluded base-metal liquor without redissolving the platinum. A small sample is calcined to sponge platinum and sent for spectrographic analysis, and the assay — not the colour — decides whether the batch proceeds or is reworked. Output: a washed ammonium chloroplatinate cake at the target assay, plus a platinum-bearing mother liquor retained for recovery.

Steps 7 — Oxidative Hydrolysis and Re-Dissolution. The second property of platinum chemistry is used to take out what precipitation alone leaves behind. In alkaline medium platinum forms a soluble hydroxo complex, NaPt(OH)₆, while the other precious metals and the base metals hydrolyse into insoluble hydroxides — so a hydrolysis step on a platinum solution separates platinum from the impurities that would otherwise follow it, which is the complementary split to the precipitation step that separated platinum with the salt. The hydrolysis precipitate and the platinum-bearing alkaline liquor are filtered separately, the hydroxide precipitate is removed to its own recovery route, and the purified platinum solution is acidified and returned to the precipitation stage. Hydrolysis is used where the feed carries amounts of rhodium, iridium or base metal that a single precipitation cycle cannot clear, and it is the reason a platinum refinery can accept feed that a precipitation-only circuit would have to reject. Output: a purified platinum solution with the hydrolysed impurity fraction removed as a separate precipitate.

Steps 8 — Repeated Precipitation and Mother-Liquor Recovery. Purity in platinum refining is produced by repetition rather than by a single perfect step, because every dissolution–precipitation cycle moves the salt further from the original impurity load. In normal operation 90% crude platinum goes through three dissolution–precipitation cycles to reach (NH₄)₂PtCl₆ pure enough to calcine into 99.99% platinum. Off-specification salt is never scrapped: it is calcined back to crude platinum and redissolved, or — the shorter and often preferred route — reduced at room temperature with hydrazine hydrate to platinum black, redissolved in hydrochloric acid with hydrogen peroxide, and precipitated again with ammonium chloride, which fixes a single contaminated batch without consuming a full cycle. The mother liquor is the second product of this step: it holds the gold, palladium and iridium that were deliberately kept out of the platinum precipitate, and it is stripped and processed rather than bled to effluent, because in a refinery that liquor is inventory and not waste. Output: purified (NH₄)₂PtCl₆ at the target assay, plus a stripped mother liquor releasing gold, palladium and iridium to their own recovery routes.

Steps 9 — Calcination to Sponge Platinum. The purified salt is dried, charged to a calciner or muffle furnace and heated to 800 °C, which decomposes the ammonium salt and drives off the ammonium chloride and chlorine, leaving sponge platinum. The calcination temperature is a controlled variable rather than a set point: below it the salt decomposes incompletely and the product retains chloride and ammonium residues; above it, at small particle size, the sponge sinters and becomes harder to dissolve for a customer who is buying platinum as a chemical feed rather than as metal. The sponge is cooled, weighed and sampled, and the sample is assayed — by fire assay with inductively coupled plasma optical emission spectrometry confirmation — before the batch is released. Output: sponge platinum at 99.95% or 99.99%, and 99.999% after a full repeated schedule, with a Certificate of Analysis.

Steps 10 — Melting and Casting to Product Specification. Sponge platinum is melted for customers who want metal rather than powder, and cast or granulated according to the form the customer’s own process needs. Melting is carried out in an induction furnace under a protective atmosphere with a working range up to about 1,600 °C — platinum melts at 1,768 °C, so the furnace has to be specified for the duty rather than chosen from a general-purpose range — and casting produces ingots and bars of 1–6 kg at a minimum purity of 99.95%, the weight and purity range that the LPPM Good Delivery specification recognises. Granulation produces a free-flowing shot or granulate instead, and where the customer wants a chemical rather than a metal, the purified solution is delivered as chloroplatinic acid or ammonium chloroplatinate without passing through metal at all. Each cast bar is stamped with its weight and purity, and each lot is released against its own assay. Output: 99.95%–99.999% platinum ingots, bars, granules or shot, or platinum salts and solutions, released against an assay certificate.

Steps 11 — NOx Scrubbing and Effluent Neutralisation. Aqua regia dissolution on platinum-bearing feed releases nitrogen oxides at roughly 30,000 mg/m³ at the reactor outlet, equivalent to about 20,000 ppm — an order of magnitude above a jewellery gold line — together with chlorine, nitrosyl chloride and acid mist. The reactor head is sealed and the vessel vapour is condensed and returned; the residual gas, the vapour above the reactor and the extraction air from the hood and the filter area are collected by hood and ductwork and pass through a multi-stage absorption train — jet absorption stages followed by an alkaline spray section with a demister — with the absorption liquor circulated and dosed automatically. Absorption efficiency is 99.5% or better, taking the stack below 150 ppm. Fluoride-bearing and chloride-bearing scrubber liquor, filter wash water and vessel rinsings are cross-reused inside the circuit wherever the chemistry allows, and the acid effluent balance is neutralised in an agitated PPH neutralisation tank to a controlled pH before discharge or reuse. Every stream that leaves the process — residue, filter cake, mother liquor, scrubber liquor and clean-up material — is weighed and assayed so that the batch metal balance closes and the recovery figure is measured rather than assumed. Output: compliant stack emission, neutralised and recyclable effluent, and a closed batch metal balance.

Product Structure (Main Equipment)

The circuit is delivered as a set of function-matched units rather than a list of tanks, because purity in platinum refining is produced by the sequence and not by any single vessel — a platinum refining machine bought on its own does not make specification platinum. Each unit below is sized to the feed assay and the required daily output, is built in the material the duty demands, and is connected to the same control system, the same ductwork and the same effluent circuit.

Reaction and dissolution unit — titanium dissolution vessel and glass-lined or enamel-lined reaction vessel with sealed head, sight glass and inspection port, charged from the feed-preparation stage and dosed with acid under controlled rate and temperature. Function: dissolve PGM residue and crude platinum into chloroplatinic acid without loss of vapour or entrained metal.
Reaction fume hood and in-vessel reaction arrangement — a fume hood enclosure in which the reaction is carried out in open, transparent vessels, so that the operator can watch a dissolution that behaves differently with every new feed and adjust the next move on what is actually happening. Function: make aqua regia chemistry on small, high-value batches observable and operable indoors.
Condenser and gas–liquid separator — glass or PP condenser with circulation cooling water and a separator that returns condensate and captured mist to the reaction vessel. Function: recover evaporated acid and metal-bearing mist instead of losing platinum up the exhaust.
Precipitation and reaction vessels — jacketed, agitated platinum precipitation equipment with reagent dosing, temperature control and pH measurement, sized for the precipitation and re-dissolution cycles. Function: precipitate ammonium chloroplatinate reproducibly at 50–80 g/L Pt with free ammonium chloride held at 5–10%.
Hydrolysis and neutralisation vessels — agitated vessels with alkali dosing, temperature control and pH control, arranged so that the hydrolysis precipitate and the platinum-bearing alkaline liquor are separated cleanly. Function: run the oxidative hydrolysis step that removes the impurities precipitation cannot.
Filtration and washing unit — vacuum filter plate, glass wheel filter, filter press and diaphragm pumps, with deionised-water and acidified ammonium chloride washing and a conductivity endpoint check. Function: separate solution from solids and wash occluded salts out of the platinum salt and the impurity hydroxide cake.
Liquid transfer and storage system — glass filter vessels, glass elevated storage tanks and PP solution tanks for aqua regia, chloroplatinic acid, ammonium chloride liquor, reductant and alkali, with vacuum-assisted liquid lift rather than pouring. Function: move and meter process liquors so that no solution is handled by hand and no platinum is left on tank walls.
Reduction vessel and reductant dosing — agitated vessel with temperature control and metered hydrazine hydrate dosing for the platinum-black rework loop. Function: reduce off-spec platinum back to metal so that a contaminated batch is fixed instead of downgraded.
Calcination furnace — muffle or calciner arrangement for the 800 °C decomposition of ammonium chloroplatinate, with thermocouple control and a programme that holds the ramp the product needs. Function: convert purified salt into sponge platinum at a controlled particle condition.
Melting furnace — induction melting furnace specified for platinum duty with a working range up to about 1,600 °C, protective atmosphere, thermocouple monitoring and tilting pour. Function: melt sponge and scrap platinum for casting and granulation.
Casting and granulation equipment — ingot moulds for 1–6 kg bars, granulation equipment for shot and granulate, and mould preheat arrangement. Function: produce the product form the customer’s own process needs — bar, granule or shot.
Centrifugal solvent-extraction and ion-exchange units — centrifugal extractors and ion-exchange columns for the streams where platinum, palladium and rhodium are separated or polished ahead of precipitation. Function: prepare and polish the platinum stream on the way to the precipitation stages.
Hydrogen reduction furnace — hydrogen-atmosphere reduction furnace for the platinum-group-metal fractions that are finished by hydrogen reduction rather than by calcination in air. Function: finish the co-metal fractions that the platinum circuit deliberately leaves in solution.
Multi-stage NOx and acid fume absorption train — jet absorption stages, alkaline spray section, demister, circulation tank, automatic chemical dosing, centrifugal fan and exhaust stack. Function: hold nitrogen oxides and acid mist at the stack below the local emission limit at 99.5% or better absorption efficiency.
Effluent neutralisation unit — agitated PPH neutralisation tank with pH control and transfer pumps, covering roughly 0.05–5 m³ of working volume and rated for atmospheric to −0.1 MPa gauge and −10 °C to 80 °C. Function: neutralise acid effluent to a controlled pH before discharge or reuse.
PLC control system with touchscreen HMI — control of dosing, heating, agitation, scrubbing and neutralisation, with monitoring of temperature, pH, level and scrubber circulation, alarm and interlock logic, and storage and recall of every batch parameter. Function: run every batch reproducibly, protect the equipment and leave a traceable parameter record for each refining lot.
Off-gas and effluent monitoring with interlocks — continuous measurement of nitrogen oxides at the stack, and of pH and conductivity in the effluent circuit, wired to alarm, to automatic dosing and to shutdown. Function: prove compliance continuously and stop the process automatically if a limit is approached.
Sampling and assay station — sample preparation for the spectrographic and fire-assay checks that release each batch, with the balance and record system that the batch metal balance is built on. Function: make the purity claim and the recovery claim verifiable per batch.

Product Features

Each feature below is a design decision taken because of a specific problem in platinum refining, not a general claim. They are listed in the order a buyer evaluates them: what the line produces, how pure, how many cycles it takes, how much metal it holds, how much it loses, and how it behaves in a real refinery building.

Both industrial platinum routes in one flow sheet — repeated ammonium chloride precipitation and oxidative hydrolysis are engineered as one circuit on one frame, so the line accepts both feed that a single precipitation pass can clear and feed that needs hydrolysis to separate platinum from the metals precipitation carries along. Function: one feed gate for the whole range of platinum-bearing material a refinery sees.
Platinum-specific chemistry, stated as parameters — the precipitation concentration of 50–80 g/L Pt, the 5–10% free ammonium chloride, the 5% ammonium chloride wash acidified to pH 1, the three-cycle schedule and the 800 °C calcination are fixed values rather than general references. Function: a buyer can compare the process that will actually be built against any competitor’s description.
Three cycles from 90% crude platinum to 99.99% — purity in platinum refining is built by repetition, and the number of repetitions is a design and cost decision, not a chemical accident. Function: the cycle count is stated up front, so reagent consumption and cycle time are predictable.
Full purity band from 99.9% to 99.999% — the circuit produces any grade in the band on the schedule the customer’s market requires, from a single precipitation pass at the lower end to a fully repeated dissolution–precipitation schedule at the top end. Function: the same plant serves a catalyst customer and a five-nines customer.
Rework loop for off-spec salt — contaminated salt is calcined back to crude platinum, or reduced with hydrazine hydrate to platinum black and redissolved in hydrochloric acid with hydrogen peroxide for re-precipitation. Function: an off-spec batch costs a rework cycle instead of a downgraded lot.
Gold, palladium and iridium deliberately kept in solution — the precipitation step is designed so that the co-metals stay in the mother liquor and are recovered as separate streams rather than being dragged into the platinum salt and having to be removed later. Function: the platinum product starts cleaner, and the co-metals are sold rather than lost.
Oxidative hydrolysis as a second separation lever — in alkaline medium platinum forms the soluble hydroxo complex NaPt(OH)₆ while the other precious and base metals hydrolyse out. Function: the impurities that precipitation alone cannot clear are removed by a different mechanism, not by more of the same.
Sealed reactor head with condensate return — dissolving platinum in aqua regia releases roughly 30,000 mg/m³ of nitrogen oxides and the vapour carries metal; the vapour is condensed and the condensate is returned to the reactor. Function: the high-temperature, high-acid duty stops being a metal-loss route and becomes part of the process.
Reaction inside a fume hood, in observable vessels — dissolution and separation are carried out in transparent vessels in a hood, with in-vessel reaction and in-filter separation. Function: the operator can judge a reaction and take the next decision, which is what small, variable, high-value batches require.
Vacuum-assisted liquid transfer — solution is moved by vacuum lift between glass filter vessels, elevated tanks and storage rather than poured. Function: no spillage of metal-bearing liquor, and no platinum left on the floor.
Materials selected against the duty — titanium for dissolution vessels, glass for condensers, filter vessels and elevated tanks, enamel-lined steel where the duty demands it, and PPH for structural framing, ductwork and effluent duty. Function: a chloride-and-acid plant built from materials a chloride-and-acid plant needs.
Nitric acid parting for silver- and palladium-bearing feed — where the feed carries silver and palladium, a nitric pre-treatment at 80–90 °C for about three hours removes them ahead of the platinum dissolution. Function: silver and palladium are recovered as separate products instead of contaminating the platinum salt.
Quantified emissions performance — an inlet above 30,000 mg/m³ brought below 150 ppm at 99.5% or better absorption, with multi-stage jet absorption and an alkaline spray section delivered as one train with automatic dosing. Function: permit applications and inspections are answered with numbers rather than with adjectives.
Closed-loop mother liquor and wash water — mother liquor is stripped for its gold, palladium and iridium content before it leaves the circuit, and wash water and scrubber liquor are cross-reused where the chemistry allows. Function: lower reagent consumption, less effluent, and no precious metal leaving in a drain.
Batch metal balance, not a claimed recovery — feed weight and assay in, product weight and assay out, and every residue, filter cake, mother liquor and clean-up stream weighed and assayed. Function: the recovery figure is measured per batch and can be audited by the customer.
Verification built into the product — every lot is released against fire assay with ICP-OES confirmation, and X-ray fluorescence is used only as a screening check, because it reads a surface and not a bar. Function: the Certificate of Analysis is defensible to a trading counterparty.
Both primary and secondary feed in one engineering frame — the line is designed so that ore-derived concentrate, anode slime, spent catalyst residue and strip liquor all enter the same refining circuit. Function: the plant does not have to be rebuilt when the customer’s feed mix changes.
PLC control with batch parameter logging — dosing, temperature, pH, agitation and scrubber parameters are controlled, logged and recallable per batch, with interlocks that act automatically when a parameter goes abnormal. Function: reproducible batches, and process problems diagnosed from data rather than from memory.
Modular and expandable — the circuit is built as function-matched units that can be laid into an existing refinery building or supplied as a compact, containerised unit, and extended later as throughput or feed range grows. Function: capacity grows with the business instead of in one capital step.
Single-supplier interface — dissolution, precipitation, hydrolysis, filtration, reduction, calcination, melting, scrubbing, neutralisation and control come from one engineering team with one control philosophy and one commissioning crew. Function: no argument between vendors when a stream underperforms.

Technical Parameters & Specifications

The table below states the engineering parameters of the platinum refining process line — the parameters that are validated in commissioning and recorded per batch. Capacities, installed power, footprint, clear height and utility loads are engineered to the customer’s feed assay and required daily output and are therefore confirmed in the technical proposal rather than fixed here; the process parameters — concentrations, free ammonium chloride, wash acidity, cycle count, calcination temperature, purity, recovery and emission limits — are fixed values that the line is guaranteed to hold.

Parameter	Specification
Applicable feed grade	Crude platinum above about 90% Pt for direct dissolution; PGM concentrate, leach liquor, solvent-extraction strip liquor, spent catalyst residue and anode slime as received after assay and pre-treatment
Feed concentration for precipitation	50–80 g/L Pt, adjusted before ammonium chloride is added
Ammonium chloride excess	Free ammonium chloride held at 5–10% in the mother liquor after precipitation
Salt wash liquor	5% ammonium chloride solution acidified with hydrochloric acid to pH 1
Dissolution chemistry	Aqua regia at approximately 1:3 HNO₃ : HCl, added in portions; sodium chlorate as an alternative oxidant for material that resists aqua regia
Dissolution temperature	80–90 °C, with the reactor head sealed and vapour condensed and returned
Nitric acid parting	Approximately 80–90 °C for about 3 hours, where the feed carries silver or palladium
Hydrolysis medium	Alkaline; platinum forms the soluble hydroxo complex NaPt(OH)₆ while other precious and base metals hydrolyse to insoluble hydroxides
Purification cycles	3 dissolution–precipitation cycles on 90% crude platinum to reach the pure salt for calcination
Rework route	Off-spec salt calcined back to crude platinum and redissolved, or reduced at room temperature with hydrazine hydrate to platinum black, redissolved in HCl + H₂O₂ and reprecipitated
Calcination temperature	800 °C, decomposing the ammonium salt to sponge platinum
Product purity	99.9% to 99.999%; 99.95% and 99.99% as the standard grades
Product forms	Sponge, powder, granules, shot, cast bars of 1–6 kg to a minimum purity of 99.95% to the LPPM Good Delivery specification, and platinum salts and solutions
Platinum recovery	98–99% on a closed batch metal balance, dependent on feed grade and on the form in which the platinum is present
Cycle time	1–4 days for a platinum or palladium cycle, against the 1–10 days general practice for platinum and palladium
Primary-route concentration	Flotation concentrate 85–850 g/t PGM; converter matte approximately 1.4 kg/t PGM; residue after base-metal removal 15–20% PGM
Ore feed grade	Approximately 2–6 g/t platinum in the ore as mined
Smelting temperature	Above 1,200 °C for concentrate smelting; approximately 1,350 °C for matte smelting and up to about 1,600 °C for chromite-bearing concentrate
Base-metal removal	Pressure leaching with sulphuric acid, dissolving copper, nickel and iron and leaving the PGMs in the residue
Nitrogen oxide inlet load	Above 30,000 mg/m³ at the reactor outlet, approximately 20,000 ppm
Nitrogen oxide outlet concentration	Below 150 ppm at the stack
Absorption efficiency	99.5% and above, with multi-stage jet absorption and an alkaline spray section
Off-gas capture	Sealed reactor head, vapour condenser and gas–liquid separator with metal-bearing condensate returned to the reactor
Effluent neutralisation	Agitated PPH tank, atmospheric to −0.1 MPa gauge, −10 °C to 80 °C, working volume approximately 0.05–5 m³, pH controlled and monitored
Wetted materials	Titanium, glass, enamel-lined steel and PPH selected against the duty
Reaction enclosure	Reaction fume hood with in-vessel reaction and in-filter separation
Liquid transfer	Vacuum-assisted liquid lift; no solution handled by pouring
Melting and casting	Induction melting with a working range up to about 1,600 °C; platinum melts at 1,768 °C; cast bars of 1–6 kg, or granulation to shot and granulate
Control system	PLC with touchscreen HMI, dosing, temperature and pH control, alarms and interlocks, and storage and recall of every batch parameter
Product verification	Fire assay with ICP-OES confirmation for every lot; X-ray fluorescence as a screening check only
Batch metal balance	Feed weight and assay, product weight and assay, and every residue, filter cake, mother liquor and clean-up stream weighed and assayed per batch
Nominal capacity	Configured to your feed assay and required daily platinum output
Installed power	Configured to capacity, unit count and local supply voltage
Footprint and clear height	Configured to throughput and laid out into your existing refinery building or supplied as a compact unit
Utilities	Configured to assay, throughput and site conditions: cooling water, deionised water, compressed air, extraction air volume, hydrogen and reagent storage

Technical Advantages

Platinum refining equipment is easy to describe and hard to verify. Almost every supplier of PGM refining equipment in this market quotes a purity figure and “high recovery”; very few publish the precipitation concentration, the free ammonium chloride, the wash acidity, the number of cycles, the calcination temperature, the nitrogen oxide load or the recovery basis that make those numbers possible. The advantages below are stated as values a buyer can test in a factory acceptance or a commissioning trial, and they are the reason this circuit performs differently from a precipitation-only plant of the same nominal capacity.

Both separation mechanisms, not one — precipitation separates platinum from the base metals and from the low-valent chloroammonium salts of gold, palladium and iridium; oxidative hydrolysis separates platinum from the metals that precipitation carries with it. A precipitation-only plant has to reject or repeatedly rework feed that this circuit routes through hydrolysis once. Advantage: a wider feed range at the same vessel count, and fewer cycles wasted on material a different mechanism would clear in one pass.
Parameters published, not described — 50–80 g/L Pt in the precipitation feed, 5–10% free ammonium chloride, a 5% ammonium chloride wash at pH 1, three dissolution–precipitation cycles and 800 °C calcination are stated as guaranteed values. Advantage: reagent consumption, cycle time and cycle count are quantities the buyer can plan against instead of inferring.
Purity built by counted repetition — the step from 90% crude platinum to 99.99% is three dissolution–precipitation cycles, and the number is a design decision that carries a known reagent and time cost. Advantage: the cost of each additional nine of purity is visible before the plant is bought, not after.
The full 99.9%–99.999% band in one plant — the same vessels serve a catalyst customer buying 99.95% and a five-nines customer requiring 99.999%, on a longer or shorter precipitation schedule. Advantage: no second plant is needed when the market moves up the purity ladder.
Off-spec material reworked inside the circuit — an off-spec salt is calcined back to crude platinum, or reduced with hydrazine hydrate to platinum black and redissolved in HCl + H₂O₂ for re-precipitation. Advantage: an off-spec batch costs a rework cycle; in a precipitation-only plant with no rework loop it costs a downgraded lot.
Co-metals kept out of the platinum precipitate by design — gold, palladium and iridium are held in the mother liquor and recovered as separate streams. Advantage: the platinum product starts cleaner, fewer cycles are needed to reach the target, and the co-metals are realised as separate sales lines rather than diluted into the platinum.
Cobalt- and ruthenium-bearing jewellery and industrial alloy feed handled — the alloying metal is taken out ahead of platinum precipitation rather than carried through it. Advantage: the circuit is not restricted to high-grade scrap, which is where most of the platinum-containing secondary material actually sits.
Nitric acid parting ahead of the platinum chemistry — silver- and palladium-bearing material is pre-treated at 80–90 °C for about three hours, so that silver and palladium become products rather than contaminants. Advantage: anode slime and ore-derived residue can be treated without a separate silver circuit.
Reactor vapour condensed and returned instead of vented — the dissolving vessel runs at 80–90 °C in aqua regia, and the vapour it produces carries platinum. Condensate is returned to the vessel. Advantage: the high-temperature, high-acid duty stops being a loss mechanism.
Emissions performance that can be quoted as a number — 99.5% or better absorption, an inlet above 30,000 mg/m³ brought below 150 ppm at the stack, with jet absorption stages and an alkaline spray section delivered as one train with automatic dosing. Advantage: permit applications, audits and local inspections are answered with measured data instead of a specification sheet.
Reaction conducted where it can be seen — dissolution and separation take place in transparent vessels inside a reaction fume hood, with in-vessel reaction and in-filter separation and vacuum-assisted liquid transfer. Advantage: the operator can judge an unfamiliar feed, and no metal-bearing solution is handled by pouring.
Materials chosen against the duty, not against a price list — titanium for dissolution duty, glass for condensers and filter vessels, enamel-lined steel where the duty demands it, PPH for framing, ductwork and effluent duty. Advantage: a chloride-and-acid plant that survives a chloride-and-acid environment.
Mother liquor stripped before it leaves the circuit — the liquor that carries the gold, palladium and iridium is processed rather than bled. Advantage: the recovery figure holds up because the biggest metal-bearing stream in the plant is closed.
Recovery reported per batch instead of claimed — feed in and product out are weighed and assayed, and so is every residue, filter cake, mother liquor and clean-up stream, against a 98–99% recovery band that depends on feed grade and on the form the platinum is in. Advantage: a buyer can audit the recovery rather than accept it.
Verification appropriate to the product — fire assay with ICP-OES confirmation for release, X-ray fluorescence only as a screening check. Advantage: the assay certificate survives scrutiny by a trading counterparty, which a surface measurement would not.
Cycle time stated against general practice — 1–4 days for a platinum or palladium cycle against the 1–10 days general practice. Advantage: less platinum tied up as work in progress and released back to sale sooner.
Small-batch operation designed for small-batch reality — PGM separation is a low-tonnage, high-value operation, so vessels, filters and transfer arrangements are matched to batch sizes rather than scaled up for appearance. Advantage: less metal held on walls, in filter media and in dead volumes.
One supplier for the whole train — dissolution, precipitation, hydrolysis, filtration, reduction, calcination, melting, casting, scrubbing, neutralisation and control come from one engineering team with one control philosophy. Advantage: single-point accountability at commissioning and afterwards.

Service Process

The circuit is delivered as an engineered plant, so the service process is a project process: the feed is tested before the flowsheet is fixed, the flowsheet is designed around the customer’s building and permit, the equipment is proved in a factory acceptance test before dispatch, and the plant is commissioned to a performance test rather than simply switched on.

Steps 1 — Raw Material Testing and Route Selection. A representative sample of the customer’s feed is received, weighed, homogenised and assayed in the laboratory — platinum, palladium, rhodium, iridium, gold and silver by fire assay with ICP-OES or ICP-MS confirmation, plus a base-metal determination, because the co-metal content decides how many precipitation cycles the route needs and how much of the mother liquor has to be stripped. Dissolution and precipitation trials establish reagent consumption, expected recovery and the achievable purity band for that specific material, and the customer receives a test report stating the recommended route before any equipment is specified. Output: a laboratory test report with assay, recommended route, reagent consumption, achievable purity band and expected recovery.

Steps 2 — Flowsheet and Plant Layout Design. The flowsheet is drawn for the tested feed and the required daily output, with equipment sized on the peak simultaneous load rather than the average, and the layout is drawn into the customer’s actual building — clear height, floor loading, fume hood and extraction routing, chemical storage and bunding, effluent route, hydrogen supply and operator access all resolved on the drawing. Where the site is new, remote or space-limited, a compact unitised arrangement is developed instead. The deliverable is a technical proposal with an equipment list, a utility schedule, a footprint drawing and the process guarantees the plant will be commissioned against. Output: a technical proposal with flowsheet, layout, equipment list, utility schedule and process guarantees.

Steps 3 — Equipment Manufacturing and Factory Acceptance Test. Equipment is manufactured to the released drawings, wetted parts are verified against the duty materials, and the dissolution vessel, precipitation vessels, filtration, scrubbing and control system are assembled and wired as a set. Before dispatch the customer is invited to witness a factory acceptance test that includes a hydrostatic and leak test on the wetted assemblies, a functional test of the PLC, dosing, temperature and pH control, scrubbing and interlocks, and where feed is available a trial batch confirming dissolution and precipitation behaviour. Output: a factory acceptance test report and released equipment.

Steps 4 — Shipment, Installation and Commissioning. Equipment is packed for sea or land freight — glassware, condensers and filter vessels crated separately with the fragile items identified, frames and vessels on cradles, with a packing list keyed to the installation drawings — and our engineers attend site to supervise installation, set the fume hood and ductwork, connect the effluent and scrubber circuits and commission the plant. Commissioning runs on the customer’s own material wherever possible and closes with a performance test on product purity, recovery, cycle time, reagent consumption and stack emission. Output: an installed and commissioned circuit with a signed performance test record.

Steps 5 — Operator Training and Production Handover. The customer’s operators and supervisors are trained on the delivered plant rather than on a generic manual: feed sampling and assay, acid handling and dosing, dissolution and off-gas control, precipitation with ammonium chloride, washing at pH 1, hydrolysis and separation, the rework route for off-spec salt, calcination, melting and casting, scrubber operation and dosing, effluent neutralisation, and what to do when a parameter goes out of range. Training combines classroom sessions on the chemistry with hands-on operation of each unit, and covers the PLC screens, alarm handling and batch record keeping. Handover is not complete until the customer’s team can run a full batch unaided. Output: trained operating and supervisory staff, and a documented handover.

Steps 6 — Warranty, Spare Parts and Preventive Maintenance. A bill of wearing and critical spares is agreed at the contracting stage and can be shipped with the plant, so that filter media, gaskets, seals, pump parts, glassware, condenser parts, dosing components and furnace elements are on site before they are needed. A preventive maintenance schedule is issued covering vessel and glassware inspection intervals, filter media replacement, dosing pump and valve calibration, condenser and duct cleaning, scrubber packing and dosing checks, furnace element inspection, and calibration of the pH, temperature and nitrogen-oxide instruments. Output: an installed spare-parts package and a scheduled preventive maintenance programme.

Steps 7 — Remote Diagnostics and Continuous Process Improvement. Process parameters logged by the control system can be shared with our engineers for review, so that a drift in product assay, a rise in reagent consumption, a fall in absorption efficiency or a change in filtration behaviour can be identified from data before it becomes a batch problem. Batch records are reviewed against the original test report, and where the feed or the product requirement changes — a new source of spent catalyst, a higher purity target, a larger daily output, a decision to make salts rather than metal — the route, the reagent charge and the precipitation schedule are revised and additional units are added to the existing frame. Output: data-based process support, with an upgrade path as the customer’s business changes.

Warranty & After-Sales Service

The warranty applies to equipment designed, manufactured and supplied by YuSai Machinery, covers defects in design, materials and workmanship under normal operating conditions, and is honoured through the same engineering team that commissioned the plant. Warranty terms, the covered scope, the excluded items and the response times are fixed in the contract so that both parties know what is included before the equipment is shipped.

Warranty period — the standard warranty runs from the date of successful commissioning, with the exact duration fixed in the contract; extended warranty is available on request. Function: a defined window in which supplier responsibility is unambiguous.
What is covered — design, materials and workmanship of the supplied equipment, including the dissolution and reaction vessels, fume hood and ductwork, condenser and gas–liquid separator, precipitation and hydrolysis vessels, filtration and washing unit, liquid transfer and storage system, reduction vessel, calcination furnace, melting and casting equipment, solvent-extraction and ion-exchange units where supplied, the absorption train, the effluent neutralisation tank, and the PLC programme and control logic as supplied. Function: the customer is not left to argue about which vendor owns a fault.
What is not covered — consumable and wearing items such as filter media, packing, seals, gaskets, glassware, dosing components and furnace elements; damage from operation outside the agreed parameters, from feed outside the agreed specification, from failure to follow the maintenance schedule, from unauthorised modification, or from reagents and utilities outside specification; and freight, import duties and site civil works. Function: a clear boundary so that both sides can plan.
Response and attendance — a service engineer responds to a reported fault within an agreed time from notification, with telephone and remote diagnosis first and site attendance where the issue requires it; the response and attendance times are set out in the contract for the customer’s region. Function: a fault is answered within a known interval rather than whenever an engineer becomes available.
Remote support — remote review of PLC logs, batch records, reagent consumption history, pH and temperature traces and scrubber readings allows most process questions to be answered without a site visit. Function: faster resolution and fewer unnecessary trips.
Spare parts — a recommended wearing and critical spares list is issued with the plant and can be supplied as an initial stock; ongoing spares are supplied against the equipment list with the parts identified by drawing and position. Function: the plant can be maintained without reverse-engineering parts.
Consumables and reagents specification — the specification of ammonium chloride, hydrochloric and nitric acid, sodium chlorate, hydrazine hydrate, hydrogen peroxide, alkali, filter media, packing and glassware is documented so that local sourcing does not compromise purity, cycle time or emission performance. Function: local supply without a drop in performance.
Training and refresher support — operator training is delivered at commissioning and can be repeated when staff change or when the plant is expanded; refresher and advanced training on precipitation control, hydrolysis separation, off-spec rework and emission control is available. Function: operating standards hold after the commissioning team leaves.
Process support on new feed — when the customer brings a new feed material, our laboratory can test it and confirm whether the existing route, reagent charge and cycle count remain valid or need revision. Function: the refinery keeps its purity guarantee as its feed range widens.
Documentation — the plant is handed over with an operation and maintenance manual, an electrical and instrument schematic, a spare parts list, a commissioning and performance test record, the equipment drawings and the batch metal balance template. Function: a plant that can be operated, maintained and audited without the supplier present.

Frequently Asked Questions

Q1. What is the platinum refining process in simple terms?
The platinum refining process turns platinum-bearing material that is already concentrated — PGM residue from a smelter, crude platinum, leach liquor or spent catalyst residue — into specification platinum metal by moving the platinum between a solid and a dissolved state until the impurities are gone. The platinum is dissolved in aqua regia to chloroplatinic acid, ammonium chloride is added to precipitate ammonium chloroplatinate while the base metals and the gold, palladium and iridium salts stay in solution, the salt is washed, redissolved and precipitated again, and the purified salt is finally calcined at 800 °C into sponge platinum of 99.95% to 99.99%.

Q2. How is platinum refining different from gold refining?
Two differences matter. First, gold is finished by electrolysis; industrial platinum is not. Molten-salt electrolysis of platinum exists but has never been industrialised, so platinum is finished by precipitation and calcination chemistry. Second, platinum is normally not alone in the solution. Gold refining handles gold with base-metal impurities; a platinum refinery handles a solution that also contains palladium, rhodium, iridium, ruthenium and often gold, so the process has to separate platinum from other precious metals, not only from base metals. That is why a platinum circuit is built around the two specific properties of platinum compounds and why the co-metals are deliberately kept in the mother liquor.

Q3. Why is platinum not refined by electrorefining?
Because the chemistry that makes gold electrolysis work does not carry across. Platinum’s chloro-complex is comparatively stable, which means the differences between the oxidation states of platinum are not large enough to drive a clean anodic–cathodic separation of the way they do for gold. Molten-salt electrolysis has been demonstrated at laboratory and pilot scale — a crude platinum anode in a potassium chloroplatinate alkaline chloride electrolyte at around 500 °C takes 95% crude platinum to about 99.9% platinum on the cathode — but the process is complex, difficult to operate and hard to scale, so industry refines platinum chemically instead.

Q4. What purity can the process reach, and how is it verified?
The circuit holds the full band from 99.9% to 99.999%, with 99.95% and 99.99% as the standard grades and 99.999% available on a fully repeated dissolution–precipitation schedule. Every lot is released against fire assay with ICP-OES confirmation on a sample taken from the product; X-ray fluorescence is used only as a screening check, because it reads the surface of a sample rather than the whole of it and cannot release a bar. A small sample of the precipitated salt is also calcined and assayed before the batch proceeds, so the decision to continue is made on an analysis rather than on a colour.

Q5. What is the role of ammonium chloride in platinum refining?
Ammonium chloride is the reagent that takes platinum out of solution. In acidic chloride medium it reacts with chloroplatinic acid to form ammonium chloroplatinate, (NH₄)₂PtCl₆, a yellow sparingly soluble salt, while the base-metal chlorides and the low-valent chloroammonium salts of gold, palladium and iridium remain dissolved. It is added in excess, so that the free ammonium chloride concentration after precipitation is 5–10% — the excess is what drives the precipitation towards completion, since the salt has a measurable solubility and platinum left in solution has to be recovered in the next cycle. The precipitate is then washed with 5% ammonium chloride acidified to pH 1, which removes occluded base-metal liquor without redissolving the platinum.

Q6. What is oxidative hydrolysis, and when is a platinum circuit needed?
In alkaline medium platinum behaves in the opposite way to most of the metals around it: it forms a soluble hydroxo complex, NaPt(OH)₆, while the other precious metals and the base metals hydrolyse into insoluble hydroxides. Precipitation therefore separates platinum with the salt and leaves the base metals and gold, palladium and iridium behind; hydrolysis separates platinum from the impurities that hydrolysis precipitates. A circuit is used where the feed carries rhodium, iridium or base metal at levels a single precipitation cycle cannot clear, because it removes those impurities by a different mechanism rather than by repeating the same one.

Q7. How many dissolution and precipitation cycles are needed?
In normal operation, crude platinum assaying about 90% Pt reaches ammonium chloroplatinate pure enough to calcine into 99.99% platinum in three dissolution–precipitation cycles. The number of cycles is not fixed by chemistry alone: it is a design choice, and a feed carrying more iridium or base metal, or a customer requiring 99.999%, takes more cycles at a known reagent and time cost. Off-specification salt does not consume a cycle — it is calcined back to crude platinum and redissolved, or reduced at room temperature with hydrazine hydrate to platinum black, redissolved in hydrochloric acid with hydrogen peroxide and precipitated again with ammonium chloride.

Q8. What happens to the gold, palladium and iridium in the feed?
They are deliberately left in the mother liquor rather than precipitated with the platinum, and they are recovered from it as separate streams. Palladium and gold are taken out of the mother liquor by their own precipitation and reduction routes, and the iridium, rhodium and ruthenium fraction that resists both acid dissolution and precipitation is washed, dried, bagged and assayed as a PGM residue for onward separation. In a well-designed platinum circuit the mother liquor is inventory rather than waste, which is why it is stripped before it is bled.

Q9. What concentration does the solution have to be at before precipitation?
The liquor is adjusted to 50–80 g/L Pt and heated before ammonium chloride is added. The lower bound exists because a dilute solution precipitates incompletely and leaves recoverable platinum behind; the upper bound exists because a concentrated solution precipitates a salt that occludes more mother liquor and therefore needs more washing. Both bounds are process parameters that the plant is built to hold, not general recommendations.

Q10. Can the line treat both ore-derived concentrate and spent catalysts?
Yes, and that is a deliberate design decision. Ore-derived material arrives after flotation, matte smelting, converting and pressure leaching as a residue carrying 15–20% PGMs; spent catalyst material arrives as a roasted, milled concentrate carrying platinum with palladium and rhodium on a carrier; anode slime arrives as a residue with silver and gold; leach liquor and strip liquor arrive as solutions ready for precipitation. All of them enter the same refining circuit, because the chemistry the circuit uses is set by the platinum solution and not by the material’s history.

Q11. Which extractants and separation technologies are used?
The separation train is configured from selective precipitation, centrifugal solvent extraction and ion exchange, and the extractant selection is fixed in the laboratory test rather than on the drawing board. In the PGM and base-metal circuits the extractant family that matters in practice is the acidic organophosphorus and phosphinic group — P204 (D2EHPA), P507 (HEHEHP), C272 (Cyanex 272) — together with TBP and DBC as the solvating and sulphide extractants used for platinum and palladium. Ion exchange is used where the precious-metal concentration in a stream is low and a resin or a ligand-loaded column is the economical way to recover it. Which of these applies to a given feed is determined by the constituent concentrations in that feed, and it is one of the outputs of the laboratory test report.

Q12. What recovery can be expected, and how is it measured?
98–99% on a closed batch metal balance, dependent on the feed grade and on the form in which the platinum is present. It is measured rather than claimed: the feed is weighed and assayed, the product is weighed and assayed, and every residue, filter cake, mother liquor, scrubber liquor and clean-up stream is weighed and assayed, with the difference reported as the loss. Platinum retained on vessel walls, in filter media and in condenser and ductwork is addressed as a design variable — glass and titanium wetted parts, vacuum-assisted transfer and condensate returned to the reactor — rather than accepted as a working loss.

Q13. How long does a platinum refining cycle take?
A platinum or palladium cycle runs in 1–4 days on this circuit, against the 1–10 days general practice for platinum and palladium; rhodium takes longer, in the region of 3–7 days on our route against about 15 days generally. Cycle time matters more in platinum refining than in most process industries, because the material in process is metal at market price and a slow cycle means more of it tied up as work in progress. The number of batches per day is set by the number of vessels in service, which is why capacity is configured to the required daily output rather than fixed by a single model.

Q14. Do I need aqua regia, and where does the nitrogen oxide go?
Aqua regia is the standard dissolution medium for platinum, at approximately one part nitric acid to three parts hydrochloric acid, and sodium chlorate is available as an alternative oxidant for material that resists aqua regia. Dissolution releases nitrogen oxides at roughly 30,000 mg/m³ at the reactor outlet, close to 20,000 ppm — roughly an order of magnitude above a jewellery gold line — so it is not treated as a nuisance stream. The reactor head is sealed, the vapour is condensed and the condensate is returned to the reactor, and the residual gas passes a multi-stage jet absorption train with an alkaline spray section at 99.5% or better absorption, taking the stack below 150 ppm. Acid effluent is neutralised to a controlled pH before discharge or reuse.

Q15. What space, power and utilities does the plant need?
Footprint, clear height, installed power and utility loads are configured to the feed assay, the required daily output and the customer’s building, and are stated in the technical proposal rather than fixed here. The process parameters are not configured: a precipitation feed of 50–80 g/L Pt with 5–10% free ammonium chloride, a pH 1 wash, three cycles, an 800 °C calcination, 99.5% or better absorption and below 150 ppm at the stack are the values the plant is guaranteed to hold. Utilities that matter most are cooling water, deionised water, compressed air, extraction air volume, hydrogen where a hydrogen reduction furnace is included, and reagent storage and bunding.

Q16. What is included with the plant, and what is not?
Included: the dissolution and reaction vessels, fume hood and ductwork, condenser and gas–liquid separator, precipitation and hydrolysis vessels, filtration and washing unit, liquid transfer and storage system, reduction vessel, calcination furnace, melting and casting equipment, solvent-extraction and ion-exchange units where specified, the multi-stage absorption train, the effluent neutralisation tank, the PLC control system with interlocks and batch logging, and the documentation, training and commissioning that go with them. Not included unless separately agreed: site civil works and foundations, building and extraction ductwork outside the equipment battery limit, chemical storage buildings and bunding, electrical supply to the plant terminal, reagents, hydrogen supply infrastructure, and local permits and approvals.

Q17. Does the process produce platinum salts as well as metal?
Yes, and for some customers the salt is the more valuable product. The purified intermediate can be delivered as chloroplatinic acid solution or crystals, as ammonium chloroplatinate, or as other platinum chloride compounds at reagent specification, without ever passing through metal — which is the shorter and cheaper route for a customer whose own process starts from solution. Where platinum is instead required on a support for catalyst manufacture, the purified solution is delivered as the impregnation feed rather than as a finished catalyst. The calcination and melting stages are skipped in those cases, and the circuit branches after purification instead of running to metal.

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