Platinum

Typical wastewaters

• hospital effluent (cisplatin and carboplatin) hydrolysed Pt(II) cytostatic drugs excreted by patients, dissolved, below 10 to 601 ng/L as daily averages and 20 to 3,580 ng/L in 2 hour composites at five European hospitals 3.3 to 12.3 percent of the estimated catalytic converter emissions in the countries studied
• road runoff (catalytic converters) platinum metal particles shed by converters, the main source of platinum to urban drainage no runoff concentration was read
• municipal sewage cytostatic platinum from hospitals and converter particles from road runoff, adsorbed to activated sludge hospital effluents are a minor source compared with cars but should not be disregarded

1 · Identity

Symbol, number

Pt, 78

Oxidation states in water

+2 and +4 as chloro and hydroxo complexes (PtCl₄²⁻, PtCl₆²⁻) and as the hydrolysed cytostatic drugs; 0 as the metal particles shed by converters.

Note

The element entry covers the metal and its salts. In water platinum is a trace pollutant measured by clean ICP-MS, not a treatment parameter.

2 · Occurrence in water

Natural sources

Negligible; native platinum in river sediments (element entry).

Anthropogenic sources

Car catalytic converters, the main source; hospital effluent from cisplatin and carboplatin, which emitted 3.3 to 12.3 percent (1.3 to 14.3 kg per year) of the estimated converter emissions in the European countries studied (Kummerer 1999); refinery and jewellery workshops in the ledger.

3 · Speciation

Platinum from converters is metallic and particulate; dissolved platinum is chloro or hydroxo complexed Pt(II) and Pt(IV), and the cytostatic drugs hydrolyse to aquated species that bind organic matter. Not sourced beyond the abstract.

Solubility

The metal is inert; the chloro complexes are soluble.

Hydrolysis

not relevant

Complexation

Chloride and amine ligands (the drugs).

Precipitates

not relevant

4 · Role in treatment

5 · Removal and control

6 · Analytics

Sampling pitfalls

Contamination from jewellery and laboratory ware; 2 hour composites vary 30 fold against daily averages in hospital sewage (Kummerer).

7 · Regulatory limits

Limits change, and many are set locally. Treat these as the published values to start from, not as your compliance target: check the standard in force at your site and the numbers written into your own permit.

8 · Health and environmental effects

Toxicity

Platinum salts are respiratory sensitisers occupationally; the cytostatic drugs are the toxic and genotoxic forms in effluent (not sourced beyond the abstract).

Bioaccumulation

not relevant

Ecotoxicity

not relevant

Flags

• Only the abstract of Kummerer 1999 was read.
• Road runoff platinum concentrations appeared only in search summaries and are not quoted.

Gaps

• No source read gives platinum in road runoff, rivers, seawater or municipal effluent as numbers.
• Speciation and removal of platinum cytostatics in sewage treatment (activated sludge sorption, advanced oxidation) were not read; the open access reviews found were not reachable.
• No GCC document mentions platinum.

Sources

Identity

Name and symbol

Platinum, Pt

Atomic number

78 protons

Position

group 10 · period 6 · d-block · transition metal

CAS number

7440-06-4

Atomic structure

Atomic mass

195.084 u

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s¹ 4f¹⁴ 5d⁹
[Xe] 6s¹⁴f¹⁴⁵d⁹

Electrons per shell

2, 8, 18, 32, 17, 1

Valence electrons

10 ns and (n-1)d

Physical properties

State at room temperature

Solid

Melting point

2,041.55 K (1,768.4 °C)

Boiling point

4,098 K (3,824.85 °C)

Density

21.46 g/cm3

Appearance

silvery white

Thermal conductivity

71.6 W/(m·K)

Electrical resistivity

105 nΩ·m at 20 °C

Electrical conductivity

9.52 MS/m

Crystal structure

face-centered cubic

Molar heat capacity

25.86 J/(mol·K)

Chemical properties

Oxidation states

+4, +2

Electronegativity

2.28 (Pauling Scale)

Ionisation energy

9 eV
1st 870, 2nd 1,791 kJ/mol

Electron affinity

2.128 eV

Atomic radius

empirical 136, covalent 136, van der Waals 209 pm

Ionic radius

Pt²⁺ 80; Pt⁴⁺ 63; Pt⁵⁺ 57 pm

Reactivity

A noble metal of group 10, one of the least reactive elements: bulk platinum does not oxidise in air at any temperature and resists single acids, so it occurs native; its chemistry is mostly square planar Pt(II) and octahedral Pt(IV), and finely divided platinum is an outstanding catalyst.

with water

Does not react with water.

with oxygen, air

The bulk metal does not oxidise in air at any temperature; hot wires lose a little weight through a thin surface film of PtO2 that decomposes above 500 C.

with acids

Insoluble in hydrochloric and in nitric acid alone, but dissolves in hot aqua regia to chloroplatinic acid: $\ce{Pt + 4 HNO3 + 6 HCl -> H2PtCl6 + 4 NO2 + 4 H2O}$, the usual entry to platinum chemistry.

with halogens

Corroded by the halogens: fluorine reacts vigorously at 500 C to the tetrafluoride: $\ce{Pt + 2 F2 -> PtF4}$, and chlorine on heating gives the chlorides: $\ce{Pt + 2 Cl2 -> PtCl4}$, with bromine and iodine also attacking it.

Typical compounds

• H₂PtCl₆ chloroplatinic acid from aqua regia, the common soluble platinum reagent
• PtCl₂ platinum(II) chloride olive-green +2 halide, starting point for complexes
• PtO₂ platinum(IV) oxide hydrogenation catalyst precursor, decomposes above 500 C
• K₂PtCl₄ potassium tetrachloroplatinate red square planar Pt(II) salt
• Pt(NH₃)₂Cl₂ cis-diamminedichloroplatinum(II) square planar complex that cross-links DNA in chemotherapy

Occurrence, production and use

Crustal abundance

5×10-3 milligrams per kilogram

Oceanic abundance

Not Applicable

Occurrence and sources

Platinum occurs natively, accompanied by small quantities of iridium, osmium, palladium, ruthenium, and rhodium, all belonging to the same group of metals. These are found in the alluvial deposits of the Ural mountains, of Columbia, and of certain western American states. Sperrylite, occurring with the nickel-bearing deposits of Sudbury, Ontario, is the source of a considerable amount of metal.

The large production of nickel makes up for the fact that is only one part of the platinum metals in two million parts of ore.

• cooperite (PtS) and other PGM minerals in layered intrusions Bushveld Complex, South Africa (largest resources and reserves); Great Dyke, Zimbabwe; Norilsk, Russia; Stillwater, Montana
• native platinum in alluvial deposits; by-product of copper and nickel refining Colombia, Urals, Sudbury
• crustal abundance 0.000037 ppm (BGS group figure for all PGMs via RSC); 0.005 mg/kg crust (PubChem)

Extraction, production

Mined PGM concentrate, smelting and refining; by-product of nickel and copper refining

no chemistry stated by the sources; historically platinum was purified by dissolution in aqua regia and precipitation, the process that yielded palladium, rhodium, osmium and iridium

Recovery from spent automotive catalysts

about 8,500 kg of platinum from US catalytic converters in 2024

Uses

Platinum is a soft, dense, ductile metal that is very resistant to corrosion. It is used to make jewelry, wire, electrical contacts and laboratory vessels. Platinum expands at nearly the same rate as soda-lime-silica glass, so it is used to make sealed electrodes in glass systems. Platinum is used to coat missile nose cones, jet engine fuel nozzles and other devices that must operate reliably for long periods of time at high temperatures. Platinum resistance wires are used in high temperature electric furnaces. Platinum anodes are used in cathodic protection systems to prevent ships, pipelines and steel piers from corroding in salt water.

Platinum is widely used as a catalyst. It will convert methyl alcohol vapors (CH4O) into formaldehyde (CH2O) on contact, glowing red hot in the process. This effect is used to make small hand warmers. Platinum is also used in a device called a catalytic converter, a device found in the exhaust systems of most cars. Catalytic converters combine carbon monoxide (CO) and unburned fuel from a car's exhaust with oxygen from the air, forming carbon dioxide (CO2) and water vapor (H2O). Platinum is also used as a catalyst in the production of sulfuric acid (H2SO4) and in the cracking of petroleum products. Fuel cells, devices that combine hydrogen and oxygen to produce electricity and water, also use platinum as a catalyst.

The metal is extensively used in jewelry, wire, and vessels for laboratory use, and in many valuable instruments including therocouple elements. It is also used for electrical contacts, corrosion-resistant apparatus, and in dentistry.

Platinum-cobalt alloys have magnetic properties. One such alloy made of 76.7% Pt and 23.3% Co, by weight, is an extremely powerful magnet that offers a B-H (max) almost twice that of Alnico V. Platinum resistance wires are used for constructing high-temperature electric furnaces.

The metal is used for coating missile nose cones, jet engine fuel nozzles, etc., which must perform reliably at high temperatures for long periods of time. The metal, like palladium, absorbs large volumes of hydrogen, retaining it at ordinary temperatures but giving it up when heated.

In the finely divided state platinum is an excellent catalyst, having long been used in the contact process for producing sulfuric acid. It is also used as a catalyst in cracking petroleum products. Much interest exists in using platinum as a catalyst in fuel cells and in antipollution devices for automobiles.

Platinum anodes are extensively used in cathodic protection systems for large ships and ocean-going vessels, pipelines, steel piers, etc. Fine platinum wire will glow red hot when placed in the vapor of methyl alcohol. It acts here as a catalyst, converting the alcohol to formaldehyde. The phenomenon has been used commercially to produce cigarette lighters and hand warmers. Hydrogen and oxygen explode in the presence of platinum.

• Automotive catalysts: catalytic converters for cars, trucks and buses about 50 percent of annual platinum demand (rsc-element-78, undated); the leading US use of PGMs (usgs-mcs2025-platinum-group-metals)
• Chemicals: platinum-rhodium gauze for ammonia oxidation in nitric acid plants; platinum hydrosilylation catalysts for silicones; benzene and other bulk-chemical catalysts
• Petroleum refining: platinum-rhenium naphtha reforming catalysts
• Pharmaceuticals: platinum-based chemotherapy drugs
• Glass, electronics and energy: glass-fibre bushings and crucibles; hard disks, thermocouples, optical fibres, LCD glass; fuel-cell catalysts, spark plugs, turbine blades
• Jewellery, medicine and investment: jewellery; pacemakers and dental fillings; investment bars and coins
• Mining: PGM mining in South Africa, Zimbabwe, Russia, Canada, United States

Safety, toxicity

GHS classification, signal word Danger

• H228 Flammable solid Flammable solids
• H315 Causes skin irritation Skin corrosion/irritation
• H319 Causes serious eye irritation Serious eye damage/eye irritation
• H334 May cause allergy or asthma symptoms or breathing difficulties if inhaled Sensitization, respiratory
• H335 May cause respiratory irritation Specific target organ toxicity, single exposure; Respiratory tract irritation

Discovery and name

Discovered by

Antonio de Ulloa

Discovered

1735

First isolated

not in sources

Named by

not in sources

Origin of the name

from Spanish platina, diminutive of plata, "silver", for their similar appearance

Platinum is a beautiful silvery-white metal, when pure, and is malleable and ductile. It has a coefficient of expansion almost equal to that of soda-lime-silica glass, and is therefore used to make sealed electrodes in glass systems. The metal does not oxidize in air at any temperature, but is corroded by halogens, cyanides, sulfur, and caustic alkalis.

It is insoluble in hydrochloric and nitric acid, but dissolves when they are mixed as aqua regia, forming chloroplatinic acid.