Ruthenium (Ru) and water
Ruthenium (Ru) and water: chemistry, occurrence and treatment
Ruthenium is a rare platinum-group metal. It is not expected at significant concentrations in ordinary source water, but it can be relevant in specialised metal-refining, catalyst-manufacturing and chemical-process streams. In water, its behaviour depends strongly on oxidation state, pH, redox conditions and the ligands present; the element name alone does not identify a single dissolved form or treatment method.
How ruthenium occurs in water
Ruthenium is commonly recovered with other platinum-group metals and as a by-product of nickel refining. Natural weathering can contribute trace amounts to the environment, while industrial handling, refining, catalyst manufacture and waste streams can provide more specific pathways to water. Environmental literature also examines releases of radioactive ruthenium isotopes from nuclear activities; these are a separate radiological issue and require isotope-specific monitoring and controls. Detection in a particular water body should be established by representative sampling and appropriate analytical methods.[1]
Aqueous chemistry and oxidation states
Ruthenium can occur in several oxidation states, and aqueous speciation is unusually sensitive to the solution's redox potential, acidity, and coordinating ions such as chloride or nitrate. In acidic solutions, Ru(III) and Ru(IV) complexes may occur; under some conditions Ru(IV) can also form poorly soluble hydrous ruthenium dioxide (RuO2·xH2O) or particle-associated material. Therefore, a measurement of total ruthenium does not by itself show how much is dissolved or which species is present.[2]
In strongly oxidising alkaline solutions, higher-valent oxoanions can form, including ruthenate(VI), RuO42−, and perruthenate(VII), RuO4−. Ruthenium tetroxide, RuO4 (ruthenium(VIII)), is a volatile, powerful oxidant associated with specialised chemical conditions; it is not a typical species expected in natural waters. It presents serious handling hazards and must be managed under suitable chemical-safety controls.[3][4]
Interpretation: Record whether the result is dissolved or total ruthenium, the analytical method and relevant pH/redox conditions. Where process chemistry could create volatile or radioactive species, involve qualified analytical, chemical-safety and radiological specialists.
Ruthenium in water electrolysis and catalysis
Ruthenium dioxide and other ruthenium-based materials are intensively studied as catalysts for the oxygen-evolution reaction (OER), the anodic half-reaction in water electrolysis. At the anode, water is oxidised to oxygen, protons and electrons: 2H2O → O2 + 4H+ + 4e−. The electrons can support hydrogen production at the cathode. Ru-based catalysts can offer high OER activity, including in acidic proton-exchange-membrane systems, but long-term stability and ruthenium loss under operating conditions remain active development topics. This catalytic use concerns engineered electrodes; it does not mean that dissolved ruthenium is needed in the product water.[5][6]
How can ruthenium be removed or recovered from water?
There is no single treatment that can be recommended from the name “ruthenium” alone. The process depends on concentration, oxidation state, complexing agents, dissolved-versus-particulate fraction, competing metals and salts, and whether the objective is discharge, water reuse or recovery of valuable metal. For suitable streams, options for evaluation may include pH/redox adjustment followed by precipitation and solids separation, adsorption or ion exchange for selected dissolved complexes, and membrane filtration where particle form and concentrate disposal or recovery have been addressed.
Before selecting a process, characterise the actual stream and run treatability tests. Include the handling and disposal or recovery route for ruthenium-bearing sludge, spent media and membrane concentrate. If radioactive isotopes or potentially volatile RuO4 are credible, use specialist monitoring and containment rather than treating the stream as routine metal-bearing wastewater.
See ion exchange for general information on this separation technology, and Ruthenium (Ru) in the periodic table for the element's properties and uses.
Last reviewed: 8 November 2026 by Lenntech.
Sources and further reading
- Royal Society of Chemistry: Ruthenium properties, uses and occurrence.
- Boglaienko et al.: Ruthenium speciation and distribution in the environment (2024 review).
- Xue and Osseo-Asare: Aqueous equilibria in the Ru–H2O, Ru–Cl–H2O and Ru–S–H2O systems.
- Ruthenium speciation during acidification of alkaline solution (2026).
- PubChem: Ruthenium tetroxide safety and chemical information.
- Royal Society of Chemistry: Ruthenium-based materials for acidic oxygen evolution and PEM water electrolysers (2024).
- Journal of Alloys and Compounds: Activity and stability of RuO2-based catalysts for acidic OER (2026).