Iridium (Ir) in Water Treatment
Quick Answer
Iridium (Ir) is a transition metal with atomic number 77. PubChem lists its standard state as solid and its relative atomic mass as 192.22.
Iridium is not a common target in ordinary water treatment but may occur in mining or specialized industrial wastewater. Total versus dissolved concentration, oxidation state, pH and complexing agents should be measured before evaluating precipitation, adsorption, ion exchange or membranes.
Interesting Facts
- Iridium is among the most corrosion-resistant metals, which makes dissolved iridium in ordinary water especially unusual.
- A worldwide iridium-rich layer helped link the end-Cretaceous mass extinction to a large asteroid impact.
- Iridium belongs to the platinum-group metals; recovery can be more sensible than disposal when it occurs in a concentrated refinery stream.
Water-treatment Design Implications
An element name alone is not enough to select treatment equipment. Confirm chemical form or speciation, total and dissolved concentration, pH, alkalinity, competing ions and the product-water target. Send the water-analysis results to Watermart to identify additional testing and shortlist processes before equipment is specified.
Summary Data Sources
1. Basic Information
| Atomic Number | 77 |
| Symbol | Ir |
| Atomic Weight | 192.2 g/mol |
| Electron Configuration | [Xe] 4f14 5d7 6s2 |
2. Physical and Chemical Properties
Iridium is a hard, brittle, shiny and dense transition metal of the platinum group. It is silvery white in color and is reputed to be the most corrosion-resistant element. It is unaffected by air, water, and acids. Iridium has a very high melting point (2450°C) and boiling point of 4527°C. It has a very high density of 22.4 g/cm3 at 20°C. Iridium is insoluble in most solvents and has exceptional chemical resistance.
3. Presence in Water and Health Effects
Iridium is not a routine drinking-water analyte and evidence for ingestion effects is limited. Occupational irritation from a dust or compound is a different exposure route and should not be presented as a drinking-water effect. Verify an unexpected result with a trace-metals laboratory before designing treatment.
4. Water Treatment Applications and Removal Methods
Although iridium is rarely a major contaminant in water, several methods can be used to remove it if needed:
- Ion exchange: Specialized anion exchange resins can be used to remove iridium chloroanion complexes from solution.
- Adsorption: Activated carbon or specialized adsorbents can bind iridium from water.
- Chemical precipitation: Precipitation of iridium as hydroxide or sulfide can be done at high pH.
- Membrane filtration: Technologies such as nanofiltration or reverse osmosis can remove nano-sized iridium particles.
5. Industrial Use in Water Treatment
Iridium has limited use in the water treatment industry due to its rare and expensive nature. However, some potential applications include:
- Catalysts: Iridium compounds can be used as catalysts in advanced oxidation processes to decompose organic contaminants in water.
- Electrodes: An iridium oxide coating on electrodes can improve efficiency in water treatment electrochemical processes.
- Sensors: Iridium-based sensors can be used to detect certain contaminants in water.
8. Environmental Impact and Sustainability Considerations
Iridium is considered to have a relatively low environmental impact due to its rarity and inert nature. However, iridium mining and processing can have environmental impacts. Sustainability considerations include:
- Rarity: As one of the rarest elements in the Earth’s crust, the use of iridium should be carefully considered.
- Recycling: Efforts to recycle iridium from used products are critical to sustainability.
- Alternatives: The development of more common alternatives for iridium applications can reduce reliance on this rare metal.