Holmium (Ho) in Water Treatment

Quick Answer

Holmium (Ho) is a lanthanide with atomic number 67. PubChem lists its standard state as solid and its relative atomic mass as 164.93033.

Holmium is not a routine drinking-water target but may matter in mining, electronics, magnet or rare-earth recovery streams. Precipitation, adsorption, ion exchange and membrane separation should be evaluated as both removal and resource-recovery options.

Interesting Facts

• Holmium has the largest magnetic moment of any naturally occurring element.
• Its name comes from Holmia, the Latin name for Stockholm.
• It is not a routine drinking-water target; rare-earth processing or recovery context is needed before selecting a separation process.

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

• PubChem — Holmium
• IUPAC Periodic Table of Elements
• WHO chemical hazards in drinking-water

Holmium (Ho)

1. Basic Information

Atomic Number	67
Symbol	Ho
Atomic Weight	164.93 g/mol
Category	Rare earth metals, lanthanides

2. Physical and Chemical Properties

Holmium is a soft, ductile metal with a yellowish silver color. It has a melting point of 1474°C and a boiling point of 2695°C. Holmium reacts slowly with oxygen and water at room temperature, but is soluble in acids. In compounds, holmium usually has an oxidation state of +3. This metal has strong magnetic properties.

3. Presence in Water and Health Effects

Holmium is rarely found in natural water at significant concentrations. Depending on pH and ligands, a result may represent dissolved Ho(III) complexes, colloids, or particles rather than bare Ho³⁺ alone. Human drinking-water toxicity data are limited, so the absence of a widely cited guideline must not be presented as evidence that a concentration is safe.

4. Water Treatment Applications and Removal Methods

Although holmium is rarely a specific target in water treatment, methods used to remove other rare earth metals are also effective for holmium:

• Ion exchange: Specialized cation exchange resins can be used to remove Ho3+ ions from water.
• Chemical precipitation: The addition of a base can precipitate holmium as hydroxide.
• Adsorption: Activated carbon or other adsorbents can bind holmium from solution.
• Membrane filtration: Techniques such as nanofiltration or reverse osmosis can remove holmium ions.

5. Industrial Use in Water Treatment

Holmium itself is rarely used directly in water treatment. However, some research is exploring the potential use of holmium-based nanomaterials to remove certain contaminants from water.

8. Environmental Impacts and Sustainability Considerations

Mining and processing of holmium, like other rare earth metals, can have significant environmental impacts. Extraction often involves the use of strong chemicals and can generate radioactive waste. Recycling and reuse of holmium from scrap products is becoming increasingly important to reduce environmental impact and ensure sustainable supply.