Barium (Ba) in Water Treatment
Quick Answer
Barium (Ba) is an alkaline earth metal with atomic number 56. PubChem lists its standard state as solid and its relative atomic mass as 137.33.
Barium can occur naturally in groundwater and can form very insoluble sulfate scale. Precipitation, ion exchange, nanofiltration or reverse osmosis may be used, with concentrate management designed to avoid barium sulfate deposition.
Interesting Facts
- Barium sulfate is both extremely insoluble and opaque to X-rays, which is why a controlled suspension can be used as medical contrast.
- That same low solubility makes barium sulfate a stubborn scale in RO and oilfield systems.
- Removing dissolved barium transfers it to brine, sludge or spent media; checking sulfate and concentrate saturation is essential.
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
Barium (Ba)
1. Basic Information
| Atomic Number | 56 |
| Symbol | Ba |
| Atomic Weight | 137.33 g/mol |
| Category | Alkaline earth metal |
| State | Solid (at room temperature) |
| Electronegativity | 0.89 (Pauling scale) |
| Melting Point | 727°C |
| Boiling Point | 1897°C |
2. Physical and Chemical Properties
Barium is a silvery soft metal that is highly reactive. It oxidizes easily in air and reacts strongly with water, forming barium hydroxide and releasing hydrogen gas. Barium is not found in its free state in nature due to its high reactivity. The most common barium compounds are barium sulfate (BaSO4) and barium carbonate (BaCO3).
In solution, barium is usually present as Ba2+ ions. Its solubility varies depending on the associated anion; barium sulfate is very insoluble, while barium chloride and nitrate are very soluble in water.
3. Presence in Water and Health Effects
Barium can enter water through weathering of barium-bearing rocks and through mining, oil-and-gas, or industrial activities. Concentrations vary greatly with local geology and sulfate availability, so a generic “natural range” should not replace sampling.
Soluble barium compounds are the relevant ingestion concern; insoluble barium sulfate behaves very differently. Drinking-water acceptance should be checked against the current rule for the project jurisdiction.
4. Water Treatment Applications and Removal Methods
Some methods used to remove barium from water include:
- Ion exchange: Using special cation exchange resins that can bind barium ions and release sodium or hydrogen ions.
- Lime-soda softening: This process can remove barium along with other water hardness.
- Reverse osmosis: RO membranes can retain most of the barium ions.
- Chemical precipitation: Addition of sulfate or carbonate can precipitate barium as an insoluble salt.
- Filtration: After precipitation, the barium precipitate can be removed through filtration, including ultrafiltration for very small particles.
The choice of method depends on the concentration of barium, other water characteristics, and treatment objectives.
5. Industrial Uses in Water Treatment
Although barium is generally considered a contaminant, some barium compounds have limited applications in industrial water treatment:
- Barium chloride is sometimes used to precipitate sulfate in industrial wastewater.
- Barium hydroxide can be used in soft water treatment to remove carbonates.
- Barium sulfide has been used in some wastewater treatment processes to remove heavy metals.
However, the use of barium compounds in water treatment should be done with extreme caution due to their potential toxicity.
6. Practical Design Note
Lime-soda softening can co-precipitate barium in suitable waters, but a bench or pilot test and residuals plan are needed before performance is claimed. For RO, model barium-sulfate saturation in the concentrate rather than assuming that an antiscalant alone will control scale.
8. Environmental Impacts and Sustainability Considerations
Barium in high concentrations can negatively affect aquatic ecosystems. Some species of fish and aquatic invertebrates are particularly sensitive to barium. Accumulation of barium in sediments may affect benthic organisms.
From a sustainability perspective, the removal of barium from water can generate solid waste that requires special handling. Treatment methods such as ion exchange and reverse osmosis also require significant energy and chemicals. Therefore, prevention of barium contamination in water sources is important for long-term sustainability.