Barium

Barium (Ba)

1. Basic Information

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 sources through weathering of barium-containing rocks and minerals, as well as through human activities such as mining, oil and gas processing, and industrial waste disposal. The concentration of barium in groundwater can vary from 0.1 mg/L to more than 1 mg/L in some areas.

Short-term exposure to high levels of barium can cause nausea, vomiting, diarrhea and breathing difficulties. Long-term exposure can cause increased blood pressure, muscle weakness, kidney and liver damage. The World Health Organization (WHO) sets the maximum limit for barium in drinking water at 0.7 mg/L.

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. Case Study and Real-World Application Example

• In a small town in Texas, USA, high concentrations of barium (up to 10 mg/L) in well water were found. A water treatment system combining lime-soda softening with multimedia filtration successfully reduced the barium levels to below 0.7 mg/L.
• An industrial wastewater treatment facility in Germany faced problems with high sulfate levels. They used a precipitation process with barium chloride to remove sulfate, followed by precipitation and filtration to remove the barium sulfate precipitate. The resulting water is then further treated to remove the remaining barium.
• At a desalination plant in the Middle East, barium was found to accumulate on the reverse osmosis membranes, causing performance degradation. The addition of a special antiscalant and optimization of coagulant dosage successfully mitigated this problem.

7. Regulatory Guidelines and Standards

Some regulatory standards for barium in drinking water include:

• WHO: 0.7 mg/L

• US EPA: 2.0 mg/L

• European Union: 1.0 mg/L

• Australia: 2.0 mg/L

• Canada: 1.0 mg/L

• Indonesia (Permenkes No. 492/2010): 0.7 mg/L

For wastewater, barium discharge limits vary depending on the country and type of receiving water body, usually ranging from 1-5 mg/L.

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.

9. Future Trends and Research in Water Treatment

Some of the research areas and emerging trends related to barium in water treatment include:

• Development of new nanomaterial-based adsorbents for more efficient barium removal.

• Integration of biological processes in barium removal, such as the use of sulfate-reducing bacteria.

• Optimization of membrane processes for better barium selectivity.

• Development of real-time sensors for barium monitoring in water distribution systems.

• Studies on the impact of climate change on barium mobilization in the environment.

• Investigation on the potential recovery and reutilization of barium from wastewater.

10. Interesting Facts Related to Water Treatment

• Barium sulfate (barite) is often used as a ballast agent in oil drilling mud, which can lead to barium contamination around oil wells.

• Certain natural mineral waters have fairly high levels of barium and are marketed with health claims, although their benefits are still debated.

• Barium can be used as an indicator to detect groundwater leakage into surface water systems.

• Some plant species have been found to accumulate barium and could potentially be used in phytoremediation of contaminated soil and water.

• The radioactive isotope barium-133 is sometimes used in hydrological studies to track groundwater movement.