Stronsium

Strontium

1. Basic Information

2. Physical and Chemical Properties

Strontium is a silver-yellow soft alkaline earth metal. It is highly reactive with water and air, so it must be stored in oil or inert gas. It has a melting point of 769°C and a boiling point of 1384°C. Its density is 2.6 g/cm3 at 20°C. Strontium forms Sr2+ ions in solution. Its chemical properties are similar to calcium and barium.

3. Presence in Water and Health Effects

Strontium is present naturally in ground and surface water, usually at concentrations of 0.3-1.5 mg/L. Sources include weathering of rocks and minerals containing strontium. Stable strontium is generally harmless at levels found in drinking water. However, the radioactive isotope strontium-90 can pose health risks if ingested in large amounts, including bone cancer and leukemia. WHO recommends a limit of 10 Bq/L for Sr-90 in drinking water.

4. Water Treatment Applications and Removal Methods

The main methods for removing strontium from water include:

• Ion exchange: Cation exchange resins can remove Sr2+ effectively.
• Reverse osmosis: RO membranes can retain up to 98% of strontium.
• Lime softening: Can reduce strontium along with other hardnesses.
• Chemical precipitation: Addition of chemicals such as sodium carbonate can precipitate strontium.
• Adsorption: Media such as activated carbon can adsorb strontium under some conditions.

The choice of method depends on the strontium concentration, water chemistry, and treatment standards required.

5. Industrial Uses in Water Treatment

Although strontium itself is rarely used in industrial water treatment, some of its compounds have limited applications:

• Strontium chloride is sometimes used in water softening systems to improve the efficiency of ion exchange resins.
• Strontium carbonate can be used in some wastewater treatment processes to precipitate certain contaminants.
• Some specialized membranes contain strontium compounds to improve performance in desalination or water purification.

6. Case Studies and Real World Application Examples

1. Fukushima, Japan: After the 2011 nuclear disaster, a specialized water treatment system was developed to remove Sr-90 from contaminated water. This multi-stage system uses a combination of ion exchange, reverse osmosis, and adsorption to reduce Sr-90 levels to below safety standards.

2. Hanford Site, USA: At this former plutonium production site, advanced ion exchange technology is used to remove Sr-90 from contaminated groundwater. The system is capable of processing millions of gallons of water each year, significantly reducing environmental risks.

3. Punjab, India: In some areas of Punjab, high levels of strontium were found in groundwater. Pilot projects using community-scale RO systems have successfully reduced strontium concentrations, providing safer drinking water to local residents.

7. Regulatory Guidelines and Standards

There are currently no established international standards for stabilized strontium in drinking water. However, some countries and organizations have established guidelines:

• The US EPA has set a Health Reference Level (HRL) for strontium of 4 mg/L in drinking water.
• Canada has a maximum guideline of 7 mg/L for strontium in drinking water.
• WHO recommends a limit of 10 Bq/L for radioactive Sr-90 in drinking water.
• The European Union has not set specific limits for strontium, but monitors its levels in water sources.

8. Environmental Impact and Sustainability Considerations

Strontium removal from water can have environmental implications:

• The use of ion exchange resins generates waste salts that require proper disposal.
• RO systems require significant energy and can produce highly concentrated wastewater.
• Chemical precipitation methods produce sludge that may contain high levels of strontium.

More sustainable approaches are being explored, including:

• Development of natural biosorbents for strontium removal.
• Phytoremediation techniques using plants to extract strontium from water and soil.
• Hybrid treatment systems that combine multiple methods for better efficiency.

9. Future Trends and Research

Some promising research areas include:

• New nanomaterials for more efficient strontium adsorption.
• Improved strontium-selective membranes for desalination and water purification.
• Advanced electrochemical techniques for strontium removal.
• Biological methods that use microorganisms to bind or convert strontium.
• Development of real-time sensors for better monitoring of strontium in water systems.

10. Interesting Facts Related to Water Treatment

• Strontium can be used as an indicator to detect seawater leakage into freshwater aquifers due to its higher concentration in seawater.
• Some deep-sea coral species incorporate strontium into their shells as strontium sulfate, indicating its natural bioremediation potential.
• The isotope ratio of strontium in water can be used by archaeologists and geologists to determine the origin of ancient artifacts and geological formations.
• Although commonly considered a contaminant, very low levels of strontium are actually beneficial for human bone health.
• Strontium emits a bright red flame when burning, a property used in fireworks and warning flares, but can also aid in the visual detection of leaks in certain water treatment systems.