Microbially formed Mn(IV) oxide as a novel adsorbent for removal of Radium

Area of Science:

• Environmental Science
• Geochemistry
• Microbiology

Background:

• Radioactivity of radium (Ra) isotopes in natural waters poses environmental risks.
• Controlling radium-226 (²²⁶Ra) concentrations in uranium mill tailings ponds is crucial for waste management.

Purpose of the Study:

• To evaluate microbially formed manganese(IV) oxide (BMO) as an adsorbent for radium removal from water.
• To assess the efficiency of BMO in treating radium-contaminated mine water.

Main Methods:

• Biogenic manganese(IV) oxide (BMO) was synthesized using the fungus Coprinopsis urticicola.
• Adsorption experiments using strontium (Sr) and barium (Ba) as radium surrogates were conducted.
• Extended X-ray absorption fine structure (EXAFS) analysis was used to determine adsorption mechanisms.

Main Results:

• Distribution coefficients for Ba and Sr onto BMO were high (∼10⁶.⁵ and ∼10⁴.³, respectively).
• EXAFS analysis confirmed inner-sphere complex adsorption of Ba and Sr onto BMO.
• A small amount of BMO (7.6 mg) removed over 98% of ²²⁶Ra from 3 L of mine water, yielding a distribution coefficient of 10⁷.⁴ mL/g.

Conclusions:

• Biogenic manganese(IV) oxide is highly effective for radium removal in water treatment.
• The high distribution coefficient indicates practical applicability for BMO in managing radium-contaminated water.
• Manganese(IV) oxide plays a significant role as a carrier and host phase for radium in natural environments.