²²⁶Ra dynamic lixiviation from phosphogypsum samples by an automatic flow-through system with integrated renewable...

Area of Science:

• Environmental Science
• Radiochemistry
• Analytical Chemistry

Background:

• Phosphogypsum (PG) is a byproduct of fertilizer production, often containing naturally occurring radioactive materials like radium-226 (²²⁶Ra).
• Understanding ²²⁶Ra leaching from PG is crucial for assessing environmental risks and exploring potential reuse applications.

Purpose of the Study:

• To develop and validate a novel, automated system for evaluating the dynamic leaching of ²²⁶Ra from phosphogypsum.
• To quantify ²²⁶Ra release under different pH conditions using dynamic and static leaching methods.

Main Methods:

• An automated system was designed for ²²⁶Ra lixiviation and pre-concentration from PG using a renewable sorbent.
• The method involved Ra adsorption onto MnO₂ followed by co-precipitation with BaSO₄, with detection via a low-background proportional counter.
• Dynamic leaching was performed using artificial rainwater at pH 5.4 and 2.0, with subsequent comparison to static leaching experiments.

Main Results:

• The automated method achieved a minimum detectable activity of 7 Bqkg^-1 and was validated using a PG reference material.
• ²²⁶Ra leaching concentrations were 105±3 Bqkg^-1 d.w. (37% lixiviation) at pH 5.4 and 168±3 Bqkg^-1 d.w. (50% lixiviation) at pH 2.0.
• Dynamic leaching resulted in up to 50% higher ²²⁶Ra release compared to static leaching across both tested pH values.

Conclusions:

• The developed automated system provides an efficient and reliable method for assessing ²²⁶Ra leaching from phosphogypsum.
• Dynamic leaching, particularly at acidic pH, significantly enhances ²²⁶Ra release, highlighting potential environmental concerns and influencing PG reutilization strategies.