Fabrication of highly efficient hydroxyapatite microtubes for uranium sequestration and immobilization

Area of Science:

• Environmental Science
• Materials Science
• Geochemistry

Background:

• Uranium mining generates wastewater containing uranyl ions (U(VI)).
• Phosphate interactions can form stable uranium phases, affecting migration.
• Effective sequestration of U(VI) is crucial for environmental remediation.

Purpose of the Study:

• To fabricate hydroxyapatite microtubes (HAP-T) for sequestering U(VI) from simulated radioactive wastewater.
• To evaluate the adsorption properties, kinetics, and mechanisms of HAP-T for U(VI).
• To compare the efficacy of HAP-T with other hydroxyapatite forms for uranium immobilization.

Main Methods:

• Fabrication of hydroxyapatite microtubes (HAP-T).
• Adsorption experiments using simulated radioactive wastewater spiked with U(VI).
• Analysis using isotherm and kinetic models (Freundlich, pseudo-second-order).
• Investigation of interfering ions (Mg2+, SO42-) and fulvic acid (FA) effects.
• Comparison of HAP-T with bio-hydroxyapatite (HAP-B) and commercial hydroxyapatite (HAP-C).

Main Results:

• HAP-T demonstrated excellent adsorption and stability, sequestering over 98.76% of U(VI) within 5 minutes at pH 4.0.
• Adsorption data fitted well with the Freundlich model and pseudo-second-order kinetics, with a maximum adsorption capacity of 356.42 mg/g.
• Adsorption was inhibited by Mg2+, SO42-, and FA; FA inhibition was due to charge competition.
• Primary sequestration mechanisms involved electrostatic interactions and surface complexation.
• HAP-T outperformed HAP-B and HAP-C in uranium immobilization and offers lower mobility in groundwater due to its structure.

Conclusions:

• Hydroxyapatite microtubes (HAP-T) are highly effective for sequestering uranyl ions from radioactive wastewater.
• The micron-sized tubular structure of HAP-T enhances its performance and reduces mobility in environmental applications.
• HAP-T presents a viable and efficient material for the immobilization of uranium contaminants.