Study on uranium leaching from uranium purification residue with ammonium hydrogen fluoride

Area of Science:

• Nuclear Chemistry
• Materials Science
• Environmental Engineering

Background:

• Uranium purification residues contain high uranium content, posing recovery and environmental challenges.
• Uranium leaching is hindered by encapsulation within silicon dioxide (SiO2) crystals.

Purpose of the Study:

• To investigate an effective method for uranium recovery from purification residues.
• To understand the mechanism of uranium leaching from SiO2-encapsulated residues.

Main Methods:

• X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) mapping for characterization.
• BCR continuous graded extraction test to analyze uranium states.
• Leaching experiments using ammonium bifluoride (NH4HF2) as the leaching agent.

Main Results:

• SiO2 crystal encapsulation was identified as the primary cause of difficult uranium leaching.
• Ammonium bifluoride effectively dissolved SiO2, releasing encapsulated uranium.
• Optimized leaching conditions (10% NH4HF2, 30:1 L/S ratio, 30°C, 120 min) achieved 98.95% uranium leaching efficiency.
• Leaching kinetics followed a mixed-controlled model (shrinking core model), indicating surface reaction and mass diffusion control.

Conclusions:

• Ammonium bifluoride is a viable leaching agent for uranium recovery from purification residues.
• The developed method offers a potential solution for resource recovery and waste treatment.
• Understanding the leaching mechanism is crucial for optimizing uranium extraction processes.