Study on Leaching Characteristics of Sandstone Uranium Ore Using Nano-microbubble Dissolved Oxygen

Based on the gas-liquid interfacial mass transfer dynamics theory, in this paper the bubble dynamic characteristics of conventional oxygenation and nano-microbubble oxygenation systems were comparatively analyzed, as well as their influence mechanisms on sandstone uranium ore leaching processes. The particle size distribution (particle size ≤280.4 nm accounting for 50%), surface potential (mean Zeta −16.8 mV), and dissolved oxygen (DO) concentration of the nano-microbubble system were characterized using a particle size analyzer, Zeta potential analyzer, and DO measuring instrument. Significant mass transfer enhancement was observed compared to conventional oxygenation (no bubbles ＜50 μm detected, mean ζ=−6.2 mV). Column leaching tests demonstrate that the nano-microbubble group achieves a cumulative uranium leaching efficiency of 50.92%, representing 6.9% improvement over the conventional group, with leaching rates exhibiting distinct stages: growth phase (0-5 d) and steady-state phase (6-15 d). The dynamic analysis results of the shrinkage core model show that the function 1+2(1−α)−3(1−α)^2/3 is linearly correlated with leaching time with R²=0.93-0.98, indicating that the leaching process is controlled by solid film diffusion. Notably, the apparent rate constant k₂ in the nano-microbubble group reaches 1.11×10⁻³ h⁻¹ during initial leaching (0-5 d), 2.34 times higher than conventional oxygenation (4.74×10⁻⁴ h⁻¹). However, in the later stage (6-15 d), the leaching of U is inhibited by iron oxidation products, and the apparent rate constant k₂ (5.52×10⁻⁵ h⁻¹) is lower than that of the conventional system (1.45×10⁻⁴ h⁻¹).

This research reveals the dual effects of nano-microbubble-enhanced leaching: promoting uranium oxidation dissolution through optimized gas-liquid mass transfer, while concurrently constraining uranium extraction through competitive iron dissolution. These findings provide theoretical foundations and technical parameters for developing green and efficient uranium ore leaching technologies.