Enhanced oxidative sulfuric acid leaching of granite-type uranium ore by oxygen nanobubbles: Kinetics and mechanism

Developing eco-friendly and highly efficient uranium-enhanced leaching technologies is crucial for ensuring the reliable supply of uranium resources. This study integrates nanobubble (NB) technology into the acid leaching process of granite-type uranium ore by employing oxygen NBs as an effective, clean oxidant to enhance uranium leaching. The feasibility of using oxygen NBs was first validated theoretically, and subsequent batch experiments were conducted to investigate the enhanced leaching kinetics and mechanism. The results demonstrate that oxygen NB-enhanced leaching follows a shrinking core model dominated by product layer diffusion, with an Arrhenius activation energy of 8.37 kJ/mol. Under optimal conditions (15 g/L H₂SO₄, 180 rpm, 5 % pulp density, and 30 °C), oxygen NBs increased uranium leaching efficiency by 8.20 % compared to conventional sulfuric acid leaching. Three key mechanisms contribute to this enhancement: (i) efficient oxidation of U(IV) to U(VI) via continuous dissolution of molecular oxygen and generation of hydroxyl radicals; (ii) expansion of leaching pathways through high-energy microarea effects that further disrupt the ore structure; and (iii) reduction of leaching inhibition by preventing sulfate precipitate deposition on mineral surfaces. These findings underscore the potential of oxygen NB-enhanced oxidative leaching for sustainable, cost-effective uranium extraction, warranting pilot-scale studies for industrial application.