Microwave Pre-Treatment for Efficient Zinc Recovery via Acid Leaching

This study presents an innovative approach to processing refractory zinc-bearing clinker using microwave thermal treatment followed by acid leaching. Microwave irradiation induces phase transformations, converting sphalerite (ZnS) to zincite (ZnO), and generates microcracks that enhance clinker porosity and reactivity. These changes significantly improve zinc dissolution during sulfuric acid leaching. Key parameters-acid concentration, temperature, solid-to-liquid ratio, and leaching time-were optimized, achieving a zinc extraction of 92.5% under optimal conditions (40 g/L H₂SO₄, solid-to-liquid ratio 1:4, 600 °C, 5-7 min) compared to 39.1% without pre-treatment. Thermodynamic analysis confirms the higher reactivity of ZnO, driven by favorable Gibbs free energy and exothermic reaction characteristics. These findings demonstrate the potential of microwave processing to intensify hydrometallurgical processes, offering energy efficiency and environmental benefits for industrial zinc recovery.