Mechanochemical induced interfacial wetting and radical synergism for enhanced gallium recovery from waste gallium nitride

Abstract

Gallium nitride (GaN), a critical third-generation semiconductor material, faces significant recycling challenges due to its increasing waste generation, which poses a threat to global Ga resource security and environmental sustainability. Traditional hydrometallurgical or pyrometallurgical GaN recycling methods often suffer from low efficiency, high energy consumption, or secondary pollution. This study introduces a mechanochemical induced interfacial wetting and radical strategy, integrating mechanical activation with in situ radical generation in a low-water-consumption system for Ga recovery. Mechanical force promotes the generation of fresh surfaces, introduces lattice defects, and disrupts the surface passivation layer, thereby altering the surface properties of GaN to enhance hydrophilicity. Combined with pre-wetting treatment, it improves the mass transfer efficiency of OH⁻ at the solid–liquid interface. Mechanical energy also promotes the generation of ˙OH and ˙O₂⁻ radicals derived from Na₂O₂, with density functional theory (DFT) confirming that the dissociation energy barrier of Ga–N bonds is reduced from 4.31 eV to 3.15 eV. Under optimized conditions, this approach achieves a Ga leaching efficiency of 96.67%, yielding high-purity Ga₂O₃. Life cycle assessment (LCA) demonstrated 38.59% lower carbon emissions and 84.61% reduced water consumption compared to traditional methods. This synergistic system provides a green and efficient pathway for the recycling of inert semiconductors by combining mechanochemical interfacial wetting with radical-driven chemical oxidation.