Electronic Waste and Semiconductor-Related Residues as Secondary Sources of Gallium: Occurrence, Processing Routes, Separation Challenges, and Circular Supply Perspectives
DOI:
https://doi.org/10.66104/c6qq5978Keywords:
Gallium; electronic waste; semiconductor residues; LEDs; GaAs; GaN; CIGS; hydrometallurgy; selective separation; circular supply chains.Abstract
Gallium is essential to GaAs- and GaN-based semiconductors used in LEDs, 5G devices, power electronics, and advanced photovoltaics, yet its primary supply remains structurally constrained because it is obtained mainly as a by-product of aluminum and zinc production. This critical review examines electronic waste, semiconductor-related residues, and selected industrial by-products as secondary gallium sources, with emphasis on concentration ranges, phase occurrence, leaching behavior, separation selectivity, and process integration. The review compares LED waste, GaAs/GaN scraps, CIGS photovoltaic waste, Bayer-related liquors, coal fly ash, zinc residues, and specialized process wastes. Hydrometallurgy remains the dominant route, but the key challenge is usually not dissolution itself; it is the selective separation of gallium from aluminum, iron, zinc, vanadium, and matrix-dependent impurities. The article identifies the strongest recovery opportunities in concentrated semiconductor and process wastes, while mixed e-waste remains limited by dilution, heterogeneity, and preprocessing costs. Emerging routes based on ionic liquids, membranes, biodismantling, and bioleaching improve selectivity in laboratory studies, but their scalability remains limited. The main research gaps are incomplete flowsheet integration, scarce techno-economic validation, and limited industrial evidence.
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