Toward circular Gallium: Recovery pathways from Bayer Liquor, red Mud, fly Ash, and e-waste

Gallium is a strategically critical metal for semiconductors, LEDs, and photovoltaics, yet current practices disperse a substantial share into wastes and low-grade residues. This review maps the full chain of gallium recovery with an explicit focus on waste- and residue-centric pathways, linking primary by-product streams from alumina production (Bayer liquor, red mud) to secondary resources (e-waste, LEDs, end-of-life solar panels, and fly ash). Despite global resources exceeding one million tons, an estimated > 80% of gallium generated during 2001-2021 was dissipated, underscoring systemic inefficiencies and the need for circular strategies. We synthesize technological progress across leaching, selective separation, and high-purity refining, benchmarking options by energy intensity, reagent demand, carbon emissions, and operational constraints in complex matrices (high alkalinity, co-ions). Particular attention is given to cleaner routes-including bioleaching, electrochemical recovery, and functionalized sorbents-that show potential to reduce resource intensity while meeting purity and selectivity targets. Integrating techno-environmental evidence with supply-risk and policy considerations, we propose a sustainability-oriented roadmap prioritizing: (i) scalable recovery from Bayer-process streams and red mud, (ii) infrastructure for e-waste and PV end-of-life collection and pre-processing, and (iii) next-generation green separation materials enabling closed-loop flows. The analysis highlights practical levers for diverting gallium from dissipation to high-value recycling, strengthening supply resilience and advancing low-carbon, cleaner production of critical metals..