Abstract
Gallium (Ga) occurrence in coal is interpreted only by coupling bulk partitioning with microscale residence. Ga distribution reflects allocation between inorganic matter and organics and links to ash yield. Al-bearing aluminosilicates dominate as hosts, with Ga retained mainly by isomorphic substitution governed by crystal chemistry rather than adsorption. Workflows compare where Ga sits versus how it is bound: density fractionation and sequential/selective leaching, constrained by XRD and supported by BSE–EDS, EMPA, and LA–ICP–MS. During combustion, Ga concentrates in fly ash/slag; recovery relies on pretreatment, acid leaching, and sorption/stripping, with calcination/roasting disrupting refractory frameworks, boosting extraction, and controlling impurity co-dissolution.