Over 15 million tons of high-alumina coal gangue are generated annually in Ordos, Inner Mongolia. The “carbothermic reduction–iron separation” process developed by Jilin University can convert about 6 million tons of this waste each year, but simultaneously produces large amounts of amorphous silicon–aluminum smelting fly ash, a by-product that has remained almost entirely unstudied and unused.
This work presents the first systematic investigation of this fly ash and proposes an efficient acid-leaching route aimed not only at impurity removal but also at the functional reuse of the leaching residue as a value-added material. Specifically, the acid-leaching process simultaneously enables selective dissolution of undesired components and in situ transformation of the residue into high–surface-area mesoporous silica (SF-A), thereby establishing a clear valorization pathway rather than a simple extraction process. Optimized HCl leaching selectively removes Al, Na, and S species and induces the in-situ formation of a Si-rich amorphous framework. The resulting SF-A exhibits a BET surface area of 607.2 m2 g−1, a pore volume of 0.507 cm3 g−1, and excellent thermal stability up to 600 °C. It also shows a methylene-blue adsorption capacity of 75.9 mg g−1, with kinetic analysis indicating that the adsorption process is predominantly governed by diffusion-controlled physical adsorption on the porous silica framework, showing competitive adsorption performance compared with common waste-derived adsorbents.
This method provides a sustainable pathway for the high-value utilization of silicon–aluminum smelting fly ash and yields thermally stable mesoporous silica suitable for adsorption-oriented utilization.
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