Synthesis of Plate-like Alumina via Synergistic Activation from the Co-combustion Ash of Coal Gangue and Corn Stalk

This study presents a short-process route for the preparation of plate-like α-Al2O3through co-combustion activation of coal gangue and corn stalk, achieving high-value utilization of solid wastes. The results demonstrate that the introduction of corn stalk significantly reduces the apparent activation energy of coal gangue combustion and increases the acid leaching efficiency of aluminum to 81.9%. Mechanism analysis reveals that titanium and iron ions in the co-combustion ash leachate act as natural morphology regulators, facilitating the formation of a plate-like structure in the alumina product, with titanium exhibiting leaching behavior consistent with that of aluminum. Furthermore, it is found that a high content of AlO6 structural units in the precursor effectively promotes the direct conversion into dense α-Al2O3 crystals during thermal treatment, thereby enhancing the product density. Under optimized conditions (800 °C, 1 h), the as-prepared α-Al2O3 exhibits a plate-like morphology, with a median particle size (D₅₀) of 5.70 μm and a density of 4.94 g/cm³. This work provides a new approach for the synergistic resource utilization of coal gangue and biomass waste.