Synergistic valorization of gold tailings and coal gangue for mullite composite ceramics

To achieve the synergistic high-value utilization of gold tailings (GT) and coal gangue (CG), mullite composite ceramics were prepared via reaction sintering using coal gangue and gold tailings as the main raw materials, with the addition of industrial alumina and AlF 3 . The effects of AlF 3 content, gold tailings content, and sintering temperature on the phase evolution, microstructure, and properties of the samples were systematically investigated. The results show that the sintered samples consist primarily of mullite, corundum, quartz, and an amorphous aluminosilicate phase. After optimization of the AlF 3 content, samples containing 40 wt% gold tailings exhibited the best overall properties when sintered at 1500 °C, with flexural strength, bulk density, apparent porosity, and water absorption reaching 110.88 MPa, 1.79 g·cm −3 , 0.73 %, and 0.41 %, respectively; the resulting low-density/high-strength characteristics are associated with the interwoven mullite framework, the intergranular aluminosilicate amorphous phase, and isolated residual pores. FactSage calculations suggest that K- and Na-bearing components promote the formation of low-melting alkali aluminosilicate liquids. The study shows that the properties of this ceramic depend on the balance between liquid-phase-assisted densification and the formation of the mullite framework. This study achieved the synergistic utilization of two types of bulk mining solid waste—coal gangue and gold tailings—and provides a reference for the preparation of mullite composite ceramics with high solid waste content and the high-value recycling of mining solid waste.