Thermodynamics-driven valorization of fluorite tailings into sustainable lightweight ceramsite: Phase evolution, sintering mechanisms, and circular economy potential

Herein, this study presents a thermodynamically-driven framework for converting fluorite tailings into waste-to-resource recovery lightweight ceramsite via phase control and sintering optimization. Combining FactSage-based computational modeling with experimental validation, we demonstrate that Al2O3 content (17.6–22.4 wt%) critically enhances the liquid phase formation via anorthite (CaAl2Si2O8) melting while reducing system melting viscosity and broadening the sintering window. Multiscale characterization reveals a dual-phase reinforcement mechanism: 1) SiO2 and spinel solid solutions (MgFe2O4, MgAl2O4) forming a load-bearing crystalline network, and 2) anorthite-derived viscous liquid mediating gas-entrapment expansion. Iterative process optimization yields the fluorite tailings-derived sustainable lightweight ceramsite with a compressive strength of 3.37 MPa, an apparent density of 833 kg/m³, and heavy metal leachates below the environmental safety limits. This process achieves dual carbon-cost breakthroughs via a closed-loop waste-to-resource strategy. 70 % tailings substitution achieves 0.54–0.59 kg CO2/kg of carbon footprint and 0.68–0.79 CNY/kg of production costs, outperforming conventional alternatives. The work establishes a paradigm shift from fluorite waste to resource valorization in sustainable development goals management.