Valorization of Mine Tailings for Sustainable Geopolymer Production

Abstract

The sustainable production of geopolymers requires innovative approaches to raw material utilization. This study investigates the valorization of sulfidic coal mine tailings as a partial substitute for metakaolin in geopolymer synthesis. A comprehensive protocol involving mechanical grinding, particle size reduction (<5 µm), and thermal treatment at 800°C was applied to enhance the reactivity of the aluminosilicate phases and eliminate harmful sulfidic content. Unlike earlier studies that only demonstrated low substitution levels or required blending with multiple precursors, this research uniquely demonstrates that thermally valorized coal tailings can replace up to 60 wt.% of metakaolin without compromising mechanical performance—geopolymers with 50 wt.% tailing substitution achieved compressive and flexural strengths of 43.3 MPa and 8.9 MPa, respectively. These are comparable to pure metakaolin-based formulations and significantly superior to untreated tailing mixes. The findings are supported by extensive mineralogical analysis (XRD, EDS, TGA, XRF) and confirm that valorized mine tailings can serve as a cost-effective, environmentally sustainable, raw materials for geopolymer production. This approach transforms hazardous waste into valuable construction materials and supports the global transition to low-carbon building technologies.