Synthesis and Characterization of Lithium Mining Waste and Metakaolin-Based Geopolymers

The growing demand for lithium has driven aggressive extraction activities, often associated with several environmental challenges, such as tailings dams. It is estimated that for every ton of lithium carbonate produced, approximately 10 tons of refinery waste are generated. In this scenario, geopolymers have emerged as a promising alternative for recycling large volumes of waste into high-value, technologically advanced products. This study presents a detailed investigation into the influence of lithium mining waste (LiMW) on the mechanical and chemical properties of metakaolin-based geopolymers. The LiMW is mainly composed of albite, quartz, and muscovite. Two types of metakaolin were employed as aluminosilicate sources, and varying proportions of alkaline solution were used to synthesize geopolymers incorporating 0 to 60% LiMW. The incorporation of mining waste, up to an adequate proportion, significantly enhanced the compressive strength of both syntheses. The best compressive strength was achieved by incorporating 40% of mining waste in both syntheses. The geopolymer produced with Sulfal Metakaolin (MKS) achieved 54.1 MPa, while the geopolymer synthesized with Metakaolin of Brazil (MKB) reached 32.4 MPa after 7 days of curing. The optimal liquid-to-solid ratios reached using MKS and MKB were 0.34 and 0.30, respectively. XRD, FT-IR, ²⁷Al and ²⁹Si NMR, and SEM/EDS characterized the resulting geopolymers of both syntheses. The results obtained in this work are comparable to or even exceed those achieved with Portland cement, highlighting the applicability of LiMW as a viable component in geopolymeric binders, especially in materials applied to the civil construction sector.