Valorization of iron-rich copper waste mine tailings from Guelb Moghrein (Mauritania) via geopolymerization: Reaction mechanisms, microstructure and mechanical performance

The increasing production of waste mine tailings constitutes a major environmental challenge, requiring the development of sustainable valorization strategies.This study assesses the feasibility of synthesizing geopolymers from Mauritanian iron-rich copper mine tailings, aiming to elucidate the influence of iron-rich phases on geopolymer formation and performance.The tailings samples were mixed with metakaolin (MK) at different mass ratios (100:0, 50:50, and 0:100).The precursors were ground, and the MK was calcined at 750 °C to ensure its amorphization.The geopolymers were activated using a 12M KOH alkaline solution (Si/Al = 1.30).The resulting materials achieved a uniaxial compressive strength of up to 8.5 MPa, demonstrating geopolymerization potential for new construction materials.Microstructural and mineralogical analyses (XRD, FTIR, SEM-EDS) supported the formation of a K-A-S-H-type geopolymeric matrix and suggested the possible contribution of iron-bearing phases to the aluminosilicate network development.Optical microscopy observations on polished thin-sections confirmed these results, highlighting the transformation of the mineral phases of the original waste mine tailings into an amorphous geopolymer matrix, thus confirming the successful alkali activation of the precursors.The research line provides with a promising pathway for sustainable mining waste management via producing new, ecofriendly, construction materials in a modern circular economy system.