Sustainable Alkali-Activated Mortars for the Immobilization of Heavy Metals from Copper Mine Tailings

This study demonstrates a successful approach for immobilizing heavy metals in alkali-activated mortars (AAMs) by incorporating copper mine tailings (CMTs) and metakaolin (MK) as potential sources of aluminosilicates. Leachate concentrations of hazardous elements from AAM specimens were investigated up to 63 days of immersion in different solutions (pH = 4.5 and 7.0) using the static monolithic leaching method. Statistical analysis revealed that heavy metals such as Fe, Cu, Pb, and Cd were effectively immobilized in AAMs, contributing to the goal of mitigating environmental pollution. oreover, the leaching of S was the highest in an acidic solution after 7 days (31 mg/L), while Si showed the highest concentration in an acidic solution after 28 days (18 mg/L). Sulfur exhibited a mean interval flux higher than those of Si and Al, indicating its faster release from AAMs. Although some elements were detected in relatively high concentration, such as Al in an acidic solution (16 mg/L), they fall within the non-enforceable guidelines set by the US Environmental Protection Agency (EPA), revealing that the manufactured AAMs can meet regulatory requirements. EDXS, FTIR, and XRD analyses provided valuable insights into the surface, chemical, and structural stabilities of AAMs, as well as the influence of pH, the presence of CMTs and MK, and the release of alkaline residues on leaching behavior.