Increasing the Sustainability of the Stabilization/Solidification of Potentially Toxic Elements Contained in Tailings from an Active Mine Using a Modified Lime Mortar

The use of a modified lime mortar as a binder for the stabilization/solidification of mine tailings presents a promising and sustainable solution for immobilizing potentially toxic elements found in these waste materials compared to cement mortars. The effectiveness of this modified lime mortar in avoiding the mobility of toxic elements, namely lead (Pb) and arsenic (As), in mine tailings has been thus studied. Encapsulating matrices of 1:1 and 2:1 tailings waste/air lime ratios were prepared. Due to the content of potentially pozzolanic compounds in the mine tailings, mainly some silicate phases, 1:1 matrices showed better mechanical strength than 2:1 samples, ascribed to a more intense pozzolanic reaction. SEM observations identified needle-shaped C-S-H structures. The hardened materials showed good endurance against freeze-thaw cycles. The semi-dynamic tank test demonstrated the effective encapsulation of the toxic components due to the use of lime mortars, yielding values of released Pb and As below the detection limit in all instances. Considering the cost-effectiveness, widespread availability, and ease of use, the use of modified lime mortar for the treatment of mine tailings can be recommended to mitigate the environmental impacts of mining activities.