Lime and pozzolan-based matrices for an efficient immobilization of hazardous waste

• Lime-pozzolan matrices demonstrated high efficiency in immobilizing hazardous metals. • Copper was effectively immobilized with leachability indices (LI) exceeding 12. • Lithium showed moderate immobilization (LI > 7) but fell short for sanitary landfill criteria. • Mixing methodology significantly influenced contaminant retention and matrix performance. • A combined wash-off and diffusion model accurately described the metal release mechanisms. Lime-pozzolan mortar was evaluated as a sustainable binder for the containment of hazardous waste, using lithium and divalent copper as representative tracers. Lithium, characterized by high mobility, and copper, with lower mobility, were selected to model a range of challenges in metal immobilization. Although lime and pozzolanic materials are widely used in construction, their application in waste immobilization is still underexplored. The mortar was characterized through physicochemical analyses, and dynamic elution tests were performed to assess the cumulative leached fraction of the metals. Key transport parameters, including the apparent and effective diffusion coefficients, as well as the leachability index (LI), were calculated. Two mixing methodologies were tested to assess their influence on immobilization efficiency. The results demonstrated the effective immobilization of copper, with LI values exceeding 12, thereby meeting hazardous waste disposal standards. However, lithium retention was insufficient to comply with sanitary landfill criteria. The mixing methodology significantly affected copper retention, with certain sequences enhancing immobilization. Overall, lime-pozzolan matrices show promise as a viable and low-carbon alternative to Ordinary Portland cement form metal immobilization. This approach offers a cost-effective and environmentally friendly solution for hazardous waste stabilization.