Pollutants leaching behaviour from solidified wastes: a selection of adapted various models

Area of Science:

• Environmental Science and Engineering
• Materials Science
• Geochemistry

Background:

• Leaching tests are critical for evaluating the environmental safety of solidified wastes.
• Understanding long-term pollutant release mechanisms from stabilized waste matrices is essential.
• Existing models for leaching from porous materials need refinement for complex chemical species.

Purpose of the Study:

• To develop tools for evaluating long-term pollutant release from solidified wastes.
• To investigate the leaching behavior of pollutants (e.g., lead) in cement matrices under varying chemical conditions.
• To validate a coupled dissolution/diffusion model for predicting pollutant release.

Main Methods:

• Discussion of various leaching models: diffusional, shrinking core, and coupled transport-chemical models.
• Experimental study of lead leaching from cement matrices under controlled chemical conditions.
• Validation of a coupled dissolution/diffusion model using leaching tests on cement and artificial porous matrices.

Main Results:

• Pollutant release, especially for species with pH-dependent solubility (e.g., amphoteric metals), is governed by local solubility and pH evolution within the matrix.
• The coupled dissolution/diffusion model effectively describes the release of chemically complex species.
• A combination of steady-state solubilization tests and long-term dynamic leaching tests can assess pollutant retention in cement matrices.

Conclusions:

• The developed coupled dissolution/diffusion model provides a robust method for assessing long-term pollutant release from stabilized wastes.
• Integrating pH-dependent solubility and matrix pH evolution is crucial for accurate leaching predictions.
• The proposed two-test approach (solubilization and dynamic leaching) aids in standardizing environmental assessment of solidified waste.