STABILISATION/ENCAPSULATION TECHNIQUES FOR MINING WASTES WITH PRESENCE OF METALLOIDS
Funding entity: Ministry of Science, Innovation and Universities (MCIU), State Research Agency (AEI) and European Regional Development Fund (ERDF).
Principal Investigator: E. Álvarez Ayuso.
Participating researchers: A. Murciego, Mª A. Rodríguez, J. Cabezas, L.F. Fernández, J.M. Naranjo and R. Mosser.
The accumulation of mining waste with the presence of metalloids such as arsenic (As) and antimony (Sb) poses a great risk to the surrounding ecosystem due to the toxic characteristics of these two elements.
Arsenopyrite (FeAsS) is the most common As mineral, ubiquitous in a wide variety of ore deposits. Processes aimed at inhibiting or preventing the oxidation of arsenopyrite are successful in reducing the release of As from arsenopyrite. However, the treatment of tailings that undergo significant oxidation has to be approached from a different perspective. The oxidation products of arsenopyrite can be very diverse. However, scorodite (FeAsO 42H 2O) is by far the main one. This mineral is an important sink for As, but this ability is seriously compromised due to the strong dependence of the solubility and stability of scorodite on the pH and redox conditions of the medium.
Stibnite (Sb 2S 3) is the most important mineral and the primary commercial source of Sb. Under atmospheric conditions stibnite oxidizes very easily, generating oxides of very different solubility. When the geochemical conditions are not suitable to favour the formation of the most insoluble compounds, a significant release of Sb into the environment can occur.
Given this problem, the present project aims precisely to develop methods to prevent or minimize the dispersion of these metalloids from mining waste. The following techniques will be studied:
- Stabilisation procedures based on the application of immobilising agents
- Encapsulation methods through the generation of cementitious matrices using various binder/binder materials.
- Encapsulation systems based on the formation of oxide coatings or very low solubility compounds.