Acid Mine Drainage (AMD) is the main environmental problem caused by mining sulphide-rich mineral deposits. In the Iberian Pyrite Belt (IPB), more than a hundred abandoned works have resulted in enormous metal wastes that seriously degrade the Odiel and Tinto watersheds. As a result, the IPB is the world paradigm of AMD and a first class natural laboratory to investigate the cycling of metals.
This proposal follows several preceding projects that studied different aspects of metal geochemistry within the Odiel river basin (SW Spain), and it is now focused on precipitates. Schwertmannite and basaluminite, two oxyhydroxysulfates of Fe (III) and Al, are ubiquitous throughout the entire cycle of the AMD, from generation to treatment systems. These solid phases are poorly crystalline and host a large number of trace elements. However, their internal structures, their potential to adsorb/desorb trace elements, and their stability in the medium/long term are still scarcely known, especially in the case of the Al precipitates.
This project aims to supply scientific bases for the development of sustainable solutions to the affection of water resources by AMD. The proposal is focused into four objectives regarding schwertmannite and basaluminite: 1) Their nucleation and growth, including the detailed analysis of the structure, at atomic scale, in relation with their high absorption potential of trace elements; 2) The ageing processes of these minerals towards a greater thermodynamic stability, which can lead to the elimination of toxic elements from their crystal lattices; 3) The formation kinetics at field scale and its implementation in transport models of rivers and reservoirs; and 4) Their potential interest as a source of critical trace elements in the residues of AMD treatment systems.
Project staff: J. Bellés, E. Torres, A. Lozano, L. Scheiber, R. Bartrolí, M. Cabañas