Understand and predict Fe(III)-promoted oxidation of abandoned sulfidic mine tailings

Reclamation of abandoned sulfidic mine tailings is challenging because these tailings, typically weathered under oxic conditions for decades, generate acid mine drainage (AMD) even after covering with oxygen barriers. Indirect oxidation due to Fe(III)-bearing secondary phases is suspected to be responsible for the poor efficiency of usual reclamation strategies. However, experimental investigation lacking to confirm that such processes are determining the patterns of mine drainage composition after reclamation. We initiated a study of the anoxic leaching of weathered sulfidic tailings from the Doyon mine, Canada, and the Folldal mine, Norway. This proposal aims at using Fe K-edge EXAFS to characterize the secondary, poorly crystalline Fe-species occurring in the initial tailings, as well as Fe-species formed after leaching under anoxic conditions. Speciation modelling will be used to test hypotheses about the reactions involved and predict the generation and composition of AMD.