Interactions des résidus miniers et du lixiviat d'une couverture de sous-produits de desencrage dans le contexte du controle du drainage minier acide

Abstract

Mine-wastes contain sulfide minerals, which are able to react with atmospheric water and oxygen to produce sulfuric acid. This production induces the decrease of pH and favors the solubilization of heavy metals. These reactions are called acid mine drainage and is one of the environmental priority of mine industry. To prevent the oxygen flow through the mine tailings, a cover of deinking by-products were set on two mine sites: Eustis and Albert (PQ, Canada). The production of an organic-rich leachate from the cellulose degradation was noticed. This leachate eventually flows through the mine tailings. This study aims at understanding the interactions between the organic leachate and mine tailings in the point of view of preventing acid mine drainage and of the biodegradation of the organic components from the leachate. In-situ observations, batch and column essays showed that the anaerobic environment induced by the cover of deinking by-products, the seepage and the organic- and carbonates-rich leachate cause an increase of the pH and improve the characteristics of the oxidized mine tailings. The initiation of acid mine drainage was not noticed in the unoxidized and mixed tailings. Moreover, sulfate-reduction and methanogenesis allowed the attenuation of the organic components from the deinking by-products leachate, producing alkalinity that improved the acid mine drainage characteristics.