An Integrated Approach to the Management of Sulphide Tailings andMitigation of Acid Mine Drainage

摘要

One of the major environmental issues in the mining industry is Acid Mine Drainage(AMD), caused by the microbial oxidation of voluminous sulphide-bearing wastes. Itsimportance is largely driven by its enduring nature following mine closure with AMDgeneration perpetuating for 10 of years or more. Changes in legislation as well as recentinitiatives under the auspices of global organisations, such as the Global Mining Initiative(GMI) and the International Council of Mining and Metals (ICMM), are placingincreasing pressure on the minerals industry to be more proactive and innovative in termsof reducing potentially harmful emissions from deposits and residues, as well as the costsof tailings management and AMD remediation, over the long-term. In particular, there is growing concern that current techniques for the prevention ofAMD formation - including layering residues with impermeable or reactive treatmentmaterials; subaqueous disposal; backfilling; and blending or co-disposing with acidconsuming materials - will not be sufficient to prevent post-closure impacts andguarantee a "walk-away" status situation. Discussions provided by Barbour and Shaw(2000), Christie, (2002), Jarvis and Younger (2000) are informative with respect to thisconcern. Increasingly, such concerns are prompting the adoption of a more holistic andintegrated approach to the management of sulphide tailings in order to minimise long-term AMD risks in a manner consistent with the principles of cleaner production andsustainable development, an example of which is illustrated by the recent investigationsof Benzaazoua et al. (2008). In keeping with such an approach, this paper explores the development of anintegrated tailings management strategy, which is based on separation of sulphide tailingsinto two fractions - viz. an acid-generating sulphide-rich stream and a benign sulphide-lean stream - using non-selective flotation techniques. As illustrated in Figure 1, thebenign tailings fraction can either be disposed of conventionally; co-disposed with wasterock; used as cover on existing tailings deposits; or as backfill material (see previousinvestigations by Benzaazoua et al., 2008; Smith and Leduc, 2003). In accordance withBenzaazoua et al. (2004), sulphide-rich tailings may also provide suitable material forbackfill purposes. Alternatively this stream can be used as a source of sulphuric acidwhich can subsequently be sold or used in other downstream process operations, such asheap leaching and hydrometallurgical applications. It is furthermore proposed that suchseparation can either be executed through the incorporation of a bulk sulphide flotationstep prior to conventional concentration of the values, or by passing tailings through a secondary flotation stage subsequent to conventional concentration, as illustrated inFigure 1.