Abstract: A permeable reactive barrier was installed in August 1995 at the Nickel Rim Mine near Sudbury, Ontario, Canada, for the passive remediation of groundwater contaminated with acid mine drainage. The reactive component of the barrier consists of a mixture of municipal and leaf compost and wood chips: the organic material promotes bacterially-mediated sulphate reduction. Hydrogen sulphide, a product of sulphate reduction, may then complex with aqueous ferrous iron and precipitate as iron sulphide. This study presents the solid phase sulphur chemistry of the reactive wall after two years of operation, and discusses the formation and accumulation of iron sulphide minerals in the reactive material. The results from the solid-phase chemical analysis of core samples indicate that there is an accumulation of reduced inorganic sulphur in the reactive wall, with levels reaching 190 mu mol g (super -1) (dry weight) by July 1997.

Abstract: Environmental desulphurization is an attractive alternative for acid generating tailings management as demonstrated during the last few years. In fact, such process placed at the end of the primary treatment circuit allows to reduce greatly the amount of problematic tailings by concentrating the sulphidic fraction. Moreover, the desulphurized tailings (non-acid generating) have the geotechnical and environmental properties for being used as fine material in a cover with capillary barrier effects. To produce desulphurized tailings, non selective froth flotation is the most adapted method as shown in many previous works. Desulphurization level is fixed by tailings sulphur content (or sulphide content) and neutralization potential NP. The final residue should have enough NP to compensate for his acid generating potential AP. In this paper, the authors present the results of laboratory tests conducted in Denver cells for studying the sulphide flotation kinetics of four mine tailings which are characterized by a weak neutralization potential (under 37 kg CaCO (sub 3) /t). Tailings 1, 2, 3 and 4 contain respectively 5.27, 10, 4.25 and 16.9 sulphur Wt. %. Tailings 1 and 2 are cyanide free and are well floated at pH around 11 by using amyl xanthate as collector. Collector dosage was optimized for these tailings and the results show that Tailing 2 need more collector. However, Tailings 3 and 4, which come from a gold cyanidation process, could not provide good sulphide recovery with xanthate collector because of the pyrite depression. To overcome this problem, amine acetate was used successfully but induces important entrainment. The consumption of this collector was also optimized. The results of kinetic tests and collector dosage were combined and modeled to establish relationships which allow to estimate the desulphurization performances.