Quantification of oxygen consumption and sulphate release rates for waste rock piles using kinetic cells: Cluff lake uranium mine, northern Saskatchewan, Canada

Oxidation rates of low sulphide (<0.5 wt.%) gneissic waste rock from the Cl uff lake U mine, northern Saskatchewan, Canada were determined using 3 inde pendent methods: O-2 consumption rates in kinetic cells, SO4 measurements o f kinetic cell effluent and humidity cell SO4 release rates. The O-2 consum ption measurements demonstrated that the oxidation of pyrite was strongly d ependent on grain size and moderately dependent on water content, temperatu re and microbiology. Oxygen consumption rates were highest at water content s of 5-10 wt.% (12-25% saturation). Measured SO4 release rates (3.1-91 mg S O4 kg(-1) wk(-1)) for the kinetic cells were comparable to rates calculated from the O-2 consumption Values (6.9-70 mg SO4 kg(-1) wk(-1)). Sulphate re lease rates determined from humidity cells were generally higher than those obtained from the kinetic cells, ranging from 6 to 64 mg SO4 kg(-1) wk(-1) for the coarsest and finest fraction, respectively. These differences were attributed to sample heterogeneity. (C) 2001 Elsevier Science Ltd. All rig hts reserved.