THE USE OF GREEN RUST TO ACCELERATE PRECIPITATION OF OCHRE FOR MINE WATER REMEDIATION

Metal-rich mine drainage is a worldwide environmental problem, its treatment can be passive or active. This paper presents examples from a series of laboratory scale experiments which investigated the accelerated precipitation of ochre for the treatment of metal-rich mine waters. This paper discusses the effects that the addition of the FeII,III hydroxy salt green rust (GR), found in an unusual deposit in the South Wales Coalfield, has on 2 polluted discharges. The Parys Mountain discharge contains 79 and 8 mg L-1 Fe and Cu respectively. The addition of GR was able to acclerate precipitation of ochre and reduce the concentration to ~10 and 0 mg L-1 for Fe and Cu respectively. The Bwlch effluent releases high levels of Zn (~20 mg L-1), the addition of GR aided its complete removal within 5 minutes. This effect is attributed to a combination of the neutralisation effect of the GR, the additional sites available for sorption and the potential for the GR to aid surface catalysed oxidation of ferrous iron. The accelerated precipitation of Fe has the potential to enhance passive and / or active treatment of mine waters. The ochre produced can be recycled back into the system to encourage precipitation of Fe oxy-hydroxides from these toxic mine waters. The rapid nature of the precipitation causes co-precipitated elements to be adsorbed, which generates a more stable solid wast