Biologically-Induced precipitation of aluminium in synthetic acid mine water

摘要

At very low pH (<2.0) aluminium is present as a free cation, Al~(3+), whereas it forms complexes with hydroxyl ions in fresh water at mildly acidic pH values and above. Acidic waters associated with metal mining are usually enriched with sulfate which complexes with aluminium to form hydroxysulfates as felsobanyaite (also known as basaluminite) or hydrobasaluminite. An anaerobic bench-scale reactor, populated by a mixed community of acidophilic sulfate-reducing (and other) bacteria was fed with synthetic acid (pH 2.5/3.0) mine water containing variable concentrations of aluminium. The sulfate-reducing bacteria utilized protons released during hydrolysis of soluble aluminium to form hydroxysulfates in the reactor, as well as those present in the acidic feed liquor, to reduce sulfate, coupling this with the oxidation of glycerol. The two aluminium hydroxysulfates formed into the bioreactor were identified as hydrobasaluminite and felsobanyaite. The bioreactor population was mainly dominated by the sulfate-reducer Desulfosporosinus acididurans and (in relatively lower abundance) Acidocella aromatica and Acidithiobacillus ferrooxidans. This study confirmed the hypothesis tested that it is possible to precipitate soluble aluminium present in acidic mine waters via biosulfidogenesis, mimicking the anoxic conditions present in some metal-mine pit lakes in the Iberian Pyrite Belt.