Bioleaching of a complex black schist ore produces process waters with high metals and sulfate concentrations and a low pH. Iron has a central role in bioleaching and bio-oxidation processes: Fe(II) produced in the dissolution of sulfidic minerals is re-oxidized to Fe(III), mostly by biological action. To control the accumulation of iron in bioleach solutions, an integrated process consisting of biological oxidation for Fe(III) regeneration from Fe(II) and a gravity settler for precipitative iron removal was demonstrated at pilot scale. To study the suitability of biological sulfate reduction for removal of metals (as their sulfides) from waste water streams, sulfate reducing bacteria were enriched from the mine site using silage as the electron donor. Batch assays and semi batch reactors were used to determine the process kinetics.
Responsible persons: Professor Jaakko Puhakka
Researchers: PhD Kathryn Wakeman, BSc Tech Toni Jaatinen
Funding: TEKES, Mondo Minerals B.V., Kemira Chemicals Oy
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