Perth Laboratory – Public Seminar Series 2009

Development and optimization of unit processes for biomining of multi-metal black schist in Northern Finland

Dr Anna Kaksonen
Tampere University of Technology, Finland

Thursday 7 May 2009 at 3.30pm, CSIRO Auditorium

Abstract

The aim of the presentation is to give an overview of the development and optimization of unit processes for the bioleaching of multi-metal black schist ore and biological control of iron in bioleach liquors. Talvivaara deposit, located in Northern Finland, is one of the largest in the world by volume with low metal grades: 640 Mt of ore with an average of 0.27% Ni, 0.14% Cu, 0.02% Co and 0.56% Zn. The possible utilization of the deposit has been extensively studied for about 30 years. Conventional methods for recovering the valuable metals were not feasible. The studies in the 1980s focused on evaluation of tank leaching of finely ground ore, whereas the recent studies aimed at showing the viability of heap bioleaching.

The effects of pH and temperature on bioleaching were studied in laboratory scale columns. Heap bioleaching was further demonstrated on site with pilot scale heaps. Moreover, biological iron regeneration and control were optimized using fluidized-bed reactors (FBR). The effects of various metals on iron oxidation kinetics were studied with batch kinetic experiments. Microbial communities in the biological unit processes were monitored using 16S rRNA gene based denaturing gradient gel electrophoresis (DGGE) followed by sequencing.

Heap bioleaching of the black schist proved to be feasible in the sub-arctic climate of Northern Finland. Moreover, a FBR can be applied to iron regeneration and control in bioleach liquors. The iron oxidizing culture dominated by Leptospirillum ferriphilum tolerated high metal (Fe³⁺, Zn, Ni) concentrations. The microorganisms detected in the bioleaching columns and heaps include Acidithiobacillus ferrooxidans, At. caldus, At. thiooxidans, L. ferrooxidans, and Sulfobacillus sp.

Commercial-scale production at Talvivaara mine started in the beginning of 2009. In addition to an annual nickel output of approximately 33,000 tons, the mine will also produce 60,000 tpa of zinc, 10,000 tpa of copper, and 1,200 tpa of cobalt as by-products.

About the speaker

Dr Anna Kaksonen of the University of Tampere, Finland, joins CSIRO as a senior research scientist on 1 May 2009. Anna completed her MSc in engineering in 2001, and her PhD in Environmental Biotechnology in 2004, for which she was awarded the prize for the best PhD thesis in Finland in that year. She has published over 30 papers in international journals on the subjects of water treatment biotechnology, mining biotechnology, and deep biosphere microbiology. She was involved in the 6th Framework European Integrated Project 'BioMinE', and has taken her research from laboratory investigations, to pilot scale and then to full scale commercial implementation.

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