Iron Oxidation and Bioleaching Potential at Low Temperatures

Abstract

Objectives The purpose of this study was to assess iron oxidation and prospects of bioleaching at low temperatures relevant in arctic and boreal environments. Iron-oxidizing acidophiles were enriched at 5°C from samples from a Ni-Cu mine site (northern Siberia) and the kinetics of iron oxidation by one of the isolates (strain SS3) was evaluated at low temperatures. Additionally, low temperature bioleaching was tested with either a pure (strain SS3) or mixed (T7 mix) culture in stirred tank reactors and column reactors, respectively. Results The oxidation kinetics at 5°C could be described with the first order rate expression. The rate of iron oxidation at 5°C by SS3 was nearly as fast as that at 30°C by a mesophilic reference strain. Iron precipitates in cultures grown at 5°C were mixtures of schwertmannite and jarosite, whereas jarosite was the exclusive solid phase at 30°C. The bioleaching potential of isolate SS3 was tested in stirred tank reactors containing pyrite, pyrite-arsenopyrite, and chalcopyrite concentrates. With SS3, the leaching rates in stirred tank reactors were much lower at 5°C than at 30°C due to slow chemical oxidation rates of sulfide minerals by Fe