Leaching of pyrite by Acidithiobacillus ferrooxidans monitored by electrochemical methods

EDUARDO CORTON; ALBERT SAAVEDRA

Freiberg

Simposio; International Biohydrometallurgy Symposium (IBS 2017); 2017

Dechema

The aim of this work was to use electrochemical methods, which can be useful to follow the corrosion of minerals, to observe the progressive attack of the bacteria on the mineral. The assays were performed in a three electrode cell, where pyrite was used as the working electrode. The effect of low concentration of iron in the media was studied. This study was conducted in three conditions: live bacteria in culture media, dead bacteria in culture media, and sterile culture media, used as a control. The initial bacterial concentration was 106 bact mL-1. The effects of the three conditions over the pyrite electrode were followed by means of corrosion current and potential measurements. Live bacteria condition showed a continuous increase of current vs. incubation time, being up to 4-times higher in the condition with iron, as the corrosion current could be related to the increase of the mineral area. The mineral area was increased by the bacterial attack, which was corroborated identifying by SEM the bacterial fingerprint on the mineral. Dead bacteria and sterile culture medium conditions showed no current increase vs. time. In addition, voltammetric studies showed that in the live bacteria system the surface area increased when the bacterial biofilm was present, whereas in the dead bacteria system only the presences of some organic compounds (originated from cellular debris) were found interacting with the mineral. The control (sterile culture medium condition) showed the presence of iron hydroxides complexes and elemental sulfur over the pyrite electrode, as product of chemical leaching and the initial phase of a passivation process.Here we demonstrated that the leaching process, including the bacterial-mineral interaction, interaction with organic molecules or inorganic corrosion can be monitored by electrochemical methods. Moreover, this procedure is a simple and effective way to identify the initial steps that can lead to mineral passivation. Our work can be useful for the development of a device that can allow in situ monitoring of biomining processes, increasing the efficiency and productivity of the process.