Bioleaching of pyrite by Thiobacillus ferrooxidans: fixed grains electrodeto study superficial oxidized compounds

An electrode with fixed pyrite grains on a graphite and silicon paste has b een used to study the electrochemical processes at the surface of powdered pyrite during bioleaching by Thiobacillus ferrooxidans. The study of an air -oxidized pyrite shows that the fixed grains electrode (FCE) is more sensit ive than the classical Carbon Paste Electrode (CPE) already used by differe nt authors to characterize various oxides and sulfurs. On the other hand, t he concommitant Raman and electrochemical analysis of autoclaved pyrite sho ws that the cleaned mineral FeS2 has no electrochemical reactivity, and poi nts out that the electrochemical response of the oxidized mineral is exclus ively due to the chemical compounds present at its surface. Therefore, the electrode acts as an efficient sensor for pyrite superficial oxidized phase s, which are fundamental for the biooxidation process and is consequently v ery well adapted for the control of the oxidation state of pyrite powder du ring bioleaching by Thiobacillus ferrooxidans. ((C) Academie des sciences / Elsevier, Paris.).