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Occurrences at mineral–bacteria interface during oxidation of arsenopyrite by Thiobacillus ferrooxidans
Author(s) -
Fernandez Marcos G. Monroy,
Mustin Christian,
de Donato Philippe,
Barres Odile,
Marion Philippe,
Berthelin Jacques
Publication year - 1995
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260460103
Subject(s) - bioleaching , chemistry , ferrous , arsenate , thiobacillus , ferric , nuclear chemistry , arsenopyrite , leaching (pedology) , sulfur , inorganic chemistry , arsenic , geology , copper , organic chemistry , chalcopyrite , soil science , soil water
The combination of an improved bacterial desorption method, scanning electron microscopy (SEM), diffuse reflectance and transmission infrared Fourier transform spectroscopy, and a desorption‐leaching device like high‐pressure liquid chromatography (HPLC) was used to analyze bacterial populations (adhering and free bacteria) and surface‐oxidized phases (ferric arsenates and elemental sulfur) during the arsenopyrite biooxidation by Thiobacillus ferrooxidans . The bacterial distribution, the physicochemical composition of the leachate, the evolution of corrosion patterns, and the nature and amount of the surface‐oxidized chemical species characterized different behavior for each step of arsenopyrite bioleaching. The first step is characterized by a slow but strong adhesion of bacteria to mineral surfaces, the appearance of a surface phase of elemental sulfur, the weak solubilization of Fe(II), As(III), and As(V), and the presence of the first corrosion patterns, which follow the fragility zones and the crystallographic orientation of mineral grains. After this short step, growth of the unattached bacteria begins, while ferrous ions in solution are oxidized by them. Ferric ions produced by the bacteria can oxidize the sulfide directly and are regenerated by Fe(II) bacterial oxidation. At this time, a bioleaching cycle takes place and a coarse surface phase of ferric arsenate (FeAsO 4 · x H 2 O where x ≈ 2) and deep ovoid pores appear. At the end of the bioleaching cycle, the high concentration of Fe(III) and As(V) in solution promotes the precipitation of a second phase of amorphous ferric arsenate (FeAsO 4 · x H 2 O where x ≈ 4) in the leachate. Then the biooxidation process ceases: The bacteria adhering to the mineral sufaces are coated by the ferric arsenates and the concentration of Fe(III) on the leachate is found to have decreased greatly. Both oxidation mechanisms (direct and indirect oxidation) have been stopped. © 1995 John Wiley & Sons, Inc.