Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 566, Issue -, Pages 1106-1119Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2016.05.143
Keywords
Arsenopyrite biooxidation; Acidithiobacillus thiooxidans; Direct cell attachment; Electrochemical impedance spectroscopy; Toxic arsenic; Biofilm modification
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Funding
- CONACYT [2012-183230, 2013-205416, 362184, 292779]
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Bioleaching of arsenopyrite presents a great interest due to recovery of valuable metals and environmental issues. The current study aims to evaluate the arsenopyrite oxidation by Acidithiobacillus thiooxidans during 240 h at different time intervals, in the presence and absence of supplementary arsenic. Chemical and electrochemical characterizations are carried out using Raman, AFM, SEM-EDS, Cyclic Voltammetry, EIS, electrophoretic and adhesion forces to comprehensively assess the surface behavior and biooxidation mechanism of this mineral. These analyses evidence the formation of pyrite-like secondary phase on abiotic control surfaces, which contrast with the formation of pyrite (FeS2)-like, orpiment (As2S3)-like and elementary sulfur and polysulfide (S-n(2)-/S-0) phases found on biooxidized surfaces. Voltammetric results indicate a significant alteration of arsenopyrite due to (bio) oxidation. Resistive processes determined with EIS are associated with chemical and electrochemical reactions mediated by (bio) oxidation, resulting in the transformation of arsenopyrite surface and biofilm direct attachment. Charge transfer resistance is increased when ( bio) oxidation is performed in the presence of supplementary arsenic, in comparison with lowered abiotic control resistances obtained in its absence; reinforcing the idea that more stable surface products are generated when As(V) is in the system. Biofilm structure is mainly comprised of micro-colonies, progressively enclosed in secondary compounds. A more compact biofilm structure with enhanced formation of secondary compounds is identified in the presence of supplementary arsenic, whereby variable arsenopyrite reactivity is linked and attributed to these secondary compounds, including S-n(2)-/S-0, pyrite-like and orpiment-like phases. (C) 2016 Elsevier B.V. All rights reserved.
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