XPS analytical approach for elucidating the microbially mediated enargite oxidative dissolution

• Published in: Analytical and bioanalytical chemistry Vol. 393; no. 8; pp. 1931 - 1941
• Main Authors: Fantauzzi, M, Rossi, G, Elsener, B, Loi, G, Atzei, D, Rossi, A
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.04.2009; Springer-Verlag; Springer
• Subjects: A. ferrooxidans; Acidithiobacillus - chemistry; Acidithiobacillus ferrooxidans; Analytical Chemistry; Applied sciences; Arsenic - chemistry; Arsenicals - chemistry; Bacteria; Biochemistry; Bioleaching; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Copper - chemistry; Copper compounds; Dissolution; Enargite; Exact sciences and technology; Extracellular polymer substance; Food Science; Global environmental pollution; Hydrogen-Ion Concentration; Iron - chemistry; Iron Compounds - chemistry; Kinetics; Laboratory Medicine; Microorganisms; Mineral sulfides dissolution; Minerals; Monitoring/Environmental Analysis; Nanostructure; Original Paper; Oxidation-Reduction; Pollution; Solubility; Spectrometric and optical methods; Spectrophotometry; Sulfides - chemistry; Surface Properties; Toxic mine effluents; X-ray photoelectron spectroscopy; X-Rays; XPS surface analysis; Bioleaching; XPS surface analysis; Enargite; Toxic mine effluents; Extracellular polymer substance; .; Mineral sulfides dissolution; Sulfide minerals; Hydrogen electrode; X ray spectrometry; Polymer; X ray; Surface analysis; Nitrogen; Dissolution; Powder; A. ferrooxidans; Bacteria; Environment; Nutrient; Photoelectron spectrometry; Redox potential; Effluent
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-009-2613-3

In this work, the microbe-mediated oxidative dissolution of enargite surfaces (Cu₃AsS₄) was studied on powdered samples exposed to 9K nutrient solution (pH 2.3) inoculated by Acidithiobacillus ferrooxidans initially adapted to arsenopyrite. These conditions simulate the acid mine environment. The redox potential of the inoculated solutions increased up to +0.72 V vs normal hydrogen electrode (NHE), indicating the increase of the Fe³⁺ to Fe²⁺ ratio, and correspondingly the pH decreased to values as low as 1.9. In the sterile 9K control, the redox potential and pH remained constant at +0.52 V NHE and 2.34, respectively. Solution analyses showed that in inoculated medium Cu and As dissolved stoichiometrically with a dissolution rate of about three to five times higher compared to the sterile control. For the first time, X-ray photoelectron spectroscopy (XPS) was carried out on the bioleached enargite powder with the aim of clarifying the role of the microorganisms in the dissolution process. XPS results provide evidence of the formation of a thin oxidized layer on the mineral surface. Nitrogen was also detected on the bioleached surfaces and was attributed to the presence of an extracellular polymer substance layer supporting a mechanism of bacteria attachment via the formation of a biofilm a few nanometers thick, commonly known as nanobiofilm. [graphic removed]