Spectroscopic and electrochemical characterization of the surface layers of chalcopyrite (CuFeS 2) reacted in acidic solutions

• Published in: Applied surface science Vol. 225; no. 1; pp. 395 - 409
• Main Authors: Mikhlin, Yuri L, Tomashevich, Yevgeny V, Asanov, Igor P, Okotrub, Alexander V, Varnek, Vladimir A, Vyalikh, Denis V
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30-03-2004; Elsevier Science
• Subjects: Chalcopyrite; Oxidative leaching; Voltammetry; X-ray absorption spectroscopy; X-ray emission; X-ray photoelectron spectroscopy; X-ray emission; Voltammetry; Chalcopyrite; X-ray absorption spectroscopy; X-ray photoelectron spectroscopy; Oxidative leaching
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2003.10.030

XPS, Fe Lα,β and Cu Lα,β X-ray emission and Fe L-, Cu L-, S L-edge and O K-edge absorption spectroscopies, Mössbauer spectroscopy and cyclic voltammetry were applied to study reacted surface layers of natural chalcopyrite, CuFeS
2. The surfaces became metal-depleted after the anodic oxidation in 1
M HCl and the leaching in 1
M H
2SO
4+0.2
M Fe
2(SO
4)
3 or 1
M HCl+0.4
M FeCl
3 solutions, with the sulfur excess and iron/copper ratio been higher in the last instance, and were enriched in copper after the electrochemical reduction. The electronic structures of the metal-deficient layers up to several tenths of micrometer thick were similar to that of chalcopyrite, except that the density of the highest occupied states depended on sulfur anions formed (predominant S
3-anions after the ferric sulfate treatment, S
4-anions after the ferric chloride leaching or the potential sweep to 0.9
V, etc.). The layers created by the preliminary oxidation had only a small effect on the chalcopyrite voltammetry. We suggest a new reaction mechanism considering a role of the surface changes, including disordering and Anderson localization of the electronic states.