Electrochemical dissolution of chalcopyrite: Detection of bornite by synchrotron small angle X-ray diffraction and its correlation with the hindered dissolution process

D. Majuste, V. S.T. Ciminelli, K. Osseo-Asare, M. S.S. Dantas, R. Magalhães-Paniago

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48 Scopus citations

Abstract

The formation of bornite (Cu 5FeS 4), an iron-deficient sulfide, and its correlation with the slow oxidation rate of chalcopyrite (CuFeS 2) in acidic media under atmospheric conditions is demonstrated. Chalcopyrite electrodes oxidized in 0.1 mol/L H 2SO 4 solutions at room temperature (25 ± 1 °C) were analyzed by micro Raman spectroscopy and synchrotron small angle X-ray diffraction (S-SAXRD), techniques indicated for thin films analysis. Anodic polarization curves of chalcopyrite electrodes showed two well-defined behaviors: quasi-potential-independent regime and potential-dependent regime. When the critical potential (Ec) is attained, which ranged from 0.75 to 0.90 V vs. Standard Hydrogen Electrode (SHE), the mineral oxidation rate becomes strongly dependent on potential. Potentiostatic current-time profiles at 0.60 and 0.70 V vs. SHE indicated a current decay, which suggests the formation of a progressively thickening protective layer. The profiles at 0.80 V vs. SHE showed a similar current decay, but also an active oxidation process for some samples. After chronoamperometry at 0.70 and 0.80 V vs. SHE, respectively, for 6 and 2 h, analyses by using S-SAXRD revealed peaks of bornite on oxidized chalcopyrite electrodes. Elemental sulfur (S 8) was also detected by S-SAXRD at 0.80 and 1.00 V vs. SHE, respectively, for 2 and 0.5 h. An unidentified metal-deficient phase and covellite (CuS) were detected on chalcopyrite by micro Raman spectroscopy after chronoamperometry at 0.60 and 0.80 V vs. SHE, respectively. The formation or absence of these product phases under a constant applied potential correlated well with a hindered dissolution or active oxidation processes. The results of this work support the hypothesis that the formation of intermediate iron-deficient sulfides contributes to the slow oxidation rate of chalcopyrite under atmospheric conditions.

Original languageEnglish (US)
Pages (from-to)114-123
Number of pages10
JournalHydrometallurgy
Volume111-112
Issue number1
DOIs
StatePublished - Jan 1 2012

All Science Journal Classification (ASJC) codes

  • Industrial and Manufacturing Engineering
  • Metals and Alloys
  • Materials Chemistry

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