TY - JOUR
T1 - Electrochemical dissolution of chalcopyrite
T2 - Detection of bornite by synchrotron small angle X-ray diffraction and its correlation with the hindered dissolution process
AU - Majuste, D.
AU - Ciminelli, V. S.T.
AU - Osseo-Asare, K.
AU - Dantas, M. S.S.
AU - Magalhães-Paniago, R.
N1 - Funding Information:
The authors are grateful to the Brazilian Synchrotron Light Laboratory (LNLS) and the government agencies CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) , FAPEMIG (Fundação de Amparo à Pesquisa do Estado de Minas Gerais) and CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) , for financial support.
PY - 2012/1
Y1 - 2012/1
N2 - 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.
AB - 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.
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U2 - 10.1016/j.hydromet.2011.11.003
DO - 10.1016/j.hydromet.2011.11.003
M3 - Article
AN - SCOPUS:84857191429
SN - 0304-386X
VL - 111-112
SP - 114
EP - 123
JO - Hydrometallurgy
JF - Hydrometallurgy
IS - 1
ER -