The effect of visible light on the dissolution of natural chalcopyrite (CuFeS2) in sulphuric acid solutions

Crundwell, Frank K.; Aswegen, A. Van; Bryson, L.J.; Biley, C.; Craig, D. Norman; Marsicano, V.D.; Keartland, J. M.

doi:10.1016/j.hydromet.2015.10.014

Cited by 33 publications

(5 citation statements)

References 42 publications

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“…An alternative explanation has been advanced in several papers (Crundwell et al, 2015 and references therein) in terms of which the passivation is due to limitations imposed by the semiconducting properties of chalcopyrite and not to the formation of the metal-deficient layer described above. This theory has recently been subject to criticism in that a) apparent photoeffects at chalcopyrite (Crundwell et al, 2015) have been shown to be thermal in origin (Nicol, 2016a) and b) capacitance measurements…”

Section: Accepted Manuscriptmentioning

confidence: 99%

The anodic behaviour of chalcopyrite in chloride solutions: Voltammetry

2017

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This paper summarizes the results of a voltammetric study of the anodic characteristics of chalcopyrite in the potential region relevant to heap leaching in concentrated chloride solutions. Distinct peaks in the potential region of 0.7 to 0.85 V have been observed in the voltammograms, the magnitude of which depend on the chloride concentration and, particularly, the pH in the range 1 to 3. Three peaks are observed at low chloride concentrations that merge into one peak at higher concentrations. The anodic reactivity increases with increasing pH but shows a complex dependence on the chloride concentration while in the presence of added copper(II) ions, the mixed potential shifts to more positive potentials and only one peak is observed. Hysteresis between the forward and backward-going sweeps has confirmed the transient nature of the processes except at potentials below about 0.75 V in which region the system approaches steady-state behaviour. The voltammetric characteristics of chalcopyrite in this system appear to be very similar to those of covellite. Measurements of the initial rates of dissolution (in the range 1-5 x 10-10 mol cm-2 s-1 depending on the conditions) have been made that confirm the voltammetric trends and compare well with previously published rates.

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Section: Accepted Manuscriptmentioning

confidence: 99%

The anodic behaviour of chalcopyrite in chloride solutions: Voltammetry

2017

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“…In a recent paper (Crundwell et al, 2015), it was shown that photocurrents could be observed at a chalcopyrite electrode when exposed to radiation from a 2 watt LED source at various anodic potentials in dilute sulfuric acid solutions. These results together with apparent correspondence between carrier concentrations determined by…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Photocurrents at chalcopyrite and pyrite electrodes under leaching conditions

Nicol

2016

Hydrometallurgy

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The use of photocurrents at transition metal sulfide minerals as a diagnostic tool to assess the relevance of semiconducting properties in the kinetics and mechanisms of dissolution should be applied with caution. It is shown that apparent photocurrents at chalcopyrite and pyrite electrodes at potentials relevant to oxidative dissolution in acidic sulfate solutions are due to thermal and not photocurrent effects when assessed with normal light sources. The use of laser diodes as light sources of variable wavelength has been shown to confirm the thermal effects in both anodic and cathodic reactions involving chalcopyrite and pyrite electrodes. No photocurrents could be detected at either of these minerals except for chalcopyrite under anodic conditions when exposed to radiation from a violet laser diode (405nm). This observation is attributed to the semiconducting properties of the so-called passivation layer formed on the mineral under anodic polarization and not to the properties of chalcopyrite itself.

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“…Furthermore, according to density functional theory calculations, S 4 2– was formed on the chalcopyrite surface. , Holmes et al and Crundwell suggested that the S n 2– and Cu 1– x Fe 1– y S 2– z are essentially the same; the only difference is the focus on either the sulfur or metal removal. However, Crundwell et al , argued that the rate of chalcopyrite dissolution is not limited by passivation films or layers but is intrinsically slow due to the semiconducting properties of chalcopyrite. Furthermore, they identified the chalcopyrite anodic dissolution as a depletion region (from 0.3 to 0.6 V vs SCE) and inversion region (>0.7 V vs SCE) for ideal n-type semiconductor.…”

Section: Resultsmentioning

confidence: 99%

Mixed Potential Plays a Key Role in Leaching of Chalcopyrite: Experimental and Theoretical Analysis

Yang

Qin

Zhao

et al. 2018

Ind. Eng. Chem. Res.

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The mixed potential plays a key role in leaching of chalcopyrite. Therefore, the impact of Fe2+ and Fe3+ on chalcopyrite leaching was investigated in this work. Simultaneously, the chalcopyrite passive film was studied by applying cyclic voltammetry (CV), potentiodynamic, potentiostatic, and Tafel polarization. X-ray photoelectron spectroscopy (XPS) was used to analyze the products formed during the electrochemical treatment of chalcopyrite. Furthermore, the band theory was used to analyze the oxidation and reduction of chalcopyrite. High copper extraction percentage was obtained at a low mixed potential or ratio of Fe3+/Fe2+. The empty states of chalcopyrite overlapped with filled states of Fe2+; chalcopyrite captured electrons from Fe2+ and was reduced to chalcocite, which was very easily oxidized by Fe3+. The Fe dissolves preferentially from the chalcopyrite surface in the potential range from 475 to 700 mV and leave behind a S2 2– and S n 2– passive film. The chalcopyrite transpassive dissolution occurs above 700 mV.

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The effect of visible light on the dissolution of natural chalcopyrite (CuFeS2) in sulphuric acid solutions

Cited by 33 publications

References 42 publications

The anodic behaviour of chalcopyrite in chloride solutions: Voltammetry

The anodic behaviour of chalcopyrite in chloride solutions: Voltammetry

Photocurrents at chalcopyrite and pyrite electrodes under leaching conditions

Mixed Potential Plays a Key Role in Leaching of Chalcopyrite: Experimental and Theoretical Analysis

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