Electrochemical oxidation of covellite (CuS) in alkaline solution

Journal Article · Mon Aug 01 04:00:00 EDT 1994 · Journal of Colloid and Interface Science; (United States)

DOI:https://doi.org/10.1006/jcis.1994.1280· OSTI ID:7229878

Yin, Q; Vaughan, D J; England, K E.R. ^[1]; Kelsall, G H ^[2]

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1. Univ. of Manchester (United Kingdom)
2. Imperial Coll., London (United Kingdom). Dept. of Mineral Resources Engineering

The anodic oxidation of the surface of natural covellite in 0.1 M Na[sub 2]B[sub 4]O[sub 7] (pH 9.2) has been investigated using cyclic voltammetry, chronoamperometry, chronopotentiometry, electrode impedance spectroscopy, and X-ray photoelectron spectroscopy. At potentials < 0.48 V vs S.C.E. (saturated calomel reference electrode), copper dissolution occurred without copper (hydr-)-oxide forming a passive film on the covellite surface; copper ion transport from the bulk covellite through a copper-depleted layer to the electrode/electrolyte interface was rate determining. In the potential range 0.48 to 0.92 V vs. S.C.E., the copper(II) solubility was exceeded locally, so that a passivating copper (hydr-)oxide film covered the electrode surface. The oxidation process was then controlled by copper ion transport from the bulk covellite, through both a copper-depleted layer and a copper (hydr-)oxide film, to the electrode/electrolyte interface. The copper (hydr-)oxide film was thin and subsequently could be dissolved chemically in 1 min at open circuit potential. At potentials > 0.92 V vs S.C.E., the copper (hydr-)oxide film thickened, retarding the covellite anodic oxidation process; this film remained on the electrode surface for longer when the electrode was switched to open circuit potential. However, because a small amount of sulfur was oxidized to sulfate at the higher potentials, the passive layers were porous and showed a smaller polarization resistance.

• OSTI ID: 7229878
• Journal Information: Journal of Colloid and Interface Science; (United States), Journal Name: Journal of Colloid and Interface Science; (United States) Vol. 166:1; ISSN 0021-9797; ISSN JCISA5
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400 -- Electrochemistry
ALKALI METAL COMPOUNDS
BORATES
BORON COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISTRY
COPPER COMPOUNDS
COPPER HYDROXIDES
COPPER SULFIDES
ELECTRIC POTENTIAL
ELECTROCHEMISTRY
ENERGY CONSERVATION
HYDROGEN COMPOUNDS
HYDROXIDES
INDUSTRY
MEASURING METHODS
METAL INDUSTRY
ORE PROCESSING
OXIDATION
OXYGEN COMPOUNDS
PASSIVATION
POLLUTION REGULATIONS
PROCESSING
REGULATIONS
SODIUM COMPOUNDS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS