Study of the impedance of a galena electrode under conditions similar to those used in sulphide mineral flotation—I. Electrode oxidation and xanthate adsorption

Ndzebet, E.; Schuhmann, D.; Vanel, P.

doi:10.1016/0013-4686(94)80019-7

Cited by 22 publications

(9 citation statements)

References 14 publications

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“…Reaction 3 has been suggested on the basis of the combined atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) data 25 obtained at pH 4.9, but it is unclear whether it is valid at alkaline pH's. Reactions 2, 4, and 5 are consistent with data provided by classical electrochemical methods 1,[5][6][7][8]12,[18][19][20][21]28,29 and measurements of the surface photovoltage, 5,6 the flotation response, 9,10 and the solution composition. 26,27 However, implications of them will always be questioned until confirmed by an in situ spectroscopic method, which is common for all indirect methods.…”

Section: Pbssupporting

confidence: 79%

“…(III) Congruent dissolution-oxidation 2,[23][24][25][26][27] which is followed by hydrolysis of the anion and cation and anodic oxidation of hydrolyzed sulfur to elemental sulfur (HSw S°+ H + + 2e at pH 9.2). 25 Decomposition at pH 7-10 in the higher overpotential region, in which galena behaves as a quasimetal, has been interpreted as reaction 2, 19,20,28,29 but yielding a bulk oxidation layer with (OH) 2 and Pb vacancies 20,21 as charge carriers. Instead of Pb(OH) 2 , lead carbonate can form.…”

Section: Introductionmentioning

confidence: 99%

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Anodic Oxidation of Galena (PbS) Studied FTIR-Spectroelectrochemically

Чернышова

2001

J. Phys. Chem. B

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The attenuated total reflection/FTIR spectra of the (100) galena/electrolyte interface were measured in situ for the first time in nitrogen-saturated borate buffers (pH 9.2) of two concentrations in the potential region of -0.5 to +0.7 V (SHE), simultaneously with the voltammograms. The experiments were conducted on the electrode previously reduced at -0.5 V and the nonreduced electrode as well. Not only vibrational bands but also monotonic absorption of free carriers was analyzed. It was concluded that at the first step galena is oxidized by the reaction PbS + 2xh + w Pb 1-x S + xPb 2+ , which is followed by the reaction PbS + 2h + w Pb 2+ + S°. Pb(OH) 2 is formed by the precipitation mechanism. The Pb(OH) 2 yield of galena oxidation increases as either the buffer concentration or the time of the galena reduction is increased, which was explained by an increase in the potential drop in the Helmholtz layer. When a more positive bias potential is applied, lead sulfite and thiosulfate are formed by the reactions PbS + 3H 2 O w PbSO 3 + 6H + + 6e and PbS + S°+ 3H 2 O w PbS 2 O 3 + 6H + + 8e, respectively. These processes were correlated with the galena floatability.

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Section: Pbssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Anodic Oxidation of Galena (PbS) Studied FTIR-Spectroelectrochemically

Чернышова

2001

J. Phys. Chem. B

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“…The anodic reactions at semiconducting sulfides at controlled potential have been studied intensively by using classical electrochemical methods, [2][3][4][18][19][20][21][22] the UV-vis solution depletion method, and IR and XPS spectroscopy (for a review, see ref 4), the system "galena-xanthate" being studied the most intensively. At least four forms of xanthate have been found or postulated for galena: chemisorbed radical, physisorbed xanthate, metal xanthate complex, dixanthogen, and monothiocarbonate (MTC) (or the dimer of MTC).…”

Section: Introductionmentioning

confidence: 99%

Anodic Processes on a Galena (PbS) Electrode in the Presence of n-Butyl Xanthate Studied FTIR-Spectroelectrochemically

Чернышова

2001

J. Phys. Chem. B

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Anodic reactions on a galena (PbS) electrode in solutions of n-butyl xanthate (X) were studied in situ using attenuated total reflection/FTIR spectroscopy within the -0.5 to +0.7 V potential range in deaerated borate buffer (pH 9.2). It was confirmed that at the first stage X is adsorbed with charge transfer (chemisorbed). It was found that n-butyl dixanthogen, (X) 2 , is formed at the reversible potential for the X -/(X) 2 pair, independently of the X concentration. The appearance of dixanthogen makes the surface most hydrophobic, which can be followed from the changes in the water spectrum. Otherwise, the mechanisms of the X adsorption at high and low concentrations have differences. At a concentration of 10 -3 M, oxidative decomposition of galena and adsorbed xanthate is inhibited by the X chemisorption, which is followed by the formation of lead xanthate, Pb(X) 2 , and (X) 2 . At 8 × 10 -5 M, bulk Pb(X) 2 is formed by the precipitation mechanism. At higher applied potentials first Pb(X) 2 transforms into Pb(OH) 2 . Afterward (X) 2 decomposes into a dimer of monothiocarbonate, while galena decomposes into lead sulfite and lead thiosulfate. The possible reactions for these processes were suggested. The results were correlated with the literature data on galena flotation.

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“…The Pb(II) species formed strongly depends on the nature of the electrolyte and may be Pb(OH) 2 or PbCl 2 in the case of a deaerated 0.1 M NaCl solution. [44][45][46] As the scan direction was reversed no corresponding reduction peak was observed and thus the anodic dissolution is an irreversible process. If a second scan was initiated it was clearly seen that this oxidation peak had vanished or, in the case of MPA-functionalized substrates, was negligibly small, indicating that almost all of the particles had been removed during the rst scan.…”

Section: Resultsmentioning

confidence: 99%