Untitled

Kozin, L. F.; Berezhnoi, E. O.; Bogdanova, A. K.

doi:10.1023/a:1005274528757

Cited by 5 publications

(21 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the initial segments of the dissolution curves, at τ < τ max , that is, before the passivation, the gold ion concentration C max (just like in thiocarbamide solutions [4]) can be described by the equation:…”

Section: Resultsmentioning

confidence: 99%

“…The large-scale application of the cyanide solutions poses environmental problems in large areas [3]. Therefore, new alternative chemical solvents for gold are searched for, such as thiourea [4], thiosulfates [5], polysulfides [6], halide-derivatives [7], etc. Halide, in particular, chloride gold solutions are widely used in protective electroplating; hypochlorite solutions, in the gold metallurgy, for its leaching from ores [7].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Kinetics and mechanism of the gold corrosion dissolution in hypochlorite solutions

2005

Self Cite

View full text Add to dashboard Cite

Kinetics and mechanism of the gold metal dissolution by means of corrosion in chloride-hypochlorite solutions are studied. The dependences of the dissolution rate on the solution pH, sodium hypochlorite concentration, and temperature are determined. Conditions of the gold passivation surface during its corrosion in the studied solutions are discussed. The first-order rate constants of the gold dissolution ( k i = 0.079-0.4030 s -1 ) at temperatures from 277 to 304 K and others are calculated. The equilibrium constants of the dissolution reactions in acid and alkaline chloride-hypochlorite solutions are different: 1.2 × 10 6 and 2.39 × 10 2 , respectively. The activation energy calculated from the temperature dependence of the rate constants (53.43 kJ/mol) evidences a kinetic control of the gold dissolution. Quantitative data on the composition of surface adsorption films, formed by oxidation gold dissolution products, are obtained using the Auger spectroscopy.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetics and mechanism of the gold corrosion dissolution in hypochlorite solutions

2005

Self Cite

View full text Add to dashboard Cite

show abstract

“…Hence, the gold electrode surface is positive in a potential range studied. Positively charged complex species [((NH 2 ) 2 C=S) 2 Au , which are formed by reaction (6) in a potential range of the first peak, should desorb according to reaction (7) and pass inside the electrical double layer, where they interact with (NH 2 ) 2 C=S molecules by reaction (8) Such a behavior of gold electrodes during the corrosion dissolution in acidic TCA solutions was attributed [1,2] to the adsorption of TCA molecules on gold and their hydrolysis to yield hydrosulfides and sulfides (AuHS -and Au 2 S), which results in the formation of adsorption layers on the gold surface.…”

Section: Resultsmentioning

confidence: 99%

“…According to earlier studies [1,2], TCA is oxidized by Fe(III) ions to give formamidine disulfide ( FADS ) : (NH 2 )NHC=S-S=CNH(NH 2 ) molecules (see Eq. (1)).…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4][5]. During the corrosion oxidation of gold in TCA solutions in the presence of iron(III) ions, FADS molecules adsorb by their sulfur atoms that carry induced negative charges ( δ -) on the positively charged gold surface [1,2]. It seemed of interest to study the kinetics of gold dissolution in TCA solutions by using a "pure" oxidant, viz., anodic current.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Kinetic Parameters and Mechanism of Gold Electrooxidation in Thiocarbamide Solutions

2005

Self Cite

View full text Add to dashboard Cite

Kinetics and mechanism of gold electrooxidation in sulfuric acid solutions of thiocarbamide ( TCA ) are studied by measuring voltammograms ( VA ) of gold and glassy carbon ( GC ) electrodes. In a potential ( E ) range from -0.2 to 1.2 V ( SCE ), VA of a gold electrode demonstrate three peaks. The first and the second peaks correspond to gold electrooxidation to [AuTCA ads ] + and [Au(TCA ads ) 3 ] 3+ ions at E of 0.152 and 0.554 V, while the third one corresponds to TCA electrooxidation. The electrooxidation of TCA on GC electrodes is characterized by two VA peaks at 0.983 and 1.437 V. The first peak corresponds to the formation of formamidine disulfide (FADS) ( k a1 = 6.40 × 10 -4 cm/s), while the second peak corresponds to TCA oxidation to sulfides and hydrosulfides ( k a2 = 7.78 × 10 -5 cm/s). The composition of adsorption layers formed at the Au electrode is analyzed by Auger spectroscopy. The introduction of sodium sulfide into TCA solutions eliminates the formation of adsorption layers and accelerates Au oxidation in such solutions. The rate constants of gold electrooxidation k a = 6.31 × 10 -3 cm/s and Au(I) electroreduction k c = 5.46 × 10 -4 cm/s in TCA solutions are estimated. Kinetic parameters (charge transfer coefficients, reactions orders in carbamide) are determined and the mechanisms of Au and TCA oxidation in sulfuric acid solutions are proposed.

show abstract

The Effect of Sodium Thiocyanate on the Corrosion Dissolution Rate of Silver in Thiosemicarbazide Solutions

Kozin

Danil’tsev

2005

Prot Met

Self Cite

View full text Add to dashboard Cite

The effect of thiocyanate on the corrosion dissolution rate of silver in thiosemicarbazide (TSC) ammonium-chloride-bromide solutions was studied by using gravimetry and rotating disc electrode technique. The corrosion dissolution of silver was shown to be preceded by the formation of dithiosemicarbazide molecules due to the oxidation with iron (III) ions. The "second ligand" phenomenon is discussed, which consists in an increase in the corrosion dissolution rate of silver upon adding sodium thiocyanate (STC) to a TSC solution because of the decrease in the adsorption layer thickness. A synergism was discovered in the case of the corrosion dissolution of silver in a solution containing both thiosemicarbazide and sodium thiocyanate. The composition of the adsorption layer formed on a silver electrode and involving silver, sulfur (AgHS and Ag 2 S), as well as carbon, nitrogen, and oxygen forming the base of adsorption layers, was investigated by means of Auger spectrometry. The kinetic parameters (rate constants and reaction orders) were determined and a mechanism of the corrosion dissolution of silver in TSC, STC, and TSC + STC solutions is proposed.

show abstract

Untitled

Cited by 5 publications

References 2 publications

Kinetics and mechanism of the gold corrosion dissolution in hypochlorite solutions

Kinetics and mechanism of the gold corrosion dissolution in hypochlorite solutions

Kinetic Parameters and Mechanism of Gold Electrooxidation in Thiocarbamide Solutions

The Effect of Sodium Thiocyanate on the Corrosion Dissolution Rate of Silver in Thiosemicarbazide Solutions

Contact Info

Product

Resources

About