The passivation of iron in ammoniacal solutions containing copper (II) ions

D'Aloya, Anna; Nikoloski, Aleksandar N.

doi:10.1016/j.hydromet.2011.10.003

Cited by 8 publications

(5 citation statements)

References 22 publications

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“…This is in contrast to the behaviour observed in the presence of copper ions, which under the same conditions were found to promote passivation even at concentrations of an order of magnitude lower (D'Aloya and Nikoloski, 2012 (Figure 1) also being observed on the pitted iron surface. This was thought to consist mainly of iron corrosion products, with the cobalt being present either in its metallic state, due to cementation, or within the iron hydroxides and carbonates, due to adsorption or co-precipitation.…”

Section: The Anodic Dissolution Of Iron In the Presence Of Dissolved contrasting

confidence: 79%

“…In contrast with the behaviour of iron observed in the presence of copper ammines (D'Aloya and Nikoloski, 2012), where increasing the ammonium bicarbonate concentration at a constant [NH 3 ] T was found to delay passivation, in the presence of cobalt and thiosulfate ions the opposite trend was observed. (Table 3).…”

Section: The Effect Of [Nh 3 ] and [Co 2 ] On Passivation Timementioning

confidence: 65%

“…Under normal conditions of aeration, or in de-oxygenated solutions, the spontaneous passivation of iron has only been observed under very specific conditions. In particular, iron and its alloys with nickel or cobalt have been found to passivate during short periods of immersion in ammoniacal-carbonate solutions containing copper (II) ions (D'Aloya and Nikoloski, 2012) or in the presence of nickel, cobalt and thiosulfate ions (Nicol et al, 2004;Nikoloski et al, 2003). Iron powder was also found to passivate after 3 days of immersion in ammoniacal-carbonate solutions containing cobalt ions at a significantly lower ammonia concentration than employed in the Caron process (Kasherininov, 1960).…”

Section: Introductionmentioning

confidence: 99%

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An electrochemical investigation of the formation of CoSx and its effect on the anodic dissolution of iron in ammoniacal-carbonate solutions

D'Aloya

Nikoloski

2013

Hydrometallurgy

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ÔØ Å ÒÙ× Ö ÔØThis is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractIt has been found that the co-presence of cobalt (II) and thiosulfate ions in ammoniacal-carbonate solutions promotes the passivation of iron, under conditions in which it would otherwise continue to dissolve anodically. Electrochemical experiments have shown a relationship between the immersion time required for passivation and the formation of a solid species on the iron surface, which is thought to be implicated in the mechanism of passivation, whilst not being itself the protective species. Based on a combination of electrochemical, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and grazing incidence X-ray diffraction (GIXRD) characterisation techniques, said species has been identified as CoS x , resulting from the interaction of cobalt (II) and thiosulfate ions. It is thought to form as a product of the cathodic reactions taking place on the iron surface during its active dissolution.These findings are particularly relevant to the Caron process, in which ammoniacal-carbonate solutions containing dissolved cobalt and thiosulfate ions are used to leach nickel and cobalt from pre-reduced laterite ores rich in metallic iron. Both the loss of cobalt into the CoS x layer and the passivation of iron and of its alloys with nickel and cobalt, are potential contributing factors to the low cobalt and nickel recoveries, which are typical of the Caron process. This study provides a better understanding of the conditions under which the CoS x layer forms and promotes the passivation of iron, and may therefore provide useful information to help minimise the effect this may have on the extraction efficiency of the process. In particular, at the cobalt and thiosulfate ion concentrations usually encountered at a Caron plant, the passivation of iron was found to be prevented by maintaining a high enough concentration of ammonia.

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Section: The Anodic Dissolution Of Iron In the Presence Of Dissolved contrasting

confidence: 79%

Section: The Effect Of [Nh 3 ] and [Co 2 ] On Passivation Timementioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

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An electrochemical investigation of the formation of CoSx and its effect on the anodic dissolution of iron in ammoniacal-carbonate solutions

D'Aloya

Nikoloski

2013

Hydrometallurgy

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“…Malachite experiences a similar case when it reacts with an alkaline ammoniacal solution of ammonium carbonate [25]. Although the conventional alkaline leaching process using cyanide and ammonia can yield recovery percentages close to 90%, its use is limited; even though the ammoniacal leaching medium is intended to selectively extract copper, its use implies technical and environmental risks [16,26,27]. According to these results, it is proposed that the global reaction for the dissolution of basic cupric carbonate (malachite) by the action of tartrate ions in aqueous alkaline medium is represented by the following equation:…”

Section: Evaluation Of the Dissolution Of Basic Cupric Carbonate (Mal...mentioning

confidence: 99%

A New Approach for Increasing the Chelating Capacity of the Tartrate Ion in the Extraction of Copper from Ores

Velarde,

Ortiz,

Apaza

et al. 2023

Metals

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The role of the tartrate ion in the extraction of copper from oxidized ore in aqueous alkaline medium is first reported. This was demonstrated by a sequential evaluation of the following: (i) The formation of an ionic complex resulting from the interaction of copper salts (CuSO4, Cu(NO3)2) with an alkaline aqueous solution of tartrate ions. (ii) The treatment of metallic copper with hydrogen peroxide. (iii) Spectrophotometric and potentiometric studies of malaquite. These studies demonstrated that the Cu(II)–tartrate interaction is only possible due to the chelating activity of tartrate ion leading to the formation of the [Cu(OH)2C4H4O6]2− anion complex and the lixiviation of the oxidized mineral is controlled by the chelating agent. The advantage of this approach relative to previous ones is discussed. Final conclusions are given.

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“…A previous study has found that iron readily passivates in the presence of millimolar amounts of dissolved copper (D'Aloya and Nikoloski, 2012). However studies conducted in ammoniacal-carbonate solutions containing both copper (II) and thiosulfate ions are complicated by the possibility of a homogeneous redox reaction between these two species (Rábai and Epstein, 1992).…”

Section: Introductionmentioning

confidence: 99%

The anodic dissolution of iron in ammoniacal–carbonate–thiosulfate–copper solutions with formation of Cu2S and dendritic copper

D'Aloya

Nikoloski

2014

Hydrometallurgy

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Please cite this article as: D'Aloya, Anna, Nikoloski, Aleksandar N., The anodic dissolution of iron in ammoniacal-carbonate-thiosulfate-copper solutions with formation of Cu 2 S and dendritic copper, Hydrometallurgy (2014), doi: 10.1016/j.hydromet.2014.02.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractThe presence of thiosulfate ions in ammoniacal-carbonate solutions containing copper(II) ions was found to prevent the passivation of iron, even though iron passivation is observed in solutions with no thiosulfate at very low copper(II) concentrations. The prolonged anodic dissolution of iron resulted in the formation of a partly crystalline sulfide layer on its surface, which based on Grazing Incidence X-Ray Diffraction (GI-XRD) analysis is thought to consist mainly of Cu 2 S. The effect of the sulfide layer was investigated using rotating disk cyclic voltammetry. Unlike the formation of an amorphous CoS x layer, which took place in similar solutions containing cobalt ions, the cuprous sulfide layer was not found to promote passivation of the iron. A significant amount of solid precipitate also became detached from the iron surface, remaining undissolved in the solution. This was analysed by X-Ray Diffraction (XRD) and scanning electron microscopy (SEM) -energy dispersive X-ray spectroscopy (EDX). Dendritic copper was observed both in the solid separated from the solution and in the precipitate still attached to the iron surface. The absence of iron passivation is thought to be due to both to the non-adherent nature of the cuprous sulfide layer, and to a disrupting effect caused by the cementation of copper.

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The passivation of iron in ammoniacal solutions containing copper (II) ions

Cited by 8 publications

References 22 publications

An electrochemical investigation of the formation of CoSx and its effect on the anodic dissolution of iron in ammoniacal-carbonate solutions

An electrochemical investigation of the formation of CoSx and its effect on the anodic dissolution of iron in ammoniacal-carbonate solutions

A New Approach for Increasing the Chelating Capacity of the Tartrate Ion in the Extraction of Copper from Ores

The anodic dissolution of iron in ammoniacal–carbonate–thiosulfate–copper solutions with formation of Cu2S and dendritic copper

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