The role of EH measurements in the interpretation of the kinetics and mechanisms of the oxidation and leaching of sulphide minerals

Nicol, M.J.; Lázaro, Isabel

doi:10.1016/s0304-386x(01)00206-7

Cited by 65 publications

(32 citation statements)

References 9 publications

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“…couple (see below) as predicted previously (Nicol and Lazaro, 2002). Note that the potentials are lower in the solution containing a higher sulfate concentration due to the greater stability of the iron(III) sulfate complexes relative to those with iron(II) (Martell and Smith, 2004) A C C E P T E D M A N U S C R I P T…”

Section: Formal and Mixed Potential Measurementsmentioning

confidence: 53%

The effects of sulphate ions and temperature on the leaching of pyrite. 1. Electrochemistry

et al. 2013

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(2013) The effects of sulphate ions and temperature on the leaching of pyrite. 1. Electrochemistry. Hydrometallurgy, http://researchrepository.murdoch.edu.a/25114/ 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. Studies of the cathodic reduction of iron(III) and dissolved oxygen have shown that the rate of the former is several orders of magnitude more reversible(rapid) than that of dissolved oxygen which only exhibits measurable reactivity at potentials well below the mixed potentials in the presence of iron(III). The reduction of iron(III) is inhibited by sulfate ions due to the formation of electrochemically less reactive sulfate complexes. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT

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Section: Formal and Mixed Potential Measurementsmentioning

confidence: 53%

The effects of sulphate ions and temperature on the leaching of pyrite. 1. Electrochemistry

et al. 2013

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“…It is apparent that the maximum potential achievable on chalcopyrite in the presence of iron(III) under these conditions is around 0.7 V. This potential is within the so-called prewave region. A more detailed interpretation of these results has been recently published [20].…”

Section: Potential Measurementsmentioning

confidence: 71%

“…A platinum rotating disk electrode (RDE) and a chalcopyrite disk/platinum ring electrode (RRDE) were fabricated as described in a previous publication [20]. The calculated theoretical collection efficiency for the RRDE electrode was 0.39.…”

Section: Methodsmentioning

confidence: 99%

A rotating ring–disk study of the initial stages of the anodic dissolution of chalcopyrite in acidic solutions

Lázaro

Nicol

2005

J Appl Electrochem

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The initial stages of the dissolution of chalcopyrite have been studied using rotating ring-disk electrode techniques in dilute sulfuric acid solutions at 60°C. It has been confirmed that the mineral undergoes a dissolution process under freely dissolving conditions in the absence of an oxidant. This process involves the formation of soluble copper(II) ions and a soluble sulfur species which is presumably H 2 S. By the use of an anodic stripping technique on the ring electrode, it has been possible to determine that the dissolution of chalcopyrite under oxidative conditions involves a soluble sulfur species such as thiosulfate. Collection efficiency measurements involving the detection of both iron(II) and copper(II) on the ring have been used to identify possible anodic reactions in the potential region relevant to the oxidative leaching of the mineral.

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“…This type of surface redox reactions can be rationalized on the basis of an electrochemical model [16] that leads to the rate equation [14] Thus, when log dFe/dt vs 0.5 log [H ϩ ][HSO 3 Ϫ ] is plotted using the actual values of [HSO 3 Ϫ ] and [H ϩ ] calculated using K for Eq. [2] (Table II), the slope is close to 1 for both goethite and magnetite (Figure 3).…”

Section: Communicationsmentioning

confidence: 99%

A surface reaction kinetic model to compare the reductive leaching of iron from goethite, magnetite, and limonitic nickel laterite ores by acidic sulfur dioxide

Senanayake

2003

Metall Mater Trans B

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The kinetic modeling of iron dissolution at low pH in the presence of SO 2 or Na 2 SO 3 is of particular interest due to the fact that iron oxides are major components in limonitic nickel laterite ores, [1] deep sea nodules, [2] weathered rare earth (RE) mud, [3] and manganiferrous ores, [4] and are common to many soils. [5] Table I lists the conditions under which the leaching experiments have been carried out by previous researchers and the pct Fe extracted from different types of iron oxide materials. The reactivity of hematite is 1/10th that of goethite, magnetite, and laterite, as shown by the pct Fe leached in 1 hour. Despite the different iron contents and the leaching conditions in the case of laterite and RE mud, the pct Fe extracted in 2 hours is similar. The relatively high reactivity of the mud at low temperature is most likely attributed to finely divided iron oxide in the particle. Nevertheless, the low rates of iron dissolution from hematite in RE mud, particularly at low pH and low SO 2 concentrations, show the selective leaching of manganese. [3] Figure 1 compares the fraction of iron leached from variously sized particles of goethite and magnetite as a function of time; the slope represents the rate of leaching. Despite the lower temperature of 20°C, the leaching of the ultra fine (0.1 m) goethite is much faster than the leaching of coarse (150 m) goethite at 110°C, which is nearly the same as that of 75-m magnetite at 50°C.Previous attempts to rationalize the kinetics of reductive leaching of iron oxides were based on the adsorption theory [5,6,7] and electrochemical studies [8,9] with limited success in some investigations. [10] Little or no attempt has been made to compare the available kinetic data for the reduction of goethite, [6] magnetite, [7] and laterite [1] by SO 2 under a range of leaching conditions, which gave the results shown in Table I and Figure 1. The effect of some of these parameters has been successfully incorporated into the well-known shrinking sphere model, which is useful for kinetic modeling and reactor design: [11] [1]where X ϭ fraction of Fe reacted at time t (s), k ϭ intrinsic rate constant of the surface reaction (cm s Ϫ1 ), r ϭ initial particle radius of solid (cm), ϭ molar density of Fe in the solid (mol cm Ϫ3 ), k ss ϭ apparent rate constant (s Ϫ1 ), andϪ ] n r Ϫ1 r Ϫ1 t ϭ k ss t m, n ϭ reaction order with respect to [H ϩ ] and [HSO 3 Ϫ ] in equilibrium with SO 2 :The shrinking sphere model takes into account the decrease in particle size and thus the surface area with time. In general, the value of k ss is obtained from the slope of a plot of 1 Ϫ (1 Ϫ X) 1/3 against t. This is used in the Arrhenius equation, k ss ϭ A exp (ϪE/RT), to examine the effect of temperature for leaching under a given set of conditions (r, , [SO 2 ], pulp density, and sufficient agitation to avoid masstransfer limitations to the surface), and to determine the activation energy E and the Arrhenius constant A. The use of the intrinsic rate constant k, instead of k ss , in the Arrhenius...

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The role of EH measurements in the interpretation of the kinetics and mechanisms of the oxidation and leaching of sulphide minerals

Cited by 65 publications

References 9 publications

The effects of sulphate ions and temperature on the leaching of pyrite. 1. Electrochemistry

The effects of sulphate ions and temperature on the leaching of pyrite. 1. Electrochemistry

A rotating ring–disk study of the initial stages of the anodic dissolution of chalcopyrite in acidic solutions

A surface reaction kinetic model to compare the reductive leaching of iron from goethite, magnetite, and limonitic nickel laterite ores by acidic sulfur dioxide

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