Hematite solubility in sulphate process solutions

Kinetics of Ferric Ion Reduction on Chalcopyrite and its Influence on Leaching up to 150 °C

“…Determination of the concentrations of free ferric and ferrous ions in H 2 SO 4 -Fe 2 (SO 4 ) 3 -FeSO 4 -H 2 O system by a speciation model between 25 • C and 150 • C According to the published literature, the iron sulfates present in sulfuric acid solution are distributed as soluble species including simple metal ions, neutral or charged complexes, as well as precipitates such as Fe 2 O 3 formed at high temperatures [46][47][48][49][50][51][52][53][54][55][56][57][58]. Therefore, a speciation model is required to quantify the concentrations of the main species involved in the acidic iron sulfate solutions, which can then be employed to study the reduction behavior of ferric ions on chalcopyrite (concentration of free ferric ions is required) and calculate the exchange current density by extrapolating the cathodic linear Tafel line to the reversible potential of the Fe 3+ /Fe 2+ couple (concentrations of free ferric and ferrous ions are required), by invoking the Nernst equation and other basic electrochemical kinetic equations.…”

Extended validation of an expression to predict ORP and iron chemistry: Application to complex solutions generated during the acidic leaching or bioleaching of printed circuit boards

“…The iron sulfates present in sulfuric acid solution are distributed as soluble species including simple metal ions, neutral or charged complexes, as well as precipitates such as Fe 2 O 3 formed at high temperatures (Dry and Bryson, 1988;Stipp, 1990;Casas et al, 2005;Cifuentes et al, 2006;Sapieszko et al, 1977;Filippou et al, 1995;Posnjak and Merwin, 1922;Sasaki et al, 1993;Umetsu et al, 1977;Papangelakis et al, 1994;Tozawa and Sasaki, 1986;Reid and Papangelakis, 2006;Liu et al, 2003). Therefore, a speciation model is required to quantify the distribution of Fe in acidic iron sulfate solutions and, further, to predict the redox potentials of the Fe 3+ /Fe 2+ couple via the Nernst equation (Sapieszko et al, 1977;Dry and Bryson, 1988;Stipp, 1990;Yue et al, 2014a).…”

Fundamentals of partial pressure oxidation of gold bearing sulphide minerals

“…This study disagrees with this statement as ferric has a higher charge density than ferrous and therefore the adsorption of ferrous should be less preferable. However, Papangelakis et al (1994) stated that the formation of neutral complex ferric species is favoured at high temperature, such as aqueous…”

“…Ferric speciation in Fe 3+ -SO4 2--H2O system has been reported over a wide range of temperatures, however, most of the reports are limited to lower temperature systems (25 -150°C) (Casas et al, 2005;Cifuentes et al, 2006;Filippou et al, 1995;Sapieszkoe et al, 1977;Stipp, 1990;Yue et al, 2014). Only two studies considered the higher temperature range relevant to pressure oxidation (Liu et al, 2003;Papangelakis et al, 1994). Table 25 summarises the aqueous ferric species reported in literature from 25°C to 250°C.…”

“…To date, Fe2(SO4)3 0 and FeHSO4SO4 are the two proposed ferric species in high acidity solution at temperatures between 200 and 250°C (Papangelakis et al, 1994;Liu et al, 2014). In this study, both ferric species are considered in the determination of their apparent thermodynamic data based on hematite solubility studies at 220°C.…”