Effect of mineralogy and oxidant type on aqueous dispersion oxidation-reduction potential at low Ph.
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Date
2010
Authors
Fung, C.Y.K.
Connor, J.N.
Addai Mensah, J.
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Chemeca 2010 proceedings: engineering at the edge, 2010, pp.1-10
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Engineering at the edge (26 Sep 2010 - 29 Sep 2010 : Adelaide, Australia)
Abstract
Oxidation-reduction potential (ORP) studies are important for quantifying the impact of process water quality and oxidative conditions on complex ores' leaching behaviour. For mineralogically and chemically complex plant pulps, ORP monitoring is often utilised during value mineral extraction but its interpretation is difficult. The objective of this work was to determine whether ORP can be practically related to the individual constituent minerals of complex ores during leaching at low pH and high temperature. To understand the relationship between mineralogy and ORP during isothermal batch leaching, two common model mineral dispersions, hematite (Fe2O3) and mica group chlorite clay ([Mg3.56Fe(II)0.39Al1.33Fe(III)0.71][Al1.30Si2.70]O10(OH)8) and their mixture (maintained at pH 1 and 70 oC over 3 h) were investigated. The effect of oxidant type (sodium chlorate vs. hydrogen peroxide) on ORP was also evaluated. The ORP was found to be controlled by the Fe(II/III) couple. The ORP remained practically constant after the first half hour in the absence of an oxidant for all mineral dispersions. Thereafter, it varied according to the mineralogy with hematite giving the highest ORP values and chlorite the lowest. The presence of oxidant caused the initial ORP to increase for all leach pulps. When chlorate was present, the ORP of the hematite increased steadily corresponding to increased Fe(III)/Fe(II) ratio while that for chlorite decreased steadily due to a decreasing Fe(III)/Fe(II) ratio. The ORP for the mixed mineral system appears to be a non-linear combination of the two. Sodium chlorate was also found to be a more effective oxidant compared with hydrogen peroxide in these experiments as it increased the ORP by a larger degree.
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Copyright 2010 Engineers Australia