Iron(II) oxidation by SO2/O-2 in acidic media - Part II. Effect of copper

Citation
Ws. Zhang et al., Iron(II) oxidation by SO2/O-2 in acidic media - Part II. Effect of copper, HYDROMETALL, 58(2), 2000, pp. 117-125
Citations number
31
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Metallurgy
Journal title
HYDROMETALLURGY
ISSN journal
0304-386X → ACNP
Volume
58
Issue
2
Year of publication
2000
Pages
117 - 125
Database
ISI
SICI code
0304-386X(200012)58:2<117:IOBSIA>2.0.ZU;2-V
Abstract
The oxidation of 0.1 and 0.5 M Fe2+ with O-2 and with SO2/O-2 mixtures is c ompared in the presence of CuSO4 at 80 degreesC, The SO2/O-2 system oxidise s Fe2+ at a faster rate than the O-2 system, particularly at low concentrat ions of Fe2+ With O-2, the rate is second order with respect to Fe2+ concen tration, and is catalysed by Cu2+. But with SO2/O-2, the rate is independen t of Fe2+ and is inhibited by Cu2+. It is proposed that copper catalyses th e oxidation of Fe2+ bq O-2 through a mechanism that involves the formation of ionic CuO2+ and H2O2 as the oxidant. In contrast, oxidation by SO2/O-2 i s catalysed by Fe3+ in a free radical mechanism involving peroxysulphate ra dical that is inhibited by Cu2+. The presence of the free radical scavenger hydroquinone also inhibits the oxidation of Fe2+ with SO2/O-2, but has lit tle effect on the oxidation with O-2. It is shown that when high concentrat ions of Fe2+ and Cu2+ are oxidised by SO2/O-2, the reaction is initially do minated by the O-2 reaction mechanism, but is overtaken by the SO2/O-2 reac tion mechanism as Fe2+. is oxidised and the concentration of Fe2+ decreases . The results indicate that the SO2/O-2 system would oxidise ferrous ions f aster than O-2 to achieve higher levels of Fe(III) in solution during fenic leaching of minerals. (C) 2000 Elsevier Science B.V. All rights reserved.