Reaction between Hydrosulfide and Iron/cerium (hydr)oxide: Hydrosulfide Oxidation and Iron Dissolution Kinetics |
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Authors: | Catalin F Petre Faïçal Larachi |
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Affiliation: | (1) Department of Chemical Engineering, Laval University, G1K 7P4 Québec, Canada |
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Abstract: | Hydrosulfide oxidation and iron dissolution kinetics were studied at normal pressure, under inert (N2) atmosphere, in a liquid–solid mechanically-stirred slurry reactor. The kinetic variables undergoing variations were: hydrosulfide
initial concentration (0.90–3.30 mmol/L), oxide initial surface area (16–143 m2/L) and pH (8.0–11.0). The hydrosulfide consumption and products (thiosulfate and polysulfide) formation were quantified by
means of capillary electrophoresis, while iron dissolution was monitored through atomic absorption spectroscopy. Most of Fe(II)
produced at pH = 9.5 remained associated with the oxide surface in the time-scale of the experiments. The hydrosulfide oxidation
by the iron/cerium (hydr)oxide was found to be surface-controlled, with rates (Ri) of both sulfide oxidation and Fe(II) dissolution expressed in terms of an empirical rate equation: Ri = kiHS−]t=0−0.5A]t=0H+]t=0−0.5
, where ki represents the apparent rate constants for the oxidation of HS− (kHS) or the dissolution of Fe(II) (kFe), HS−]t = 0 is the initial hydrosulfide concentration, A]t = 0 is the initial Fe/Ce (hydr)oxide surface area and H+]t = 0 is the initial proton concentration. The rate constant, kHS, for the oxidation of hydrosulfide at pH = 9.5 was (3.4219 ± 0.65) × 10−4 mol2 L−1 m−2 min−1, with the rate of hydrosulfide oxidation being ca. 10 times faster than the rate of Fe(II) dissolution (assuming a 1:2 stoichiometric
ratio between HS− oxidized and Fe(II) produced; kFe = (3.9116 ± 0.41) × 10−5 mol2 L−1 m−2 min−1). |
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Keywords: | pulp and paper industry desulfurization kinetics bifunctional process hydrosulfide oxidation iron/cerium (hydr)oxide polysulfide |
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