Zinc complexation in aqueous sulfide solutions: Determination of the stoichiometry and stability of complexes via ZnS(cr) solubility measurements at 100 °C and 150 bars |
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Authors: | B.R. Tagirov O.M. Suleimenov |
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Affiliation: | a Institute for Mineralogy and Petrography, ETH Zurich, Universitaetstrasse 16, CH 8092 Zurich, Switzerland b IGEM RAS, Staromonetnyi per. 35, 119017 Moscow, Russia |
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Abstract: | The solubility of ZnS(cr) was measured at 100 °C, 150 bars in sulfide solutions as a function of sulfur concentration (m(Stotal) = 0.02-0.15) and acidity (pHt = 2-11). The experiments were conducted using a Ti flow-through hydrothermal reactor enabling the sampling of large volumes of solutions at experimental conditions, with the subsequent concentration and determination of trace quantities of Zn. Prior to the experiments, a long-term in situ conditioning of the solid phase was performed in order to attain the reproducible Zn concentrations (i.e. solubilities). The ZnS(cr) solubility product was monitored in the course of the experiment. The following species were found to account for Zn speciation in solution: Zn2+ (pHt < 3), (pHt 3-4.5), (pHt 5-8), and ZnS(HS)− (pHt > 8) (pHt predominance regions are given for m(Stotal) = 0.1). Solubility data collected in this study at pHt > 3 were combined with the ZnS(cr) solubility product determined at lower pH to yield the following equilibrium constants (t = 100 °C, P = 150 bars): |
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