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Nickel sulfide formation at low temperature: initial precipitates, solubility and transformation products
Citation:
WILKIN, R. T. AND D. A. Rogers. Nickel sulfide formation at low temperature: initial precipitates, solubility and transformation products. ENVIRONMENTAL CHEMISTRY. CSIRO Publishing, Collingwood Victoria, Australia, 7:514-523, (2010).
Impact/Purpose:
Solubility data at pH>3 suggest that Ni-bisulfide complexation is important in controlling the solubility of Ni in sulfidic solutions.
Description:
The formation of nickel sulfides has been examined experimentally over the temperature range from 25 to 60°C. At all conditions studied, hexagonal (α-NiS) was the initial precipitate from solution containing Ni2+ and dissolved sulfide. The formation of millerite (β- NiS, rhombohedral) was not detected in any of the synthesis experiments. In the presence of elemental sulfur, hexagonal NiS converted to polydymite (Ni3S4) and vaesite (NiS2). Thus, conversion of nickel monosulfide to thiospinel and disulfide structures appears to be redox dependent, analogous to aging and transformation processes of iron sulfides. In the absence of elemental sulfur or with only hydrogen sulfide or bisulfide present, transformation of hexagonal NiS was not observed after 1680 h at 60ºC. Low-pH solubility experiments yielded a solubility product for hexagonal NiS of log Ks0 =-2.69 ± 0.26. Solubility data at pH>3 suggest that Ni-bisulfide complexation is important in controlling the solubility of Ni in sulfidic solutions.
