Solubility measurements of crystalline beta-Ni(OH)(2) in aqueous solution as a function of temperature and pH
- ORNL
- Oak Ridge National Laboratory (ORNL)
Experimental results on the solubility of crystalline nickel hydroxide (theophrastite), according to the dissolution reaction, -Ni(OH)2(cr) + 2H+ Ni2+ + 2H2O(l), are reported as functions of temperature (0 200 C) and pH at pressures slightly exceeding saturation vapor pressure. The experiments were carried out in either various flow-through cells or a hydrogen-electrode concentration cell (HECC). The results were treated with a thermodynamic model incorporating only the unhydrolyzed aqueous nickel species (namely, Ni2+) whose solubility constants were fitted as a function of temperature. The thermodynamic quantities obtained at infinite dilution are: (25 C) = (11.67 0.20), (25 C) = (66.6 1.1) kJ mol 1, (mean value 5 200 C) = (82.1 0.8) kJ mol 1, = (mean value 5 200 C) = (52 5) J K 1 mol 1, (mean value 5 200 C) = 0 J K 1 mol 1, where the uncertainties quoted are 2 . These results are internally consistent, but differ from most of those reported in the literature. A significantly lower temperature for the thermodynamic stability of -Ni(OH)2(cr) versus NiO(cr), namely, 77 C, is proposed based on the current measurements. Additional batch experiments at 50 C and 80 C within aqueous NaClO4 media established and quantified a particle-size dependence of the solubility constant of -Ni(OH)2(cr) that extended to larger particle sizes than normally observed for metal oxide/hydroxides.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1055155
- Journal Information:
- Journal of Coordination Chemistry, Vol. 63, Issue 14-16; ISSN 0095--8972
- Country of Publication:
- United States
- Language:
- English
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