Nickel Aqueous Speciation and Solubility at Ambient Conditions: A Thermodynamic Elegy

Abstract

This review reveals that, in contrast to the general opinion, the aqueous speciation of nickel is poorly known. Besides the fairly well established first hydrolysis constant, data are scarce and only poor estimates can be derived for higher Ni hydrolysis constants from a few solubility studies. The situation is even worse in the case of aqueous carbonate complexes. No reliable experimental study has been published so far and almost all numbers reported in thermodynamic databases are unacceptable estimates. In this review we scrutinise all these published estimates and propose expectation ranges of nickel carbonate complex stability through correlation with other known thermodynamic constants. Solubility constants for a few simple nickel solids are known or have been estimated from thermochemical data. However, none of these simple solids is of geochemical relevance at ambient conditions. Based on field evidence, classes of solids are identified which potentially govern nickel concentrations in ground and surface waters. Recent spectroscopic data indicate that magnesium clay minerals and layered double hydroxides are the most prominent candidates for nickel-bearing solids at ambient conditions.

Immobilization of Ni by Al-modified montmorillonite: A novel uptake mechanism

“…Nickel, from an acidified 0.1 M NiCl 2 stock solution, was added in 0.5 mL aliquots to the Al-montmorillonite suspensions to achieve an initial Ni concentration of 0.1 mM. Except for the pH 8 solution, all solutions were undersaturated with respect to homogeneous precipitation of Ni(OH) 2 (Hummel and Curti, 2003). Samples were reacted with Ni for 1 month in a batch setup, with a pH stat to control the pH.…”

“…The scientific interest in the sorption mechanisms of Ni onto clay minerals arises from the following reasons: (1) Ni belongs to the suite of toxic metals (Ni, Cu, Zn, Cd, Pb, and Hg) that are subject to concentration limits in drinking water, and (2) large amounts of 59 Ni and 63 Ni, with half-lives of 75,000 and 125 yrs, respectively, occur as fission products in nuclear waste (Hummel and Curti, 2003).…”

Development of an In Situ Ion-Exchange Technique for the Determination of Free Cd, Co, Ni, and Zn Concentrations in Freshwaters

“…\ 11.7 (at zero ionic strength). These constants, which are more than 30 times lower than the Mattigod and Sposito constants, are in the expected ranges given by Hummel and Curti (2003) [K NiCO3 = (4-5.5) and log K NiHCO3-= (11.3-12.…”

“…= 13.41, and log K NiCO3 = 5.78). The reliability of these Ni-carbonate constants, which were derived by estimation procedures, has been questioned (Hummel and Curti 2003). With an ion-exchange method, Baeyens et al (2003) measured a log K NiCO3 of 4.2 ± 0.3 and estimated a log K NiHCO3?…”

Solubility equilibria and geochemical modeling in the field of radioactive waste disposal

“…However, in the course of the review process for the Nagra/PSI Chemical Thermodynamic Data Base 01/01 [2], which served as the basis for such chemical equilibrium calculations [3,4] for a recent Swiss safety study [5], important cases of insufficient chemical knowledge were identified, leading to gaps in the database [6,7].…”