Nickel incorporation in Fe(II, III) hydroxysulfate Green Rust: effect on crystal lattice spacing and oxidation products

Abstract

SUMMARY Ni(II)-Fe(II)-Fe(III) layered double hydroxides (LDH) orNi-containing sulfate green rust (GR2) samples were prepared from Ni(II), Fe(II) and Fe(III) sulfate salts and analyzed with X ray diffraction. Nickel is readily incorporated in the GR2 structure and forms a solid solution between GR2 and a Ni(II)-Fe(III) LDH. There is a correlation between the unit cell a-value and the fraction of Ni(II) incorporated into the Ni(II)-GR2 structure. Since there is strong evidence that the divalent/trivalent cation ratio in GR2 is fixed at 2, it is possible in principle to determine the extent of divalent cation substitution for Fe(II) in GR2 from the unit cell a-value. Oxidation forms a mixture of minerals but the LDH structure is retained if at least 20 % of the divalent cations in the initial solution are Ni(II). It appears that Ni(II) is incorporated in a stable LDH structure. This may be important for two reasons, first for understanding the formation of LDHs, which are anion exchangers, in the natural environment. Secondly, this is important for understanding the fate of transition metals in the environment, particularly in the presence of reduced Fe compounds.

Fougerite: the not so simple progenitor of the first cells

“…Fougerite, GR's naturally occurring cousin, is not restrained by researchers' quest for simplicity and reproducibility. Fougerite can and does partially replace iron by other cationic metals such as Mg [28,56] and Ni [57]. Since Mg, for example, replaces specifically Fe 2+ sites, the effective redox potential of the so-obtained fougerite variants will differ substantially from their Mg-free form [28].…”

Controlled cobalt doping in biogenic magnetite nanoparticles

“…The amount of cobalt in the nanoparticles was measured at 4.4 per cent, 12.8 per cent, 13.9 per cent, 18. [25,26].…”

Characteristic of the Nanoparticles Formed on the Carbon Steel Surface Contacting with 3d-Metal Water Salt Solutions in the Open-Air System

“…At the same time, such cations as Cu 2+ , Ni 2+ , Zn 2+ , Cd 2+ , Co 2+ , and Mg 2+ may isomorphically substitute Fe(II) during green rust formation [ 18 ]. The relative stability of mixed LDHs is higher in comparison with the individual hydroxides: it strongly depends on the kind of included divalent cations and increases in the row: Co 2+ ~ Ni 2+ < Zn 2+ and, generally, it is higher in comparison with the individual hydroxides [ 19 ].…”