ISSN:
1435-0661
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
R Si, increased with an increase in the aqueous concentration of Ni. A rate law was developed representing a fractional-order dissolution reaction with respect to the surface concentration of Ni. Absorption spectra were obtained from kaolinite samples washed with 0.10 M NaNO3 adjusted to pH 3.4 to remove amorphous Al-hydroxide surface deposits or adsorbed Al and from kaolinite that was untreated. For all samples, EXAFS results revealed the presence of multinuclear Ni surface complexes with a similar, but not identical, local structural environment to pure crystalline Ni(OH)2. The Ni-Ni bond distances were shorter (3.06-3.11 Å) than in Ni(OH)2(s) (3.13 Å) and increased with an increase in surface coverage. Additionally, Al was present in all but the highest surface coverage (γ≤ 0.406 μmol m-2), Al is present at 2.69 Å, indicating the formation of a bidentate Ni surface complex. With increased surface coverage, the d(Ni-Al) increases to 2.96 Å, which is believed to result from a Ni,Al-hydroxide precipitate. No significant structural differences were found between kaolinite pretreatments. Based on these results, a hypothesized mechanism for Ni sorption on kaolinite is proposed.
Type of Medium:
Electronic Resource
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