The kinetics of mixed Ni-Al hydroxide formation on clay and aluminum oxide minerals: A time-resolved XAFS study

Journal Article · Wed Jul 01 04:00:00 EDT 1998 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(98)00136-7· OSTI ID:655490

Scheidegger, A M ^[1]; Strawn, D G; Sparks, D L ^[1]; Lamble, G M ^[2]

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1. Univ. of Delaware, Newark, DE (United States). Dept. of Plant and Soil Sciences
2. Lawrence Berkeley National Lab., CA (United States). Earth Sciences Div.

In this study kinetic investigations were combined with X-ray Absorption Fine Structure (XAFS) measurements to determine Ni sorption processes on pyrophyllite, gibbsite, and montmorillonite over extended time periods (min-months). XAFS data revealed the presence of a mixed Ni/Al phase in the Ni/pyrophyllite and Ni/gibbsite systems after a reaction time of minutes. These results suggest that adsorption and nucleation processes (mixed Ni/Al phase formation) can occur simultaneously over time scales of only minutes. However, the finding of a fast growing mixed Ni/Al phase cannot be extrapolated to other sorption systems. The study suggests that three phenomena occur at the mineral/liquid interface: (1) nonspecific (i.e., outer-sphere complexation) and/or specific adsorption (i.e., inner-sphere complexation), (2) dissolution of Al, and (3) nucleation of a mixed Ni/Al phase. The rate-limiting step is the dissolution of Al from the surface, which depends on the mineral substrate. Using the Ni linear sorption rates observed in the Ni/gibbsite and Ni/montmorillonite systems and assuming the Ni/Al ratios in the sorption samples are within the range of Ni/Al ratios provided in the literature, one can estimate an average Al dissolution rate which seems to be enhanced compared to the Al dissolution rates of the minerals alone. This finding indicates that the dissolution of clay and aluminum oxide minerals can be promoted by metal ions such as Ni(II) through the formation of a mixed Ni/Al phase.

• OSTI ID: 655490
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 13 Vol. 62; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ADSORPTION
AQUATIC ECOSYSTEMS
DISSOLUTION
ENVIRONMENTAL TRANSPORT
GIBBSITE
GROUND WATER
MONTMORILLONITE
NICKEL
PHASE STUDIES
PYROPHYLLITE
SORPTIVE PROPERTIES