Lead adsorption at the calcite-water interface: Synchrotron x-ray standing wave and x-ray reflectivity studies

Journal Article · Wed Jan 01 04:00:00 EST 1997 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(96)00326-2· OSTI ID:577510

Sturchio, N C; Chiarello, R P; You, Hoydoo ^[1]

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1. Argonne National Lab., IL (United States); and others

By combining synchrotron X-ray standing wave (XSW) measurements with synchrotron X-ray reflectivity measurements, we have determined: (1) the precise three-dimensional location within the calcite unit cell of submonolayer Pb ions adsorbed at the calcite (104) surface from dilute aqueous solutions, and (2) the precise one-dimensional location of these unit cells relative to the calcite surface. Our XSW measurements, using three separate calcite Bragg reflections for triangulation, show that most adsorbed Pb ions occupy Ca sites in the calcite lattice with an ordered coverage of 0.05 equivalent monolayers, while the remaining Pb ions are disordered with a coverage of 0.03 equivalent monolayers. Our X-ray reflectivity measurements show that the ordered Ph ions occur primarily (>70%) in the surface atomic layer of calcite. Atomic force microscopy (AFM) was used to characterize the topography of the calcite (104) surface under conditions similar to the X-ray experiments. The quantitative morphological information obtained by AFM was used to develop realistic models of the calcite surface. The calculated X-ray reflectivities for these model surfaces were compared with the measured X-ray reflectivities. The new combined X-ray method that we have developed can be used to determine the atomic-scale structure of other metals adsorbed at mineral-water interfaces. Such high-resolution structural determinations are essential before detailed conceptual and theoretical models can be further developed to understand and predict the behavior of dissolved metals in mineral-water systems. 60 refs., 8 figs., 3 tabs.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• DOE Contract Number: AC02-76CH00016; AC06-76RL01830
• OSTI ID: 577510
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 2 Vol. 61; ISSN 0016-7037; ISSN GCACAK
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
ADSORPTION
ECOLOGICAL CONCENTRATION
ENVIRONMENTAL TRANSPORT
GROUND WATER
LEAD
ROCK-FLUID INTERACTIONS
SOILS
SYNCHROTRON RADIATION
TOXIC MATERIALS