X-ray Absorption Spectroscopic Studies of Cadmium and Selenite Adsorption on Aluminum Oxides

Papelis, Charalambos; Brown, Gordon E.; Parks, George S.; Leckie, James O.

doi:10.1021/la00006a033

Cited by 66 publications

(67 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As will be remembered, UE18R 2228 was the densely welded tuff sample that had by far the lowest porosity and specific surface area three to five times lower compared to the rest of the samples. It has been shown before (Papelis, 1995), that the structure and porosity of the solid does affect the apparent surface coverage determined by XPS. This fact may be due to the orientation of the sample and counting resulting from several layers in a porous sample compared to a nonporous one.…”

Section: Countsmentioning

confidence: 93%

“…The adsorbed layer thickness was estimated by comparing the photoelectric peak of the metal of interest to the photoelectric peak of the most abundant cation on the surface, Si. Specifically, the adsorbed layer thickness was calculated based on Equation (13), a generalization of the equation used by Papelis (1995) to calculate surface coverages of adsorbents.…”

Section: Countsmentioning

confidence: 99%

“…As explained in more detail in Papelis (1995), the angle between the sample normal and the detector was assumed to be zero and the attenuation length was assumed to be 15 Å. The normalized area is calculated by the ESCAVB software and is a function of peak area, the number of scans collected, the peak photoionization cross section, a sensitivity exponent, and the position of the photoelectric peak.…”

Section: Countsmentioning

confidence: 99%

“…XPS is a surface sensitive technique that is used to examine the composition of the outmost layers of mineral surfaces (Hochella, 1988;Biino and Gröning, 1998). Several introductory papers to the XPS technique and applications are available (Jean and Bancroft, 1985;Hochella, 1988Hochella, , 1990Paterson and Swaffield, 1994;Papelis, 1995). Because XPS can measure only the top surface layers of the adsorbents, surface precipitates resulting in an increase of average adsorbed layer thickness on the external surface of the particles could be differentiated from the uniform coverage of the entire particle surface by intraparticle diffusion followed by adsorption (Papelis, 1995).…”

Section: Introductionmentioning

confidence: 99%

“…Several introductory papers to the XPS technique and applications are available (Jean and Bancroft, 1985;Hochella, 1988Hochella, , 1990Paterson and Swaffield, 1994;Papelis, 1995). Because XPS can measure only the top surface layers of the adsorbents, surface precipitates resulting in an increase of average adsorbed layer thickness on the external surface of the particles could be differentiated from the uniform coverage of the entire particle surface by intraparticle diffusion followed by adsorption (Papelis, 1995). Based on differences in surface coverage of particle surfaces by reactive solutes, XPS was expected to allow differentiation between different sorption mechanisms (e.g., sorption controlled by intraparticle diffusion and surface precipitation) of Pb, Sr, and Cs sorption on fracture surfaces and matrix.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Evaluation of Cesium, Strontium, and Lead Sorption, Desorption, and Diffusion in Cores from Western Pahute Mesa, Nevada Test Site, based on Macroscopic and Spectroscopic Investigations

Papelis¹,

Um²

2003

View full text Add to dashboard Cite

EXECUTIVE SUMMARYThe interaction of radionuclides and other contaminants with minerals and other aquifer materials controls the rate of migration of these contaminants in groundwater. The stronger these interactions, the more a radionuclide will be retarded. Processes such as sorption and diffusion often control the migration of inorganic compounds in aquifers. These processes are often controlled by the nature of the ions of interest, the nature of the aquifer materials, and the specific geochemical conditions. Parameters describing sorption and diffusion of radionuclides and other inorganic ions on aquifer materials are used in transport codes to predict the potential for migration of these contaminants into the accessible environment. Sorption and diffusion studies can reduce the uncertainty of radionuclide transport modeling on the Nevada Test Site (NTS) and other nuclear testing areas.Equilibrium sorption, desorption, and core diffusion experiments were conducted with five different core samples from Western Pahute Mesa (WPM) on the NTS. These cores included samples PM-1 4823, PM-2 4177, UE18R 2228, UE20c 2855, and UE20c 2908. For three of the samples, PM-1 4823, UE18R 2228, and UE20c 2855, a distinction was made between matrix and fracture sub-samples. The samples were characterized based on mineralogy, specific surface area, morphology, density, and porosity. Sample UE18R 2228, a densely welded tuff, was the only sample that had substantially lower porosity and specific surface area compared to the rest. All samples were mainly composed of feldspars and quartz.Based on sorption data with different solid and metal concentrations, linear sorption isotherms were derived for sorption at pH 8.3, representing a common NTS groundwater pH. Following sorption, desorption experiments were conducted to determine the reversibility of the sorption reactions. Lead was the most reactive metal ion and exhibited strong pH-dependent behavior. Typical K d s for Pb sorption were 1x10 -3 to 5x10 -3 m 3 /g. The sorption of Cs was much less pH-dependent and was overall substantially reduced compared to Pb. Typical K d s for Cs were approximately one order of magnitude less than Pb K d s (1 to 3x10 -4 m 3 /g). Strontium sorption was almost negligible for all solids, especially at lower concentrations. The minimal Sr sorption was caused, at least partly, by the substantial amount of Sr already present in the cores. Under these conditions, therefore, Sr would be very mobile. In all cases, K d s obtained from desorption experiments were higher than the K d s obtained from sorption experiments, typically by a factor of 2 to 10.Diffusion experiments with the entire core were conducted with a nonreactive tracer, bromide, before experiments with the reactive tracers, Pb, Cs, and Sr. Based on the bromide diffusion experiments, effective diffusivities and tortuosities were estimated. The effective diffusivities appeared to be directly correlated to sample porosity. The lowest tortuosity, 8.94, was observed for sample PM-1 4823 Matrix, wh...

show abstract

Section: Countsmentioning

confidence: 93%

Section: Countsmentioning

confidence: 99%

Section: Countsmentioning

confidence: 99%