Comparison of Different Site Binding Models for Cation Sorption: Description of pH Dependency, Salt Dependency, and Cation–Proton Exchange

Venema, P.; Hiemstra, Tjisse; Riemsduk, Willem H. van

doi:10.1006/jcis.1996.0355

Cited by 137 publications

(85 citation statements)

References 10 publications

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“…Other electrostatic surface adsorption models have been proposed (e.g., constant capacitance and triple layer models) but all electrostatic models can describe limited experimental sorption data sets (Westall and Hohl, 1980;Venema et al, 1996). Models that use one site type generally require more than one complex species (e.g., Dyer et al, 2003).…”

Section: Surface Complexation Models (Scm)mentioning

confidence: 99%

Lead coprecipitation with iron oxyhydroxide nano-particles

Lü

Nuhfer

Kelly

et al. 2011

Geochimica et Cosmochimica Acta

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Pb 2+ and Fe 3+ coprecipitation was studied with sorption edge measurements, desorption experiments, sorbent aging, High Resolution Transmission and Analytical Electron Microscopy (HR TEM-AEM), and geochemical modeling. Companion adsorption experiments were also conducted for comparison. The macroscopic chemical and near atomic scale HRTEM data supplemented our molecule scale analysis with EXAFS (Kelly et al., 2008). Coprecipitation of Pb 2+ with ferric oxyhydroxides occurred at $pH 4 and is more efficient than adsorption in removing Pb 2+ from aqueous solutions at similar sorbate/sorbent ratios and pH. X-ray Diffraction (XRD) shows peaks of lepidocrocite and two additional broad peaks similar to fine particles of 2-line ferrihydrite (2LFh). HRTEM of the Pb-Fe coprecipitates shows a mixture of 2-6 nm diameter spheres and 8-20 by 200-300 nm needles, both uniformly distributed with Pb 2+ . Geochemical modeling shows that surface complexation models fit the experimental data of low Pb:Fe ratios when a high site density is used. Desorption experiments show that more Pb 2+ was released from loaded sorbents collected from adsorption experiments than from Pb to Fe coprecipitates at dilute EDTA concentrations. Desorbed Pb 2+ versus dissolved Fe 3+ data show a linear relationship for coprecipitation (CPT) desorption experiments but a parabolic relationship for adsorption (ADS) experiments.Based on these results, we hypothesize that Pb 2+ was first adsorbed onto the nanometer-sized, metastable, iron oxyhydroxide polymers of 2LFh with domain size of 2-3 nm. As these nano-particles assembled into larger particles, some Pb 2+ was trapped in the iron oxyhydroxide structure and re-arranged to form solid solutions. Therefore, the CPT contact method produced more efficient removal of Pb 2+ than the adsorption contact method, and Pb 2+ bound in CPT solids represent a more stable sequestration of Pb 2+ in the environment than Pb 2+ adsorbed on iron oxyhydroxide surfaces.

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Section: Surface Complexation Models (Scm)mentioning

confidence: 99%

Lead coprecipitation with iron oxyhydroxide nano-particles

Lü

Nuhfer

Kelly

et al. 2011

Geochimica et Cosmochimica Acta

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“…The macroscopic proton-ion adsorption ratio is less than stoichiometric. This might be rationalized by placing the adsorbed charge at a finite distance from the surface, leading to a weaker interaction (Fokkink et al, 1987;Venema et al, 1996b). Although the macroscopic proton-ion adsorption is non-stoichiometric for all ions, it is interesting that the quotient of the stoichiometries for the group of trivalent ions (vanadate, phosphate and arsenate) and the group of bivalent ions (chromate, molybdate and tungstate) is nearly equal to the quotient of the ionic charge of these ions (3/2).…”

Section: The Macroscopic Proton-ion Adsorption Stoichiometrymentioning

confidence: 99%

The relationship between molecular structure and ion adsorption on variable charge minerals

Rietra¹,

Hiemstra²,

Riemsdijk³

1999

Geochimica et Cosmochimica Acta

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130

164

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“…Ion adsorption and surface charging have been studied most frequently as a function of pH, at the macroscopic scale Dzombak and Morel, 1990;Boily and Fein, 1996;Boily et al, 2000;Wesolowski et al, 2000;Ridley et al, 2005;Machesky et al, 2006;Stachowicz et al, 2006). The resulting data have typically been rationalized by various surface complexation models (SCM), which combine chemical descriptions of surface protonation and ion adsorption reactions with electrostatic descriptions of the EDL (Westall and Hohl, 1980;Dzombak and Morel, 1990;Venema et al, 1996a). However, numerous shortcomings of these techniques and models have been identified.…”

Section: Introductionmentioning

confidence: 99%