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Title: Surface complexation modeling of proton and metal sorption onto graphene oxide

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Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Nuclear Energy (NE)
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Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Colloids and Surfaces. A, Physicochemical and Engineering Aspects
Additional Journal Information:
Journal Volume: 466; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-05-30 15:07:33; Journal ID: ISSN 0927-7757
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Citation Formats

Duster, Thomas A., Szymanowski, Jennifer E. S., Na, Chongzheng, Showalter, Allison R., Bunker, Bruce A., and Fein, Jeremy B.. Surface complexation modeling of proton and metal sorption onto graphene oxide. Netherlands: N. p., 2015. Web. doi:10.1016/j.colsurfa.2014.10.049.
Duster, Thomas A., Szymanowski, Jennifer E. S., Na, Chongzheng, Showalter, Allison R., Bunker, Bruce A., & Fein, Jeremy B.. Surface complexation modeling of proton and metal sorption onto graphene oxide. Netherlands. doi:10.1016/j.colsurfa.2014.10.049.
Duster, Thomas A., Szymanowski, Jennifer E. S., Na, Chongzheng, Showalter, Allison R., Bunker, Bruce A., and Fein, Jeremy B.. 2015. "Surface complexation modeling of proton and metal sorption onto graphene oxide". Netherlands. doi:10.1016/j.colsurfa.2014.10.049.
title = {Surface complexation modeling of proton and metal sorption onto graphene oxide},
author = {Duster, Thomas A. and Szymanowski, Jennifer E. S. and Na, Chongzheng and Showalter, Allison R. and Bunker, Bruce A. and Fein, Jeremy B.},
abstractNote = {},
doi = {10.1016/j.colsurfa.2014.10.049},
journal = {Colloids and Surfaces. A, Physicochemical and Engineering Aspects},
number = C,
volume = 466,
place = {Netherlands},
year = 2015,
month = 2

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.colsurfa.2014.10.049

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  • The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonitemore » edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites (‘spillover’ effect).« less
  • Pb(II) sorption on goethite and hematite powders was studied at room temperature as a function of pH (6-8), sorption density (2-10 {mu}moles/m{sup 2} ), and [Pb]{sub eq} (0.2 {mu}M - 1.2 mM) in 0.1 M NaNO{sub 3} electrolyte using XAFS spectroscopy. Pb(II) ions were found to be hydrolyzed and adsorbed as mononuclear bidentate complexes to edges of FeO{sub 6} octahedra on both goethite and hematite under all conditions. Hydrolysis of Pb(II) appears to be a primary source of proton release associated with surface complexation of Pb(II). A bond-valence model was used to relate the relative stabilities of iron-oxide surface functionalmore » groups and Pb(II) adsorption complexes to their structures and compositions. This combined approach suggests that Pb(II) adsorption occurs primarily at unprotonated [Fe {sub Fe}{sup Fe}(>)O{sup -{1/2}}] sites and at [Fe-OH{sub 2}{sup +}{sup +{1/2}}] sites. Several adsorption reactions are proposed. Comparison to EXAFS results from Pb(II) adsorption on aluminum oxides suggests that the edge lengths of surface AlO{sub 6} or FeO{sub 6} octahedra partially determine the reactivities and densities of available surface sites. The results of this study provide a basis for constructing chemically realistic descriptions of Pb(II) surface complexation reactions on Fe hydroxides. 46 refs., 7 figs., 4 tabs.« less
  • The surface reactivity and sorption of Nd and Eu onto K{sup +}-saturated Marblehead illite at 25 C, measured in aqueous 0.01, 0.1, and 1.0 M KCl solutions, were interpreted with a multi-site-surface complexation model. Model potentiometric titration and sorption curves (computed using the Gibbs free energy minimization code, Selektor-A) resolve into reactions on variable-charge amphoteric sites on edge surfaces and on permanent-charge siloxane surfaces ({phi}{sub x}). Standard partial molal Gibbs free energy of formation from elements (g{sub 298}{sup 0}) for surface complexes were derived from oxide surface deprotonation K{sub A1}{sup 0}, K{sub A2}{sup 0} and electrolyte adsorption constants K{sub Cl}{supmore » 0}, K{sub Na}{sup 0}. Because surface complexation reactions on siloxane basal surfaces are negligible in 1 M KCl, models of surface charge and adsorption edges of Nd and Eu presumed that C{sub 1} is equal to 1.6 Fm{sup {minus}2} for amphoteric site types, and a maximum site density of 1.2 {+-} 0.2 sites nm{sup {minus}2} for the outer-sphere species. To obtain values of g{sub 298}{sup 0} for exchangeable cations and charged X{sup {approximately}}REE complexes, ion exchange sites were assumed to be fully deprotonated in 1.0 M KCl solutions (pH > 2.7). Proton release and REE{sup 3+} uptake on ion exchange sites were then simulated using a nonelectrostatic model and assuming a 50% contribution to the total surface area at {Gamma}{sub max.X} of 3.0 sites nm{sup {minus}2} whereas the contributions of the silanol and aluminol surface types were described using a TLM. At pH < 4.5 and I {le} 0.1 M KCl, frayed edges of interlayer site play a dominant role in controlling surface reactions on ion exchange sites; the contribution to total surface area of frayed edges decay exponentially from initial values of 20 to 48%. The application of Gibbs free energy minimization to sorption processes is innovative in that simultaneous treatment of surface complexation reactions and minerals stability is feasible in any system without introducing mass-balance constraints particular to surface species.« less
  • This work presents an investigation of the interaction mechanisms between uranyl ions and a solid phosphate, the zirconium oxophosphate: Zr{sub 2}O(PO{sub 4}){sub 2}. Both thermodynamic and structural points of view are developed. Indeed, prior to any simulation of the retention data, it is necessary to precisely characterize the system under study in order to gain information at a molecular scale. First, the intrinsic surface properties of this synthetic compound have been investigated for different temperatures ranging from 25 to 90 C. Mass and potentiometric titrations show that the surface site density remains constant between 25 and 90 C, while themore » experimental point of zero charge slightly decreases from 4.8 to 4.5 with an increasing temperature. The potentiometric titration data are simulated, for each temperature, using the constant capacitance model and taking into account two surface sites ({triple_bond}Zr{_}O and {triple_bond}P{_}O) with a total surface site density equal to 7.0 sites nm{sup -2}. For both reactive sites, the intrinsic protonation constants do not change with the temperature, while the deprotonation ones increase. These results led to the determination of the associated enthalpy and entropy changes according to the van't Hoff relation. Second, the speciation of U(VI) at the solid/solution interface has been studied using two complementary spectroscopic techniques probing the sorbed uranyl ions: time-resolved laser-induced fluorescence spectroscopy (TRLFS) and X-ray absorption spectroscopy (EXAFS). The substrate presents two different reactive surface sites against uranium retention, which are constituted by the oxygen atoms of the surface PO{sub 4} groups and the oxygen atoms linked to the zirconium atoms. Two inner-sphere complexes are thus present on the substrate, their relative proportion depending on the pH value of the suspension. The effects of the temperature (25-90 C) on the surrounding uranium were checked using the TRLFS technique. The uranyl sorption constants onto the Zr{sub 2}O(PO{sub 4}){sub 2} substrate were determined taking into account the structural investigation. The surface complexation modeling was performed using the constant capacitance model included in the FITEQLv4.0 code. The four adsorption edges obtained at 25, 50, 75, and 90 C were simulated. The modeling of these experimental data was realized considering two surface complexes (({triple_bond}ZrOH){sub 2}UO{sup 2+}{sub 2}, ({triple_bond}PO){sub 2}UO{sub 2}) according to the structural investigation. The constant value associated with the {triple_bond}ZrO site does not change with the temperature, while the one corresponding to the {triple_bond}PO site increases. Finally, the enthalpy and entropy changes associated with the uranyl sorption constants have been determined using the van't Hoff relation.« less