Modeling of Yb(III) Sorption on Kaolinite by Using Single Oxide Surface Complexation Models

1994 ◽  
Vol 353 ◽  
Author(s):  
Nicolas Marmier ◽  
Jacques Dumonceau ◽  
Joël Chupeau ◽  
Francine Fromage
Keyword(s):  
Surface Acidity ◽  
Surface Complexation ◽  
Oxide Surface ◽  
Complexation Constants ◽  
Acidity Constants ◽  
Surface Complexation Model

AbstractSurface complexation model was used to describe ytterbium sorption on kaolinite using surface acidity constants and surface complexation constants determined on alumina and silica.

Uranyl Sorption Onto Alumina

1996 ◽  
Vol 465 ◽  
Author(s):  
Anna-Maria M. Jacobsson ◽  
Robert S. Rundberg
Keyword(s):  
Metal Ion ◽  
Dissociation Constants ◽  
Surface Complexation ◽  
Uranyl Complex ◽  
Acid Dissociation ◽  
Oxide Surface ◽  
Acid Dissociation Constants ◽  
Surface Complexation Model ◽  
Surface Hydroxyl ◽  
Free Environment

ABSTRACTThe mechanism for the adsorption of uranyl onto alumina from aqueous solution was studied experimentally and the data were modeled using a triple layer surface complexation model. The experiments were carried out at low uranium concentrations (9×10-11 - 5×10-8M) in a CO2 free environment at varying electrolyte concentrations (0.01 – 1 M) and pH (4.5 – 12). The first and second acid dissociation constants, pKal and pKa2, of the alumina surface were determined from potentiometric titrations to be 7.2 ± 0.6 and 11.2 ± 0.4, respectively. The adsorption of uranium was found to be independent of the electrolyte concentration. We therefore conclude that the uranium binds as an inner sphere complex. The results were modeled using the code FITEQL. Two reactions of uranium with the surface were needed to fit the data, one forming a uranyl complex with a single surface hydroxyl and the other forming a bridged or bidentate complex reacting with two surface hydroxyls of the alumina. There was no evidence from these experiments of site heterogeneity. The constants used for the reactions were based in part on predictions made utilizing the Hard Soft Acid Base, HSAB, theory, relating the surface complexation constants to the hydrolysis of the sorbing metal ion and the acid dissociation constants of the mineral oxide surface.

Actinide Sorption onto Silica in the Presence of Humic Substances: Proposal of Retentionmechanisms

1991 ◽  
Vol 257 ◽  
Author(s):  
N. Labonne ◽  
V. Moulin ◽  
D. Stammose
Keyword(s):  
Ionic Strength ◽  
Humic Substances ◽  
Humic Acids ◽  
Surface Complexation ◽  
Complexing Agents ◽  
Complexation Constants ◽  
Surface Complexation Model ◽  
Physico Chemical ◽  
Ph Range ◽  
Geological Formations

ABSTRACTThe experimental investigation and modelling of radionuclides sorption processes is an essential part of safety analyses of an underground repository of radioactive wastes in geological formations. Physico—chemical phenomena at oxide/solution interfaces have been studied in the case of the system constituted by amorphous silica and americium (III) in the presence of humic substances as organic complexing agents. The retention behaviour of Am(III) onto silica appears dependent on pH, ionic strength and in particular humic concentration. At a ionic strength of 0.1 M, the presence of low concentration of humic acids (1 mg/l) enhances the Am(III) retention in the pH range 3-5.5, whereas at higher pH, its uptake is largely decreased. At lower ionic strength (0.001 M), Am(III) retention on silica is highly lowered, in the pH range 3-7 in the presence of humic acids. Reversibility experiments show the desorption of americium in the absence of humic substances, and also the desorption of the humics on the silica with respect of the pH. The surface complexation model has been applied to our results in the different systems and apparent surface complexation constants have been determined.

Comparison of a Non Electrostatic Surface Complexation Model and Surface Phase Theories for Prediction of Future Sorption Properties.

2004 ◽  
Vol 824 ◽  
Author(s):  
Allan T. Emrén ◽  
Anna-Maria Jacobsson
Keyword(s):  
Aqueous Solution ◽  
Chemical Potential ◽  
Surface Complexation ◽  
Sorption Properties ◽  
Phase Method ◽  
Detailed Knowledge ◽  
Surface Phase ◽  
Surface Complexation Model ◽  
Advantages And Disadvantages ◽  
The One

AbstractIn performance assessments, sorption of radionuclides dissolved in groundwater is mostly handled by the use of fixed Kd values. It has been well known that this approach is unsatisfying. Only during the last few years, however, tools have become available that make it possible to predict the actual Kd value in an aqueous solution that differs from the one in which the sorption properties were measured.One such approach is surface complexation (SC) that gives a detailed knowledge of the sorption properties. In SC, one tries to find what kinds of sorbed species are available on the surface and the thermodynamics for their formation from species in the bulk aqueous solution. Recently, a different approach, surface phase method (SP), has been developed. In SP, a thin layer including the surface is treated as a separate phase. In the bulk aqueous solution, the surface phase is treated as a virtual component, and from the chemical potential of this component, the sorption properties can be found.In the paper, we compare advantages and disadvantages of the two kinds of models. We also investigate the differences in predicted sorption properties of a number of radionuclides (Co, Np, Th and U). Furthermore, we discuss under which circumstances, one approach or the other is preferable.

Measurements of Metal Adsorption in Oxide-Clay Mixtures: “Competitive-Additivity” Among Mixture Components

1992 ◽  
Vol 294 ◽  
Author(s):  
V. S. Tripathi ◽  
M.D. Siegel ◽  
Z. S. Kooner
Keyword(s):  
Surface Complexation ◽  
Particle Interactions ◽  
Complexation Constants ◽  
Lead Adsorption ◽  
Adsorption Sites ◽  
Adsorption Behaviors ◽  
Limited Success ◽  
Ph Dependent ◽  
Waste Repositories ◽  
Zinc Adsorption

ABSTRACTAn important question concerning the transport of radionuclides from nuclear waste repositories is whether the adsorption of metals by rocks and soils can be predicted from the properties of the constituent minerals. Attempts by previous researchers to use sorption models based on linear adsorption or weighted "sorptive additivity" have met with limited success. In this study, a “competitive-additivity” model based on surface complexation theory was used to model the pH-dependent adsorption of lead by goethite/Ca-montmorillonite mixtures using complexation constants obtained from single sorbent systems. Measurements of lead adsorption by goethite, Ca-montmorillonite, and goethite-Ca-montmorillonite mixtures (and similar studies of copper and zinc adsorption) demonstrate that the two adsorbents compete for adsorption of metals over wide ranges of pH and concentrations of adsorbents and metals. The adsorption behaviors of the mixtures are determined by the relative concentrations of the adsorbents and their respective affinities for the adsorbate metal. Particle-particle interactions such as heterocoagulation of the oxide and clay do not appear to be significant for the majority of the adsorption sites in this system.

Variable charges of a red soil from different depths: Acid-base buffer capacity and surface complexation model

2018 ◽  
Vol 159 ◽  
pp. 107-115 ◽  
Author(s):  
Ying Wang ◽  
Pengfei Cheng ◽  
Fangbai Li ◽  
Tongxu Liu ◽  
Kuan Cheng ◽  
...  
Keyword(s):  
Buffer Capacity ◽  
Surface Complexation ◽  
Red Soil ◽  
Acid Base ◽  
Surface Complexation Model ◽  
Different Depths

Investigation of radionuclide 60Co(II) binding to TiO2 by batch technique, surface complexation model and DFT calculations

2012 ◽  
Vol 55 (9) ◽  
pp. 1752-1759 ◽  
Author(s):  
XueMei Ren ◽  
ShiTong Yang ◽  
XiaoLi Tan ◽  
ChangLun Chen ◽  
XiangKe Wang
Keyword(s):  
Dft Calculations ◽  
Surface Complexation ◽  
Surface Complexation Model ◽  
Batch Technique

Surface Chemistry of Mesoporous Materials: Effect of Nanopore Confinement

2002 ◽  
Vol 751 ◽  
Author(s):  
Yifeng Wang ◽  
Charles Bryan ◽  
Huifang Xu ◽  
Huizhen Gao
Keyword(s):  
Surface Chemistry ◽  
Surface Acidity ◽  
Scale Space ◽  
Acid Base ◽  
Acidity Constants ◽  
Solution Interface ◽  
Ion Sorption ◽  
Alumina Particles ◽  
The Difference ◽  
Nanopore Confinement

AbstractAcid-base titration and metal sorption experiments were performed on both mesoporous alumina and alumina particles under various ionic strengths. It has been demonstrated that surface chemistry and ion sorption within nanopores can be significantly modified by a nano-scale space confinement. As the pore size is reduced to a few nanometers, the difference between surface acidity constants (ΔpK = pK2 – pK1) decreases, giving rise to a higher surface charge density on a nanopore surface than that on an unconfined solid-solution interface. The change in surface acidity constants results in a shift of ion sorption edges and enhances ion sorption on that nanopore surfaces.

Sign in / Sign up

Export Citation Format

Share Document