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.

Magnetite Sorption Capacity for Strontium as a Function of pH

2008 ◽  
Vol 1107 ◽  
Author(s):  
Joan de Pablo ◽  
Miquel Rovira ◽  
Javier Giménez ◽  
Ignasi Casas ◽  
Frederic Clarens
Keyword(s):  
Spent Nuclear Fuel ◽  
Surface Complexation ◽  
Retardation Factor ◽  
Alkaline Ph ◽  
Layer Model ◽  
Surface Complexation Model ◽  
Ph Values ◽  
End Products ◽  
Diffuse Layer Model ◽  
Ph Range

AbstractThe ubiquity of iron oxide minerals and their ability to retain metals on their surface can represent an important retardation factor to the mobility of radionuclides. In a deep repository for the spent nuclear fuel, the intrusion of the groundwater might produce the anoxic corrosion of the iron, with magnetite as one of the end-products. In this study, as expected considering the strontium speciation in solution, strontium is sorbed onto magnetite at alkaline pH values while at acidic pH the sorption is negligible. Magnetite is able to sorb more than the 50% of the strontium from a 8·10-6 mol·dm-3 solution at the pH range representative of most groundwater (7-9). A surface complexation model has been applied to the experimental data, allowing to explain the results using the Diffuse Layer Model (DLM) and considering the formation of the inner-sphere complex >FeOHSr2+ (with a calculated logK=2.7±0.3). Considering these data, the magnetite capacity to retain strontium and other radionuclides is discussed

Modeling the sorption of Np(V) on Na-montmorillonite – effects of pH, ionic strength and CO2

2019 ◽  
Vol 107 (7) ◽  
pp. 615-622
Author(s):  
Raphael Scholze ◽  
Samer Amayri ◽  
Tobias Reich
Keyword(s):  
Ionic Strength ◽  
Surface Complexation ◽  
Ambient Air ◽  
Batch Type ◽  
Wide Range ◽  
Effects Of Ph ◽  
Ph Range

Abstract Results from batch type experiments were modeled using the 2 SPNE SC/CE model developed by Bradbury and Baeyens. This work focused on the applicability of this model to the sorption of Np(V) on Na-montmorillonite under high saline conditions (0.1–3.0 M NaCl) in the pH range of 2–10 and in the presence of dissolved CO2 (p(CO2) = 10−3.3 atm). Under ambient air conditions two additional surface complexation species had to be taken into account, which are ternary species involving one carbonate ligand (≡SONpO2(CO3)2−, ≡SONpO2(CO3)Na−). The gained set of complexation parameters was successfully tested over a wide range of Np(V) concentrations (10−4 to 10−12 M) under Ar atmosphere and ambient air condition.

scholarly journals Contribution of Ternary Reaction to Pd Sorption on MX-80 in Na-Ca-Cl Solution at High Ionic Strength

2019 ◽  
Vol 2019 ◽  
pp. 1-6
Author(s):  
Shinya Nagasaki ◽  
Justin Riddoch ◽  
Joshua Racette
Keyword(s):  
Ionic Strength ◽  
Cation Exchange ◽  
Concentration Ratio ◽  
Surface Complexation ◽  
High Ionic Strength ◽  
Molar Concentration ◽  
Complexation Constants ◽  
Ternary Reaction

In this study, we first examined the sorption of Pd on MX-80 in Na-Ca-ClO4 solution as a function of pHc (3–9) and ionic strength (0.1 M–4 M) and confirmed that the experimentally derived Kd values could be fitted by a 2-site protolysis nonelectrostatic surface complexation and cation exchange (2SPNE SC/CE) model using three binary surface complexation constants previously estimated. Then, we investigated the sorption of Pd on MX-80 in Na-Ca-Cl-ClO4 solution as a function of pHc (3–9) and Cl-/ClO4- molar concentration ratio (0–∞) at the ionic strength = 4 M. We found that the sorption of Pd on MX-80 in Na-Ca-Cl-ClO4 solution could be simulated only by the three binary and one ternary surface complexations (S-OH+Pd2++4Cl-↔S-OPdCl43-+H+). This suggests that the contribution of other ternary surface complexations such as ≡S-OH +  Pd2++xCl-↔ ≡S-OPdClxx-1-+H+ (x = 1, 2 and 3) to Pd sorption in Na-Ca-Cl-ClO4 solution with ionic strength = 4 M was negligibly small.

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.

Adsorption Mechanism of Humic Acid on Attapulgite Based on Stumm-Schindle Surface Complexation Model

2012 ◽  
Vol 630 ◽  
pp. 99-105 ◽  
Author(s):  
Nan Sun ◽  
Shui Li Yu
Keyword(s):  
Humic Acid ◽  
Ionic Strength ◽  
Zeta Potential ◽  
Adsorption Capacity ◽  
Adsorption Mechanism ◽  
Ph Value ◽  
Surface Complexation ◽  
Practical Significance ◽  
Surface Complexation Model ◽  
Coordination Reaction

Attapulgite from Xuyi in Jiangsu was characterized by X-ray spectrometer and FT-IR spectrophotometer, the coordination reaction degree of attapulgite/water interface and adsorption mechanism of humic acid(HA) on attapulgite was analyzed by Stumm-Schindle(SS) surface complexation model. The results showed that the main component of attapulgite is magnesia-alumina acid salt, the surface charge on attapulgite adapted from hydrolysates of Si-O and Al-O broken bond. After adsorption, zeta potential decreased firstly and then increased with ionic strength increasing, reduced with a pH value increasing. The zero point charge (pHzpc) of attapulgite was about 4~5, zeta potential and adsorption capacity reached the maximum values when pH= 4 and the minimum values when pH=12. The adsorption capacity increased with ionic strength rising. SS surface complexation model could well explain attapulgite / water interfacal coordination reaction, ionic strength can promote the interfacial coordination reaction and reduce electrostatic repulsion effects on adsorption, which has a definite theoretical and practical significance for guiding adsorption experiment and application of attapulgite in water-treatment technology.

The function of carboxyls in the structure of humic acids to binding of organic substances

2020 ◽  
Author(s):  
Jiri Smilek ◽  
Anna Belusova ◽  
Michal Kalina ◽  
Petr Sedlacek
Keyword(s):  
Humic Substances ◽  
Organic Compounds ◽  
Humic Acids ◽  
Hydrophobic Interactions ◽  
Organic Dyes ◽  
Strong Impact ◽  
Spectroscopic Techniques ◽  
Surface Active Agents ◽  
Physico Chemical ◽  
Surface Active

<p>The humic substances, the major and the most important part of soil organic matter, are responsible for the immobilization of organic compounds (e.g. heavy metal ions, organic dyes, surface active agents, etc.) in the soil. Unfortunately, there are a lot of gaps in the knowledge in the complex mechanism of binding of organic charged compounds by humic substances.</p><p>The unconventional diffusion and dialysis (transport) techniques have been developed for the purpose of study on the interactions between humic substances and organic charged substances.  In our contribution we are focusing on one fraction of humic substances – humic acids. The binding between humic acids with/without selectively blocking of carboxylic functional groups (methylation by –CH3) with organic charged compounds (e.g. organic dyes, surface active agents) has been studied by diffusion and dialysis approach using the spectroscopic techniques as analytical method. The strong impact of methylation on the positive affinity of humic acids towards organic compounds has been expected. These expectations were not confirmed by diffusion and dialysis techniques. The role of carboxyls in the structure of humic acids is not so essential as was expected and mentioned in the literature. The other effects (e.g. hydrophobic interactions, pi-pi stacking, etc.) are more important in the binding of organic compounds as was expected. The positive binding as well as kinetics of this process is also strongly depending on the physico-chemical circumstances of the system (e.g. pH, ionic strength, temperature, etc.).</p>

scholarly journals OBTAINING DERIVATIVES OF HUMIC SUBSTANCES FROM OXIDIZED COAL AND STUDY OF PHYSICO-CHEMICAL AND ADSORPTION PROPERTIES

2020 ◽  
Vol 6 (444) ◽  
pp. 57-64
Author(s):  
B.T. Yermagambet ◽  
◽  
M.K. Kazankapova ◽  
Zh.M. Kassenova ◽  
A.T. Nauryzbayeva ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Humic Substances ◽  
Humic Acids ◽  
Aqueous Media ◽  
Amino Groups ◽  
Chelate Complexes ◽  
High Adsorption ◽  
Oxidized Coal ◽  
Physico Chemical ◽  
Derivatives Of

In the work, a chemical analysis of humic substances based on oxidized coal of the Maikuben basin (Kazakhstan) is carried out. Humic acids were obtained on the basis of potassium humates by acidification with a 20% acid solution to pH = 3-4.5. The optimal conditions for obtaining nitrohumic acids from oxidized coals are: the duration of the process is 3 hours, the ratio of S:L = 1:5, the content of nitric acid is 64%, sulfuric acid is 96% and the composition of the nitrating mixture is 1:1 (g/g). Amminohumic derivatives were obtained in the presence of a 3% aqueous solution of ammonia using mechanical activation and ultrasonic treatment. The samples obtained were tested as an adsorbent for water purification from heavy metals. Humic acids and aminohumate showed the highest degrees of purification for zinc (99.0-100.0%) and cadmium (80.0-96.7%), and nitrohumic acid showed a high adsorption capacity for heavy metals like copper - 100.0 % and lead 82.9%. This is due to the fact that when interacting with heavy metals, humic acids and their derivatives (amino and nitro) form chelate complexes due to carboxyl, phenolic, nitro and amino groups. As a result of the study, the possibility of using them as non-toxic available sorbents for the purification of heavy metals in aqueous media has been shown.

scholarly journals Characterization of Soil Organic Matter Individual Fractions (Fulvic Acids, Humic Acids, and Humins) by Spectroscopic and Electrochemical Techniques in Agricultural Soils

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1067
Author(s):  
Aleksandra Ukalska-Jaruga ◽  
Romualda Bejger ◽  
Guillaume Debaene ◽  
Bożena Smreczak
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Humic Substances ◽  
Humic Acids ◽  
Agricultural Soils ◽  
Fulvic Acids ◽  
Sorption Properties ◽  
Aliphatic Chains

The objective of this paper was to investigate the molecular characterization of soil organic matter fractions (humic substances (HS): fulvic acids-FAs, humic acids-HAs, and humins-HNs), which are the most reactive soil components. A wide spectrum of spectroscopic (UV–VIS and VIS–nearIR), as well as electrochemical (zeta potential, particle size diameter, and polydispersity index), methods were applied to find the relevant differences in the behavior, formation, composition, and sorption properties of HS fractions derived from various soils. Soil material (n = 30) used for the study were sampled from the surface layer (0–30 cm) of agricultural soils. FAs and HAs were isolated by sequential extraction in alkaline and acidic solutions, according to the International Humic Substances Society method, while HNs was determined in the soil residue (after FAs and HAs extraction) by mineral fraction digestion using a 0.1M HCL/0.3M HF mixture and DMSO. Our study showed that significant differences in the molecular structures of FAs, Has, and HNs occurred. Optical analysis confirmed the lower molecular weight of FAs with high amount of lignin-like compounds and the higher weighted aliphatic–aromatic structure of HAs. The HNs were characterized by a very pronounced and strong condensed structure associated with the highest molecular weight. HAs and HNs molecules exhibited an abundance of acidic, phenolic, and amine functional groups at the aromatic ring and aliphatic chains, while FAs mainly showed the presence of methyl, methylene, ethenyl, and carboxyl reactive groups. HS was characterized by high polydispersity related with their structure. FAs were characterized by ellipsoidal shape as being associated to the long aliphatic chains, while HAs and HNs revealed a smaller particle diameter and a more spherical shape caused by the higher intermolecular forcing between the particles. The observed trends directly indicate that individual HS fractions differ in behavior, formation, composition, and sorption properties, which reflects their binding potential to other molecules depending on soil properties resulting from their type. The determined properties of individual HS fractions are presented as averaged characteristics over the examined soils with different physico-chemical properties.

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.

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