Sorption Of Europium Research Articles

Effect of temperature on the sorption of europium on alumina: Microcalorimetry and batch experiments

The determination of enthalpies of reactions (aqueous and surface complexation) is used in this work to model the temperature effect on the adsorption processes. Microcalorimetry experiments were carried out to determine the enthalpy of adsorption of europium on γ-alumina at 25°C. The stability constants at 50°C were then calculated with the van’t Hoff equation, and a 2-pK approach was used to model the adsorptive behavior of Eu on alumina at 50°C, as a function of pH. The results have shown that the adsorption of Eu3+ on the alumina surface is weakly endothermic. In the experimental conditions considered in the present study, the temperature has only a small effect on the adsorption reaction.

A proton NMR study on the specific sorption of yttrium(III) and europium(III) on gamma-alumina [γ-Al2O3

The specific sorption of Eu(III) and Y(III) on γ-alumina was investigated with solid-state 1H NMR. Solution pH was shown to influence the recorded 1H NMR spectra of γ-alumina, and thus, metal ion-containing samples were prepared under constant pH conditions, 8.00±0.05. The metal ion concentration in the samples was varied between 6.58×10−7 M–3.95×10−4 M in case of Y3+ and 6.58×10−8 M–1.32×10−4 M in case of Eu3+. The mineral concentration was kept constant at 4g/l. After separation of the liquid phase, the samples were dried under vacuum to remove physisorbed water from the mineral surface. However, even after 48h of drying at 150°C and 20 mTorr, water was still detected in the proton spectra as two distinct peaks with chemical shifts at 1.3 and 0.9ppm. The europium addition to the γ-alumina samples induced significant spectral changes in comparison with yttrium-containing samples. These changes were attributed to the paramagnetism of europium rather than to complexation reactions occurring on the mineral surface. Proton spectra obtained for yttrium samples were therefore used to detect the spectral changes induced by the sorption reaction itself. The results revealed a large distribution of protons being removed from the mineral surface upon yttrium complexation. Removed protons were assigned to both bridging surface hydroxyls such as (AlVI)2–OH as well as to terminal hydroxyls, e.g., of type AlVI–OH. Acidic protons belonging to (AlVI)3–OH groups were not observed to participate in the surface reaction.

Sorption of Eu(III) onto titanium dioxide: Measurements and modeling

In the present study, the sorption of europium and lutetium onto titanium dioxide from aqueous solutions is presented, as a function of pH, ionic strength and concentration. An acid base model for the titanium dioxide surface was determined from potentiometric titrations and zeta-potential measurements. The common intersection point of potentiometric titrations coincided with the isoelectric point from electrokinetic experiments, resulting in a pristine point of zero charge of about 6.1. The experimental data were in agreement with previously published results and a previously published MUSIC-type model was used as the basis to model the acid–base behavior. Comparison of europium and lutetium showed no difference in the adsorption behavior. Furthermore, no difference was observed both in uptake and spectroscopic studies whether carbonate was absent or present. The absence of a noticeable effect of the ionic strength on the adsorption behavior was indicative of strong binding. EXAFS revealed rough conservation of the coordination with 9–8 water and surface hydroxyl groups upon sorption. EXAFS results suggested the existence of different metal–oxygen distances, more varied than that observed for the respective aquo complex and thus indicative for inner-sphere surface complexation. A clear differentiation of surface complexation denticity was not possible based on spectroscopic data. A multisite surface complexation model approach was applied by assuming monodentate and multidentate binding to describe the trivalent metal uptake data. It is conceivable that mono- and multidentate species contribute to lanthanide sorption to titanium dioxide. In other words a distribution of states occurs in cation surface complexation reactions.

Sorption of europium on a MX-80 bentonite sample: experimental and modelling results

In this paper, the adsorption of europium on a natural bentonite was studied and modelled using the component additivity (CA) approach of the surface complexation theory. The experimental results were modelled considering the formation of monodentate species at the edge sites of the bentonite and two exchange reactions at the interlayer sites. The CA approach was compared to the most common approach of the surface complexation theory (the general composite (GC)), by modelling in a predictive way, experimental results obtained from the literature. This comparison allowed us to conclude that (i) the CA approach successfully described the behaviour of europium on montmorillonite on a restricted pH range and on a large range of concentrations, (ii) five surface stoechiometries for the GC approach were necessary to model the europium sorption versus four surface stoechiometries for the CA approach, (iii) some improvement of the CA approach are necessary concerning the consideration of impurities.

Sorption of 137Cs, 133Ba and 154Eu by synthesized sodium aluminosilicate (Na-AS)

Sodium aluminosilicate has been synthesized by solution route for use as a sorbent for various radionuclides. It was characterized by XRD, zeta potential, BET surface area, FTIR spectroscopy and site density measurement. Sorption studies of 137Cs, 133Ba and 154Eu on synthesized sodium aluminosilicate have been carried out at varying pH (3–10). Sorption of all the metal ions was found to increase with pH of suspension with the saturation value increasing with the oxidation state of metal ion. Effect of Aldrich humic acid (2 mg/l) on sorption was also investigated. In case of 137Cs, the sorption was not affected by the presence of humic acid, while in case of 133Ba and 154Eu, sorption was enhanced at lower pH and decreased at higher pH in presence of HA. A series of experiments were carried out for 154Eu sorption on sodium aluminosilicate at various conditions. Sorption of europium was analyzed by different sorption isotherms, viz., Freundlich and D-R isotherm. Thermodynamic data reveal sorption phenomena as endothermic and spontaneous. Studies were further extended to find out effect of diverse ions (Ca 2+ and CO 3 2−) on sorption of europium.

Influence of geochemical parameters on the sorption and desorption behaviour of europium and gadolinium onto kaolinite

In this study we investigated the sorption and desorption behaviour of europium and gadolinium (homologues of the actinides americium and curium) onto the clay mineral kaolinite KGa-1b. In the model system metal/kaolinite, sorption isotherms and pH-edges were determined in different batch experiments. Calcium and magnesium as competing cations were used to simulate the influence of water hardness on the sorption and desorption processes. After centrifugation, the free metal ions in the supernatant solution were analysed by ICP-MS. With increasing lanthanide concentration, especially the relative desorption of these metals from kaolinite rises significantly before the cation exchange capacity (CEC) of 0.94 meq per 100 g is reached. This indicates that low lanthanide concentrations will result in a relatively lower metal migration due to sorption reactions at higher active sites in comparison with higher lanthanide concentrations. The K(d)-values and sorption isotherms of Eu(iii) and Gd(iii) were determined at pH 5.0 (+/-0.02) and analysed with Freundlich and Langmuir sorption models. The experimental data can best be fitted by Langmuir sorption isotherm. The pH-value has only a minor influence on the sorption onto kaolinite. Only at low pH-values (<pH 4), relevant changes in migration behaviour have to be expected. One important influence factor on lanthanide sorption found in our study is naturally occurring competing cations such as alkaline earth metals. With Ca and Mg concentrations close to those found in nature, lanthanide sorption decreases dramatically. Desorption experiments show that after four consecutive equilibration steps, nearly all the lanthanide has been mobilised from kaolinite to the aquifer.

Europium sorption to sediments in the presence of natural organic matter: A laboratory and modeling study

Abstract Cellulosic materials, such as wood, paper products and cardboard that have been co-disposed with low-level nuclear waste have been shown to produce leachate with natural organic matter (NOM) concentrations of hundreds of mg/L C and, as such, have the potential to influence the fate and transport of radionuclides in the subsurface environment. The objective of this study was to examine the influence of NOM on the sorption of Eu (an analogue for trivalent radionuclides) to two coastal plain sediments from the US Department of Energy’s Savannah River Site. Particular attention was directed at quantifying Eu interactions with NOM sorbed to sediments (NOMsed) in laboratory experiments and developing conditional stability constants for that interaction using the thermodynamic equilibrium speciation model MINTEQA2. Europium sorption to the two sediments systematically increased as pH increased from 3.9 to 6.7. With increasing additions of NOM to the aqueous phase from 0 to 222 mg/L C, Eu sorption initially increased to a maximum at 10 mg/L C NOMaq and then decreased with increasing NOMaq concentrations. Increases in Eu sorption at low NOM additions was attributed to the sorption of NOM to the sediment surface increasing the number of sorption sites on the low cation-exchange capacity sediments and/or increasing the association constant (log K) for the Eu-sediment surface reaction. Decreases in Eu sorption at higher NOM levels was attributed to Euaq complexation to NOMaq being more favored than Eu sorption to the solid phase. A component additivity model was developed to describe the Eu–NOM-sediment system by the additive effects of the three binary system models: Eu–NOM, Eu-sediment and NOM-sediment. The model generally captured the data trends in the ternary system. Conditional stability constants developed from the experimental data for the complexation of Eu to NOMsed were as much as four orders of magnitude greater than Eu complexation with NOMaq, presumably due to the NOMsed deriving additional negative (attractive) charge from the sediment surface. At high initial NOMaq levels, >99 mg/L C, the model captured the trend of reduced Eu sorption but tended to over-estimate Eu sorption. The additivity approach of combining binary models to form a ternary model was only successful when the unique complexation properties of the NOMsed were properly calculated.

Temperature effects on the interaction mechanisms between U(VI) and Eu(III) and ZrP2O7: experiment and modelling

In the field of nuclear waste management, prediction of the radionuclides migration through the geosphere has to take into account the effects of temperature. The chosen substrate, zirconium diphosphate, was previously described concerning its surface acidity properties for several temperatures (25 °C, 50 °C, 75 °C, 90 °C). Edges for uranyl sorption were obtained in NaClO4medium, and the europium(III) sorption edges were realized in KNO3medium to evaluate the influence of the complexing nitrate ions. Influence of the temperature, the nature of the cation and the nature of the substrate were pointed out by comparing the edges for the different systems. A structural investigation (TRLFS) was carried out to define experimentally, at the microscopic level, the sorption equilibria. Only UO22+and Eu3+were sorbed on both ZrP2O7surface sites (≡Zr–O and ≡P–O), the nitrate medium having no influence on the sorbed species. Furthermore, temperature did not change the sorption mechanisms. The surface complexation modelling of both investigated systems was realized using i) the constant capacitance model ii) the results of the substrate characterizations iii) uranyl sorbed complex determinations. The formation of bidentate surface complexes onto the ≡Zr–O site is not accompanied by a proton release, whereas the formation of bidentate surface complexes onto the ≡P–O site is followed by a release of 2 protons, for both cations and at all temperatures studied. The determined sorption constants increase with temperature, as was expected from the analysis of the sorption edge positions.

Effect of complexing anions on europium sorption on suspended silica: a TRLFS study for ternary complex formation

The sorption of europium, Eu(III), on suspended silica was studied in perchlorate media under varying concentrations of Eu(III) and silica, at pH 4 to 8, and ionic strength from 0.20 to 1.40 M NaClO4at 298 K. The complexing anions, carbonate, acetate, citrate, oxalate, phosphate and EDTA, affected the sorption of Eu(III). A synergistic enhancement in the sorption of Eu(III) was observed for oxalate and phosphate ligands. Other anions suppressed the sorption in the order: acetate &lt; carbonate &lt; citrate &lt; EDTA. The results of TRLFS studies were consistent with ternary Eu/silica/ligand complexation for oxalate and phosphate anions.

Sorption of Eu3+ on dickite particles studied by Raman, luminescence, and X-ray photoelectron spectroscopies

Abstract The sorption of europium(III) species from EuCl 3 solution at pH = 5.4 onto dickite particles is investigated using spectroscopic methods. Thanks to the neutrality of phyllosilicate sheets of dickite, cation exchange is prevented. X-ray photoelectron spectroscopy reveals that chloride atoms probably remain in the ligand sphere of the europium(III) cation. The edge site-specific reactivity is evidenced by epifluorescence microscopy and Raman spectroscopy. Comparison between dickite/europium(III) samples rinsed or not with distilled water shows that the surface processes not only involve inner-sphere complex formation, but also either outer-sphere complex or surface precipitation. Raman spectra also indicate that europium(III) surface complexes are preferentially localised at the edge of tetrahedral silica sheets.

Highly sensitive sorption-luminescence determination of trace europium with preconcentration on silica chemically modified with iminodiacetic acid

Features of a sorption-luminescence method for the determination of trace europium were studied. The method includes the preliminary sorption of europium at pH 7.1 from solutions with silica chemically modified with iminodiacetic acid, the subsequent treatment of the sorbent with 2-thenoyltrifluoroacetone at pH 8.0, and the measurement of the intensity of luminescence of the surface three-component europium complex at 613 nm. The effect of moisture as the quencher of luminescence of the surface europium complex was studied, and techniques for its removal were proposed. Sorption in the static mode provides the detection limit of europium of 7 × 10−5 µg/mL. The calibration plot is linear in the range of two orders of magnitude of europium concentration in solutions. The relative standard deviation in the determination of 1.5 × 10−2 µg/mL europium is 5%. In the dynamic mode of sorption from 1000 mL of an analyzed solution with the use of sorption-desorption, the detection limit of europium of 8 × 10−7 µg/mL was attained.

Sorption of europium(III) on polymeric silica in perchlorate media

Sorption of europium, Eu(III) with polymeric silicic acid has been studied under varying experimental conditions such as pH, ionic strength (I), concentration of silicic acid and of Eu(III), the presence of carbonate ions, and aging time. Sorption studies of Eu(III) at pH 7.50 ± 0.50) andI= 0.20 M NaClO4indicate 1.32 ± 0.06 × 10-5M Eu as the Critical Coagulation Concentration, CCC. Sorption of Eu(III) on colloidal silica increases with increased ionic strength from 80% (0.20 M NaClO4) to 93% (0.89 M NaClO4). The coagulation process is favored by an increase in silica concentration. The influence of CO32-(1.00 × 10-3M) on the reaction of Eu(III) with polysilicic acid was negligible in the pH range 7.0 to 9.0. Dissolved Eu3+binds more strongly to the silicate polymers than do Cs+and Cu2+.

Sorption of cesium, cobalt and europium on low-rank coal and chitosan

Potential low-cost sorbents of metals based on combined action of coal and chitosan have been investigated. Sorption of Cs, Co and Eu on oxidized coals in mixture with chitosan was studied as function of pH (∼3–6) in batch experiments using radiotracer method. An improved sorption efficiency of the coal sorbents at neutral pH was obtained in mixture with chitosan, namely for oxihumolite at sorption of Eu and Co. Chitosan prevented deterioration of the sorption ability of coal with pH increase probably via retaining the soluble complexes with humic substances leached from coal by formation of an insoluble complex. The effect of chitosan addition was negligible or reverse in case of lignite upon acidification, where the interaction takes place preferentially on the coal surface and may restrict availability of the binding sites for metal ions.

Separation of europium, cobalt and zinc on zirconium tungstate ion exchanger

Amorphous zirconium tungstate inorganic ion-exchanger has been prepared under optimum conditions and characterized by IR, X-ray and thermal analysis. Surface area and capacity are determined. It has characteristic IR absorption peaks at 3242, 1628, 955, 868 and 432 cm-1 and is thermally stable up to 450 °C. Its surface area was 16 m2/g with an exchange capacity of 0.541 meq/g. The sorption of radioactive europium from different media at ambient temperature by the zirconium tungstate (ZW) exchanger has been studied. The aim was to optimize the conditions for sorbing Eu from radioactive waste and cleaned the ZW from for recycling. The effect of contact time, metal concentration, pH and temperature has been measured. Percentual uptake of Eu(III) reaches 95% for HCl at pH 4 and increases with temperature indicating an endothermic sorption process. Uptake of Zn(II) and Co(II) on ZW from acetic acid was found to be 42% and 24% for cobalt and zinc, respectively. Desorption after saturation and the effect of other radioactive ions on the percentual uptake of Eu on ZW were investigated. A solution of 3M HCl releases 90%, 25% and 13% of the loaded Eu(III), Co(II) and Zn(II), respectively.

Separation of europium from aqueous solutions using Al3+- and Fe3+-doped zirconium and titanium phosphates

The sorption of europium from aqueous solutions (Eu-concentration: 10 to 250 mg/l) by Fe3+- and Al3+-doped zirconium- and titanium-phosphates was investigated using a batch technique and 152Eu tracer. The initial pH of the solutions was adjusted to 3, 4, 5 and 6. All investigations were performed under constant ionic strength, I=0.15 established by NaCl. Although zirconium phosphates generally showed a higher Eu-uptake capacity than the titanium ones, all investigated materials possessed the ability to remove considerable amounts of europium from aqueous solutions. The Eu-sorption properties of the studied phosphate materials seem to be not especially affected by the type of trivalent cations used for the doping (i.e., Al3+or Fe3+).

Effect of aqueous acetic, oxalic, and carbonic acids on the adsorption of europium(III) onto α-alumina

Chemical retention, i.e., partition of the element between aqueous solution and mineral surface, is a key phenomenon for assessing the safety of possible nuclear waste disposal. For this purpose, the sorption of Eu(III) onto a model mineral— α-alumina—is studied here, including the effects of groundwater chemistry: pH and concentrations of small organic and inorganic ligands (acetate, oxalate, and carbonate anions). This work presents some experimental evidence for a synergic mechanism of sorption of europium–ligand complexes onto the alumina. Only cationic complexes were necessary to consider to model experimental results. Using the ion-exchange theory (IET) and a corresponding restricted set of parameters—exchange capacities and thermodynamic equilibrium constants—the whole set of sorption experiments of Eu(III) cationic species onto the α-alumina was modeled under various chemical conditions.

An Experimental Approach on the Effect of Rock Alteration on Sorption Behavior

ABSTRACTIn the geological disposal of radioactive wastes, cement used for the repository construction alters the condition of groundwater to highly alkaline of pH about 13. Such alkaline groundwater around the repository would alter the surfaces of the rocks in the flow paths to the amorphous phase. Once the surface is altered, it takes a geological period (so much long time) to restore the surface to its former condition. This study examined the sorption behavior of europium (Eu-152 (tracer), Eu-151 (5×10-5 M, carrier) onto some silica minerals with polymeric silicic acid. Polymeric silicic acid also affects the alteration of the solid surface.The results showed that the kinds of silica minerals strongly affect the sorption behavior in the range of 5&lt;pH&lt;8. The main difference was due to the degree of crystallization of the solid phase, the specific surface area and the concentration of polymeric silicic acid. Since the amorphous silica or polymeric silicic acid takes a loose structure, the isoelectric point is high compared to the crystal ones such as opal-CT and cristobalite, which in turn decreases the sorption. The crystalline silica with polymeric silicic acid remarkably decreased the sorption of europium. This suggested that the surface of solid phase was altered by polymeric silicic acid.

Temperature effected sorption of europium(III) onto 1-(2-pyridylazo)-2-naphthol impregnated polyurethane foam

The sorption of Eu(III) ions onto PAN loaded PUF has been optimized and investigated under the influence of various temperatures, i.e., 303, 313 and 323 K. Maximum retention (>96%) of Eu(III) ions (1.79. 10-5M) onto PAN loaded PUF (7.75 mg. ml-1) was achieved after 30-minute equilibration time from pH 7 buffer solution. The variation of sorption with temperature yields the thermodynamic parameters ΔH=79±2 kJ. mol-1, ΔS=276±7 kJ. mol-1. K-1and ΔG=-1.4±0.1 kJ. mol-1at 298 K. The positive value of enthalpy and negative free energy show endothermic and spontaneous nature of sorption, respectively. The sorption data followed Freundlich, Dubinin-Radushkevich (D-R) and Langmuir isotherms at all the three given temperatures. The Freundlich constant 1/n=0.70, 0.62 and 0.55 and sorption capacities C m=10.8 mmol. g-1, 6.1 mmol. g-1and 4.4 mmol. g-1, respectively, decreased with increasing temperature. Similarly, the sorption capacities of D-R isotherm X m=197.6 µmol. g-1, 201.2 µmol. g-1and 137.4 µmol. g-1, also decreased with temperature. However, the sorption free energy E=10.2 kJ. mol-1, 11.2 kJ. mol-1and 12.7 kJ. mol-1, increased with temperature. The monolayer coverage (Q) computed from Langmuir isotherm was 11.1±0.6 µmol. g-1and remains constant at all the three temperatures investigated. However, the binding energy constant bincreased with temperature. The relationship of bwith temperature and differential heat of adsorption (ΔH diff) have been evaluated and discussed.

Influence of temperature on sorption of europium onto smectite: The role of organic contaminants

In the near field environment of a spent fuel or vitrified high level waste repository the temperature in the bentonite buffer will remain elevated for a long time period (>70–90 °C for 1000 years). To analyze the effect of temperature on the sorption, the sorption process of Eu(III) at 25°, 60° and 80 °C was investigated. To examine the sorption process and the influence of organic contaminants, wet chemistry, time-resolved laser fluorescence spectroscopy (TRLFS), XRD and soft X-ray spectromicroscopy (STXM) measurements were performed.Within the experimental time no changes in smectite mineralogy between 25° and 60 °C was observed. At 80 °C with increasing time an increase in the layer charge of the smectite was noticed. The formation of secondary phases was not observed in the experiments. In quartz cuvettes we observed no macroscopic or spectroscopic differences for the Eu(III) sorption from 25° to 80 °C. At low pH values (<5.5) the formation of outer-sphere complexes was observed at the temperatures studied independent of the reaction vessel. In the sorption experiments at higher pH values (>5.5) we noticed differences between the different reaction vessels at 60° and 80 °C. Whereas in quartz cuvettes we measured inner-sphere complexation at all temperatures, the experiments in the high density polyethylene (HDPE) reaction vessels indicated the incorporation of Eu(III) at 60° and 80 °C. It became evident that organic material released out of the HDPE reaction vessels was able to complex Eu(III).

Influence of Ionic Strength on Curium(III and Europium(III) Sorption on Halomonas elongata

(2004). Influence of Ionic Strength on Curium(III and Europium(III) Sorption on Halomonas elongata. Journal of Nuclear Science and Technology: Vol. 41, No. 11, pp. 1125-1127.