Sorption of small amounts of europium(III) on iron(III) hydroxide and oxide

The sorption of small amounts of europium(III) on iron(III) hydroxide and oxide has been studied as a function of pH. The mechanism of sorption is discussed. Optimum conditions have been found for the preconcentration of small or trace amounts of europium(III) by iron(III) hydroxide and oxide. The influence of complexing agents (EDTA, oxalate, tartrate and 5-sulfosalicylic acid) on the sorption of small amounts of europium(III) on iron(III) oxide has also been studied.     

Sorption of a complex of europium (III) with acetylacetone on hydrophobized hexadecyl silica gel and hyper crosslinked polysterene

The sorption of a complex of europium (III) with acetylacetone on silica gel chemically modified with hexadecyl groups (SiO₂-C₁₆) and hyper crosslinked polystyrene (HLPS) was studied. Maximum extraction was observed at pH 5–7 when SiO₂-C₁₆ was used as the sorbent and at pH 4–7 in the case of crosslinked polystyrene. The partition coefficients for HLPS and silica gel were calculated as 7 × 10³ and 1 × 10² cm³/g, respectively. Quantitative extraction of the europium (III) complex was possible in dynamic conditions using a microcolumn (length, 10 mm; internal diameter, 3mm) packed with HLPS at pH 5 (10–50 mL sample volume). Desorption of europium using solutions of nitric acid at different concentrations was investigated. Quantitative desorption was achieved using 5 mL of 1 M HNO₃. A linear range of detection was observed at an amount of europium from 5 to 25 μg in a 10-mL sample (650 nm).     

Aqueous speciation studies of europium(III) phosphotungstate

The incorporation of lanthanide ions into polyoxometalates may be a unique approach to generate new luminescent, magnetic, and catalytic functional materials. To realize these new applications of lanthanide polyoxometalates, it is imperative to understand the solution speciation chemistry and its impact on solid-state materials. In this study we find that the aqueous speciation of europium(III) and the trivacant polyoxometalate, PW9O34 9-, is a function of pH, countercation, and stoichiometry. For example, at low pH, the lacunary (PW11O39)7- predominates and the 1:1 Eu(PW11O39)4-, 2, forms. As the pH is increased, the 1:2 complex, Eu(PW11O39)2 11- species, 3, and (NH4)22[(Eu2PW10O38)4(W3O8(H2O)2(OH)4].44H2O, a Eu8 hydroxo/oxo cluster, 1, form. Countercations modulate this effect; large countercations, such as K+ and Cs+, promote the formation of species 3 and 1. Addition of Al(III) as a counterion results in low pH and formation of [Eu(H2O)3(alpha-2-P2W17O61)]2, 4, with Al(III) counterions bound to terminal W-O bonds. The four species observed in these speciation studies have been isolated, crystallized, and characterized by X-ray crystallography, solution multinuclear NMR spectroscopy, and other appropriate tech-niques. These species are 1, (NH4)22[(Eu2PW10O38)4(W3O8(H2O)2(OH)4].44H2O (P; a=20.2000(0), b=22.6951(6), c=25.3200(7) A; alpha=65.6760(10), beta=88.5240(10), gamma=86.0369(10) degrees; V=10550.0(5) A3; Z=2), 2, Al(H3O)[Eu(H2O)2PW11O34].20H2O (P, a=11.4280(23), b=11.5930(23), c=19.754(4) A; alpha=103.66(3), beta=95.29(3), gamma=102.31(3) degrees; V =2456.4(9) A3; Z=2), 3, Cs11Eu(PW11O34)2.28H2O (P; a=12.8663(14), b=19.8235(22), c=21.7060(23) A; alpha=114.57(0), beta=91.86(0), gamma=102.91(0) degrees ; V=4858.3(9) A3; Z=2), 4, Al2(H3O)8[Eu(H2O)3(alpha-2-P2W17O61)]2.29H2O (P; a=12.649(6), b=16.230(8), c=21.518(9) A; alpha=111.223(16), beta=94.182(18), gamma=107.581(17) degrees ; V=3842(3) A3; Z=1).     

Sorption studies of strontium on hydrous zirconium dioxide

Summary Hydrous zirconium dioxide was prepared to study the sorption behavior and the removal of strontium from radioactive waste solutions. The hydrous zirconium dioxide were identified and characterized. The parameters affecting the strontium adsorption were investigated. Sorption data have been interpreted in terms of Langmuir equations. Thermodynamic parameters for the sorption system have been determined at 303, 313, 323 and 333 K temperatures. The values ofDH°=102.30 kJ/mol andDG°=-26.03 kJ/mol at 313 K prove that the sorption of strontium on hydrous zirconium oxide is an endothermic and a spontaneous process.     

Kinetic and thermodynamic studies of cesium(I) sorption on hydrous silica

Summary Batch sorption experiments of cesium, Cs⁺, on SiO₂ ^. xH₂O (silica gel) have been conducted with variable times of equilibration, amounts of silica gel (0.10-1.00 g), cesium concentrations (5.00 ^. 10^-5-2.40 ^. 10^-3M), ionic strengths (0.20-1.40M NaClO₄), pH (2.50-7.70), and temperatures (273-333 K). The diffusion coefficient of Cs⁺ ion was calculated to be (9.19±0.86) ^. 10^-11 m^{2 .} s^-1 under particle diffusion-controlled conditions. The sorption rate was (3.94±0.65) ^. 10^-3 s^-1 at 298 K, pH 7.70±0.05 in 0.20M NaClO₄. The sorption data fits the Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Cesium sorption on 0.20 g silica gel decreased with ionic strength from (40.42±0.34)% in 0.20M NaClO₄ to (6.35±0.40)% in 1.40M NaClO₄, at pH_(initial) 8.20±0.05. A gradual decrease in pH with increased ionic strength is consistent with a cation-exchange mechanism. Sorption of Cs⁺ on silica gel decreased with increased temperature, indicating an exothermic enthalpy. The presence of anions such as fluoride, carbonate, phosphate and oxalate in the aqueous medium did not influence the cesium sorption profile.     

Sorption of trace amounts of ruthenium,manganese and europium on iron(III) hydroxide

Summary The effect of pH on the sorption of trace amounts of ruthenium, manganese and europium on iron(III) hydroxide was studied by radiotracer techniques. The effect of amount of sorbent and duration of the contact between the sorbate and the sorbent were also studied. The results indicate that an iron(III) hydroxide precipitate can be used for the preconcentration of traces of ruthenium, manganese and europium.

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Zusammenfassung Der Einfluß des pH auf die Adsorption von Spuren Ruthenium, Mangan und Europium an Eisen (III) hydroxid wurde untersucht. Die Wirkung der Menge Adsorptionsmittel und die Dauer des Kontaktes zwischen diesem und dem Adsorbat wurden gleichfalls geprüft. Die Ergebnisse zeigen, daß Eisen(III)hydroxidniederschläge für die Anreicherung der erwähnten Spuren geeignet sind.

     

Sorption of uranyl ion on hydrous silica: Effects of ionic strength and ethylenediaminetetraacetic acid (EDTA)

The effects of ionic strength and of ethylenediamin et etraacetic acid (EDTA) on the sorption of uranyl ion, UO₂ ²⁺, to SiO₂·xH₂O (silica gel) were investigated. It was observed that pH and the ions present in the supporting electrolytes influence the ionic strength effects. The presence of different sodium salts in the concentration range (0.20 to 1.40M) suppressed the sorption of UO₂ ²⁺ in the order: NaNO₃ < NaClO₄ < NaCl < NaOCOCH₃ < Na₂SO₄ [pH 2.75(±0.05)], while the presence of perchlorate salts of Li⁺, Na⁺ and Ca²⁺ (0.20 to 1.40M) promoted the sorption of UO₂ ²⁺ on silica gel in the order: LiClO₄∼NaClO₄<Ca(ClO₄)₂ at pH 2.80(±0.05). The ionic strength effect on UO₂ ²⁺ sorption was studied in presence of EDTA (0–1.00·10⁻³M) in the pH range 2.90 to 5.57. The sorption data and speciation calculation suggest negligible complexation of UO₂ ²⁺ with EDTA at I≥1.00M NaClO₄. On leave from Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400 085, India.     

Facile synthesis and luminescence properties of europium(III)-doped silica nanotubes

Photoluminescent nanomaterials had emerged as an amazing field in a wide range of applications during the past few decades. In this article, fibrous europium tartrates and photoluminescent silica nanotubes were conveniently synthesized by using sol–gel method, in which europium ions entered silica matrix. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, fourier transform infrared spectra, energy-dispersive X-ray spectroscopy and photoluminescence (PL) spectra analysis were used to characterize the growth, structure, morphology and optical property of the products. The results indicated that europium tartrates nanofibers as a template can transform tetraethylorthosilicate into silica nanotubes effectively. Meanwhile, europium(III) was transferred from the fibers to the tubes successfully. A hard template mechanism was proposed to explain the formation process of europium(III)-doped silica nanotubes. Moreover, different morphologies of silica-based nanomaterials were obtained due to varying NH₄OH addition or stirring time. PL spectra from nanofiber and nanotube show a typical emission of europium(III), and 13 % is the quenching concentration of europium(III) in silica matrix for this system. The novel silica nanotubes can be applied potentially in optical and biological areas.     

Luminescent properties of silica and zirconia xerogels doped with europium(III) salts and europium(III) cryptate incorporating 3,3-biisoquinoline-2,2-dioxide

Eu⁺³ cryptate with 3,3^′-biisoquinoline-2,2^′-dioxide unit was incorporated into glass films consisting of zirconia dioxide and into hybrid ormosil films. The absorption and the emission intensities of the europium complex were compared to the intensity of the non-complexed europium ion in the films. The transition probabilities of the complex are increased as a result of the mixing of the europium orbitals with the ligand orbitals. The emission is additionally increased as the non-radiative relaxation is diminished by the cage effect.     

Sorption studies of europium on cerium phosphate using Box-Behnken design

Amorphous cerium phosphate was prepared and characterized. Three-level Box-Behnken design (BBD) was employed to analyze the effect of process variables such as initial pH (2–6), contact time (60–180 min), and sorbent amount (0.05–0.15 g) on the sorption capacity of europium. Analysis of variance (ANOVA) revealed that the main effect of initial pH and sorbent amount has a substantial impact on the sorption of Eu(III). Probability F-value (F = 3 × 10^-3) and correlation coefficient (R2 = 0.97) point out that the model is in good accordance with experimental data. The maximum sorption capacity of Eu(III) was found to be 42.14 mg g^-1 at initial pH 6, contact time of 180 min, and a sorbent amount of 0.05 g. Sorption isotherm data was well explained by the Langmuir model and monolayer Eu(III) sorption capacity was obtained as 30.40 mg g^-1. Kinetic data were well described by the pseudo-second-order model. Thermodynamic data suggested that the process is endothermic and spontaneous.     

Sorption of hydrolytic products of iron(III), aluminium(III) and chromium(III) on the silica column and its analytical use

Summary The influence of pH upon the sorption of hydrolytic products of Fe³⁺, Al³⁺, and Cr³⁺ on silica was studied under kinetic conditions. The capacity of the silica column and the influence of ionic strength upon the sorption were investigated. The results obtained are utilized for the pre-concentration of trace amounts of Al³⁺, and Fe³⁺ and their separation from an excess of several other metals (e.g. Cr, Cu, Zn, Co) at pH 4.5. The separation of Al³⁺ traces from an excess of Fe³⁺ was achieved by reduction and masking of Fe with thioglycollic acid.

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Zusammenfassung Es wurde eine Untersuchung durchgeführt über die Sorption von Hydrolyseprodukten von Fe(III), Al(III) und Cr(III) an Silicasäulen und die Abhängigkeit vom pH-Wert, von der Kapazität der Säule und der Konzentration an Fremdsalzen (KCl, KNO₃) wurde geprüft. Analytische Anwendungsmöglichkeiten ergaben sich in der Anreicherung von Al³⁺- und Fe³⁺-Spuren und ihrer Trennung von anderen Elementen (z.B. Cr, Cu, Zn, Co) sowie in der Trennung von Al³⁺-Spuren von überschüssigem Fe³⁺, wobei letzteres mit Hilfe von Thioglykolsäure reduziert und maskiert wurde.

     

Sorption of iron(III) in ionic and colloidal states on iron(III) oxide deposited on a silica gel sufrace

The sorption of iron(III) in ionic and colloidal states on iron(III) oxide deposited on a silica gel surface has been studied as a function of pH of aqueous solution by batch equilibrations. The behaviour of Fe³⁺ and colloidal Fe(III) on the sorbent column has also been investigated. Conditions for sorption of iron from aqueous solutions are given. The colloidal iron(III) can be quantitatively separated from Fe³⁺ on the sorbent column under given experimental conditions.     

Sorption of europium and actinides by means of octyl(phenyl)-N,N-diisobutyl carbamoylmethyl phosphine oxide (CMPO) loaded on silica

The octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), loaded as stationary phase on silica, has been used for the sorption of Eu and actinides from acidic aqueous solution. Different commerical solid support were investigated and, finally SiO₂ was chosen. Experiments were performed to obtain basic data on actinide removal. Distribution coefficients, kinetics, sorption isotherms (three adsorption model correlations were tested) and the acidic concentration effect were studied.     

A triboluminescent europium(III) complex

The crystal structure of (4,4′‐di­methyl‐2,2′‐bipyridyl)­tris­[3,3,3‐tri­fluoro‐1‐(2‐thenoyl)propan‐2‐onato]­europium(III), or more commonly (4,4′‐dimethyl‐2,2′‐bipyridyl)tris(2‐thenoyltrifluoro­acetonato)europium(III), [Eu(C₈H₄F₃O₂S)₃(C₁₂H₁₂N₂)], has been determined. Crystals of the complex emit vivid red light when scratched or fractured. This triboluminescent activity seems to correlate with the non‐centrosymmetric crystal structure and disorder of the thienyl rings and CF₃ groups which is present here and in similar compounds. While modeling the thienyl‐ring disorder, it was noted that the bond angle at the C atom replaced by S is a sensitive sign of even small rotational ring disorder. The coordination geometry of the Eu^III ion can be described as square antiprismatic, with coordination by the six O atoms of the three chelating β‐diketonate ligands and the two N atoms of the neutral bipyridyl ligand.     

Ionic liquid modified silica gel for the sorption of americium(III) and europium(III) from dilute nitric acid medium

The imidazolium bis(2-ethylhexyl) phosphate moiety was chemically attached on silica gel by chemical modification. The resulting product ([SG-Im]⁺ [DEHP]^?) was characterized by FT-IR spectroscopy, thermogravimetry and elemental analysis. The sorption behavior of Am(III) and Eu(III) on [SG-Im]⁺ [DEHP]^? was studied from dilute nitric acid medium for the separation of Am(III) and Eu(III) from aqueous waste. The effect of time, concentrations of nitric acid and europium in aqueous phase on the distribution coefficient (K _d) was studied. The study indicated the possibility of using modified silica for the separation of Eu(III) from Am(III) with high separation factors (>50 at 0.1 M HNO₃).     

Tetracycline determination by sensitized luminescence of europium(III) sorbed on silica with chemically grafted iminodiacetic acid

The formation of mixed-ligand europium(III) complexes with tetracycline and iminodiacetic acid grafted to the surface of silica has been studied. This complex is suggested for luminescence determination of tetracycline in solutions.     

Sorption of iron(II) and ruthenium(III)-triazine complexes on silica gel and its analytical applicability

2,4,6-Tri(2′-pyridyl)-s-triazine (TPTZ) complexes with iron(II) and ruthenium(III) were prepared. Their sorption and desorption features on silica gel have been investigated. Both complexes were strongly adsorbed. This has been utilized for separating and preconcentrating iron(II) and ruthenium(III) using TPTZ-impregnated silica gel. The chromatographic behavior of TPTZ on silica gel column was examined and found to be effective modifier for silica gel surface. The sorption capacity of silica gel for those metal-triazine complexes has been determined under static conditions and was found to be 5.28 × 10^–3 mM (Fe(TPTZ)₂²⁺) and 2.9 × 10^–3 mM (Ru(TPTZ)₂³⁺). Saturated methanolic solutions of KI or 25% NaClO₄ solutions desorbed both complexes quantitatively from the silica gel surface.     

Photoresponsive europium(III) complex based on photochromic reaction

Luminescence properties and their photoinduced control of the electric dipole transitions of a Eu(III) complex that has photochromic triangle terarylenes ligands, tris(hexafluoroacetylacetonato)bis[4,5-bis(5-methyl-2-phenylthiazol-4-yl)-2-phenylthiazole]europium(III) (Eu(hfa)3(THIA)2), were studied. Fairly high photochromic reactivity of the ligand between the open-ring and closed-ring forms were found to be maintained even in the complex, and reversible color change could be observed many times. The photocyclization and the cycloreversion quantum yields of the Eu(hfa)3(THIA)2 were found to be 37% and 3.4%, respectively. The thermal stability of the closed-ring form of THIA ligand is significantly improved in the Eu(III) complex. The (5)D0-(7)F2 transition intensity of the Eu(III) complex with open-ring form ligands (Eu(hfa)3(THIA)2-O) is larger than that of the Eu(III) complex with closed-ring form ligands (Eu(hfa)3(THIA)2-C). The radiative rate constants of Eu(hfa)3(THIA)2-O and Eu(hfa)3(THIA)2-C are estimated to be 1.7 x 10(2) and 1.5 x 10(2) s(-1), respectively. The reversible control of the emission properties of the Eu(III) complex by the photochromic reactions is demonstrated for the first time.     

pH-sensitive fluorescent sensors based on europium(III) complexes

New europium(III) complexes Eu(TTA)(2)-DSQ and Eu(TTA)(3)-DR1 were designed and synthesized as new fluorescent pH probes (where HDSQ = 5-(dimethylamino)-N-(4-(2-((8-hydroxyquinolin-2-yl)methylene)hydrazinecarbonyl)phenyl)naphthalene-1-sulfonamide, DR1 = N(1)-(4-(dimethylamino)benzylidene)-N(2)-(rhodamine-6G) lactamethylene-diamine and TTA = thiophentrifluoroacetone). Eu(TTA)(2)-DSQ exhibited high sensitivity in monitoring pH changes in neutral aqueous solution with negligible background fluorescence. Eu(TTA)(3)-DR1 comprised a green light emitting Rhodamine 6G fluorophore and a Eu(III) moiety as the origin of red light. These pH-sensitive emitter components have pK(a) values of 5.0 and 7.2 respectively, and exhibit isolated protonated steps within one molecule. Luminescence titrations demonstrate that Eu(TTA)(3)-DR1 was able to detect pH values at both near neutral pH and acidic pH ranges, and was also able to detect pH in both cultured cells and in vivo.