Do the lanthanides form inner sphere complexes with ClO4− ions in competition with H2O molecules?

1992 ◽  
Vol 31 (1-2) ◽  
pp. 117-122 ◽  
Author(s):  
E. Huskowska ◽  
J. Legendziewicz ◽  
Th. Schleid ◽  
G. Meyer
Keyword(s):  
Inner Sphere ◽  
Inner Sphere Complexes

Surface Complexation of Neptunium(V) with Goethite

2006 ◽  
Vol 985 ◽  
Author(s):  
James L Jerden ◽  
A Jeremy Kropf
Keyword(s):  
Sodium Chloride ◽  
Sodium Silicate ◽  
Outer Sphere ◽  
Distribution Coefficients ◽  
Batch Adsorption ◽  
Inner Sphere ◽  
Show Evidence ◽  
X Ray Absorption ◽  
Outer Sphere Complexes ◽  
Inner Sphere Complexes

AbstractBatch adsorption experiments in which neptunium bearing solutions were reacted with goethite (alpha-FeOOH) have been performed to study uptake mechanisms in sodium chloride and calcium-bearing sodium silicate solutions. This paper presents results identifying and quantifying the mechanisms by which neptunium is adsorbed as a function of pH and reaction time (aging). Also presented are results from tests in which neptunium is reacted with goethite in the presence of other cations (uranyl and calcium) that may compete with neptunium for sorption sites. The desorption of neptunium from goethite has been studied by resuspending the neptunium-loaded goethite samples in solutions containing no neptunium. Selected reacted sorbent samples were analyzed by x-ray absorption spectroscopy (XAS) to determine the oxidation state and molecular speciation of the adsorbed neptunium. Results have been used to establish the pH adsorption edge of neptunium on goethite in sodium chloride and calcium-bearing sodium silicate solutions. The results indicate that neptunium uptake on goethite reaches 95% at a pH of approximately 7 and begins to decrease at pH values greater than 8.5. Distribution coefficients for neptunium sorption range from less than 1000 (moles/kg)sorbed / (moles/kg)solution at pH less than 5.0 to greater than 10,000 (moles/kg)sorbed / (moles/kg)solution at pH greater than 7.0. Distribution coefficients as high as 100,000 (moles/kg)sorbed / (moles/kg)solution were recorded for the tests done in calcite equilibrated sodium silicate solutions. XAS results show that neptunium complexes with the goethite surface mainly as Np(V) (although Np(IV) is prevalent in some of the longer-duration sorption tests). The neptunium adsorbed to goethite shows Np-O bond length of approximately 1.8 angstroms which is representative of the Np-O axial bond in the neptunyl(V) complex. This neptunyl(V) ion is coordinated to 5 or 6 equatorial oxygens with Np-O bond lengths of 2.45 angstroms. The absence of a clearly recognizable Np-Fe interaction for the sodium chloride sorption tests suggests that neptunium in these solutions adsorbs as an outer-sphere complex. XAS results from the calcium-bearing sodium silicate sorption tests show evidence for a neptunyl(V) inner-sphere surface complex with a Np-Fe interaction at 3.5 angstroms. Desorption tests indicate that samples in which neptunium is bound as inner-sphere complexes show significant sorption hysteresis relative to samples in which neptunium is bound largely as outer-sphere complexes.

Quantum chemical study of inner-sphere complexes of trivalent lanthanide and actinide ions on the corundum (0001) surface

2010 ◽  
Vol 98 (9-11) ◽  
pp. 627-634 ◽  
Author(s):  
Robert Polly ◽  
Bernd Schimmelpfennig ◽  
Thomas Rabung ◽  
Mathias Flörsheimer ◽  
Reinhardt Klenze ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Trivalent Lanthanide ◽  
Inner Sphere ◽  
Actinide Ions ◽  
Inner Sphere Complexes

Enthalpies of formation of Cr3+(aq) and the inner sphere complexes CrF2+(aq), CrCl2+(aq), CrBr2+(aq), and CrSO4+(aq)

1976 ◽  
Vol 54 (9) ◽  
pp. 1383-1387 ◽  
Author(s):  
Ingemar Dellien ◽  
Loren G. Hepler
Keyword(s):  
Enthalpies Of Formation ◽  
Calorimetric Measurements ◽  
Inner Sphere ◽  
Inner Sphere Complexes

We have carried out calorimetric measurements leading to ΔHf0 = −60 kcal mol−1 for Cr3+(aq). Further calorimetric measurements have led to enthalpies of reaction of Cr3+(aq) with HF(aq), Cl−(aq), Br−(aq), and SO42−(aq) to form the 'inner sphere' complexes CrF2+(aq), CrCl2+(aq), CrBr2+(aq), and CrSO4+(aq). Results of our measurements lead to ΔHf0 = (−60.0 ± 1.5) kcal mol−1 for Cr3+(aq), ΔHf0 = −136.8 kcal mol−1 for CrF2+(aq), ΔHf0 = −93.7 kcal mol−1 for CrCl2+(aq), ΔHf0 = −80.1 kcal mol−1 for CrBr2+(aq), and ΔHf0 = −269.7 kcal mol−1 for CrSO4+(aq).

Formation of Outer- and Inner-Sphere Complexes of Lanthanide Elements at Montmorillonite-Water Interface

2000 ◽  
Vol 29 (6) ◽  
pp. 700-701 ◽  
Author(s):  
Yoshio Takahashi ◽  
Akisa Tada ◽  
Takaumi Kimura ◽  
Hiroshi Shimizu
Keyword(s):  
Water Interface ◽  
Lanthanide Elements ◽  
Inner Sphere ◽  
Inner Sphere Complexes

Intensity Analysis and Luminescence Spectra of Non-Aqueous Solutions of Europium Compounds

1983 ◽  
Vol 38 (1) ◽  
pp. 47-55 ◽  
Author(s):  
Janina Legendziewicz ◽  
Grażyna Oczko ◽  
Wiesław Stręk
Keyword(s):  
Oscillator Strengths ◽  
Luminescence Spectra ◽  
Intensity Analysis ◽  
High Concentration ◽  
Predominant Form ◽  
Inner Sphere ◽  
Common Opinion ◽  
Hypersensitive Bands ◽  
The Common ◽  
Inner Sphere Complexes

Abstract The oscillator strengths of the f-f transitions as well the fluorescence spectra for europium Perchlorate, chloride and nitrate in mono- and disubstituted amides have been measured. The Judd-Ofelt parameters are calculated. The formation of inner-sphere europium complexes is discussed on the basis of intensity analysis of the absorption and luminescence spectra. In mono- and disubstituted amides solutions the f-f transitions of Eu+3 have been analysed and the three parameters fitted with satisfactory accuracy. Among all f-f transitions the hypersensitive ones in absorption 7 F0 → 5 D0 and fluorescence 5 D0 → 7 F2 varied most markedly. From an analysis of the data it was concluded that only Eu(NO3)3 and EUCl3 in DMF form inner-sphere complexes. At low concentration of EUCl3 in DMF the predominant form is [EuCl(DMF)y−1]+2 , whereas at high concentration the predominant form is [EUCl2(DMF)y−2]+1 . The intensity of the hypersensitive bands decreases with increasing EUC1 3 concentration, contrary to the common opinion that complexation increases the intensity of hypersensitive bands.

Role of carboxylic and phenolic groups in NOM adsorption on minerals: a review

2006 ◽  
Vol 6 (6) ◽  
pp. 155-164 ◽  
Author(s):  
X.H. Guan ◽  
D.L. Li ◽  
C. Shang ◽  
G.H. Chen
Keyword(s):  
Organic Matter ◽  
Aluminium Hydroxide ◽  
Interaction Strength ◽  
Outer Sphere ◽  
Hydroxyl Groups ◽  
Aromatic Carboxylates ◽  
Inner Sphere ◽  
Outer Sphere Complexes ◽  
Inner Sphere Complexes

This paper presented the current state of our understanding of the roles of carboxylic and phenolic groups in NOM adsorption and reviewed the contradictory opinions in the literatures. Previous studies carried out by other researchers indicated that aromatic carboxylates were adsorbed onto metal (hydr)oxides via outer-sphere complexes under most conditions and phenolic groups were very crucial for formation of inner-sphere complexes between organic acids and metal (hydr)oxides. Adsorption test with in-situ ATR-FTIR spectroscopic investigation were carried out to verify the role of aromatic carboxylic and phenolic groups in the NOM adsorption onto aluminium hydroxide surfaces by using a series of aromatic carboxylic acids and dihydroxybenzoic acids as the surrogate of NOM. Our studies suggested that the formation of outer-sphere complexes dominated the adsorption of most of the aromatic carboxylates over the pH range of 5–9; inner-sphere complexes were only detected at some pH levels for some aromatic carboxylates adsorption; and the aromatic carboxylates were most likely to be adsorbed to the first surface layer of hydroxyl groups and water molecules without forming coordinative bonds with the aluminium hydroxide surfaces but strong hydrogen bonds were formed in this process. Our study also revealed that (1) the presence of phenolic groups can increase the interaction strength of carboxylate groups with aluminium hydroxide; (2) chelate formation involving a carboxylate oxygen atom and ortho-phenolic-oxygen is important for the adsorption of organic matter on aluminium hydroxide at acidic pH; and 3) the phenolic groups adjacent to each other are more important than the carboxylic groups at alkaline pH for organic matter adsorption.

Quantum chemical study of inner-sphere complexes of trivalent lanthanide and actinide ions on the corundum (110) surface

2013 ◽  
Vol 101 (9) ◽  
pp. 561-570
Author(s):  
R. Polly ◽  
B. Schimmelpfennig ◽  
M. Flörsheimer ◽  
Th. Rabung ◽  
T. Kupcik ◽  
...  
Keyword(s):  
Metal Ions ◽  
Density Functional ◽  
Single Point ◽  
Quantum Chemical Study ◽  
Basis Sets ◽  
Water Molecules ◽  
Point Energy ◽  
Inner Sphere ◽  
Sphere Complex ◽  
Inner Sphere Complexes

Summary Sorption plays a major role in the safety assessment of nuclear waste disposal. In the present theoretical study we focused on understanding the interaction of trivalent lanthanides and actinides (La3+, Eu3+ and Cm3+) with the corundum (110) surface. Optimization of the structures were carried out using density functional theory with different basis sets. Additionally, Møller-Plesset perturbation theory of second order was used for single point energy calculations. We studied the structure of different inner-sphere complexes depending on the surface deprotonation and the number of water molecules in the first coordination shell. The most likely structure of the inner-sphere complex (tri- or tetradentate) was predicted. For the calculations we used a cluster model for the surface. By deprotonating the cluster a chemical environment at elevated pH values was mimicked. Our calculations predict the highest stability for a tetradentate inner-sphere surface complexes with five water molecules remaining in the first coordination sphere of the metal ions. The formation of the inner-sphere complexes is favored when a coordination takes place with at most one deprotonated surface aluminol group located beneath the inner-sphere complex. The mutual interaction between sorbing metal ions at the surface is studied as well. The minimal possible distance between two inner-sphere sorbed metal ions at the surface was determined to be 530 pm.

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