Selective and Reversible Fluoride Complexation from Water by a Cyclic Tri(phosphonio)methanide Dication

2017 ◽  
Vol 56 (27) ◽  
pp. 7907-7911 ◽  
Author(s):  
Sivathmeehan Yogendra ◽  
Felix Hennersdorf ◽  
Antonio Bauzá ◽  
Antonio Frontera ◽  
Roland Fischer ◽  
...  
Keyword(s):  
Fluoride Complexation

Minerály řady bavenit-bohseit z pegmatitu Schinderhübel I v Maršíkově (silezikum, Česká republika)

2020 ◽  
Vol 28 (2) ◽  
pp. 353-358
Author(s):  
Zdeněk Dolníček ◽  
Miroslav Nepejchal ◽  
Milan Novák
Keyword(s):  
Czech Republic ◽  
Early Stage ◽  
Chemical Fractionation ◽  
Potential Importance ◽  
Pegmatite Body ◽  
Fluoride Complexation ◽  
Hydrothermal Stage ◽  
Ca 50 ◽  
Primary Minerals ◽  
Identical Behaviour

Bavenite and bohseite were found in an archive sample from Schinderhübel I granitic pegmatite, situated ca. 50 m NE from the famous chrysoberyl-bearing pegmatite body Schinderhübel III near Maršíkov (Silesicum, Czech Republic). Minerals of the bavenite-bohseite series together with minor quartz, muscovite and albite form chalky white radial aggregates up to 3.5 cm in size within a fissure cutting the pegmatite. The electron microprobe data revealed 29.0 - 65.4 mol. % of bavenite component, 0.03 - 0.12 apfu Na and 0.05 - 0.20 apfu F. Bavenite seems to be older than bohseite in the studied aggregate. The collected data suggest significant increase of Be/Al during growth of the studied aggregate, which could be explained in two ways. First, one can assume that different primary minerals with contrasting Be/Al ratios were dissolved during different stages of alteration (i.e., chrysoberyl in the early stage giving rise to bavenite-rich compositions and beryl during late stage giving rise to bohseite-rich members). Second, chemical fractionation of Be and Al due to complexation by fluoride anions is suggested from negative correlation between Al and F in the studied members of the bavenite-bohseite series. Identical behaviour is observed also in bavenite-bohseite from Piława Górna and Maršíkov D6e pegmatites, suggesting potential importance of fluoride complexation during hydrothermal stage of evolution of granitic pegmatites.

Fluoride Complexation of Element 104, Rutherfordium

2004 ◽  
Vol 126 (16) ◽  
pp. 5219-5224 ◽  
Author(s):  
Hiromitsu Haba ◽  
Kazuaki Tsukada ◽  
Masato Asai ◽  
Atsushi Toyoshima ◽  
Kazuhiko Akiyama ◽  
...  
Keyword(s):  
Fluoride Complexation

Unraveling Zr/Hf fractionation: Hydrothermal zirconium and hafnium fluoride complexation up to 400°C

2020 ◽  
Author(s):  
Anselm Loges ◽  
Marion Louvel ◽  
Max Wilke ◽  
Sthephan Klemme ◽  
Timm John ◽  
...  
Keyword(s):  
Hydrothermal Systems ◽  
Effect Of Temperature ◽  
Data Sets ◽  
Strong Temperature Dependence ◽  
Aqueous Solvent ◽  
Fluoride Complexation ◽  
Fluoride Complexes ◽  
The Stability ◽  
Hydrothermal Environments ◽  
Aqueous Complexes

<p>High field strength elements (HFSE) such as Zr and Hf are relatively insoluble in most natural hydrothermal solutions and consequently immobile in most geological systems. However, fluoride forms stable aqueous complexes with many HFSE ions, including Zr<sup>4+</sup> and Hf<sup>4+</sup>, and is thus a potent mobilizer of these elements. Due to their identical charge and similar ionic radius (590 pm and 580 pm, respectively), Zr and Hf behave almost identically in geological system and are therefore referred to as geochemical twins. Fluoride complexation in hydrothermal environments is one of few processes in the Earth's crust that can effectively fractionate them from one another. This fact can be used to trace past fluoride activity in fossil hydrothermal systems by investigating Zr/Hf ratios, if fluoride complexation of Zr and Hf is sufficiently well understood. Mobility of metals as complexes is controlled by two distinct but related mechanisms: Formation of the complex itself and solvation of that complex in the solvent. Poly(hydrogen-fluoride) bridging of fluoride complexes to the surrounding aqueous solvent is crucial to the understanding of the solvation and therefore the mobility of fluoride complexes.</p><p>We report geometries of Zr and Hf fluoride complexes up to 400°C, determined by extended X-Ray absorption fine structure (EXAFS) in a hydrothermal autoclave. Existing data sets on the stability of those complexes at lower temperatures are extended to 400°C. Our data show strong temperature dependence of the complex stability for both metals. However, the effect of temperature is not equally strong for Zr and Hf. Fractionation of the twin pair is thus a function of temperature as well as fluoride activity.</p>

Kinetics of aluminium fluoride complexation in single- and mixed-ligand systems

Talanta ◽  
1992 ◽  
Vol 39 (11) ◽  
pp. 1531-1535 ◽  
Author(s):  
Geoffrey S. Townsend ◽  
Bryon W. Bache
Keyword(s):  
Mixed Ligand ◽  
Aluminium Fluoride ◽  
Fluoride Complexation ◽  
Kinetics Of

Modeling and Simulation studies for Aluminium - Fluoride Interactions in Nalgonda Defluoridation Process

2009 ◽  
Vol 4 (1) ◽  
Author(s):  
Suja George ◽  
Prabhat Pandit ◽  
Akhilendra Bhushan Gupta ◽  
Madhu Agarwal
Keyword(s):  
Secondary Data ◽  
Fluoride Ions ◽  
Treated Water ◽  
Preferential Adsorption ◽  
Aluminium Fluoride ◽  
Fluoride Complexation ◽  
Charged Site ◽  
Minimum Residual ◽  
Complexation Reactions ◽  
Residual Al

A model simulator NALD-2 has been developed to study the interactions of fluoride and aluminium in the Nalgonda Defluoridation Process, which principally involves the preferential adsorption of fluoride ions onto insoluble aluminium hydroxides that are formed from alum hydrolysis reactions and undergo precipitation. This model represents the defluoridation mechanism taking into account the charged behavior of the amphoteric aluminium hydroxide colloids, charged site densities, and fluoride complexation reactions in order to predict the extent of defluoridation and concentrations of dissolved and colloidal aluminium in the treated water as functions of pH, alum dosage and raw fluoride concentrations. Model validations were carried out using secondary data of Selvapathy & Arjunan (1995) for total residual aluminium in Nalgonda treated water. Slight variations in pH into the acidic range cause substantial increase in colloidal aluminium and hence pH and alum dosages are important control parameters to limit residual aluminium in treated water. The NALD-2 simulator helps in predicting optimum alum dosages for minimum residual aluminium in the treated water. It was concluded that the dosages of alum recommended in the Nalgonda method cannot bring down the residual Al below the permissible limit of 0.2mg/L in the treated water.

ChemInform Abstract: Solution Thermodynamics of Europium-Fluoride Complexation.

ChemInform ◽  
1987 ◽  
Vol 18 (25) ◽  
Author(s):  
P. A. BAISDEN ◽  
P. M. GRANT ◽  
W. F. KINARD ◽  
R. A. TORRES
Keyword(s):  
Solution Thermodynamics ◽  
Fluoride Complexation

scholarly journals Fluoride complexation of rutherfordium (Rf, element 104)

2000 ◽  
Vol 88 (5) ◽  
Author(s):  
E. Strub ◽  
Jens Volker Kratz ◽  
A. Kronenberg ◽  
A. Nähler ◽  
P. Thörle ◽  
...  
Keyword(s):  
Group 4 ◽  
Fluoride Complexation

The fluoride complexation of the group-4 elements Zr, Hf and Rf, and of the pseudo-homolog Th, has been investigated in mixed HNO

Sign in / Sign up

Export Citation Format

Share Document