Distribution of microamounts of some M2+ ions during ZnSO4·7H2O crystallization

2000 ◽  
Vol 78 (7) ◽  
pp. 993-1002 ◽  
Author(s):  
Marek Smolik
Keyword(s):  
Solid Solutions ◽  
Ionic Radius ◽  
Electronic Configuration ◽  
Distribution Coefficients ◽  
Octahedral Coordination ◽  
Crystal Chemical ◽  
Trace Impurities ◽  
Ionic Radii ◽  
Sulfate Heptahydrate ◽  
D Values

Distribution coefficients (D) of trace amounts of Ni2+, Co2+, Mg2+, Cd2+, Cu2+, Mn2+, Ca2+, and Fe2+ have been determined during crystallization of ZnSO4·7H2O. Their dependencies on the ionic radii of M2+ ions, solubilities and structures of the corresponding sulfates as well as their abilities to form solid solutions with ZnSO4·7H2O have been analyzed. The D values are in the range <0.006 (DCa) - 1.61 (DNi) and depend mainly on similarity of the structures of the corresponding sulfates and the ability of MSO4·nH2O to form solid solutions with ZnSO4·7H2O. The order of lowering some of the determined distribution coefficients (DNi > DMg > DCo > DFe > Dcu) exactly agrees with increase of the deformation trend of octahedral coordination of corresponding ions resulting from their electronic configuration. The D coefficients do not depend on similarity of size of ionic radii of microcomponent (rM2+) to macrocomponent (rZn2+), however for ions forming monoclinic sulfate hydrates at 20°C (Co2+, Fe2+, Cd2+, Ca2+) this dependence of distribution coefficients on rM2+ is linear in a plot of log D against ionic radius. The effect of solubilities of corresponding sulfates in water on the D coefficients is complex and clouded by crystal-chemical factors.Key words: crystallization, zinc(II) sulfate heptahydrate, cocrystallization, distribution coefficients D (Henderson-Kracek, Khlopin), distribution of trace impurities.

Crystal chemical incorporation of high level waste species in aluminotitanate-based ceramics: Valence, location, radiation damage, and hydrothermal durability

1987 ◽  
Vol 2 (3) ◽  
pp. 387-414 ◽  
Author(s):  
P. E. Fielding ◽  
T. J. White
Keyword(s):  
Solid Solutions ◽  
High Level Waste ◽  
Crystal Chemical ◽  
Extended Defects ◽  
Ionic Radii ◽  
Space Groups ◽  
Atomic Displacements ◽  
Compositional Variations ◽  
High Level ◽  
Induced Changes

A compilation is made of the crystallographic mechanisms whereby (simulated) radwaste species are incorporated in the “synroc” phases zirconolite, perovskite, hibonite, and “hollandite.” From these data and consideration of the crystal chemical criteria of valence and effective ionic radii, the most probable host phases for transuranic isotopes are identified. The distinction is drawn between incorporation of radwaste species as dilute homogeneous, continuous solid solutions and as heterogeneous, noncontinuous solid solutions. It is shown that compositional variations at the nanometer level are frequently accompanied by the generation of new interstices within extended defects, which are suitable for the location of radwaste. Nuclides that are unstable towards beta and gamma decay lead to transmutation-induced changes in stoichiometry. Crystallochemical mechanisms that minimize structural disruption during the formation of radiogenic species are discussed. Thermally promoted recovery of metamict phases, which were rendered aperiodic by direct atomic displacements of alpha-recoil nuclei, are examined in terms of recrystallization via the hierarchial arrangement of space groups. An evaluation is made of the hydrothermal durability of synroc phases under conditions likely to be experienced by the wasteform should the repository be breached by groundwaters shortly after disposal.

scholarly journals COMPOSITION AND STRUCTURE OF THE HUNTITE-FAMILY COMPOUNDS

2018 ◽  
Vol 13 (6) ◽  
pp. 42-51 ◽  
Author(s):  
I. A. Kaurova ◽  
D. M. Gorshkov ◽  
G. M. Kuz'micheva ◽  
V. B. Rybakov
Keyword(s):  
Rare Earth ◽  
Solid Solutions ◽  
Initial Mixture ◽  
Crystal Chemical ◽  
Ionic Radii ◽  
Composition And Structure ◽  
Polymorphic Modifications ◽  
Rare Earth Borate ◽  
The Difference

The literature data on the composition and structure of rare-earth borate compounds of the huntite family with the general composition LnM3(BO3)4, where Ln3+ = Y, La = Lu and M3+ = Al, Fe, Cr, Ga, Sc as well as a number of solid solutions with М3+ = Sc are systematized. The difference between the real compositions of crystals and the compositions of the initial mixture, the most characteristic of rare-earth scandium borates, is shown. The significant role of the composition in the manifestation of the compounds symmetry is established. The necessity of determining the crystals symmetry only on single-crystals with detailed analysis of diffraction reflections is proved. Morphotropic series were selected depending on changes in the ionic radii of Ln and M. Attention is paid to the peculiarity of the structural behavior of Cr3+ ions. It was revealed that the formation of solid solutions and internal solid solutions is most likely for rare-earth scandium borates. The implementation of polytypic modifications for LnM3(BO3)4, where M3+ = Al, Cr, and polymorphs for a number of Ln ions with M3+ = Fe, the existence of which is not excluded for M3+ = Sc, is demonstrated. Crystal-chemical effects observed for huntite-like crystals (morphotropy, isomorphism, polymorphism, polytypy; internal solid solutions; phase order-disorder phase transitions of different nature) with specific features of scandium borates are presented. The realization of polymorphism and polytypism for compounds of the huntite family confirms the crystal-chemical situation, according to which hightemperature polymorphic modifications should form more symmetrical compounds, but it is not typical of polytypic modifications.

scholarly journals Conductivity inversion in CdSeхTe1-х solid solutions

2019 ◽  
Vol 60 (11) ◽  
pp. 16-20
Author(s):  
Alexey P. Belyaev ◽  
◽  
Vladimir P. Rubetz ◽  
Vladimir V. Antipov ◽  
Dmitry A. Mokhorov ◽  
...  
Keyword(s):  
Solid Solutions ◽  
Hall Mobility ◽  
Ionic Radius ◽  
High Resistivity ◽  
Sharp Change ◽  
Potential Relief ◽  
Ionic Radii ◽  
Long Time ◽  
The Difference ◽  
High Concentrations

The results of electrical studies of CdSeхTe1-х solid solutions synthesized using the zone of additional heating of the vapor phase are presented. It is established that solid solutions are dishonorable systems. It was found that CdSeхTe1-х solid solutions are characterized by: high resistivity (at T = 298 K up to 109 Ohm∙cm), which increases with tellurium content. It was found that a high value of activation energy (up to 0.64 eV), monotonously decreasing with temperature; an abnormally long time to establish equilibrium after a sharp change in temperature; low Hall mobility (at T = 413 K no more than 100 cm2V-1s-1). It is established that the solid solutions are systems with a high degree of compensation and an inhomogeneous potential relief of the bands due to disordering of the structure. The disordering of the structure in CdSeхTe1-х solid solutions is due to the difference in ionic radii. The ionic radius of cadmium is small (1.03Å), and the ionic radius of tellurium is large (2.21Å). Such systems are characterized by the Frenkel type of natural disorder. An increase in the tellurium content in them promotes the formation of cadmium VCd vacancies with acceptor properties, which at high concentrations lead to an inversion of the type of conductivity from electron to hole. Temperature and concentration dependences of conductivity and Hall mobility are given.

Partition of Microamounts of Some M2+ Ions During MgSO4.7H2O Crystallization

1999 ◽  
Vol 52 (6) ◽  
pp. 425 ◽  
Author(s):  
Marek Smolik
Keyword(s):  
Solid Solutions ◽  
Partition Coefficients ◽  
Ionic Radii ◽  
D Values

Partition coefficients (D) of trace amounts of Ni2+, Co2+, Zn2+, Cd2+, Cu2+, Mn2+, Ca2+, and Fe2+ have been determined during crystallization of MgSO4.7H2O. Their dependences on the ionic radii of the M2+ ions, solubilities and structures of the corresponding sulfates, as well as the abilities of the microcomponents to form solid solutions with MgSO4.7H2O have been analysed. The D values are in the range from <0·005 (DCa) to 1·13 (DNi) and depend mainly on the ionic radii of the M2+ ions, as well as the structures of the corresponding sulfates and the ability to form solid solutions with the macrocomponent.

Quantification of excess 231Pa in late Quaternary igneous baddeleyite

2020 ◽  
Vol 105 (12) ◽  
pp. 1830-1840 ◽  
Author(s):  
Yi Sun ◽  
Axel K. Schmitt ◽  
Lucia Pappalardo ◽  
Massimo Russo
Keyword(s):  
Late Quaternary ◽  
Central Italy ◽  
Direct Analysis ◽  
Weight Percent ◽  
Volcanic Field ◽  
Distribution Coefficients ◽  
Secular Equilibrium ◽  
Melt Distribution ◽  
D Values ◽  
Significant Figures

Abstract Initial excess protactinium (231Pa) is a frequently suspected source of discordance in baddeleyite (ZrO2) geochronology, which limits accurate U/Pb dating, but such excesses have never been directly demonstrated. In this study, Pa incorporation in late Holocene baddeleyite from Somma-Vesuvius (Campanian Volcanic Province, central Italy) and Laacher See (East Eifel Volcanic Field, western Germany) was quantified by U-Th-Pa measurements using a large-geometry ion microprobe. Baddeleyite crystals isolated from subvolcanic syenites have average U concentrations of ~200 ppm and are largely stoichiometric with minor abundances of Nb, Hf, Ti, and Fe up to a few weight percent. Measured (231Pa)/(235U) activity ratios are significantly above the secular equilibrium value of unity and range from 3.4(8) to 14.9(2.6) in Vesuvius baddeleyite and from 3.6(9) to 8.9(1.4) in Laacher See baddeleyite (values within parentheses represent uncertainties in the last significant figures reported as 1σ throughout the text). Crystallization ages of 5.12(56) ka (Vesuvius; MSWD = 0.96, n = 12) and 15.6(2.0) ka (Laacher See; MSWD = 0.91, n = 10) were obtained from (230Th)/(238U) disequilibria for the same crystals, which are close to the respective eruption ages. Applying a corresponding age correction indicates average initial (231Pa)/(235U)0 of 8.8(1.0) (Vesuvius) and 7.9(5) (Laacher See). For reasonable melt activities, model baddeleyite-melt distribution coefficients of DPa/DU = 5.8(2) and 4.1(2) are obtained for Vesuvius and Laacher See, respectively. Speciation-dependent (Pa4+ vs. Pa5+) partitioning coefficients (D values) from crystal lattice strain models for tetra- and pentavalent proxy ions significantly exceed DPa/DU inferred from direct analysis of 231Pa for Pa5+. This is consistent with predominantly reduced Pa4+ in the melt, for which D values similar to U4+ are expected. Contrary to common assumptions, baddeleyite-crystallizing melts from Vesuvius and Laacher See appear to be dominated by Pa4+ rather than Pa5+. An initial disequilibrium correction for baddeleyite geochronology using DPa/DU = 5 ± 1 is recommended for oxidized phonolitic melt compositions.

scholarly journals Interactions of tervalent lanthanide ions with bacterial collagenase (clostridiopeptidase A)

1981 ◽  
Vol 195 (3) ◽  
pp. 677-684 ◽  
Author(s):  
Christopher H. Evans
Keyword(s):  
Ionic Radius ◽  
Substrate Inhibition ◽  
Volume Ratio ◽  
Binding Pocket ◽  
Lanthanide Ions ◽  
Ionic Radii ◽  
Apparent Dissociation Constant ◽  
Substrate Complex ◽  
Bacterial Collagenase ◽  
Hydrolysis Of

Tervalent cations of the lanthanide (rare-earth) elements reversibly inhibit bacterial collagenase (clostridiopeptidase A; EC 3.4.24.3). Sm3+, whose ionic radius is closest to that of Ca2+, is the most effective inhibitor, completely suppressing clostridiopeptidase activity at a concentration of 100μm in the presence of 5mm-Ca2+. Er3+ and Lu3+, which both have ionic radii smaller than either Ca2+ or Sm3+, inhibit less efficiently, and La3+, which is slightly larger than Ca2+ or Sm3+, inhibits only weakly. These findings indicate a closely fitting, stereospecific, Ca2+-binding pocket in clostridiopeptidase, which excludes ions that are only slightly larger than Ca2+ [ionic radius 0.099nm (0.99 Ȧ)]. By contrast, trypsin, an enzyme whose activity does not depend on Ca2+, requires lanthanide concentrations 50–100-fold greater for inhibition. Furthermore, the relative efficiency of inhibition of trypsin by lanthanides increases as the lanthanide ions become smaller and the charge/volume ratio increases. At a concentration of 50μm, Sm3+ lowers the apparent Km for the hydrolysis of Pz-peptide by clostridiopeptidase from 5.4mm to 0.37mm and the apparent Vmax. from 0.29 Wünsch–Heidrich unit to 0.018 unit. Thus Sm3+ enhances the affinity of this enzyme for its substrate; inhibition of hydrolysis of Pz-peptide may result from the excessive stability of the enzyme–Sm3+–substrate complex. Inhibition by Sm3+ is competitive with regard to Ca2+. The apparent dissociation constant, Kd, of Ca2+ is 0.27mm, where the Ki for Sm3+ is 12μm. Clostridiopeptidase is more thermolabile in the absence of Ca2+. With Sm3+, thermoinactivation of the enzyme at 53°C or 60°C is initially accelerated, but then becomes retarded as heating continues. Lanthanide ions bind to gelatin and collagen. In so doing, they appear to protect these substrates from lysis by clostridiopeptidase through mechanisms additional to supplanting Ca2+ at its binding site on the enzyme. Collagen and gelatin sequester sufficient lanthanide ions to gain partial protection from clostridiopeptidase in the absence of an extraneous source of these inhibitors.

Influence of doping on crystal growth, structure and optical properties of nanocrystalline CaTiO3: a case study using small-angle neutron scattering

2015 ◽  
Vol 48 (3) ◽  
pp. 836-843 ◽  
Author(s):  
Oindrila Mondal ◽  
Manisha Pal ◽  
Ripandeep Singh ◽  
Debasis Sen ◽  
Subhasish Mazumder ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Optical Properties ◽  
Crystal Growth ◽  
Small Angle Neutron Scattering ◽  
Ionic Radius ◽  
Ionic Radii ◽  
Growth Structure ◽  
Transmission Electron ◽  
The Difference

The effect of dopant size (ionic radius) on the crystal growth, structure and optical properties of nanocrystalline calcium titanate, CaTiO3(CTO), have been studied using small-angle neutron scattering. X-ray diffraction, along with high-resolution transmission electron microscopy, confirms the growth of pure nanocrystalline CTO. Rietveld analysis reveals that the difference of ionic radii between dopant and host ions induces strain within the lattice, which significantly affects the lattice parameters. The induced strain, due to the difference of ionic radii, causes the shrinkage of the optical band gap, which is manifested by the redshift of the absorbance band. Mesoscopic structural analysis using scattering techniques demonstrates that the ionic radius of the dopant influences the agglomeration behaviour and particle size. A high-resolution transmission electron microscopy study reconfirms the formation of pure highly crystalline CTO nanoparticles.

scholarly journals The origins of binding specificity of a lanthanide ion binding peptide

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Takaaki Hatanaka ◽  
Nobuaki Kikkawa ◽  
Akimasa Matsugami ◽  
Yoichi Hosokawa ◽  
Fumiaki Hayashi ◽  
...  
Keyword(s):  
Water Molecule ◽  
Ionic Radius ◽  
Binding Specificity ◽  
Lanthanide Ions ◽  
Ion Binding ◽  
Deep Insight ◽  
Ionic Radii ◽  
Linear Peptide ◽  
High Affinity ◽  
Insight Into

Abstract Lanthanide ions (Ln3+) show similar physicochemical properties in aqueous solutions, wherein they exist as + 3 cations and exhibit ionic radii differences of less than 0.26 Å. A flexible linear peptide lanthanide binding tag (LBT), which recognizes a series of 15 Ln3+, shows an interesting characteristic in binding specificity, i.e., binding affinity biphasically changes with an increase in the atomic number, and shows a greater than 60-fold affinity difference between the highest and lowest values. Herein, by combining experimental and computational investigations, we gain deep insight into the reaction mechanism underlying the specificity of LBT3, an LBT mutant, toward Ln3+. Our results clearly show that LBT3-Ln3+ binding can be divided into three, and the large affinity difference is based on the ability of Ln3+ in a complex to be directly coordinated with a water molecule. When the LBT3 recognizes a Ln3+ with a larger ionic radius (La3+ to  Sm3+), a water molecule can interact with Ln3+ directly. This extra water molecule infiltrates the complex and induces dissociation of the Asn5 sidechain (one of the coordinates) from Ln3+, resulting in a destabilizing complex and low affinity. Conversely, with recognition of smaller Ln3+ (Sm3+ to Yb3+), the LBT3 completely surrounds the ions and constructs a stable high affinity complex. Moreover, when the LBT3 recognizes the smallest Ln3+, namely Lu3+, although it completely surrounds Lu3+, an entropically unfavorable phenomenon specifically occurs, resulting in lower affinity than that of Yb3+. Our findings will be useful for the design of molecules that enable the distinction of sub-angstrom size differences.

scholarly journals Structure feature of ternary state diagrams of Cr-Ti-V and Cr-Mn-V systems

2018 ◽  
Vol 243 ◽  
pp. 00014 ◽  
Author(s):  
Anatoliy Klopotov ◽  
Irina Kurzina ◽  
Alexander Potekaev ◽  
Artem Ustinov ◽  
Taras Dement ◽  
...  
Keyword(s):  
Solid Solution ◽  
Intermetallic Compounds ◽  
Solid Solutions ◽  
Crystal Chemical ◽  
Electron Number ◽  
Isothermal Sections ◽  
State Diagrams ◽  
Bcc Lattice ◽  
Existence Domain ◽  
Chemical Factors

This paper presents the research results of features of structural and phase states in Cr-Ti-V and Cr-Mn-V systems based on analysis of crystal-geometric and crystal-chemical factors. The diagrams of isothermal sections of state diagrams of Cr-Ti-V and Cr-Mn-V systems were built in coordinates of the electron number (s+d) per atom with homogeneity regions of solid solutions and intermetallic compounds. It was shown that in the Cr-Ti-V system, addition of Mn atoms leads to substantial extension of the existence domain of the disordered solid solution based on the BCC lattice.

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