scholarly journals Thermodymanic Considerations on Gold Dissolution in Different Lixiviants (I)

2019 ◽  
Vol 70 (8) ◽  
pp. 2727-2732
Author(s):  
Catalin Alexandru Barbu ◽  
Ion Constantin ◽  
Mihnea Cosmin Costoiu ◽  
Mihai Buzatu ◽  
Augustin Semenescu
Keyword(s):  
Stability Constants ◽  
Thermodynamic Stability ◽  
Gold Dissolution ◽  
Gold Complexes ◽  
Electrode Potentials ◽  
Electrochemical Mechanism ◽  
The Stability ◽  
Cyanide Solutions ◽  
Gold Industry

The paper presents the main thermodynamic aspects related to gold dissolution in different lixiviants. We analyzedthe thermodynamic stability of the gold complexes with the most representative lixiviants with potential for use in the gold industry. Based on the stability constants we determined the electrode potentials of the gold dissolution reactions in variouslixiviants and we presented the electrochemical mechanism of gold dissolution is alkaline cyanide solutions.

scholarly journals Thermodynamic Considerations on Gold Dissolution in Different Lixiviants (II)

2019 ◽  
Vol 70 (11) ◽  
pp. 4013-4020
Keyword(s):  
Thermodynamic Stability ◽  
Reaction Mechanisms ◽  
Gold Dissolution ◽  
Gold Complexes ◽  
Gold Industry

The paper presents the main thermodynamic aspects related to the gold dissolution with thiosulphate, thiourea and thiocyanate. The thermodynamic stability of the gold complexes and the reaction mechanisms that ensure the gold dissolution in the most representative lixiviants with potential for use in the gold industry are analyzed. The performances of the lixiviants are analyzed in several ways in antithesis with those of the cyanide: ecological, technological and economic. Keywords: gold, alternative lixiviants, thiosulfate, thiourea, thiocyanate, thermodynamics, reaction mechanisms

scholarly journals Thermodynamic Considerations on Gold Dissolution in Different Lixiviants (II)

2019 ◽  
Vol 70 (11) ◽  
pp. 4013-4020
Author(s):  
Catalin Alexandru Barbu ◽  
Ion Constantin ◽  
Mihnea Cosmin Costoiu ◽  
Mihai Buzatu ◽  
Augustin Semenescu
Keyword(s):  
Thermodynamic Stability ◽  
Reaction Mechanisms ◽  
Gold Dissolution ◽  
Gold Complexes ◽  
Gold Industry

The paper presents the main thermodynamic aspects related to the gold dissolution with thiosulphate, thiourea and thiocyanate. The thermodynamic stability of the gold complexes and the reaction mechanisms that ensure the gold dissolution in the most representative lixiviants with potential for use in the gold industry are analyzed. The performances of the lixiviants are analyzed in several ways in antithesis with those of the cyanide: ecological, technological and economic.

scholarly journals Complexes of Bifunctional DO3A-N-(α-amino)propinate Ligands with Mg(II), Ca(II), Cu(II), Zn(II), and Lanthanide(III) Ions: Thermodynamic Stability, Formation and Dissociation Kinetics, and Solution Dynamic NMR Studies

Molecules ◽  
2021 ◽  
Vol 26 (16) ◽  
pp. 4956
Author(s):  
Zoltán Garda ◽  
Tamara Kócs ◽  
István Bányai ◽  
José A. Martins ◽  
Ferenc Krisztián Kálmán ◽  
...  
Keyword(s):  
Stability Constants ◽  
Thermodynamic Stability ◽  
Formation Rate ◽  
Mri Contrast Agents ◽  
Dissociation Kinetics ◽  
Nmr Studies ◽  
Mri Contrast ◽  
Order Of Magnitude ◽  
The Stability ◽  
Targeted Mri

The thermodynamic, kinetic, and structural properties of Ln3+ complexes with the bifunctional DO3A-ACE4− ligand and its amide derivative DO3A-BACE4− (modelling the case where DO3A-ACE4− ligand binds to vector molecules) have been studied in order to confirm the usefulness of the corresponding Gd3+ complexes as relaxation labels of targeted MRI contrast agents. The stability constants of the Mg2+ and Ca2+ complexes of DO3A-ACE4− and DO3A-BACE4− complexes are lower than for DOTA4− and DO3A3−, while the Zn2+ and Cu2+ complexes have similar and higher stability than for DOTA4− and DO3A3− complexes. The stability constants of the Ln(DO3A-BACE)− complexes increase from Ce3+ to Gd3+ but remain practically constant for the late Ln3+ ions (represented by Yb3+). The stability constants of the Ln(DO3A-ACE)4− and Ln(DO3A-BACE)4− complexes are several orders of magnitude lower than those of the corresponding DOTA4− and DO3A3− complexes. The formation rate of Eu(DO3A-ACE)− is one order of magnitude slower than for Eu(DOTA)−, due to the presence of the protonated amine group, which destabilizes the protonated intermediate complex. This protonated group causes the Ln(DO3A-ACE)− complexes to dissociate several orders of magnitude faster than Ln(DOTA)− and its absence in the Ln(DO3A-BACE)− complexes results in inertness similar to Ln(DOTA)− (as judged by the rate constants of acid assisted dissociation). The 1H NMR spectra of the diamagnetic Y(DO3A-ACE)− and Y(DO3A-BACE)− reflect the slow dynamics at low temperatures of the intramolecular isomerization process between the SA pair of enantiomers, R-Λ(λλλλ) and S-Δ(δδδδ). The conformation of the Cα-substituted pendant arm is different in the two complexes, where the bulky substituent is further away from the macrocyclic ring in Y(DO3A-BACE)− than the amino group in Y(DO3A-ACE)− to minimize steric hindrance. The temperature dependence of the spectra reflects slower ring motions than pendant arms rearrangements in both complexes. Although losing some thermodynamic stability relative to Gd(DOTA)−, Gd(DO3A-BACE)− is still quite inert, indicating the usefulness of the bifunctional DO3A-ACE4− in the design of GBCAs and Ln3+-based tags for protein structural NMR analysis.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

Extraction of strontium and barium salts by the nitrobenzene solution of dicarbolide in the presence of glymes

1985 ◽  
Vol 50 (3) ◽  
pp. 581-599 ◽  
Author(s):  
Petr Vaňura ◽  
Emanuel Makrlík
Keyword(s):  
Stability Constants ◽  
Organic Phase ◽  
Equilibrium Constants ◽  
Minor Role ◽  
Nitrobenzene Solution ◽  
Ligand Structure ◽  
Stability Constants Of Complexes ◽  
Separation Factors ◽  
The Stability ◽  
A Minor

Extraction of microamounts of Sr2+ and Ba2+ (henceforth M2+) from the aqueous solutions of perchloric acid (0.0125-1.02 mol/l) by means of the nitrobenzene solutions of dicarbolide (0.004-0.05 mol/l of H+{Co(C2B9H11)2}-) was studied in the presence of monoglyme (only Ba2+), diglyme, triglyme, and tetraglyme (CH3O-(CH2-CH2O)nCH3, where n = 1, 2, 3, 4). The distribution of glyme betweeen the aqueous and organic phases, the extraction of the protonized glyme molecule HL+ together with the extraction of M2+ ion and of the glyme complex with the M2+ ion, i.e., ML2+ (where L is the molecule of glyme), were found to be the dominating reactions in the systems under study. In the systems with tri- and tetraglymes the extraction of H+ and M2+ ions solvated with two glyme molecules, i.e., the formation of HL2+ and ML22+ species, can probably play a minor role. The values of the respective equilibrium constants, of the stability constants of complexes formed in the organic phase, and the theoretical separation factors αBa/Sr were determined. The effect of the ligand structure on the values of extraction and stability constants in the organic phase is discussed.

Studies on the Coordination Reaction of VO2+ and Tannic Acid in the Tannin Extract Desulfurization

2012 ◽  
Vol 239-240 ◽  
pp. 1573-1576
Author(s):  
Zhu Qing Gao ◽  
Xiao Dong Cai ◽  
Kai Cheng Ling
Keyword(s):  
Stability Constants ◽  
Tannic Acid ◽  
Ph Value ◽  
Protonation Constants ◽  
Conditional Stability ◽  
Tannin Extract ◽  
Acid Effect ◽  
Different Temperatures ◽  
The Stability ◽  
Apparent Stability

At different temperatures, the protonation constants of tannic acid and the complex apparent stability constants between tannic acid and VO2+ were determined by using pH potentimetric method. The results showed that the protonation constants and the complex apparent stability constants slightly decreased with the raising temperature. In accordance with the pH value in the tannin extract technology, the conditional stability constants of the complex were calculated on the basis of the acid effect of tannic acid and the hydrolysis effect of VO2+. It was found that pH greatly affected the stability constants of the complex , so pH must be strictly controlled in the tannin extract technology.

Complexation of Iron with the Orally Active Decorporation Drug L1 (3-Hydroxy-1,2-Dimethyl-4-Pyridinone)

1992 ◽  
Vol 38 (4) ◽  
pp. 562-565 ◽  
Author(s):  
M A Kline ◽  
C Orvig
Keyword(s):  
Blood Plasma ◽  
Potentiometric Titration ◽  
Stability Constants ◽  
Computer Model ◽  
Chelating Agent ◽  
Glass Electrode ◽  
Simple Computer ◽  
Active Iron ◽  
The Stability ◽  
Orally Active

Abstract The stability constants for the Fe(III) complexes of the orally active iron decorporation drug L1 (3-hydroxy-1,2-dimethyl-4-pyridinone) have been determined by potentiometric titration [glass electrode, 25.0 degrees C, mu = 0.15 mol/L (isotonic) NaCl]. A simple computer model of blood plasma (citrate 100 mumol/L, transferrin 37 mumol/L) has been used to compare the Fe(III) binding efficacies in blood of L1 and the clinically used intravenously administered chelating agent deferoxamine.

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