Calcium-zinc and calcium-cadmium exchange in suspensions of various types of clays

Clay Minerals ◽  
1993 ◽  
Vol 28 (1) ◽  
pp. 33-38 ◽  
Author(s):  
R. van Bladel ◽  
H. Halen ◽  
P. Cloos
Keyword(s):  
Heavy Metals ◽  
Free Energy ◽  
Ionic Strength ◽  
Clay Minerals ◽  
Thermodynamic Equilibrium ◽  
Equilibrium Constants ◽  
Standard Free Energy ◽  
Exchangeable Cation ◽  
Adsorption Sites ◽  
Complete Exchange

AbstractCalcium-cadmium and calcium-zinc exchange equilibria were studied at 20°C and constant ionic strength (0·015) on four clay minerals, viz. montmorillonite, bentonite, illite and vermiculite. Vermiculite and, to a lesser extent, illite and bentonite showed the strongest affinity for Cd2+ or Zn2+ over Ca2+ ions, whereas on the Camp Berteau montmorillonite nearly nonpreferential exchange isotherms were observed. With this one exception, selectivity for the heavy metals was greatly enhanced in the trace Cd or Zn regions, suggesting the presence of specific adsorption sites in these clays. Generally, the adsorption increased with the polarizing power of the exchangeable cation. Thermodynamic equilibrium constants and standard free energy changes for the complete exchange of Ca-clay to Cd- or Zn-clay were calculated.

scholarly journals The equilibrium constants of the glutamate dehydrogenase systems

1967 ◽  
Vol 105 (2) ◽  
pp. 691-695 ◽  
Author(s):  
P. C. Engel ◽  
K. Dalziel
Keyword(s):  
Free Energy ◽  
Ionic Strength ◽  
Glutamate Dehydrogenase ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Standard Free Energy ◽  
Free Energy Change ◽  
Energy Change ◽  
Heat Of Reaction ◽  
Standard Free Energy Change

1. Equilibrium constants for the oxidation of glutamate by NAD+ and NADP+, catalysed by glutamate dehydrogenase, have been measured in phosphate buffers of different ionic strengths and at several temperatures. 2. The equilibrium constants for both systems vary markedly with ionic strength. Thermodynamic values for the two systems obtained by extrapolation to zero ionic strength differ significantly from one another. The standard free-energy change for NADP+ reduction has been calculated from that for NAD+ reduction. 3. The heat of reaction has been estimated and is the same with both coenzymes. 4. The thermodynamic data are discussed in relation to earlier data.

The thermodynamics of the ionization of 3-hydroxypyridine and pyridoxine in water–dioxane mixtures

1992 ◽  
Vol 70 (6) ◽  
pp. 1635-1639 ◽  
Author(s):  
Salvador B. Asensio ◽  
Enrique Lopez-Cantarero ◽  
Juan Llor
Keyword(s):  
Free Energy ◽  
Thermodynamic Function ◽  
Thermodynamic Equilibrium ◽  
Equilibrium Constants ◽  
Weight Fraction ◽  
Tautomeric Equilibrium ◽  
Potentiometric Method ◽  
Standard Thermodynamic Function ◽  
Net Zero ◽  
Ionization Processes

A potentiometric method has been used to determine the thermodynamic equilibrium constants for the macroscopic ionization processes of 3-hydroxypyridine and pyridoxine in water–dioxane mixtures (0–70% weight fraction in dioxane) at temperatures from 10 to 50 °C. From these data the reaction standard thermodynamic function changes were obtained for the processes in various water–dioxane mixtures at 25 °C. It was found, in both molecules, that during the first ionization process the contributions of entropy and enthalpy to free energy are similar but that during the second ionization the main contribution comes from entropy, especially in mixtures with a high dioxane content. The effect of the solvent on the tautomeric equilibrium in the net zero charge specie could explain this behaviour.

The association of bovine SH-κ-casein at pH 7·0

1979 ◽  
Vol 46 (2) ◽  
pp. 271-276 ◽  
Author(s):  
Henk J. Vreeman
Keyword(s):  
Free Energy ◽  
Ionic Strength ◽  
Critical Micelle Concentration ◽  
Spherical Particle ◽  
Standard Free Energy ◽  
The Self ◽  
Self Association ◽  
Polymer Type

SUMMARYThe self-association of SH-κ-casein at pH 7·0 in 0·01 m-EDTA, 0·001 m-dithiothreitol buffer, containing 0·1, 0·2, 0·5 or 1·0 m-NaCl is of a monomer–polymer type. The polymer is a spherical particle, diam. 23 nm and mol. wt 570000 (30 monomers). These parameters are not greatly influenced by variations in ionic strength above 0·1. The critical micelle concentration, which is a property of a monomer–polymer equilibrium, decreases with increasing ionic strength. The standard free energy of association is about – 36 kJ/mol. monomer at 20 °C.

CALCULATION AND PLOTTING OF STANDARD FREE ENERGY CHANGES AND EQUILIBRIUM CONSTANTS FOR CVD HARD COATINGS REACTIONS

2005 ◽  
Vol 12 (05n06) ◽  
pp. 727-731 ◽  
Author(s):  
SHA LIU ◽  
JING QIU ZHANG
Keyword(s):  
Free Energy ◽  
Computer Program ◽  
Equilibrium Constants ◽  
Standard Free Energy ◽  
Chemical Vapor ◽  
Hard Coatings ◽  
Accurate Calculation ◽  
Materials Synthesis ◽  
Synthesis And Processing ◽  
General Computer Program

CVD (chemical vapor deposition) coatings such as TiC , TiN , Al 2 O 3 and so on are widely used as tools' surface preserved materials with corrosion resistance and wear resistance. Standard Gibbs free energy changes for reactions are widely used to approximately analyze the trends of substance reactions and phase transitions in chemical reactions, metallurgy processes, materials synthesis and processing. Hard coatings and thin films can be prepared by CVD process. Accurate calculation and plotting of the standard free energy changes and equilibrium constants for CVD TiC , TiN , Al 2 O 3 coatings reactions are realized using the developed general computer program. Only inputting the basic thermodynamic data tabulated in data books into the computer program, the relationships of the standard free energy changes and equilibrium constants for most reactions with the temperatures can be gained in the same diagrams.

Study of the Cu(II) removal from aqueous solutions by adsorption on titania

2013 ◽  
Vol 12 (3) ◽  
pp. 239-247
Keyword(s):  
Heavy Metals ◽  
Ionic Strength ◽  
Toxic Metals ◽  
Low Cost ◽  
Lateral Interaction ◽  
Tio2 Surface ◽  
High Toxicity ◽  
Removal Of Heavy Metals ◽  
Solution Parameters ◽  
Kinetics Of

The removal of heavy metals from wastewaters is a matter of paramount importance due to the fact that their high toxicity causes major environmental pollution problems. One of the most efficient, applicable and low cost methods for the removal of toxic metals from aqueous solutions is that of their adsorption on an inorganic adsorbent. In order to achieve high efficiency, it is important to understand the influence of the solution parameters on the extent of the adsorption, as well as the kinetics of the adsorption. In the present work, the adsorption of Cu(II) species onto TiO2 surface was studied. It was found that the adsorption is a rapid process and it is not affected by the value of ionic strength. In addition, it was found that by increasing the pH, the adsorbed amount of Cu2+ ions and the value of the adsorption constant increase, whereas the value of the lateral interaction energy decreases.

Adsorption of Liquids and Swelling of Wood. Part VI. Saturated Amounts and Some Thermodynamic Values of Adsorption

Holzforschung ◽  
2002 ◽  
Vol 56 (1) ◽  
pp. 91-97
Author(s):  
Kei Morisato ◽  
Yutaka Ishimaru ◽  
Hiroyuki Urakami
Keyword(s):  
Free Energy ◽  
Standard Free Energy ◽  
Molecular Size ◽  
Free Energy Change ◽  
Energy Change ◽  
Multilayer Adsorption ◽  
Monolayer Adsorption ◽  
Wood Part ◽  
Cohesive Interaction

Summary To understand the swelling phenomenon of wood in liquids,the saturated amount of adsorption of liquids onto wood and the standard free energy changes of the adsorption were determined. The saturated amount of adsorption obtained by regression for several liquids decreased with increasing molecular size of the solvents. The mechanism of wood swelling is discussed systematically taking all the liquids examined in previous experiments into account. Since methanol molecules require more energy for release from cohesive interactions within bulk liquids in the adsorption onto pre-swollen wood,the values of free energy change of adsorption for methanol were lower than the values for acetone,although the relative swelling with methanol was higher. These results suggest that although the cohesive interaction within the bulk liquids reduces adsorptivity,the phenomenon of wood swelling is influenced not only by monolayer adsorption but also by multilayer adsorption. Therefore,the cohesive interaction within the bulk liquids reduces adsorptivity but enhances the condensation which strongly influences the swelling of wood.

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