scholarly journals Adsorption of Tributyl Phosphate on Silica Gel

2001 ◽  
Vol 19 (3) ◽  
pp. 211-217 ◽  
Author(s):  
V.F. Sazonova ◽  
M.A. Kojemyak ◽  
O.V. Perlova
Keyword(s):  
Free Energy ◽  
Silica Gel ◽  
Tributyl Phosphate ◽  
Physical Nature ◽  
Entropy Change ◽  
Enthalpy Change ◽  
Water Molecules ◽  
Adsorption Behaviour ◽  
Free Energy Of Adsorption ◽  
Adsorption Layers

The adsorption behaviour of tributyl phosphate (TBP) on silica gel was studied. It was found that the adsorption isotherm shapes were complicated, being considered as S- and L-type isotherms according to the Giles classification. Adsorption itself was polymolecular and of a physical nature, the first adsorptive layer involving hydrogen bonding between the protons of surface silanol groups and the electron-donating oxygen atom of the adsorbate molecule. Subsequent adsorption layers were formed via van der Waals interaction. The free energy of adsorption of the system lay between −22.1 kJ/mol and −23.8 kJ/mol. The enthalpy change was negative and very small, i.e. −6.3 kJ/mol, while the entropy change was positive and in the range 53.9 J/(mol K) to 55.4 J/(mol K). The increase in entropy was explained in terms of the mobility of the TBP molecules in the adsorptive layer arising from their replacement on the silica gel surface by water molecules derived from the aqueous medium.

scholarly journals Thermodynamics of electrochemical reactions in Lead-acid Battery

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Adebayo Akinbulu ◽  
Toafeek Ogunbayo
Keyword(s):  
Free Energy ◽  
Temperature Coefficient ◽  
Electromotive Force ◽  
Electrochemical Reaction ◽  
Entropy Change ◽  
Enthalpy Change ◽  
Electrochemical Reactions ◽  
Positive Entropy ◽  
Lead Acid Battery ◽  
Lead Acid

Thermodynamics of the electrochemical reaction in lead-acid battery was investigated. A negative value of change in Gibbs’ free energy, ?G, and a positive entropy change, ?S, were obtained for the reaction. ?G was more negative at increased temperature. The reaction was exothermic, with a negative value of enthalpy change, ?H. A relatively small value of temperature coefficient of the electromotive force of the cell, (?E/?T)_P, was also obtained for the reaction.

scholarly journals PROCESS FOR REMOVAL OF CHROMIUM ION FROM LEATHER INDUSTRIAL WASTES BY ACTIVATED PURE RICE HUSK

2021 ◽  
Vol 4 (4) ◽  
pp. 334-338
Author(s):  
Yakubu Abdulkadir ◽  
A. Halid ◽  
A. Y. Abdulazeez ◽  
N. S. Gulumbe ◽  
M. Rukaiyat ◽  
...  
Keyword(s):  
Free Energy ◽  
Rice Husk ◽  
Entropy Change ◽  
Enthalpy Change ◽  
Industrial Wastes ◽  
Solution Temperature ◽  
Chromium Ion ◽  
Exothermic Process ◽  
Stay Time ◽  
G Value

The removal of (Cr) ions from industrial wastage by adsorption on rice husk was investigated based on activated pure rice husk dosage, stay time, metal concentration and solution temperature. The optimum values of activated pure rice husk dosage and stay time were determined to be 0.5gm/50ml solution and 60 mins, respectively, for the adsorption of (Cr) ions. The constant for the Freundlich, D-R and Langmuir isotherms were 50%, calculated at 50 . The adsorption of (Cr) from industrial wastage was found to be exothermic. Thermodynamic parameters such as free energy change ( G°), enthalpy change ( H°) and entropy change ( S°) of adsorption also calculated and interpreted from the slope and intercept of the plots of lnkD vs I/T. The G° value decreases with rise in temperature and the negative values of H° indicate that the adsorption of (Cr) from industrial wastage was an exothermic process while positive values of change in entropy ( S°) were also observed

Separation of static and dynamic thermodynamic parameters for the interaction between pyropheophorbide methyl ester and copper

2014 ◽  
Vol 18 (04) ◽  
pp. 297-304 ◽  
Author(s):  
Saleh Al-Omari
Keyword(s):  
Free Energy ◽  
Methyl Ester ◽  
Fluorescence Quenching ◽  
Thermodynamic Function ◽  
Binding Constant ◽  
Entropy Change ◽  
Enthalpy Change ◽  
Gibbs Free Energy Change ◽  
Quenching Process ◽  
Different Temperatures

The interaction between pyropheophorbide methyl ester (PPME) and the ionic metal of copper ( Cu 2+) was investigated using fluorescence and UV-vis techniques. By analysis of the fluorescence spectra, it was observed that Cu 2+ has a strong ability to quench the intrinsic fluorescence of PPME through dynamic and static quenching process. The binding constants of Cu 2+ with PPME were determined at different temperatures depending on the results of fluorescence quenching. Based on the modified form of the Stern–Volmer equation, static binding constant (kS) and the dynamic binding constant (kD) of Cu 2+-PPME association were obtained at different temperatures. The static thermodynamic function of the enthalpy change (ΔHS), the dynamic thermodynamic function of the enthalpy change (ΔHD), the static thermodynamic function of the entropy change (ΔSS), and the dynamic thermodynamic function of the entropy change (ΔSD) for the binding interaction were determined according to the van't Hoff equation. The values of static Gibbs free energy change (ΔGS) and dynamic Gibbs free energy change (ΔGD) were determined to be negative indicating that the interaction process was a spontaneous. ΔHD and ΔSD values were positive indicating that the dynamic quenching process of Cu 2+-PPME interaction was driven mainly by hydrophobic forces. For the static binding quenching, ΔHS and ΔSS values were negative which indicated that hydrogen bond, electrostatic interaction, and van der Waals interaction were important driving forces for PPME- Cu 2+ association. Both static and dynamic fluorescence quenching were related to the distance between PPME and Cu 2+ indicating that the electron transfer process occurred.

scholarly journals Effect of Blends of Benzotriazole and Thiourea on the Anodic Dissolution of Copper

2002 ◽  
Vol 20 (5) ◽  
pp. 485-494 ◽  
Author(s):  
E.A. Ashour ◽  
H.S. Hegazy ◽  
B.G. Ateya
Keyword(s):  
Free Energy ◽  
Anodic Dissolution ◽  
Hydrogen Sulphide ◽  
Copper Surface ◽  
Antagonistic Effect ◽  
Adsorption Behaviour ◽  
Free Energy Of Adsorption ◽  
Antagonistic Effects ◽  
Low Concentrations ◽  
The Individual

The blending of benzotriazole (BTAH) and thiourea (TU) was shown to exert synergistic or antagonistic effects on the anodic dissolution of copper at pH ≈ 1.8 depending on their concentrations in the blend. While synergism was observed in blends with low concentrations of TU and BTAH, antagonism was observed in blends containing higher, i.e. ≥ 10−2 M, concentrations of TU to an extent which increased with the concentration of TU. The antagonistic effect of TU was discussed in the light of its tendency to produce hydrogen sulphide which promotes the anodic dissolution of copper. Analysis of the adsorption behaviour of the individual compounds using the Langmuir isotherm revealed stronger interaction of the copper surface with BTAH than with TU, as judged by free energy of adsorption values of −18.8 and −8.7 kJ/mol for BTAH and TU, respectively.

scholarly journals PENENTUAN KESETIMBANGAN, TERMODINAMIKA DAN KINETIKA ADSORPSI ARANG AKTIF TEMPURUNG KELAPA SAWIT PADA ZAT WARNA REACTIVE RED DAN DIRECT BLUE

Alotrop ◽  
2017 ◽  
Vol 1 (1) ◽  
Author(s):  
Rensy Aula Sari ◽  
M. Lutfi Firdaus ◽  
Rina Elvia
Keyword(s):  
Free Energy ◽  
Palm Oil ◽  
Entropy Change ◽  
Enthalpy Change ◽  
Free Energy Change ◽  
Energy Change ◽  
Kinetics And Thermodynamics ◽  
Synthetic Dye ◽  
Direct Blue ◽  
Isotherm Adsorption

This perpose of this research was to know the isotherm, kinetics and thermodynamics adsorption of synthetic  dye onto activated carcoal from palm oil shell. The synthetic dye were Reactive Red and Direct Blue. The model of isotherm were Langmuir and Freundlich, kinetics adsorption tested were Pseudo orde-1 and Pseudo orde-2, and also thermodynamics were free energy change (?Go), enthalpy change (?Ho), and entropy change (?So). The dominant isotherm adsorption was isotherm Freundlich, kinetic adsorption Pseudo 2 th order  with the value (?So), (?Go) and (?Ho), Reactive Red were 0,0028 Kj/mol.K , -3,93 Kj/mol, and -36,12 Kj/mol respectively. Whereas in direct blue were 0,0034 Kj/mol.K, -1,67 Kj/mol,and -30,16 Kj/mol respectively. 

Molecular orientation of liquid aliphatic hydrocarbons on the surface and at the interface with water

1989 ◽  
Vol 54 (12) ◽  
pp. 3171-3186 ◽  
Author(s):  
Jan Kloubek
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Molecular Orientation ◽  
Phase Changes ◽  
Aliphatic Hydrocarbons ◽  
Water Molecules ◽  
Free Energies ◽  
Dispersion Component ◽  
System Water ◽  
Orientation Of Molecules

The validity of the Fowkes theory for the interaction of dispersion forces at interfaces was inspected for the system water-aliphatic hydrocarbons with 5 to 16 C atoms. The obtained results lead to the conclusion that the hydrocarbon molecules cannot lie in a parallel position or be randomly arranged on the surface but that orientation of molecules increases there the ration of CH3 to CH2 groups with respect to that in the bulk. This ratio is changed at the interface with water so that the surface free energy of the hydrocarbon, γH, rises to a higher value, γ’H, which is effective in the interaction with water molecules. Not only the orientation of molecules depends on the adjoining phase and on the temperature but also the density of hydrocarbons on the surface of the liquid phase changes. It is lower than in the bulk and at the interface with water. Moreover, the volume occupied by the CH3 group increases on the surface more than that of the CH2 group. The dispersion component of the surface free energy of water, γdW = 19.09 mJ/m2, the non-dispersion component, γnW = 53.66 mJ/m2, and the surface free energies of the CH2 and CH3 groups, γ(CH2) = 32.94 mJ/m2 and γ(CH3) = 15.87 mJ/m2, were determined at 20 °C. The dependence of these values on the temperature in the range 15-40 °C was also evaluated.

Electrochemical Measurement of the Free Energy of Adsorption ofn-Alkanethiolates at Ag(111)

1998 ◽  
Vol 120 (5) ◽  
pp. 1062-1069 ◽  
Author(s):  
David W. Hatchett ◽  
Rory H. Uibel ◽  
Keith J. Stevenson ◽  
Joel M. Harris ◽  
Henry S. White
Keyword(s):  
Free Energy ◽  
Electrochemical Measurement ◽  
Free Energy Of Adsorption

The Equilibrium and the Determination of D00 (H—CN)

1975 ◽  
Vol 53 (16) ◽  
pp. 2365-2370 ◽  
Author(s):  
Don Betowski ◽  
Gervase Mackay ◽  
John Payzant ◽  
Diethard Bohme
Keyword(s):  
Free Energy ◽  
Standard Enthalpy ◽  
Transfer Reaction ◽  
Standard Free Energy ◽  
Proton Transfer Reaction ◽  
Enthalpy Change ◽  
Standard Free Energy Change ◽  
Flowing Afterglow ◽  
Standard Enthalpy Change

The rate constants and equilibrium constant for the proton transfer reaction [Formula: see text] have been measured at 296 ± 2 K using the flowing afterglow technique: kforward = (2.9 ± 0.6) × 10−9 cm3molecule−1s−1, kreverse = (1.8 ± 0.4) × 10−10 cm3 molecule1 s−1, and K = 16 ± 2. The measured value of K corresponds to a standard free energy change, ΔG296°, of −1.6 ± 0.1 kcal mol−1 which provides values for the standard enthalpy change, ΔH298°= −1.0 ± 0.2 kcal mol−1, the bond dissociation energy, D00(H—CN) = 124 ± 2 kcal mol−1, and the proton affinity, p.a.(CN−) = 350 ± 1 kcal mol−1.

scholarly journals Thermodynamics of ligand binding by the yeast mRNA-capping enzyme reveals different modes of binding

2004 ◽  
Vol 384 (2) ◽  
pp. 411-420 ◽  
Author(s):  
Isabelle BOUGIE ◽  
Amélie PARENT ◽  
Martin BISAILLON
Keyword(s):  
Ligand Binding ◽  
Entropy Change ◽  
Enthalpy Change ◽  
Mrna Capping ◽  
Capping Enzyme ◽  
Eukaryotic Mrnas ◽  
Entropic Effect ◽  
A Minor ◽  
Rna Capping ◽  
Capping Enzymes

RNA-capping enzymes are involved in the synthesis of the cap structure found at the 5′-end of eukaryotic mRNAs. The present study reports a detailed study on the thermodynamic parameters involved in the interaction of an RNA-capping enzyme with its ligands. Analysis of the interaction of the Saccharomyces cerevisiae RNA-capping enzyme (Ceg1) with GTP, RNA and manganese ions revealed significant differences between the binding forces that drive the interaction of the enzyme with its RNA and GTP substrates. Our thermodynamic analyses indicate that the initial association of GTP with the Ceg1 protein is driven by a favourable enthalpy change (ΔH=−80.9 kJ/mol), but is also clearly associated with an unfavourable entropy change (TΔS=−62.9 kJ/mol). However, the interaction between Ceg1 and RNA revealed a completely different mode of binding, where binding to RNA is clearly dominated by a favourable entropic effect (TΔS=20.5 kJ/mol), with a minor contribution from a favourable enthalpy change (ΔH=−5.3 kJ/mol). Fluorescence spectroscopy also allowed us to evaluate the initial binding of GTP to such an enzyme, thereby separating the GTP binding step from the concomitant metal-dependent hydrolysis of GTP that results in the formation of a covalent GMP–protein intermediate. In addition to the determination of the energetics of ligand binding, our study leads to a better understanding of the molecular basis of substrate recognition by RNA-capping enzymes.

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