scholarly journals Equilibrium and thermodynamic studies of stearic acid adsorption on Celtek clay

2007 ◽  
Vol 72 (5) ◽  
pp. 485-494 ◽  
Author(s):  
Ahmet Sari ◽  
Mustafa Soylak
Keyword(s):  
Free Energy ◽  
Stearic Acid ◽  
Thermodynamic Parameters ◽  
Enthalpy Change ◽  
Isotherm Models ◽  
Gibbs Free Energy Change ◽  
Linear Forms ◽  
Considerable Potential ◽  
Olive Oils ◽  
Increasing Temperature

This paper presents the equilibrium and thermodynamic parameters of the adsorption of stearic acid on Celtek clay as a function of temperature. It was found that the adsorption of stearic acid on Celtek clay decreased with increasing temperature from 293 to 313 K. The equilibrium modelled data fitted well with the linear forms of both the Langmuir and the Freundlich models (R2 = 0.99 in both cases). The R L and 1/n values determined from the isotherm models proved that Celtek clay is a suitable adsorbent for stearic acid. The Dubinin-Radushkevich (D-R) isotherm was applied to describe the nature of the adsorption of stearic acid on Celtek clay and it was found that the adsorption occurred physically. Thermodynamic parameters of adsorption, such as Gibbs free energy change (?G0), enthalpy change (?H0) and enthropy change (?S0) were also calculated. These parameters showed that the adsorption of stearic acid on Celtek clay was feasible, spontaneous, and exothermic in nature. On the basis of the results, it can be concluded that Celtek clay has considerable potential for the removal of stearic acid from the main sources, such as raw and edible soybean, sunflower and olive oils.

The endothermic nature of the binding of anionic bile salts to a cationic adsorbent

2002 ◽  
Vol 80 (1) ◽  
pp. 89-93 ◽  
Author(s):  
Celia K Williams ◽  
William C Galley ◽  
G Ronald Brown
Keyword(s):  
Bile Salt ◽  
Thermodynamic Parameters ◽  
Driving Force ◽  
Bile Salts ◽  
Cationic Polymer ◽  
Langmuir Equation ◽  
Enthalpy Change ◽  
Polymer Sorbents ◽  
Sodium Chenodeoxycholate ◽  
Increasing Temperature

The binding of a hydrophobic bile salt, sodium chenodeoxycholate, by a polyacrylamide with N,N,N-trimethylammonium dodecyl chloride (QPDA12) pendant groups was studied to evaluate the thermodynamic parameters associated with the binding. The Langmuir equation was used in interpreting the data obtained from HPLC measurements. An increase in binding affinity was observed with increasing temperature indicating that the driving force for binding is derived from an increase in entropy (ΔS° = 253 J mol–1 K–1) despite the positive, or unfavourable, enthalpy change (ΔH° = 53 kJ mol–1). The positive thermodynamic parameters associated with the binding suggest that the disruption of hydrophobic and (or) ionic hydration associated with the bile salts and cationic polymer is the driving force for the binding.Key words: bile salts, endothermic binding, polymer sorbents, solvent randomization.

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 Theoretical investigations on the phase transition of pure and Li-doped AlH3

RSC Advances ◽  
2017 ◽  
Vol 7 (67) ◽  
pp. 42024-42029 ◽  
Author(s):  
Zheng Mei ◽  
Feng-Qi Zhao ◽  
Si-Yu Xu ◽  
Xue-Hai Ju
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Aluminum Hydride ◽  
Enthalpy Change ◽  
Free Energy Change ◽  
Gibbs Free Energy Change ◽  
Α Phase ◽  
Theoretical Investigations

The calculated Gibbs free energy change and enthalpy change for the γ → α phase transition and heat capacity indicate that the aluminum hydride synthesized in experiments is Li-doped.

Adsorption of Humic Acid from Aqueous Solution onto PAA Nanofiber: Thermodynamic Study

2019 ◽  
Vol 811 ◽  
pp. 99-103
Author(s):  
Muhammad Ali Zulfikar ◽  
D. Maulina ◽  
Henry Setiyanto ◽  
Muhamad Nasir
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Humic Acid ◽  
Thermodynamic Parameters ◽  
Polyacrylic Acid ◽  
Adsorption Process ◽  
Experimental Conditions ◽  
Electrospinning Technique ◽  
Batch System ◽  
Increasing Temperature

The potential of polyacrylic acid (PAA) nanofiber prepared by the electrospinning technique for the humic acid (HA) adsorption from aqueous solution was investigated. In this study, the adsorption experiments were carried out to investigate the effect of temperatures in a batch system. From experiment it can be seen that the HA adsorption using PAA nanofiber increased with increasing temperature. Thermodynamic parameters data indicated that the HA adsorption process was non-spontaneous and endothermic under the experimental conditions, with the Gibbs free energy (∆Go) in the range of 1.721-0.980 kJ mol-1, enthalpy (∆Ho) and entropy (∆So) of 7.24 kJ mol-1 and 18.52 J mol-1 K-1, respectively.

scholarly journals Sorption of Metal Ions on a Mixed Oxide [0.5 M SiO2:0.5 M Fe(OH)3]

2002 ◽  
Vol 20 (3) ◽  
pp. 215-230 ◽  
Author(s):  
S. Mustafa ◽  
B. Dilara ◽  
A. Naeem ◽  
N. Rahana ◽  
P. Shahida
Keyword(s):  
Metal Ions ◽  
Cation Exchange ◽  
Thermodynamic Parameters ◽  
Mixed Oxide ◽  
Binding Constants ◽  
Exchange Mechanism ◽  
Sorption Data ◽  
Linear Forms ◽  
Langmuir Adsorption ◽  
Increasing Temperature

The sorption of Zn2+, Ni2+, Cd2+, Ca2+ and Mg2+ ions on to a mixed oxide of iron and silicon was found to increase with increasing temperature, concentration and pH of the system. The selectivity of this mixed oxide was Cd2+ ≥ Zn2+ ≥ Ni2+ > Ca2+ > Mg2+, indicating that the mixed oxide was more selective as an exchanger towards Cd2+ ions relative to its components, SiO2 and Fe(OH)3. The sorption data fitted the linear forms of the Kurbatov and Langmuir adsorption equations. The sorption of metal cations was accompanied by the release of H+ ions to the bulk phase. On average 1 mol H+ was released for every cation sorbed. The values of the binding constants were used to estimate the apparent thermodynamic parameters, ΔH and ΔS. The phenomenon of enthalpy/entropy compensation showed that the adsorption of metal ions by the mixed oxide occurred typically through a cation-exchange mechanism.

Survival of Endocronartium harknessii teliospores in a simulated airborne state

1989 ◽  
Vol 67 (3) ◽  
pp. 928-932 ◽  
Author(s):  
Kan-Fa Chang ◽  
P. V. Blenis
Keyword(s):  
Relative Humidity ◽  
Liquid Nitrogen ◽  
Long Distance ◽  
Spider Webs ◽  
Considerable Potential ◽  
Good Ability ◽  
Endocronartium Harknessii ◽  
Spore Longevity ◽  
Effects Of Temperature ◽  
Increasing Temperature

The effects of temperature and relative humidity (RH) on the survival of Endocronartium harknessii teliospores and the longevity of these spores out of doors during daylight hours were studied. In one experiment, fresh and liquid-nitrogen-stored spores of E. harknessii were impacted onto spider webs or plastic threads and incubated in darkness at temperatures of 6, 15, and 24 °C and RHs of 39 and 98%. Survival was measured after 1, 2, 4, 8, and 16 days. Spore longevity decreased with increasing temperature and was lower at 98 than at 39% RH. In a second experiment, spores were impacted onto spider webs and placed out of doors on clear days. Viability decreased linearly with time and averaged 33% after 12 h. The data suggest that E. harknessii has relatively good ability to survive in an airborne state and thus would have considerable potential for long distance spread.

The Calculation of Physicochemical Parameters in the Mimetite Dissolving Process

2013 ◽  
Vol 860-863 ◽  
pp. 1035-1039
Author(s):  
Shuang Cao ◽  
Zong Lan Zhang ◽  
Liu Qin Dai ◽  
Yi Nian Zhu ◽  
Zong Qiang Zhu ◽  
...  
Keyword(s):  
Free Energy ◽  
Physicochemical Parameters ◽  
Solubility Product ◽  
Acidic Environment ◽  
Initial Ph ◽  
Increasing Temperature

Solubility of the artificial synthesis Pb(AsO_4 )_3 Cl was studied at different pH and same temperature to get its solubility product Pb(AsO_4 )_3 Cl and formation free energy (∆G_f^0). The results showed that the solubility and stability of Pb(AsO_4 )_3 Cl were related to pH in the same temperature. The solubility of Pb(AsO_4 )_3 Cl was high in acidic environment (initial pH=2) and in initial pH=4,6 conditions its solubility as near as makes no difference. The ∆G_f^0 increased with increasing temperature.

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.

The Free Energy Simulation Approach to Grain Boundary Segregation In Cu-Ni

1990 ◽  
Vol 209 ◽  
Author(s):  
H. Y. Wang ◽  
R. Najafabadi ◽  
D. J. Srolovitz ◽  
R. Lesar
Keyword(s):  
Monte Carlo ◽  
Free Energy ◽  
Grain Boundary ◽  
Chemical Potential ◽  
Boundary Segregation ◽  
Configurational Entropy ◽  
Accurate Method ◽  
Increasing Temperature ◽  
Atomic Coordinates ◽  
Good Agreement

ABSTRACTA new, accurate method for determining equilibrium segregation to defects in solids is employed to examine the segregation of Cu to grain boundaries in Cu-Ni alloys. The results are in very good agreement with the ones given by Monte Carlo. This method is based upon a point approximation for the configurational entropy, an Einstein model for vibrational contributions to the free energy. To achieve the equilibrium state of a defect in an alloy the free energy is minimized with respect to atomic coordinates and composition of each site at constant chemical potential. One of the main advantages this new method enjoys over other methods such as Monte Carlo, is the efficiency with which the atomic structure of a defect, segregation and thermodynamic properties can be determined. The grain boundary free energy can either increase or decrease with increasing temperature due to the competition between energetic and configurational entropy terms. In general, the grain boundary free energy increases with temperature when the segregation is strongest.

scholarly journals Acclimation of leaves to low light produces large grana: the origin of the predominant attractive force at work

2012 ◽  
Vol 367 (1608) ◽  
pp. 3494-3502 ◽  
Author(s):  
Husen Jia ◽  
John R. Liggins ◽  
Wah Soon Chow
Keyword(s):  
Thylakoid Membranes ◽  
Enthalpy Change ◽  
Attractive Force ◽  
Gibbs Free Energy Change ◽  
Photosynthetic Membrane ◽  
Low Light ◽  
Cyclic Photophosphorylation ◽  
Thylakoid Stacking ◽  
Endothermic Process ◽  
Fine Tune

Photosynthetic membrane sacs (thylakoids) of plants form granal stacks interconnected by non-stacked thylakoids, thereby being able to fine-tune (i) photosynthesis, (ii) photoprotection and (iii) acclimation to the environment. Growth in low light leads to the formation of large grana, which sometimes contain as many as 160 thylakoids. The net surface charge of thylakoid membranes is negative, even in low-light-grown plants; so an attractive force is required to overcome the electrostatic repulsion. The theoretical van der Waals attraction is, however, at least 20-fold too small to play the role. We determined the enthalpy change, in the spontaneous stacking of previously unstacked thylakoids in the dark on addition of Mg 2+ , to be zero or marginally positive (endothermic). The Gibbs free-energy change for the spontaneous process is necessarily negative, a requirement that can be met only by an increase in entropy for an endothermic process. We conclude that the dominant attractive force in thylakoid stacking is entropy-driven. Several mechanisms for increasing entropy upon stacking of thylakoid membranes in the dark, particularly in low-light plants, are discussed. In the light, which drives the chloroplast far away from equilibrium, granal stacking accelerates non-cyclic photophosphorylation, possibly enhancing the rate at which entropy is produced.

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