scholarly journals Thermodynamics of the Adsorption of Cobalt on Lead Dioxide from Aqueous Solution

1995 ◽  
Vol 12 (2) ◽  
pp. 139-149 ◽  
Author(s):  
H. Ahmad ◽  
M. Afzal ◽  
M. Saleem ◽  
S.M. Hasany
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Distribution Coefficient ◽  
Lead Dioxide ◽  
Optimum Conditions ◽  
Different Temperatures ◽  
Increasing Temperature

The adsorption of cobalt on lead dioxide from aqueous solutions has been optimized with respect to the shaking time, the amount of adsorbent, the pH and the concentration of adsorbate at 293 K. Under such optimum conditions, the adsorption of cobalt on lead dioxide has been studied at different temperatures and the process found to be endothermic with the distribution coefficient (KD) increasing with increasing temperature. The data fitted very well to the Langmuir, Freundlich and Dubinin–adushkevich isotherms, allowing the corresponding constants to be calculated. Values of ΔH0 and ΔS0 were calculated from the slope and intercept of the plots of In KD versus 1/T. The value of ΔG0, which decreased with increasing temperature, showed that the adsorption is more favourable at higher temperatures.

THE DISSOCIATION OF α- AND β-LIPOVITELLIN IN AQUEOUS SOLUTION: PART I. EFFECT OF pH, TEMPERATURE, AND OTHER FACTORS

1962 ◽  
Vol 40 (3) ◽  
pp. 363-372 ◽  
Author(s):  
R. W. Burley ◽  
W. H. Cook
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Effect Of Ph ◽  
Reversible Dissociation ◽  
Lipoprotein Concentration ◽  
Irreversible Aggregation ◽  
Increasing Temperature

The effect of pH, temperature, ionic strength, and lipoprotein concentration on the reversible dissociation of α- and β-lipovitellin in aqueous solutions above pH 6 has been examined by ultracentrifugal measurements. Under otherwise similar conditions α- and β-lipovitellin are 50% dissociated at pH 10.5 and 7.8, respectively. Both lipovitellins undergo an irreversible aggregation above about pH 11; β-lipovitellin is sometimes converted to a non-dissociable form upon aging. Dissociation of both lipovitellins decreases with increasing ionic strength and increasing temperature. Although the ultracentrifugal method has limitations, provisional equilibrium constants and thermodynamic data were obtained from it that are comparable with those obtained for certain protein systems.

scholarly journals Selective Transport of Ag(I) through a Polymer Inclusion Membrane Containing a Calix[4]pyrrole Derivative from Nitrate Aqueous Solutions

2020 ◽  
Vol 21 (15) ◽  
pp. 5348
Author(s):  
Anna Nowik-Zajac ◽  
Iwona Zawierucha ◽  
Cezary Kozlowski
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Metal Ions ◽  
Aqueous Phase ◽  
Cellulose Triacetate ◽  
Inclusion Membrane ◽  
Selective Transport ◽  
Effective Transport ◽  
Different Temperatures ◽  
Nitrate Solutions

Cellulose-triacetate-based polymer inclusion membranes (PIMs) with different concentrations of a calixpyrrole ester derivative as the membrane carrier were studied to determine their ability to transport Ag(I) from aqueous nitrate solutions. The effects of the concentrations of ion carriers and metal ions, the pH of the source aqueous phase, and stripping agents on the effective transport of Ag(I) were assessed. All studied parameters were found to be important factors for the transport of Ag(I) metal ions. The initial fluxes were determined at different temperatures. The prepared membranes were found to be highly permeable. The selectivity of silver transport from an aqueous solution containing Ag(I), Cu(II), Pb(II), Cd(II), Ni(II), Zn(II), and Co(II) ions was also investigated.

scholarly journals A study on the removal of prednisone from aqueous solutions by adsorption onto a vegetal activated carbon

2018 ◽  
Vol 78 (11) ◽  
pp. 2328-2337 ◽  
Author(s):  
Jéssica C. Zanette ◽  
Márcia T. Veit ◽  
Gilberto C. Gonçalves ◽  
Soraya M. Palácio ◽  
Fernando R. Scremin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Activated Carbon ◽  
Aqueous Solutions ◽  
Batch Adsorption ◽  
Maximum Adsorption Capacity ◽  
Order Model ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Central Composite ◽  
Adsorbent Dose

Abstract This study evaluated the prednisone removal from aqueous solutions using adsorption by an activated carbon of vegetal origin (VAC). A central composite rotatable design (CCRD) and the response surface methodology (RSM) were used to verify the influence of the parameters: pH, adsorbent dose and prednisone concentration in a batch adsorption process. Among the analyzed parameters, only the adsorbent dose and the prednisone concentration were statistically significant (α = 0.05) and the critical values obtained were adsorbent dose: 1.87 g/L, pH 7.56 and prednisone concentration: 3.66 mg/L with 77.51% of prednisone removal by VAC. The kinetic study of the adsorption of prednisone reached the equilibrium in 4 h. The pseudo-first-order model described adequately the kinetics data behavior. The equilibrium experimental data obtained at different temperatures showed that the VAC has a maximum adsorption capacity of 18.04 mg/g at a temperature of 30 °C. The prednisone removal decreased by the increasing temperature and the Langmuir isotherm well described the experimental data (R² > 0.98). Thermodynamic results shown that the prednisone removal of aqueous solutions by VAC is spontaneous and favorable process.

scholarly journals Thermodynamics of porphyrin dimerization in aqueous solutions

1984 ◽  
Vol 219 (2) ◽  
pp. 445-450 ◽  
Author(s):  
R Margalit ◽  
M Rotenberg
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Enthalpy Change ◽  
Aggregation Process ◽  
Neutral Ph ◽  
Similar Temperature ◽  
Increasing Temperature ◽  
Phosphate Buffered Saline ◽  
Hydrophobic Bonding

The dimerization equilibrium of deuteroporphyrin IX and of mesoporphyrin IX in aqueous solutions were studied by fluorimetric techniques over the 0.01-1 microM concentration range, where dimerization is the dominant aggregation process. Deuteroporphyrin IX was studied at several temperatures over the range 22-37 degrees C, and mesoporphyrin at 25 and 37 degrees C. The magnitudes determined for the dimerization equilibrium constants (25 degrees C, neutral pH, phosphate-buffered saline) are 2.3 × 10(6)M-1 and 5.4 × 10(6)M-1 for the deutero and meso derivatives respectively. The meso, deutero and haemato species tested show a similar temperature effect, namely dimerization decreasing with increasing temperature, indicating the involvement of a negative enthalpy change. Van't Hoff isochore of the dimerization constants determined for deuteroporphyrin IX was linear within the temperature range of 22-37 degrees C, allowing the calculation of the thermodynamic parameters. For deuteroporphyrin dimerization, those were found to be delta G0 = −36. 4kJ X mol-1; delta H0 = −46. 0kJ X mol-1 and delta S0 = −32.2J X K-1 X mol-1 (at neutral pH, 25 degrees C, phosphate-buffered saline), showing the process to be enthalpy-driven. Similar trends have been found for porphyrin species other than those studied here. Our data fit with a hypothesis giving a major role to the solvent in driving porphyrins to aggregate in aqueous solution. The magnitudes and directions of the energetic changes fit better with the expectation of the ‘ solvophobic force’ theory predicting enthalpy-driven association, than with the classic hydrophobic bonding, predicting the association to be entropy-driven.

THE DISSOCIATION OF α- AND β-LIPOVITELLIN IN AQUEOUS SOLUTION: PART I. EFFECT OF pH, TEMPERATURE, AND OTHER FACTORS

1962 ◽  
Vol 40 (1) ◽  
pp. 363-372 ◽  
Author(s):  
R. W. Burley ◽  
W. H. Cook
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Effect Of Ph ◽  
Reversible Dissociation ◽  
Lipoprotein Concentration ◽  
Irreversible Aggregation ◽  
Increasing Temperature

The effect of pH, temperature, ionic strength, and lipoprotein concentration on the reversible dissociation of α- and β-lipovitellin in aqueous solutions above pH 6 has been examined by ultracentrifugal measurements. Under otherwise similar conditions α- and β-lipovitellin are 50% dissociated at pH 10.5 and 7.8, respectively. Both lipovitellins undergo an irreversible aggregation above about pH 11; β-lipovitellin is sometimes converted to a non-dissociable form upon aging. Dissociation of both lipovitellins decreases with increasing ionic strength and increasing temperature. Although the ultracentrifugal method has limitations, provisional equilibrium constants and thermodynamic data were obtained from it that are comparable with those obtained for certain protein systems.

scholarly journals Solubility Study and purification Of Industrial triple superphosphate in aqueous solution

2013 ◽  
Vol 9 (2) ◽  
pp. 1943-1952
Author(s):  
Khouloud Nasri ◽  
Chaker Chtara ◽  
Hassen Chekir ◽  
Hafed EL Feki
Keyword(s):  
Aqueous Solution ◽  
Ionic Conductivity ◽  
Calcium Phosphate ◽  
Phosphoric Acid ◽  
Aqueous Solutions ◽  
Chemical Fertilizer ◽  
Triple Superphosphate ◽  
Solubility Study ◽  
Different Temperatures ◽  
Insoluble Compounds

Triple Superphosphate (TSP) is a chemical fertilizer, acknowledged by its important content of phosphorus, necessary element for plants. It’s obtained by adding phosphoric acid to phosphate ore, consisting of calcium phosphate containing many impurities. TSP was dissolved at different temperatures and in various amounts of water, filtered to remove insoluble compounds. Then the ionic conductivity was monitored for each solution as a function of the added amount of TSP. Aqueous solutions were evaporated to dryness and analyzed the P2O5. The starting materials and final products were analyzed by several methods (XRD, IR, NMR, SEM) confirming that after dissolution the product was purified.

scholarly journals STANDARD FORMATION ENTHALPIES OF HYDROXYETHYLIDENEDIPHOSPHONIC ACID AND PRODUCTS OF ITS DISSOCIATION IN AQUEOUS SOLUTION

2018 ◽  
Vol 61 (4-5) ◽  
pp. 37
Author(s):  
Alexander I. Lytkin ◽  
Viktor V. Chernikov ◽  
Olga N. Krutova ◽  
Ivan A. Skvortsov
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Enthalpies Of Formation ◽  
Formation Enthalpies ◽  
Different Temperatures ◽  
Heat Value ◽  
Standard Enthalpies Of Formation ◽  
Changes Over Time ◽  
Stepwise Dissociation

This study aimed the measuring the standard enthalpies of formation of hydroxyethylidenediphosphonic acid and the products of its dissociation in aqueous solutions at 298.15 K. In the literature there is a large amount of data on the constants of stepwise dissociation of the acid. The works were done at different temperatures and the values of the ionic strength of the solution on the background of the different nature of the supporting electrolytes. In order to compare the values of the constants of stepwise dissociation of the acid, obtained by different authors, we recalculated the values of рK1, рK2, рK3, рК4, рК5 at zero ionic strength by the Davies equation. The most probable values of thermodynamic constants of dissociation of hydroxyethylidenediphosphonic acid were the following: рК10 = 1.7±0.03; рК20 = 2.47±0.05; рК30 = 7.78±0.05; рК40 = 10.29±0.05 and pK50 = 11.13±0.05. Calorimetric measurements were performed on an ampoule calorimeter equipped with an isothermal shell and a KMT-14 thermistor temperature sensor, and the automatic recording the temperature changes over time. The operation of installation was verified with the integral enthalpies of dissolution in water of crystalline potassium chloride and was considered suitable for measurements, if certain it ∆solН298.15 (KCl ∞ H2O)=17.234± 0.018 kJ/mol, corresponding to the standard SRM 1655NBS. The heat value of the calorimeter water was 87±12 Дж/mol virtually coincided with the thermal value of the calorimeter for potassium hydroxide. The volume of the calorimetric liquid was 43.12 ml. The hydroxyethylidenediphosphonic acid samples were weighed on a VLR-200 balance with 2∙10-4 g accuracy. The confidence range of the average ΔН value was determined at 0.95 probability. The equilibrium compositions of solutions were calculated using RRSU software. The standard enthalpies of formation of hydroxyethylidenediphosphonic acid and the products of its dissociation in aqueous solutions were calculated.Forcitation:Lytkin A.I., Chernikov V.V., Krutova O.N., Skvortsov I.A. Standard formation enthalpies of hydroxyethylidenediphosphonic acid and products of its dissociation in aqueous solution. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 4-5. P. 37-42

Effect of thermal history of aqueous solutions of KCl on the metastable zone width

1984 ◽  
Vol 49 (3) ◽  
pp. 559-569 ◽  
Author(s):  
Jaroslav Nývlt
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Thermal History ◽  
Equilibrium Solubility ◽  
Metastable Zone Width ◽  
Zone Width ◽  
Preceding Experiment ◽  
History Of ◽  
Metastable Zone ◽  
The Given

The metastable zone width of an aqueous solution of KCI was measured as a function of the time and temperature of overheating above the equilibrium solubility temperature. It has been found that when the experiments follow close upon one another, the parameters of the preceding experiment affect the results of the experiment to follow.The results are interpreted in terms of hypotheses advanced in the literature to account for the effect of thermal history of solution. The plausibility and applicability of these hypotheses are assessed for the given cause of aqueous solution of a well soluble electrolyte.

Study of potential oscillations during reaction of an aluminium single crystal with an aqueous KOH solution

1990 ◽  
Vol 55 (2) ◽  
pp. 345-353 ◽  
Author(s):  
Ivan Halaša ◽  
Milica Miadoková
Keyword(s):  
Aqueous Solutions ◽  
Single Crystal ◽  
Single Crystals ◽  
Periodic Potential ◽  
Optimum Conditions ◽  
Potential Oscillations ◽  
Dilute Aqueous Solutions ◽  
Experimental Findings ◽  
Kinetics Of

The authors investigated periodic potential changes measured on oriented sections of Al single crystals during spontaneous dissolution in dilute aqueous solutions of KOH, with the aim to find optimum conditions for the formation of potential oscillations. It was found that this phenomenon is related with the kinetics of the reaction investigated, whose rate also changed periodically. The mechanism of the oscillations is discussed in view of the experimental findings.

scholarly journals I. Thermo-electric behaviour of aqueous solutions with mercurial electrodes

1879 ◽  
Vol 29 (196-199) ◽  
pp. 472-482 ◽  
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Internal Diameter ◽  
Thermo Electric ◽  
Thin Glass ◽  
Mercury Surface

In order to investigate this subject, I devised and constructed the following apparatus :—A and B are two thin glass basins, 81 millims. internal diameter (= 5,153 sq. millims. of mercury surface), and 6·0 centims. deep; each containing a layer of mercury about 1·0 centim. deep, covered by a layer, about 3 centims. deep, of the aqueous solution to be examined.

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