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1.
S. Olmez Aytas S. Akyil M. Eral 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(1):119-125
Adsorptive behavior of natural clinoptilolite-rich zeolite from Balikesir deposites in Turkey was assessed for the removal
of uranium from aqueous solutions. The uranium uptake and cation exchange capacities of zeolite were determined. The effect
of initial uranium concentrations in solution was studied in detail at the optimum conditions determined before (pH 2.0, contact
time: 60 minutes, temperature: 20 °C). The uptake equilibrium is best described by Langmuir adsorption isotherm. Some thermodynamic
parameters (ΔH°, ΔS°, ΔG°) of the adsorption system were also determined. Application to fixation of uranium to zeolite was performed. The uptake
of uranium complex on zeolite followed Langmuir adsorption isotherm for the initial concentration (25 to 100 μg/ml). Thermodynamic
values of ΔG°, ΔS° and ΔH° found show the spontaneous and exothermic nature of the process of uranium ions uptake by natural zeolite.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
In this paper, the crosslinked polyester resin containing acrylic acid functional groups was used for the adsorption of uranium
ions from aqueous solutions. For this purpose, the crosslinked polyester resin of unsaturated polyester in styrene monomer
(Polipol 353, Poliya) and acrylic acid as weight percentage at 80 and 20%, respectively was synthesized by using methyl ethyl
ketone peroxide (MEKp, Butanox M60, Azo Nobel)-cobalt octoate initiator system. The adsorption of uranium ions on the sample (0.05 g copolymer
and 5 mL of U(VI) solution were mixed) of the crosslinked polyester resin functionalized with acrylic acid was carried out
in a batch reactor. The effects of adsorption parameters of the contact time, temperature, pH of solution and initial uranium(VI)
concentration for U(VI) adsorption on the crosslinked polyester resin functionalized with acrylic acid were investigated.
The adsorption data obtained from experimental results depending on the initial U(VI) concentration were analyzed by the Freundlich,
Langmuir and Dubinin–Radushkevich (D–R) adsorption isotherms. The adsorption capacity and free energy change were determined
by using D–R isotherm. The obtained experimental adsorption data depending on temperature were evaluated to calculate the
thermodynamic parameters of enthalpy (ΔH°), entropy (ΔS°) and free energy change (ΔG°) for the U(VI) adsorption on the crosslinked polyester resin functionalized with acrylic acid from aqueous solutions. The
obtained adsorption data depending on contact time were analyzed by using adsorption models such as the modified Freundlich,
Elovich, pseudo-first order and pseudo-second-order kinetic models. 相似文献
3.
R. Donat K. Esen H. Cetisli S. Aytas 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):253-261
Ulva sp. and sepiolite were used to prepare composite adsorbent. The adsorption of uranium(VI) from aqueous solutions onto Ulva sp.-sepiolite has been studied by using a batch adsorber. The parameters that affect the uranium(VI) adsorption, such as solution
pH, initial uranium(VI) concentration, and temperature, have been investigated and the optimum conditions determined. The
adsorption patterns of uranium on the composite adsorbent followed the Freundlich and Dubinin-Radushkevich (D-R) isotherms.
The Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) models have been applied and the data correlate well with Freundlich
model. The sorption is physical in nature (sorption energy, E = 4.01 kJ/mol). The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated from the slope and intercept of lnK
d
vs. 1/T plots. Thermodynamic parameters (ΔH
ads
= −22.17 kJ/mol, ΔS
ads
= −17.47 J/mol·K, ΔG
o
ads
(298.15 K) = −16.96 kJ/mol) show the exothermic heat of adsorption and the feasibility of the process. The results suggested
that the Ulva sp-sepiolite composite adsorbent is suitable as a sorbent material for recovery and biosorption/adsorption of uranium ions from
aqueous solutions. 相似文献
4.
Galán J. J. González-Pérez A. Rodríguez J. R. 《Journal of Thermal Analysis and Calorimetry》2003,72(2):465-470
Specific conductivity of aqueous solutions of dodecyldimethylethylammonium bromide has been determined in the temperature
range of 15-40°C. The critical micelle concentration (cmc) and ionization degree of the micelles, b, were determined from
the data. Thermodynamic functions, such as standard Gibbs free energy, ΔG
m°, enthalpy, ΔG
m°, and entropy, ΔG
m°, of micellization, were estimated by assuming that the system conforms to the mass action model. The change in heat capacity
upon micellization, ΔG
m°, was estimated from the temperature dependence of ΔG
m°. An enthalpy-entropy compensation phenomenom for the studied system has been found.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Sabriye Yusan Mahmoud A. A. Aslani D. Alkim Turkozu Hasan A. Aycan Sule Aytas Sema Akyil 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(1):231-238
In this work, sorption of uranium ions on volcanic tuff collected from the deposits located at the Tendurek of Eastern Turkey
was investigated in batch technique. The effect of different parameters such as pH of the medium, contact time, uranium concentration
and temperature were investigated. The maximum removal of U(VI) was found to be 68% at pH 5.0, initial U(VI) concentration
of 75 mg L−1 and 30 °C. Thermodynamic parameters, such as enthalpy of adsorption ∆H°, free energy change ∆G° and entropy change ∆S° have been also calculated and interpreted. The suitability of the Langmuir, Freundlich and Dubinin-Radushkhevic adsorption
models to the equilibrium data was investigated for uranium-volcanic tuff system. The results suggest that volcanic tuff can
be used as efficient and cost effective adsorbents for uranium ion removal. 相似文献
6.
P. Senthil Kumar R. V. Abhinaya K. Gayathri Lashmi V. Arthi R. Pavithra V. Sathyaselvabala S. Dinesh Kirupha S. Sivanesan 《Colloid Journal》2011,73(5):651-661
The adsorption of methylene blue (MB) dye from aqueous solution onto a cashew nut shell (CNS) was investigated as a function
of parameters such as solution pH, CNS dose, contact time, initial MB dye concentration and temperature. The CNS was shown
to be effective for the quantitative removal of MB dye, and the equilibrium was reached in 60 min. The experimental data were
analysed by two-parameter isotherms (Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models) using nonlinear regression
analysis. The characteristic parameters for each isotherm and the related correlation coefficients were determined. Thermodynamic
parameters such as ΔG°, ΔH° and ΔS° were also evaluated, the sorption process was found to be spontaneous and exothermic. Pseudo-first-order, pseudo-second-order
and Elovich kinetic models were used to analyze the adsorption process. The results of the kinetic study suggest that the
adsorption of MB dye matches the pseudo-second-order equation, suggesting that the adsorption process is presumably chemisorption.
The adsorption process was found to be controlled by both surface and pore diffusion. Analysis of adsorption data using a
Boyd kinetic plot confirmed that the external mass transfer is a rate determining step in the sorption process. A single-stage
batch adsorber was designed for different CNS doses to effluent volume ratios using the Freundlich equation. The results indicated
that the CNS could be used effectively to adsorb MB dye from aqueous solutions. 相似文献
7.
Abdelhakim Kadous Mohamed Amine Didi Didier Villemin 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(2):553-561
Removal of uranium(VI) ions from acetate medium in aqueous solution was investigated using Lewatit TP260 (weakly acidic, macroporous-type
ion exchange resin with chelating aminomethylphosphonic functional groups) in batch system. The parameters that affect the
uranium(VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, adsorbent dose and temperature
have been investigated. Results have been analyzed by Langmuir and Freundlich isotherm; the former was more suitable to describe
the sorption process. The moving boundary particle diffusion model only fits the initial metal adsorption on the resin. The
rate constant for the uranium sorption by Lewatit TP260 was 0.441 min−1 from the first order rate equation. The total sorption capacity was found to be 58.33 mg g−1 under optimum experimental conditions. Thermodynamic parameters (ΔH = 61.74 kJ/mol; ΔS = 215.3 J/mol K; ΔG = −2.856 kJ/mol) showed the adsorption of an endothermic process and spontaneous nature, respectively. 相似文献
8.
L. A. Kochergina A. V. Emel’yanov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(10):1742-1747
Heats of reaction of glycylglycine with nitric acid and potassium hydroxide solutions are determined by two calorimetric procedures
at 288.15, 298.15, 308.15 K and an ionic strength of solution of 0.25, 0.50, and 0.75 in the presence of KNO3. Standard thermodynamic characteristics (Δr
H°, Δr
G°, Δr
S°, and Δp
C°) are calculated for the acid-base reactions in aqueous peptide solutions. The effects of the concentration of background
electrolyte and temperature on the heats of dissociation of glycylglycine are considered. 相似文献
9.
G. S. Murthy M. V. Sivaiah S. S. Kumar V. N. Reddy R. M. Krishna S. Lakshminarayana 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(1):109-114
The applicability of zirconium phosphate-ammonium molybdophosphate (ZrP-AMP) for the efficient removal of cesium from aqueous
acidic solutions by adsorption has been investigated. The adsorption data analysis was carried out using the Freundlich, Dubinin-Raduskevich
(D-R) and Langmuir isotherms for the uptake of Cs in the initial concentration range of 3.75.10-5-7.52.10-3 mol.dm-3 on the ZrP-AMP exchanger from nitric acid medium. The mean free energy (E) values for the adsorption of Cs were obtained from the D-R isotherm. Equilibrium adsorption values at different temperatures
have been utilized to evaluate the change in enthalpy, entropy and free energy (ΔH°, ΔS°, ΔG°). The adsorption of cesium on the ZrP-AMP exchanger was found to be endothermic.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
Yating Liu Yunhai Liu Xiaohong Cao Rong Hua Youqun Wang Cui Pang Ming Hua Xiaoyan Li 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(2):231-239
The cross-linked chitosan (CS) gels synthesized by using glutaraldehyde (GLA), epichlorohydrin (EC), and ethylene glycol diglycidyl
ether (EGDE) as cross-linkers respectively were used to investigate the adsorption of U(VI) ions in an aqueous solution. The
pure chitosan (PCS) and the cross-linked chitosan gels were characterized by FTIR and SEM analysis. The kinetic, thermodynamic
adsorption and adsorption isotherms of U(VI) ions onto unmodified and modified cross-linked chitosan were studied in a batch
adsorption experiments. The effect of pH, contact time and temperature on the adsorption capacity were also carried out. At
the optimum pH, the maximum adsorbed amount of PCS, GLACS, ECCS and EGDECS were 483.05, 147.05, 344.83 and 67.56 mg/g, respectively.
The uranium (VI) adsorption process of PCS and ECCS followed better with pseudo-second-order kinetic model, while GLACS and
EGDECS followed pseudo-first-order kinetic model well. The results obtained from the equilibrium isotherms adsorption studied
of U(VI) ions were analyzed in two adsorption models, namely, Langmuir and Freundlich isothms models, the results showed that
the Langmuir isotherm had better conformity to the equilibrium data. The thermodynamic parameters such as enthalpy (ΔHo), entropy (ΔSo), and Gibbs free energy (ΔGo) showed that the adsorption process was both spontaneous and endothermic. 相似文献
11.
R. Zarganian A. K. Bordbar R. Amiri M. Tamannaei A. R. Khosropour I. Mohammadpoor-Baltork 《Journal of solution chemistry》2011,40(6):921-928
Pentanediyl-1,5-bis (hydroxyethylmethylhexadecylammonium bromide) was synthesized and characterized as a type of novel gemini
cationic surfactant. Its solution properties were determined at various temperatures by conductivity measurements and the
fluorescence quenching technique. The CMC increased in the range of 1.85 to 2.77 μmol⋅L−1 as the temperature increased. The aggregation number was determined at various concentrations of NaBr solutions by the fluorescence
quenching of pyrene. The thermodynamic parameters of micellization were determined using the mass law equation and the values
of ΔG °, ΔH °and ΔS ° were determined for the micellization process. 相似文献
12.
X. Y. Feng X. P. Geng J. J. Peng H. Y. Hou Q. Bai 《Journal of Thermal Analysis and Calorimetry》2010,102(2):799-807
The displacement adsorption enthalpies (ΔH) of denatured α-Amylase (by 1.8 mol L−1 GuHCl) adsorbed onto a moderately hydrophobic surface (PEG-600, the end-group of polyethylene glycol) from solutions (x mol L−1 (NH4)2SO4, 0.05 mol L−1 KH2PO4, pH 7.0) at 298 K are determined by microcalorimeter. Further, entropies (ΔS), Gibbs free energies (ΔG) and the fractions of ΔH, ΔS, and ΔG for net adsorption of protein and net desorption of water are calculated in combination with adsorption isotherms of α-Amylase
based on the stoichiometric displacement theory for adsorption (SDT-A) and its thermodynamics. It is found that the displacement
adsorptions of denatured α-Amylase onto PEG-600 surface are exothermic and enthalpy driven processes, and the processes of
protein adsorption are accompanied with the hydration by which hydrogen bond form between the adsorbed protein molecules favor
formation of β-sheet and β-turn structures. The Fourier transformation infrared spectroscopy (FTIR) analysis shows that the
contents of ordered secondary structures of adsorbed α-Amylase increase with surface coverages and salt concentrations increment. 相似文献
13.
Composites could be more effective adsorbents than inorganic and organic components individually. In the present study, the
red macro marine algae, Jania Rubens and yeast, Saccharomyces cerevisiae immobilized on silica gel were used as a constituent of bi-functionalized biosorbent to remove thorium ions from aqueous
solution. Optimum biosorption conditions were determined as a function of pH, initial Th(IV) concentration, contact time,
temperature, volume/mass ratio and co-ion effect. The morphological analysis of the biocomposite was performed by the scanning
electron microscopy and functional groups in the biosorbent were determined by FT-IR spectroscopy. In order to find the adsorption
characteristics, Langmuir, Freundlich, and Dubinin–Radushkevich adsorption isotherms were applied to the adsorption data.
The data were well described by Langmuir adsorption isotherms while the fit of Freundlich adsorption isotherms and Dubinin–Radushkevich
equation to adsorption data was poor. Using the equilibrium constant value obtained at different temperature, the thermodynamics
properties of the biosorption (ΔG°, ΔH° and ΔS°) were also determined. The results show that biosorption of Th(IV) ions onto biocomposite was exothermic nature, spontaneous
and more favorable at lower temperature under examined conditions. 相似文献
14.
R. Donat G. K. Cılgı S. Aytas H. Cetisli 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):271-280
This paper discusses the sorption properties for U(VI) by alginate coated CaSO4·2H2O sepiolite and calcined diatomite earth (Kieselguhr) (ACSD). The removal of U(VI) from aqueous solution by sorption onto
ACSF in a single component system with various contact times, pH, temperatures, and initial concentrations of U(VI) was investigated.
The sorption patterns of uranium on the composite adsorbent followed the Langmuir, Freundlich and Dubinin-Radushkhevic (D-R)
isotherms. The Freundlich, Langmuir, and D-R models have been applied and the data correlated well with Freundlich model and
that the sorption was physical in nature (sorption energy, E
a
= 17.05 kJ/mol). The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated from the slope and intercept of lnK
0 vs. 1/T plots. Thermodynamic parameters (ΔH
ads = 31.83 kJ/mol, ΔS
ads = 167 J/mol·K, ΔG
o
ads (293.15 K) = −17.94 kJ/mol) showed the endothermic heat of sorption and the feasibility of the process. The thermodynamics
of U(VI) ion/ACSD system indicates the spontaneous and endothermic nature of the process. It was noted that an increase in
temperature resulted in a higher uranium loading per unit weight of the adsorbent. 相似文献
15.
Liming Zuo Shaoming Yu Hai Zhou Jun Jiang Xue Tian 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(2):579-586
The adsorption behavior of Eu(III) from aqueous solution to mesoporous molecular sieves (Al-MCM-41) is investigated as a function
of contact time, solid content, ionic strength, pH, foreign ions and temperature by using batch technique. The experimental
results show that Eu(III) adsorption is strongly dependent on pH values, but independent of ionic strength and foreign cations
under our experimental conditions. The kinetic process is described by a pseudo-second-order rate model very well. The adsorption
isotherms are simulated by Langmuir model very well. The thermodynamic parameters (∆G°, ∆S°, ∆H°) are calculated from the temperature dependent adsorption isotherms at 293, 313 and 333 K, respectively, and the results
suggest that the adsorption of Eu(III) on Al-MCM-41 is a spontaneous and endothermic process. Desorption studies indicate
that the adsorbed Eu(III) is very difficult to be desorbed from the solid surface. Al-MCM-41 is a suitable material for the
preconcentration and solidification of Eu(III) from large volumes of aqueous solutions. 相似文献
16.
R. Donat 《The Journal of chemical thermodynamics》2009,41(7):829-835
The adsorption of uranium (VI) from aqueous solutions onto natural sepiolite has been studied using a batch adsorber. The parameters that affect the uranium (VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, and temperature, have been investigated and optimized conditions determined. Equilibrium isotherm studies were used to evaluate the maximum sorption capacity of sepiolite and experimental results showed this to be 34.61 mg · g?1. The experimental results were correlated reasonably well by the Langmuir adsorption isotherm and the isotherm parameters (Qo and b) were calculated. Thermodynamic parameters (ΔH° = ?126.64 kJ · mol?1, ΔS° = ?353.84 J · mol?1 · K?1, ΔG° = ?21.14 kJ · mol?1) showed the exothermic heat of adsorption and the feasibility of the process. The results suggested that sepiolite was suitable as sorbent material for recovery and adsorption of uranium (VI) ions from aqueous solutions. 相似文献
17.
Thermodynamic characteristics of alanine-18-crown-6 ether complexes in binary water-acetone solvents
T. R. Usacheva I. A. Kuz’mina V. A. Sharnin I. V. Chernov E. Matteoli 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(1):36-39
The formation of 18-crown-6 ether (18C6) complexes with D,L-alanine (Ala) in mixed wateracetone solvents with 0.0, 0.08, 0.17,
0.22, and 0.30 mole fractions of acetone (T = 298.15 K) was investigated by means of calorimetry. Thermodynamic characteristics of the reaction of the molecular [Ala18C6]
complex formation (Δr
G°, Δr
H°, and TΔr
S°) were calculated on the basis of calorimetric data. Analysis of solvation contributions of reagents into the enthalpy of
the [Ala18C6] formation reaction showed that the changes in the reaction energy when the solvent composition is varied are
determined by the changes in the solvate state of 18C6. 相似文献
18.
H. Temel B. Ziyadanogullari H. Alp I. Aydın F. Aydın S. İlhan 《Russian Journal of Coordination Chemistry》2006,32(4):282-286
The Cu(II) and Zn(II) complexes of aromatic bidentate diamines were prepared and characterized by different analytical and
spectral methods. Thermodynamic parameters of complexes of Cu(II) and Zn(II) cations with 1,3-bis(p-aminophenoxy)propane were determined in 60 vol. % DMF-H2O at various ionic strengths (0.07, 0.13, 0.2 M NaNO3) and different temperatures (45, 50, 55, 60 ± 0.1°C) using a spectrophotometric method. The NaNO3 solution was used to maintain the ionic strength. The stability constants show an inverse relationship with ionic strengths.
The thermodynamic parameters of 60 vol. % DMF-H2O (ΔG°, ΔH°, ΔS°) based on these formation constants were determined.
The text was submitted by the authors in English. 相似文献
19.
M. Mufazzal Saeed Abdul Ghaffar 《Journal of Radioanalytical and Nuclear Chemistry》1998,232(1-2):171-177
The nature of adsorption behavior of Au(III) on polyurethane (PUR) foam was studied in 0.2M HCl aqueous solution. The effect
of shaking time and amount of adsorbent were optimized for 3.16·10−5M solution of Au(III) in 0.2M HCl. The classical Freundlich and Langmuir adsorption isotherms have been employed successfully.
The Freundlich parameters 1/n and adsorption capacityK are 0.488±0.016 and (1.40±0.22)·10−2 mol·g−1, respectively. The Langmuir constants of saturation capacityM and binding energyb are (1.66±0.08)·10−4mol·g−1 and 40294±2947 l·g−1, respectively, indicating the monolayer chemical sorption. The mean free energy (E) of adsorption of Au(III) on PUR foam has been evaluated using D-R isotherm and found to be 11.5±0.16 kJ·mol−1 reflecting the ion exchange type of chemical adsorption. The effect of temperature on the adsorption has also been studied.
the isosteric heat of adsorption was found to be 44.03±1.66 kJ·mol−1. The thermodynamic parameters of ΔG, ΔH, ΔS and equilibrium constantK
c
have been calculated. The negative values of ΔG, ΔH and ΔS support that the adsorption of Au(III) on PUR foam is spontaneous, exothermic and of ion exchange chemisorption. The nature
of the Au(III) species sorbed on PUR foam have been discussed. 相似文献
20.
Adsorption kinetic,thermodynamic and desorption studies of phosphate onto hydrous niobium oxide prepared by reverse microemulsion method 总被引:1,自引:0,他引:1
A type of Nb2O5⋅3H2O was synthesized and its phosphate removal potential was investigated in this study. The kinetic study, adsorption isotherm,
pH effect, thermodynamic study and desorption were examined in batch experiments. The kinetic process was described by a pseudo-second-order
rate model very well. The phosphate adsorption tended to increase with a decrease of pH. The adsorption data fitted well to
the Langmuir model with which the maximum P adsorption capacity was estimated to be 18.36 mg-P g−1. The peak appearing at 1050 cm−1 in IR spectra after adsorption was attributed to the bending vibration of adsorbed phosphate. The positive values of both
ΔH° and ΔS° suggest an endothermic reaction and increase in randomness at the solid-liquid interface during the adsorption. ΔG° values obtained were negative indicating a spontaneous adsorption process. A phosphate desorbability of approximately 68%
was observed with water at pH 12, which indicated a relatively strong bonding between the adsorbed phosphate and the sorptive
sites on the surface of the adsorbent. The immobilization of phosphate probably occurs by the mechanisms of ion exchange and
physicochemical attraction. Due to its high adsorption capacity, this type of hydrous niobium oxide has the potential for
application to control phosphorus pollution. 相似文献