共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Fujiwara T. Okano T. -H. Nakashima A. A. Nakamura G. Sugihara 《Colloid and polymer science》1997,275(5):474-479
For a sodium salt of α-sulfonatomyristic acid methyl ester (14SFNa), one of the α-SFMe series surfactants, critical micellization
concentration (CMC), solubility and degree of counterion binding (β) were determined by means of electrocon-ductivity measurements
at different temperatures (at every 5 °C) ranging from 15 to 50 °C. The phase diagram of 14SFNa in pure water was constructed
from the CMC- and solubility-temperature data, in which the Krafft temperature (critical solution temperature) was found around
0 °C. The changes in the Gibbs energy, ΔG
0
m, enthalpy, ΔH
0
m, and entropy, ΔS
0
m, upon micelle formation as a function of temperature were evaluated taking βvalues into calculation.
Received: 28 August 1996 Accepted: 5 November 1996 相似文献
2.
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
3.
The molality dependence of specific conductivity of pentadecyl bromide, cetylpyridinium bromide and cetylpiridinium chloride
in aqueous solutions has been studied in the temperature range of 30–45 °C. The critical micelle concentration (cmc) and ionization
degree of the micelles, β, were determined directly from the experimental data. Thermal parameters, such as standard Gibbs free energy
\Updelta Gm0 , \Updelta G_{m}^{0} , enthalpy
\Updelta Hm0 \Updelta H_{m}^{0} and entropy
\Updelta Sm0 , \Updelta S_{m}^{0} , of micellization were estimated by assuming that the system conforms to the pseudo-phase separation model. The change in
heat capacity on micellization
\Updelta Cp , \Updelta C_{p} , was estimated from the temperature dependence of
\Updelta Hm0 . \Updelta H_{m}^{0} . An enthalpy–entropy compensation phenomenon for the studied system has been found. 相似文献
4.
Micellar properties of dodecylpyridinium chloride (DPC) were investigated by means of electrical conductometry with emphasis
on the influences of cosolvent-water content and temperature. Ethanol was used as a cosolvent. Conductivity measurements gave
information about critical micelle concentration and micellar ionization degree of the water-ethanol micellar solutions at
different temperatures. In all solvent mixtures, it was observed that the critical micelle concentration of DPC and the degree
of the counterion dissociation increase with an increasing concentration of ethanol and increasing temperature. Micellar and
thermodynamics data were obtained from the temperature dependence of critical micelle concentrations in various aqueous mixtures
of ethanol. In order to explain the effect of the cosolvent, the differences in the Gibbs energies of micellization of DPC
between water and binary cosolvent were determined. The standard free energy (ΔG°mic) of micellization was found to be negative as the concentration of the solvent increases, but it is roughly independent of
temperature. Although the enthalpic contribution was found to be larger than the entropic one, in particular at lower temperatures,
an entropy-enthalpy compensation effect was observed for all systems. Also, enthalpy (ΔH°mic) and entropy (ΔS°mic) of micellization are strongly temperature dependent and decrease with increasing temperature and cosolvent content.
The text was submitted by the authors in English. 相似文献
5.
Hong-Lin Zhang Zhe Kong Yong-Mei Yan Gan-Zuo Li Li Yu Fei Geng 《Journal of solution chemistry》2008,37(12):1631-1644
The power-time curves for the micelle formation process were determined for two anionic surfactants, sodium laurate (SLA)
and sodium dodecyl sulfate (SDS), in mixed alcohol + N,N-dimethylacetamide (DMA) solvent using titration microcalorimetry.
From the data of the lowest point and the area of the power-time curves, their critical micelle concentration (CMC) and ΔH
mo were obtained. The other thermodynamic functions of the micellization process (ΔG
mo and ΔS
mo) were also calculated with thermodynamic equations. For both surfactants, the effects of the carbon number (chain length)
of the alcohol, the concentration of alcohol, and the temperature on the CMC and thermodynamic functions are discussed. For
systems containing identical concentrations of a different alcohol, values of the CMC, ΔH
mo and ΔS
mo increased whereas ΔG
mo decreased with increasing temperature. For systems containing an identical alcohol concentration at the same temperature,
values of the CMC, ΔH
mo,ΔG
mo and ΔS
mo decrease with increasing carbon number of alcohol. For systems containing the same alcohol at the same temperature, the CMC
and ΔG
mo values increase whereas ΔH
mo and ΔS
mo decrease with increasing alcohol concentration. 相似文献
6.
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
7.
A novel surfactant peptide consisting of an arginine cation with laurate anion has been synthesized, purified and characterized.
The critical micellar concentration (cmc) of peptide in aqueous solutions has been determined using spectroscopic techniques
and is found to increase from 0.06 to 0.11 mM with increasing temperature (15–45 °C). Cmc is also determined in the presence
of salts like NaCl, KCl and sodium acetate and it is found that these electrolytes hinder aggregation with a significant increase
in the case of sodium acetate. The aggregation number of the surfactant peptide has been determined using fluorescence quenching
measurements and is observed to decrease from 14 to 6 with increasing temperature (15–45 °C). The standard free energy change
(ΔG
0
m) and standard enthalpy change (ΔH
0
m) of the peptide aggregate are found to be negative with a small positive value for standard entropy change (ΔS
0
m). The peptide aggregate seems to undergo phase transition above 50 °C as observed from UV–vis and fluorescence spectroscopy.
From pyrene binding studies, it is shown that the interior dielectric constant increases from 5.08 at 34 °C to 8.77 at 50 °C
and further decreases with increase in temperature indicating a phase change at 50 °C. Also, the ratio of excimer intensity
to monomer intensity, which is a measure of microviscosity of the aggregate, decreases with increase in temperature with a
change at 50 °C indicating a phase change.
Received: 14 February 1997 Accepted: 13 August 1997 相似文献
8.
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
9.
Hong-lin Zhang Yue Zhu Ke Zhang Ting-ting Hou Hai-ying Liu Mao-jin Cui Gan-zuo Li Li Yu 《Journal of solution chemistry》2009,38(2):187-198
The power-time curves of the micelle formation process were determined at four temperatures for a cationic surfactant [cetyltrimethylammonium
bromide (CTAB)] in a non-aqueous solvent [N,N-dimethylformamide (DMF)] by titration microcalorimetry. From the data of the
minimum of the titration point and the area of the power-time curves, values of their CMC and ΔH
m
θ
were obtained. Values of ΔG
m
θ
and ΔS
m
θ
were also calculated according to standard thermodynamic relations. For the cationic surfactant CTAB, the relationships involving
the carbon numbers of the alcohols, the alcohol’s concentration, and the temperature on the CMC, and also the thermodynamic
functions for micellization are discussed. For systems containing an identical concentration of various alcohols, values of
the CMC, ΔH
m
θ
and ΔS
m
θ
increased whereas those of ΔG
m
θ
decreased with increasing temperature. For systems containing identical alcohol concentrations at the same constant temperature,
values of the CMC, ΔH
m
θ
,ΔG
m
θ
and ΔS
m
θ
decreased with increasing carbon number of the alcohol. For systems containing the same alcohol at the same temperature,
the CMC and ΔG
m
θ
values increased whereas ΔH
m
θ
and ΔS
m
θ
decreased with increasing alcohol concentration. 相似文献
10.
Surface tension measure-ments in aqueous cetyltrimethyl ammonium bromide were performed in presence of various amounts of
9-(hydroxymethyl)anthracene (AM), 9-[1-(1-hydroxy)ethyl]anthracene (THAE), and 9-[1-(1-hydroxy-2,2,2-trifluoro)ethyl]anthracene
(TFAE). Free energies ΔG
⊖
m and ΔG
⊖
i of micellization and of adsorption to the air–water interface, respectively, were determined as well as the corresponding
enthalpies and entropies. ΔG
o−
m of micellization increased in the presence of AM and THAE, but became more negative when TFAE was added. In contrast to AM
and THAE, TFAE addition decreases ΔS
⊖
i. For this peculiarity of TFAE, its location and orientation in micellar solution was investigated by means of UV and 19F-NMR spectroscopy.
Received: 26 March 1997 Accepted: 16 May 1997 相似文献
11.
A 56.56-kDa extracellular chitinase from Paenibacillus sp. D1 was purified to 52.3-fold by ion exchange chromatography using SP Sepharose. Maximum enzyme activity was recorded
at pH 5.0 and 50 °C. MALDI-LC-MS/MS analysis identified the purified enzyme as chitinase with 60% similarity to chitinase
Chi55 of Paenibacillus ehimensis. The activation energy (E
a) for chitin hydrolysis and temperature quotient (Q
10) at optimum temperature was found to be 19.14 kJ/mol and 1.25, respectively. Determination of kinetic constants k
m, V
max, k
cat, and k
cat/k
m and thermodynamic parameters ΔH*, ΔS*, ΔG*, ΔG*E–S, and ΔG*E–T revealed high affinity of the enzyme for chitin. The enzyme exhibited higher stability in presence of commonly used protectant
fungicides Captan, Carbendazim, and Mancozeb compared to control as reflected from the t
1/2 values suggesting its applicability in integrated pest management for control of soil-borne fungal phytopathogens. The order
of stability of chitinase in presence of fungicides at 80 °C as revealed from t
1/2 values and thermodynamic parameters E
a(d) (activation energy for irreversible deactivation), ΔH*, ΔG*, and ΔS* was: Captan > Carbendazim > Mancozeb > control. The present study is the first report on thermodynamic and kinetic characterization
of chitinase from Paenibacillus sp. D1. 相似文献
12.
Bojan Šarac Janez Cerkovnik Bernard Ancian Guillaume Mériguet Gaëlle M. Roger Serge Durand-Vidal Marija Bešter-Rogač 《Colloid and polymer science》2011,289(14):1597-1607
The complex aggregation processes of dodecyltrimethylammonium chloride (DTAC) have been studied in dilute solutions of sodium
salicylate (NaSal) by isothermal titration calorimetry and electrical conductivity at temperatures between 278.15 K and 318.15 K.
A structural transformation that was dependent on the concentrations of DTAC and NaSal was observed. The micellization process
in dilute solutions of DTAC has been subjected to a detailed thermodynamic analysis and shown to occur at considerably lower
critical micelle concentrations than reported for DTAC in water and NaCl solutions. Gibbs free energy, Δ
mic
G
o, and entropy, Δ
mic
S
o, were deduced by taking into account the degree of micelle ionization, β, estimated from conductivity measurements. From the temperature dependence of the enthalpy of micellization, Δ
mic
H
o, the heat capacities of micellization, Dmic cpo {\Delta_{{{\rm mic} }}}c_p^o were determined and discussed in terms of the removal of large areas of non-polar surface from contact with water upon micellization.
The process is exothermic at all temperatures, indicating, in addition to the hydrophobic effect, the presence of strong interactions
between surfactant and salicylate ions. These were confirmed by 1H NMR spectroscopy and diffusion NMR experiments. Salicylate ions not only interact with the headgroups but also insert further
into the micelle core. At c
NaSal/c
DTAC > 2.5, the structural rearrangements occur even at relatively low concentrations of NaSal. 相似文献
13.
The effect of cosolvent on micellization of hexadecyltrimethyl ammonium bromide (CTAB) in aqueous solutions was studied. The
conductivity of a mixture (cosolvent + water) as function of CTAB concentration was measured at different temperatures. Ethylene
glycol and ethanol were used as a cosolvent. The conductivity data were used to determine the critical micelle concentration
(CMC) and the effective degree of counterion dissociation of micelle in the temperature range 303.2 to 313.2 K. In all the
cases studied, a linear relationship between log([CMC]mix/mol dm−3) and the mass fraction of cosolvent in solvent mixture has been observed. The free energy (ΔG
mic
0
), enthalpy (ΔH
mic
0
), and entropy (ΔS
mic
0
) of micellization were determined using the temperature dependence of CMC. The dependence of these thermodynamic parameters
on solvent composition was determined. The standard free energy of micellization was found to be negative in all cases and
becomes less negative as the cosolvent content increases. The enthalpy and entropy of micellization are independent of temperature
in pure water, while ΔH
mic
0
and ΔS
mic
0
decrease dramatically with temperature in mixed cosolvents. Furthermore, the entropic contribution is larger than the enthalpic
one in pure water, while in the mixed solvents, the enthalpic contribution predominates.
The text was submitted by the authors in English. 相似文献
14.
The specific micro- and mesopore volumes (V) of alumina compacts fired between 900 and 1250 °C for 2 h were determined from nitrogen adsorption/desorption data. The
V value was taken as a sintering equilibrium parameter. An arbitrary sintering equilibrium constant (K
a) was estimated for each firing temperature by assuming K
a = (V
i − V)/V, where V
i is the largest value at 900 °C before sintering. Also, an arbitrary Gibbs energy (ΔG
a
°) of sintering was calculated for each temperature using the K
a value. The graph of ln K
a versus 1/T and ΔG
a
° versus T were plotted, and the real enthalpy (ΔH°) and the real entropy (ΔS°) of sintering were calculated from the slopes of the obtained straight lines, respectively. On the contrary, real ΔG° and K values were calculated using the real ΔH° and ΔS° values in the ΔG° = −RT lnK = 165814 − 124.7T relation in SI units. 相似文献
15.
In this article, the enthalpy of dissolution for oxymatrine in 0.15 M citric acid solution is measured using a RD496-2000
Calvet Microcalorimeter at 36.5 °C under atmospheric pressure. The differential enthalpy (Δ
dif
H
m) and molar enthalpy (Δ
sol
H
m) were determined for oxymatrine dissolution in 0.15 M citric acid solution. On the basis of these experimental data and calculated
results, the kinetic equation, half-life, Δ
sol
H
m, Δ
sol
G
m, and Δ
sol
S
m of the dissolution process were also obtained. 相似文献
16.
Honglin Zhang Zhe Kong Yongmei Yan Ganzuo Li Li Yu Zhen Li 《Frontiers of Chemistry in China》2008,3(1):57-63
The critical micelle concentration (CMC) and the thermodynamic function of the anionic surfactant, sodium laurate (SLA) and
sodium dodecyl sulfate (SDS) in the N,N-dimethyl acetamide (DMA)/long-chain alcohol systems were studied using titration microcalorimetric method. The power-time
curves of SLA and SDS in the presence of a long-chain alcohol (n-heptanol, n-octanol, n-nonanol, n-decanol) in the DMA medium were determined. Then, from the curves, the critical micelle concentration (CMC) and the thermodynamic
standard formation functions (ΔH
ϑ
m, ΔG
ϑ
m and ΔS
ϑ
m) were obtained through thermodynamic theories. The relationships between temperature, alcohol’s carbon number, concentration
and thermodynamic properties were discussed. For SLA or SDS in a DMA solution, under the same concentration of alcohol, the
values of CMC, ΔH
ϑ
m and ΔS
ϑ
m increase, while the value of ΔG
ϑ
m decrease with the increase of temperature. Under the same condition of identical temperature and alcohol concentration, the
values of CMC, ΔH
ϑ
m, ΔG
ϑ
m and ΔS
ϑ
m decrease with the increase of the alcohol’s carbon number. In the presence of the same kind of alcohol, the values of CMC
and ΔG
ϑ
m increase, but the values of ΔH
ϑ
m and ΔS
ϑ
m decrease with the concentration increases in alcohol series at the same temperature.
__________
Translated from Acta Chimica Sinica, 2007, 65(10): 906–912 [译自: 化学学报] 相似文献
17.
Cui Pang Yunhai Liu Xiaohong Cao Rong Hua Caixia Wang Chunqing Li 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):185-193
Chitosan-coated attapulgite beads were prepared by coating chitosan on naturally and abundantly available attapulgite, and
made into spherical beads to adsorb uranium from aqueous solutions. The beads were characterized by SEM, EDS and FT-IR. The
characteristics of beads of adsorbing uranium(VI) from aqueous solutions were studied at different conditions of pH, initial
uranium concentration, contact time, biomass dosage and temperature. The pseudo-second order rate equation was used to describe
the kinetic data, and isotherm data were fitted to Langmuir and Freundlich adsorption models. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) of the biosorption were also calculated. Thermodynamic parameters of the CAAB, viz., ΔG°(308 K), ΔH°, and ΔS° were determined to be −21.59, 6.29l and 90.51 J/mol K, respectively. The experimental results demonstrate that the beads
of chitosan coated onto attapulgite exhibit considerable potential for application in both adsorption and removal of uranium
from aqueous solutions. 相似文献
18.
Mercury-mercury (II) sulphide electrode has been prepared and its electrochemical and thermodynamic behaviour has been studied
in different media. The electrode is found to show Nernstian response to pS (− log [S2−]) over the range 5.19–10.38. In the pH range 7.96–11.98, at constant [S2−]v, its response is also Nernstian. The values of thermodynamic functions, viz., ΔG0. ΔH0, and ΔS0 for the electrode reaction: Hg(3)+S2−
aμ
⇌HgS(s)+2e, have been determined. Further, the standard free energy of formation (ΔG
f
0
) and solubility product constant (K
vp
) of HgS in aqueous medium at 25±0.1°C have also been determined. 相似文献
19.
Enthalpies of mixing ΔH
m
of aqueous solutions of CdCl2, CuCl2, and ZnCl2 with MgCl2 solutions were measured at ionic strengths of 1.0, 2.0, and 3.0 at 25°C. The excess enthalpy equations of Pitzer were then
fitted to the resulting ΔH
m
data. The resulting parameters are the temperature derivatives of the activity coefficient mixing parameters in the Pitzer
system. 相似文献
20.
Narayanasamy Kumaraguru Sankarlingam Arunachalam Mahadevimanglam Narayanasamy Arumugham Kannappan Santhakumar 《Transition Metal Chemistry》2006,31(2):250-255
A number of mixed ligand chromium(III)–surfactant coordination complexes, of the type cis-[Cr(en)2(A)X]2+ and cis-α-[Cr(trien)(A)X]2+ (A = Dodecyl or Cetylamine; X = F−, Cl−, Br−) were synthesized from the corresponding dihalogeno complexes by ligand substitution. These compounds form foam in aqueous
solution when shaken. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution
were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for evaluation of the
temperature-dependent critical micelle concentration (cmc) and the thermodynamics of micellization (Δ Gm0, Δ Hm0 and Δ Sm0). 相似文献