Nonionic micelles grow with increasing temperature

Lindman, Bjoern; Wennerstroem, Haakan

doi:10.1021/j100168a063

Cited by 106 publications

(74 citation statements)

References 2 publications

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“…Some authors have proposed that it would be due to an increase in the micellar aggregation number (an increase in micelle size) when temperature is increased. 23,24 Others have suggested that the phase-separation mechanism would be caused by a change in micellar interactions, which are repulsive at low temperatures, but predominantly attractive at high temperatures. 25 The fact that the presence of salts favors phase separation, when ionic surfactants are used, has been interpreted as being due to the shielding of the repulsive electrostatic effects.…”

Section: Resultsmentioning

confidence: 99%

Simultaneous Cloud-Point Extraction of Nine Cations from Water Samples and Their Determination by Flame Atomic Absorption Spectrometry

Farajzadeh

Fallahi

2006

ANAL. SCI.

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Several analytical techniques, such as atomic absorption spectrometry (AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS), are available for the determination of trace metals with sufficient sensitivity for most applications. However, the determination of trace metal ions in natural water samples is difficult due to various factors, particularly their low concentration and matrix effects.Preconcentration and separation can solve these problems and lead to a higher confidence level and an easy determination of trace elements by less sensitive, but more accessible instrumentation, such as flame atomic absorption spectrometry (FAAS) Cloud-point extraction (CPE) is related to the conventional LLE, and is used in micellar liquid chromatography (MLC). 7The first applications of phase separation based on the cloudpoint phenomenon refer to the extraction of metal ions forming complexes that are sparingly soluble in water. The efficiency of the process depends on the hydrophobicity of the ligand and of the complex formed, on the apparent equilibrium constants in the micellar medium, and on the formation kinetics of the complex and on the transference between the phases. This type of extraction by the cloud-point method was initially described by Watanabe and coworkers 8 for the preconcentration of Zn(II) using 1-(2-pyridylazo)naphthol (PAN) as a ligand and PONPE 7.5 as an extractant. Later, this methodology was also applied to the determination of different metal ions in different types of samples. 9 Like for all other established LLE methods, the metal ion is required to be in the uncharged chelated form prior to its extraction to the organic phase.The phase separation phenomenon has also been used for the extraction and preconcentration of metal ions after the formation of sparingly water-soluble complexes. 10 U, 11 Er 12 and Gd 13 were determined by spectrophotometry by room temperature phosphorescence; Cu, 14 Cd, 15 Ni and Zn, 16 Ag and Au, 17 by FAAS after CPE using complexing agents. Gold and lead were extracted efficiently without a complexing agent, using a non-ionic surfactant, such as poly oxyethylene nonyl phenyl ether (PONPE 7.5). Gold 18 in the aqueous phase was determined by ICP-MS and in the surfactant phase by a calculation based on mass balances. Lead 19 in the surfactant-rich phase was determined by FAAS after diluting with ethanol. Recently, the determination of trace elements by X-ray fluorescence spectrometry 20 and ultrasonic nebulization ICP-MS using phase separation with a surfactant have been reported. reviewed the use of surfactant-based assemblies in analytical atomic spectrometry. Also, concentration by CPE has been established for a number of trace organic pollutants from an aqueous phase. 22Based on the present work we report on the results obtained in a study of the simultaneous cloud-point preconcentration of Cu 2+ , Mn 2+ , Ni 2+ , Cd 2+ , Fe 3+ , Co 2+ , Zn 2+ , Cr 3+ and Pb 2+ after the formation of a compl...

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Section: Resultsmentioning

confidence: 99%

Simultaneous Cloud-Point Extraction of Nine Cations from Water Samples and Their Determination by Flame Atomic Absorption Spectrometry

Farajzadeh

Fallahi

2006

ANAL. SCI.

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“…Most of nonionic surfactant aggregation number), N A is Avogadro's number, M 1 is the systems have the lower critical solution temperature (T c ) molecular weight of the surfactant monomer, N w is the and the problem concerning attractive interactions between weight averaged aggregation number of micelles (see Eq. micelles or the critical effects led to debate on micellar [A12]), and c and c 1 are the weight concentrations in g growth with increasing temperature (10,11,(37)(38)(39). In our cm 03 ) of total surfactant molecules and surfactant monomers, respectively.…”

Section: Effects Of Intermicellar Interactionsmentioning

confidence: 99%

A Thermodynamic Model for Micellar Growth on the Basis of Light Scattering Intensities from Extremely Dilute Solutions of Nonionic Surfactant

Kato

Kanada

Seimiya

1996

Journal of Colloid and Interface Science

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“…When the surfactant molecule concentration increases above the CMC, colloidal-sized clusters (micelles) are spontaneously formed in various shapes (depending on the specific surfactant and solution conditions). 15 Many theories were proposed for the explanation of the separation and include increase in micellar size when temperature is increased, 31,32 change in micellar interactions, 32 and the dehydration process. 33 However, the mechanism by which separation occurs is not yet clear.…”

Section: Resultsmentioning

confidence: 99%

Removal of Polyphenols from Wine Sludge Using Cloud Point Extraction

Chatzilazarou

Katsoyannos

Gortzi

et al. 2010

Journal of the Air & Waste Management Association

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Cloud point extraction (CPE), a promising and simple technique for the separation of organic compounds using surfactants (Genapol X-080 [oligoethylene glycol monoalkyl ether] and PEG 8000 [polyethylene glycol with molecular weight of 8000]), was used to recover polyphenols from wine sludge (wine production waste). The effect of various parameters such as surfactant concentration, temperature, and pH on the percentage of phenol recovery and phase volume ratio during phenol separation from wine sludge was investigated, and the derived optimum parameters were used as the basis for the selection of CPE conditions. When a two-step CPE with a total of 4% v/v of Genapol X-080 (pH ϭ 3.5, temperature ϭ 55°C, and time ϭ 30 min) or 10% v/v of PEG 8000 (pH ϭ 2.5, temperature ϭ 55°C, and time ϭ 30 min) was applied the phenol recovery values achieved were 75.8 or 98.5%, respectively. Phenols recovered from wine sludge using the above surfactants maintained high antiradical activity as determined by the 1,1-diphenyl-2-picrylhydrazyl method.

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Nonionic micelles grow with increasing temperature

Cited by 106 publications

References 2 publications

Simultaneous Cloud-Point Extraction of Nine Cations from Water Samples and Their Determination by Flame Atomic Absorption Spectrometry

Simultaneous Cloud-Point Extraction of Nine Cations from Water Samples and Their Determination by Flame Atomic Absorption Spectrometry

A Thermodynamic Model for Micellar Growth on the Basis of Light Scattering Intensities from Extremely Dilute Solutions of Nonionic Surfactant

Removal of Polyphenols from Wine Sludge Using Cloud Point Extraction

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