The Effect of Small Quantities of Calcium on the Adsorption of Sodium Dodecyl Sulfate and Calcium at the Gas-Liquid Interface

Cross, A.W.; Jayson, G. G.

doi:10.1006/jcis.1994.1006

Cited by 55 publications

(54 citation statements)

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“…Several authors find that the results of the Gibbs adsorption isotherm and independent adsorbed density measurements agree well, thus seeming to simultaneously support both the equation and their experiments (10,(16)(17)(18)(19)(20). Others have found that in general the calculated densities underestimate the measured densities and have attributed this fact to divalent impurities not taken into account in the calculation (21)(22)(23). Although little work has been reported for gemini surfactants, there is significant discussion regarding whether m, in the absence of added electrolyte, should indeed be equal to a value of m = 3 or equal to a value of m = 2, suggesting that only one counterion associates with the divalent surfactant head group (24,25).…”

Section: Introductionmentioning

confidence: 64%

Modeling of Equilibrium Adsorption and Surface Tension of Cationic Gemini Surfactants

Prosser

Franses

2001

Journal of Colloid and Interface Science

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Section: Introductionmentioning

confidence: 64%

Modeling of Equilibrium Adsorption and Surface Tension of Cationic Gemini Surfactants

Prosser

Franses

2001

Journal of Colloid and Interface Science

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“…However, the surface potential and surface excess determined by different experimental techniques do not agree well. The discrepancies in surface excess between NR, radiotracer, and tensiometry are a well-known but not yet resolved issue [136,137], as discussed in detail by Xu et al [138,139]. The discrepancy between the surface potential determined by different techniques is even bigger.…”

Section: Accepted Manuscript 50mentioning

confidence: 99%

A critical review of the model fitting quality and parameter stability of equilibrium adsorption models

Peng

Nguyen

Wang

et al. 2018

Advances in Colloid and Interface Science

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We reviewed eight commonly used equilibrium adsorption models and examined their underlying assumptions, fitting qualities, and parameter stabilities. We compared several objective functions that have been applied to curve fitting analysis and a few statistics tests that have been performed to evaluate regression quality. The iteratively reweighted least squares algorithm was selected as the most suitable regression method for adsorption models in the presence of heteroscedasticity. The fraction of unexplained variance was selected to indicate the model fitting quality. Two sources of parameter instability were identified: residue instability and function instability. While the definition of the instability caused by residue is well established, we are the first to consider the instability caused by an adsorption model. The models discussed in this article can be applied to many surfactants, such as normal alcohols, polyglycol ethers, and sodium dodecyl sulfate at different salt concentrations. Our results show that both the model fitting quality and parameter instability increase with the number of parameters subject to curve fitting. For the Frumkin-type of reorientation model, the parameter instability can be as high as 25%. The high degree of instability in some complicated adsorption models may invalidate the estimated parameters.Therefore, additional measurements or simulations are required for complicated models to extract reliable model parameters.

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“…For example, contamination was shown explicitly by Cross and Jayson who used radiotracers to identify the presence of Ca 2+ in adsorbed sodium dodecyl sulfate (SDS). 11 Contamination at a low level by Ca 2+ ions leads to a Gibbs prefactor of 3 for the divalent surfactant salt with an approximately halved surfactant ion coverage because there are two surfactant ions in the divalent salt. The nett result is that the apparent Gibbs prefactor is approximately 3/2 instead of the expected value of 2, and this leads to a substantial underestimate of the coverage.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Methyl Ester Sulfonate at the Air–Water Interface: Can Limitations in the Application of the Gibbs Equation be Overcome by Computer Purification?

Xu¹,

et al. 2017

Langmuir

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We describe a new laboratory synthesis of the α-methyl ester sulfonates, based on direct sulfonation of the methyl ester by SO 3 introduced from the vapour phase. This was used to synthesize a chain deuterated sample of αC 14 MES, which was then used to measure the surface excess of αC 14 MES directly at the air/water interface over a wide range of concentration using neutron reflection. The adsorption isotherm could be fitted to an empirical equation close to a Langmuir isotherm and gave a limiting surface excess of 3.4 ± 0.1 × 10 −6 mol m −2 in the absence of added electrolyte. The neutron measured surface excesses were combined with the integrated Gibbs equation to fit the variation of surface tension with concentration (σ − ln C curve). The fit was exact provided that we used a prefactor consistent with the counterion at the surface being an impurity divalent ion, as has previously been found for sodium diethylhexylsulfosuccinate (Aerosol OT or AOT) and various perfluorooctanoates. The critical micelle concentration (CMC) was determined from this fit to be 2.4 ± 0.3 mM in the absence of electrolyte. In the presence of 100 mM NaCl this contamination was suppressed and the σ − ln C curve could be fitted using the integrated Gibbs equation with the expected prefactor of 1. The new data were used to reinterpret measurements by Danov et al. on an unpurified sample of αC 14 MES for which a computer refinement was used to try and eliminate the effects of the impurities.

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The Effect of Small Quantities of Calcium on the Adsorption of Sodium Dodecyl Sulfate and Calcium at the Gas-Liquid Interface

Cited by 55 publications

References 0 publications

Modeling of Equilibrium Adsorption and Surface Tension of Cationic Gemini Surfactants

Modeling of Equilibrium Adsorption and Surface Tension of Cationic Gemini Surfactants

A critical review of the model fitting quality and parameter stability of equilibrium adsorption models

Adsorption of Methyl Ester Sulfonate at the Air–Water Interface: Can Limitations in the Application of the Gibbs Equation be Overcome by Computer Purification?

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