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

Abstract

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.

Surface and bulk properties of surfactants used in fire-fighting

“…For nonionic and zwitterionic surfactants, a value of 1 for the pre-factor has been confirmed [19,20], and for 1:1 ionic surfactants, in the absence of extra electrolyte, m = 2 has been confirmed [18]. Recently, it has been shown that traces of multivalent ionic impurities can lead to changes in this prefactor, therefore leading to problems employing the Gibbs adsorption isotherm [21]. In this study, a prefactor of 1 has been used for the non-ionic and zwitterionic surfactants, and a prefactor of 2 has been used for the anionic surfactants, following literature [18][19][20].…”

Design of Surfactant Tails for Effective Surface Tension Reduction and Micellization in Water and/or Supercritical CO2

“…30 it has been shown that traces of multivalent ionic impurities can lead to changes in this prefactor, therefore leading to problems employing the Gibbs adsorption isotherm. 33 In this study, only anionic surfactants are being studied and therefore a prefactor of 2 has been used in all calculations as indicated in the literature. [30][31][32]…”

Methyl Ester Sulfonate: A High‐Performance Surfactant Capable of Reducing Builders Dosage in Detergents

“…The physicochemical properties of α‐MES have been investigated (Danov et al, ; Ohbu et al, ; Patil et al, ; Stirton et al, ; Wong et al, ; Xu et al, ), with its superiority under hard water conditions. However, there are not many references on its cleaning performance against the dominant workhorse in the Home Care product—linear alkylbenzene sulfonate (LAS).…”

“…The study showed that the binding energy of the Ca 2+ ions (2.39 КT) to the headgroup of α-MES is smaller than that of Na + (2.91 КT), which helps explain the superiority of α-MES under challenging conditions. The physicochemical properties of α-MES have been investigated (Danov et al, 2015;Ohbu et al, 1998;Patil et al, 2004;Stirton et al, 1962;Wong et al, 2012;Xu et al, 2017), with its superiority under hard water conditions. However, there are not many references on its cleaning performance against the dominant workhorse in the Home Care product-linear alkylbenzene sulfonate (LAS).…”

“…α‐Sulfo fatty‐methyl ester sulfonate (α‐MES) is an anionic surfactant derived from renewable feedstocks and is considered as an attractive green alternative for petroleum‐derived surfactants (Danov et al, ; Xu et al, ). The raising consumer awareness regarding renewable and green products has led to increased demand for green surfactants such as plant‐based/vegetable‐based surfactants or biosurfactants from the microbial origin (Chen, ; Chen et al, ).…”