Formulation of ultralow interfacial tension systems using extended surfactants

Abstract

Inspired by the concept of lipophilic and hydrophilic linkers, extended surfactants have been proposed as highly desirable candidates for the formulation of microemulsions with high solubilization capacity and ultralow interfacial tension (IFT), especially for triglyceride oils. The defining characteristic of an extended surfactant is the presence of one or more intermediate‐polarity groups between the hydrophilic head and the hydrophobic tail. Currently only limited information exists on extended surfactants; such knowledge is especially relevant for cleaning and separation applications where the cost of the surfactant and environmental regulations prohibit the use of concentrated surfactant solutions. In this work, we examine surfactant formulations for a wide range of oils using dilute solutions of the extended surfactant classes sodium alkyl polypropyleneoxide sulfate (R‐(PO)x−SO4Na), and sodium alkyl polypropyleneoxide‐polyethyleneoxide sulfate (R‐(PO)y‐(EO)z−SO4Na). The IFT of these systems was measured as a function of electrolyte and surfactant concentration for polar and nonpolar oils. The results show that these extended surfactant systems have low critical micelle concentrations (CMC) and critical microemulsion concentrations (CμC) compared with other surfactants. We also found that the unique structure of these extended surfactants allows them to achieve ultralow IFT with a wide range of oils, including highly hydrophobic oils (e.g., hexadecane), triolein, and vegetable oils, using only ppm levels of these extended surfactants. It was also found that the introduction of additional PO and EO groups in the extended surfactant yielded lower IFT and lower optimum salinity, both of which are desirable in most formulations. Based on the optimum formulation conditions, it was found that the triolein sample used in these experiments behaved as a very polar oil, and all other vegetable oils displayed very hydrophobic behavior. This unexpected triolein behavior is suspected to be due to uncharacterized impurities in the triolein sample, and will be further evaluated in future research.

Styrene Solubilization and Adsolubilization on an Aluminum Oxide Surface Using Linker Molecules and Extended Surfactants

“…Extended surfactants have a region of intermediate polarity, such as polypropylene oxide or polyethylene oxide, inserted between the surfactant hydrocarbon tail and head group [30] and thus have been referred to as internal linker systems. Due to their unique molecular structures, extended surfactants protrude further into the oil phase, thereby providing a smoother transition from water to oil phases while also providing a more suitable region for solubilizing both hydrophilic and lipophilic solutes [39]. Witthayapanyanon et al [39] formulated ultralow interfacial tension (IFT) systems using extended surfactants for a wide range of oils, including both polar and nonpolar oils.…”

The effect of ethoxylate nonionic surfactants on phase inversion temperature and salinity: an alternative approach for vegetable oil recovery from spent bleaching earth

“…According to the linear regression, the ACNs of vegetable oils were 17.60±0.28, 15.41±0.35 and 13.71±0.41 for soybean oil, crude rice bran oil and crude palm oil, respectively. This was a result of the structure of each oil and the differences in their main fatty acid composition [12]. Dehydol LS3 TH 39 36 34 Dehydol LS5 TH 53 48 45 Dehydol LS7 TH 65 61 57 Moreover, at high ACN of oils, the system requires more free energy (high temperature) for transferring oil molecule from oil phase to microemulsion phase.…”

Physiochemical and Phase Behaviour Study of Jatropha curcus Oil - Ethanol Microemulsion Fuels Using Sorbitane Fatty Esters

“…Thus, it has proven that the branching and number of OH groups affected the hydrophobicity and hydrophilicity of MEs system respectively. It is also evident that the oils containing triglycerides are highly hydrophobic with longer and bulkier alkyl chains of triglycerides [41,42], and thus, the span 80 is identified as the potential surfactant to achieve a single phase ME with less amount. …”