Effects of Micellar Structuring and Solubilized Oil on the Kinetic Stability of Aqueous Foams

Microscopic Understanding of Interfacial Performance and Antifoaming Mechanism of REP Type Block Polyether Nonionic Surfactants

In many practical applications involving surfactants, achieving defoaming without affecting interfacial activity is a challenge. In this study, the antifoaming performance of REP-type block polymer nonionic surfactant C12EOmPOn was determined, and molecular dynamics simulation method was employed to investigate the molecular behaviors of surfactants at a gas/water interface, the detailed arrangement information of the different structural segments of the surfactant molecules and the inter-/intra-interactions between all the structural motifs in the interfacial layer were analyzed systematically, by which the antifoaming mechanisms of the surfactants were revealed. The results show that the EO and PO groups of REP-type polyether molecules are located in the aqueous phase near the interface, and the hydrophobic tails distribute separately, lying almost flat on the gas/water interface. The interaction between the same groups of EOs and POs is significantly stronger than with water. REP block polyethers with high polymerization degrees of EO and PO are more inclined to overlap into dense layers, resulting in the formation of aggregates resembling "oil lenses" spreading on the gas/water interface, which exerts a stronger antifoaming effect. This study provides a smart approach to obtaining efficient antifoaming performance at room temperature without adding other antifoam ingredients.

Effect of microemulsion on foam stability

Microemulsion–foam interactions are significant in the low tension gas process, an emerging enhanced oil recovery method. As oil–water–surfactant systems are subjected to various salinity environments and microemulsion phase behavior varies, foam strength has also been observed to vary. This may be due to the action of oil-swollen micelles within liquid lamellae. Winsor Type I microemulsions were characterized according to surface tension, oil content, oil-swollen micelle size, and viscosity. Their impact on foam stability was quantified via dynamic Bikerman-style glass column tests and static decay tests in a physical rock network microfluidic chip to observe behavior and trends across scales. Foam stability tests demonstrated up to 90% decrease in stability with similar trends at both scales as oil-swollen micelle diameter increased from 9.30 to 27.08 nm and concentration decreased over 80%. Decrease in micelle availability and micellar structuring effectiveness, with interaction effects, explains the impact of microemulsion on foam stability.

Achieving foaming control smartly: pre-solubilized flavor oil serves as an in situ homogeneous defoamer

In the wide application of aqueous foam, creating abundant foam and processing appropriate foaming control are both essential, depending upon the actual situation; the latter process is not only harder to achieve, but also more complicated to comprehensively understand on the molecular level. In this paper, a type of natural flavor oil, carvone, was solubilized in a micelle solution of sodium dodecyl sulfate (SDS) to study the effect on the foaming properties. The foamability and foam stability of the swollen micelle solutions were experimentally characterized, and the molecular behavior of the surfactant and oil molecules before, during and after the foaming process were investigated. It was found that the solubilized carvone co-adsorbed with SDS at the gas/water interface and caused a prominent effect on the foam film stability in several approaches, thereby making the flavor oil a possible foam controller that would not inhibit foam formation, but could eliminate foam efficiently once foam was undesired. Interestingly, it was found that the release of flavor in the foaming process was promoted. Detailed discussion of the interfacial behavior of carvone and the effect on the foaming properties of surfactants in different stages of foam may provide a theoretical foundation for exploring green and smart approaches in achieving foaming control.