Characterisation of egg white adsorption layers under equilibrium and dynamic conditions

Dynamic interfacial properties and foam behavior of licorice root extract solutions

Licorice (Glycyrrhiza glabra) is a useful plant of the family Fabaceae, with sweet-tasting roots. The root extract of this plant is rich in saponins, so it can be considered a source of natural surfactants. This research provides some applicable information about the dynamic surface tension and foam behavior of aqueous solutions of licorice root extract (LRE). The pendant drop shape analysis was utilized to study the surface tension and dilational surface rheology of LRE at the water/air interface. The Bikerman type experiment was used to measure foamability and foam stability of aqueous LRE solutions. The equilibrium surface tensions reveal that the LRE contains surface-active components and is capable of reducing the surface tension by 25 mN/m at the critical aggregation concentration (CAC). The surface dilational visco-elasticity measurements proved that the adsorption layers are predominantly of elastic nature. Also the foamability and foam stability show a meaningful correlation with the dynamic surface properties. This study aims to contribute to the development of appropriate utilization of the benefits provided by a biosurfactant source in foam-related commercial applications.

Effects of N-Alkanol Adsorption on Bubble Acceleration and Local Velocities in Solutions of the Homologous Series from Ethanol to N-Decanol

The influence of n-alkanol (C2-C10) water solutions on bubble motion was studied in a wide range of concentrations. Initial bubble acceleration, as well as local, maximal and terminal velocities during motion were studied as a function of motion time. Generally, two types of velocity profiles were observed. For low surface-active alkanols (C2-C4), bubble acceleration and terminal velocities diminished with the increase in solution concentration and adsorption coverage. No maximum velocities were distinguished. The situation is much more complicated for higher surface-active alkanols (C5-C10). In low and medium solution concentrations, bubbles detached from the capillary with acceleration comparable to gravitational acceleration, and profiles of the local velocities showed maxima. The terminal velocity of bubbles decreased with increasing adsorption coverage. The heights and widths of the maximum diminished with increasing solution concentration. Much lower initial acceleration values and no maxima presence were observed in the case of the highest n-alkanol concentrations (C5-C10). Nevertheless, in these solutions, the observed terminal velocities were significantly higher than in the case of bubbles moving in solutions of lower concentration (C2-C4). The observed differences were explained by different states of the adsorption layer in the studied solutions, leading to varying degrees of immobilization of the bubble interface, which generates other hydrodynamic conditions of bubble motion.