Dynamic and equilibrium surface tension of Rhamnolipid: Effect of real-time temperature.

Surfactants are used in the soil for many purposes such as for aiding water infiltration into hydrophobic soils or remediating soil contamination. The effectiveness of surfactants in such applications relies greatly on surfactant surface properties - affected by environmental conditions such as temperature. Under the effect of climate change, soil temperature may fluctuate unpredictably, leading to an ambiguation on the appropriate use of surfactants. Therefore, for precise decisions of surfactant application in the soil, it is necessary to evaluate the impact of temperature on surfactant properties. In this study, we chose Rhamnolipid (RLP) -  a biosurfactant that potentially could be used in soils as an alternative for other non-sustainable synthetic surfactants. Our objective was to investigate the surface properties of RLP under the effect of temperature. Previous studies pre-treated RLP with heat and thereafter characterized its surface properties after reaching room temperature. Our study, on the other hand, monitored the dynamic surface tension of RLP at real-time temperature, ranging from 10 to 45 ºC. For a given temperature, the surface tension as a function of time was measured using the pendant drop technique by an optical tensiometer (OCA-22, Data Physics). The diffusion coefficient of RLP to the liquid/air interface and equilibrium surface tension was calculated. In this presentation, both the dynamic and equilibrium surface properties of the RLP mixture (mono and di-rhamnolipid) as a function of temperature will be shown and discussed.