Interfacial performance of cationic, anionic and non-ionic surfactants; effect of different characteristics of crude oil

In this study, the performance of a large number of anionic (SDS, SLS, and SDBS), cationic (CTAB), and non-ionic (Triton X-100 and Tween 80) surfactants on the surface activity, emulsion size, and surface charge of five oil samples was investigated in aqueous solution with two different salinities, with the aid of interfacial tension (IFT) measurement, zeta potential, and dynamic light scattering (DLS) analysis. In addition, the most important pa-rameters that can affect the IFT of crude oil/surfactant solutions (i.e. charge of the hydrophilic group and chain length of the hydrophobic hydrocarbon group of the surfactants and different characteristics of crude oil such as API, acidity, weight percentage of the asphaltene and resin fractions, their aromaticity and polarity, and asphaltene stability parameter) were comprehensively analyzed. The results showed that IFT values, surface charge of the aggregates, and the size of microemulsions depend on the crude oil type, ionic strength, and type of surfactants, however, without any straightforward proportionality with the examined parameters. Among the considered surfactants, the cationic and non-ionic surfactant showed the lowest and highest dependency to the crude oil type, respectively. A paramount efficiency was obtained for CTAB cationic surfactant with the microemulsion size of 102 nm and surface charge at near isoelectric point (zeta potential of 3.5 mV).

Automated summary

This study investigated the performance of different types of surfactants on the surface activity, emulsion size, and surface charge of five oil samples. The effects of various parameters on the interfacial tension of crude oil/surfactant solutions were comprehensively analyzed. The results showed that the properties of the surfactants, crude oil type, and ionic strength influenced the interfacial tension, surface charge, and microemulsion size, but not in a straightforward manner. Among the surfactants considered, the cationic surfactant showed the lowest dependency on the crude oil type, while the non-ionic surfactant showed the highest dependency. CTAB cationic surfactant exhibited the most efficient performance with a microemulsion size of 102 nm and surface charge near the isoelectric point.