Study on surface property and adsorption of nonionic Gemini surfactants on solid-liquid interface

The surface tensions of nonionic alkyl-phenol polyoxyethylene Gemini surfactants (GSmn) and nonyl-phenol polyoxyethylene (S910) were determined at 40°C by bubble pressure tensiometer and static adsorption experiments. The effects of molecular structure of Gemini surfactant on its surface properties and adsorption properties on solid-liquid interface were investigated. The experimental results show that at certain temperature, the critical micelle concentration (CMC) and the minimum surface tension of GSmn with same hydrophilic groups decrease when the alkyl chain length increases. As to GSmn with same hydrophobic groups, their CMC values increase, while the minimum surface tension decreases with the number of ethoxy group on GSmn molecules increasing. Despite some similarities between interfacial properties of S910 and GS910, the latter seems to be more easily adsorbed onto the solution surface. The saturated adsorption amount of GSmn molecules on kaolinite increases with greater alkyl chain length value, and decrease with the number of ethoxy group on GSmn molecules increasing. The amount of GS910 molecule adsorbed on the kaolinite surface was less than that of S910.