An anionic derivative of alkyl polyglycoside (AG) was synthesized, and characterized and applied as an oil spill dispersant and a coating material for calcium carbonate particles.
By modifying the hydroxyl group with maleic anhydride, the an ionic derivative of AG was obtained. Pyridine as a solvent was refluxed for 12 hours during reaction. Nitrogen gas was used to prevent the possible oxidation of AG during the reaction. After purification, synthesis of AG derivative was confirmed by nuclear magnetic resonance(NMR) spectroscopy. Surface tension of AG synthesized with maleic anhydride was measured in various concentration ranges and CMC was about 0.3 wt%.
The zetapotentials of nanobubbles generated by ultrasonication in surfactant solutions, using palladium electrode were determined for the ionic nature of AGs. Monolayer was stabilized in 5 M NaCl solution. From zetapotential and monolayer at air-water interface, new charging mechanisms in the AGs were proposed. Unlike the usual nonionic surfactants, AG showed negative charges in the aqueous solutions. Ion adsorption onto the surface of OH groups in AGs aqueous solutions might play an important role on the charging. As the hydrophobic character of AG molecules increases, zetapotential decreases negatively. This may be attributed to the preferential adsorption of OH- at the interface. The adsorption of OH- canbe more accelerated by increasing hydrophobicity of interface by AG molecules. According to Langmuir monolayer study, the molecular area of AG at concentrated electrolyte solutions increased because of the electrical repulsion by ion adsorption. Even in the nonionic surfactant, it is interesting that electrical repulsion is important. On the other hand, the molecular area of ionic surfactants (stearic acid) was not influenced by the electrolyte concentration. Interface of ionic surfactants seems to induce no ion adsorption because it is very hydrophilic compared with nonionic surfactants.
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