Interaction between crystal violet and anionic surfactants at silica/water interface using evanescent wave-cavity...

Area of Science:

• Surface Chemistry
• Spectroscopy
• Colloid Science

Background:

• Anionic surfactants form hemimicelles on surfaces, influencing substance removal.
• Understanding surfactant behavior is crucial for applications like chromatography.

Purpose of the Study:

• To characterize anionic surfactant micellization on silica surfaces.
• To determine the capability of surfactants in removing cationic substances.
• To investigate the effect of electrolyte and carbon-chain length on surfactant behavior.

Main Methods:

• Evanescent wave-cavity ring-down spectroscopy (EW-CRDS) was utilized.
• Crystal violet (CV(+)) cationic dye served as a molecular probe.
• Critical hemimicelle concentration (HMC) was measured for various surfactants.

Main Results:

• HMC values decreased with increasing surfactant carbon-chain length (C-10 to C-16).
• Surface HMC values were approximately half of those observed in solution.
• NaCl addition reduced HMC, indicating facilitated surfactant aggregation.
• Desorption rates of CV(+) above HMC varied with surfactant chain length.

Conclusions:

• Hydrophobic interactions significantly influence micellization concentration.
• Electrolytes promote surfactant aggregation on surfaces.
• Surface interactions and desorption are complex, influenced by hemimicelle size and density.
• Findings provide insights for surfactant applications in chromatographic separations.