Adsorption of Aroma Chemicals on Cotton Fabric in Different Aqueous Environments

Abstract

Surfactants enhance adsorption of an aroma chemical on cotton fiber. Strong hydrophobic and electrostatic interactions between surfactant and fiber substrate result in higher adsorption of surfactant/aroma chemical aggregates than for the aroma chemical alone, with higher adsorption for cationic systems than for anionic systems. Adsorption is attributed to solution physical entrapment, hydrophobic interaction, dispersion forces, and interaction with surfactant molecules adsorbed on fiber. Log P and water solubility are important factors in aroma chemical adsorption. Hydrophobicity increased selective partitioning of aroma chemicals on the fiber surface particularly in the presence of surfactants. Statistical analyses indicate some evidence of polar–polar interaction between aroma chemicals and cellulose. With no surfactant, more adsorption is often observed in systems with a higher concentration of NaCl. The screening effect of electrolytes increases with the electrolyte reducing the energy of the liquid–solid interface. Lower interfacial energy results in increased adsorption of an aroma chemical on the fiber surfaces. Electrolyte screening affects aroma chemical adsorption most for anionic surfactant systems. Increase in the concentration of the electrolyte increases the screening effect that reduces the repulsive forces between the anionic molecules and weakly electronegative cotton fiber surfaces. In a cationic system, the screening effect of the electrolyte reduces adsorption of aroma chemicals with increased electrolyte concentration, due to the screening-reducing attraction between cationic surfactant molecules and the fiber surface. Chemical functionality shows a significant effect (alkanol ≥ ketone ≥ aldehyde > ester) on adsorption. Adsorption increased with increasing molecule ovality. Statistical analyses indicate that molecular shape within a chemical class of compounds influences adsorption of the aroma chemical.