13 research outputs found
Influence of Conformational Free Energy of Hydrocarbon Chains on Adsorption of Nonionic Surfactants at the Air/Solution Interface
Effect of Counterions on the Adsorption of Ionic Surfactants at FluidâFluid Interfaces
Nonequivalent adsorption of pH-responsive dicephalic sugar surfactants at the air/solution interface
The present work contributes to the analysis of the effect of electrolyte and pH on the adsorption of dicephalic N-dodecyl-N,N-bis[(3-D-aldonylamido) propyl]amines (aldonyl = gluconyl and lactobionyl) at the air/water interface. The headgroup of these surfactants consists of two amide groups connected by a central tertiary amine, which may be protonated in an aqueous environment. We performed measurements of surface tension isotherms of aqueous solutions of the studied dicephalics in the presence of NaCl and NaOH and applied the STDE model for evaluation of the experimental results. They showed that the adsorption of the surfactants at the air/water interface was pH- and electrolyte- dependent, since addition of NaCl and NaOH had different effects on the surface activity and critical micelle concentration values (CMC). The theoretical model reflected well the surface tension isotherms obtained for a broad range of surfactants concentration, confirming the theoretical predictions concerning the protonation of tertiary amines, which was additionally supported by the measurements of solution pH
Experimental and Theoretical Approach to Nonequivalent Adsorption of Novel Dicephalic Ammonium Surfactants at the Air/Solution Interface
Surface Potential of Methyl Isobutyl Carbinol Adsorption Layer at the Air/Water Interface
The surface potential (ÎV) and surface tension (Îł) of MIBC (methyl isobutyl carbinol) were measured on the subphase of pure water and electrolyte solutions (NaCl at 0.02 and 2 M). In contrast to ionic surfactants, it was found that surface potential gradually increased with MIBC concentration. The ÎV curves were strongly influenced by the presence of NaCl. The available model in literature, in which surface potential is linearly proportional to surface excess, failed to describe the experimental data. Consequently, a new model, employing a partial charge of alcohol adsorption layer, was proposed. The new model predicted the experimental data consistently for MIBC in different NaCl solutions. However, the model required additional information for ionic impurity to predict adsorption in the absence of electrolyte. Such inclusion of impurities is, however, unnecessary for industrial applications. The modeling results successfully quantify the influence of electrolytes on surface potential of MIBC, which is critical for froth stability