Abstract

BARNABA, C.; GARCIA-ALVARADO, M.A.; MEDINA-MEZA, I.G.  and  TEJERO-ANDRADE, J.M.. Langmuir adsorption isotherms for different organic solutions of cholesterol. Rev. Mex. Ing. Quím [online]. 2013, vol.12, n.2, pp.283-292. ISSN 1665-2738.

In this work, the surfactant properties of cholesterol in organic solvents are studied. Hexane, iso-octane, iso-dodecane and toluene were used as the hydrophobic phase, and bidistilled water was used as the water phase. The captive bubbles were supported on a quartz surface and the axisymmetric drop shape analysis (ADSA) routine was performed to obtain contact angles (θ) and surface tension values (γ). Cholesterol was effective in reducing the interfacial tension of the oil/water system in all organic solvents. The appearance of turbidity associated with cholesterol crystallization is observed to be below concentration limits in all samples, because the liquid-liquid interface reduces the energy barrier required for nucleation. Experimental values of γ were adjusted with theoretical values obtained by applying Szyszkowski-Langmuir isotherm, showing good correlation between data. Finally, Szyszkowski-Langmuir constant (K_L) and Gibbs energy of absorption were calculated for the binary systems.

Keywords : cholesterol; ADSA; surface tension; captive bubble; Szyszkowski-Langmuir equation.