Adsorption of Methylene Blue at solid/liquid and water/air interfaces

Determinations of the adsorption of Methylene Blue (MB) at both solid/liquid and water/air interfaces have been performed. The solid adsorbents were two ZrO2 samples prepared in the laboratory. For both oxides the adsorption isotherms presented a langmuirian shape with a long plateau and a final slight upward bend. Parameters describing the adsorption at the solid surfaces were obtained by processing data by both the Langmuir and the BET equations. At the water/air interface, measurements of the surface tension as a function of the bulk concentration of MB were performed. The resulting isotherm exhibited two regions differing in the slopes of the curves. The orientation, degree of association and packing of the adsorbed MB molecules are discussed, and the data obtained at the two interfaces are compared. © 1993.