Revistes Catalanes amb Accés Obert (RACO)

Análisis electrocinético y termodinámico del proceso de adsorción de azul ácido 45 sobre tejido de poliamida

Manuel Espinosa Jiménez, Alfonso Ontiveros Ortega, Regina Padilla Weigand

Resum


An experiment was carried out on the adsorption, electrokinetics and surface thermodynamics of the Polyamide 6.6/Acid Blue 45 system. The variation in zeta potential of the polyamide and the dye as a function of the pH of the liquid phase shows that both surfaces are negatively charged. In the dye, this is probably due to the presence of two sulphonate groups which are
ionised in the aqueous titration. In the Polyamide 6.6, it is due to the presence of terminal carboxide groups, which are also ionised in the aqueous titration. The absolute zeta potential of the Acid Blue-dyed Polyamide system (10-4 M) increases
considerably according to the pH of the liquid phase, due to the presence on the surface of the dyed fabric of the dye’s sulphonate groups. The negative zeta potential of the Polyamide 6.6/Acid Blue 45 system increases considerably with the concentration of the dye in the liquid phase, and the adsorption experiments show an increase in the amount of dye adsorbed as a function of the initial dye concentration. This adsorption also increases with temperature. In this light, we can conclude that the chemical reaction of the phenolic hydroxide groups in the dye and the terminal carboxide groups in the fabric probably constitutes the dye’s mechanism of adsorption on the substrate, thus resulting in an esterification of the fabric by the dye. The surface thermodynamics data, obtained within the framework of the extended DLVO theory (Oss et al.) also validates this hypothesis.

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