Thermodynamics, Kinetics and Isotherms Studies for Sorption of Direct Dye onto the Pectinase Pre-treated Jute Yarn

In this paper, jute yarns were bio-treated with pectinase enzyme. Then, the untreated and bio-treated yarns were dyed with Direct Yellow 24. The biotreated jute yarn showed higher dye sorption compared to that of untreated jute yarn. The sorption isotherms were fitted with the Nernst, Freundlich, Langmuir, Temkin and BET models. At all temperatures studied, the experimental data were better described with the Freundlich model. Thermodynamic parameters such as a change in free energy (ΔG0), the enthalpy (ΔH0), and the entropy (ΔS0) were also evaluated. The values of ΔH0 and ΔG0 indicated that the sorption of direct dye onto jute yarn was a physical sorption process. Furthermore, the sorption process was exothermic and spontaneous. The results indicated that bio-treated jute yarn was more favorable (1/n < 1) for the sorption of direct dye as compared to that of untreated jute yarn (1/n > 1). Among the kinetic models studied, it was found that the pseudo second-order kinetic model was the best model to describe the sorption process of Direct Yellow 24 onto the bio-treated and untreated jute yarns.