Ultrasound-assisted of poly (trimethylene terephthalate) dyeing with nano-disperse blue 79: isotherms, kinetics, and thermodynamics insights

Abstract

In the present study, the dyeing of Poly(trimethylene terephthalate) (PTT) were performed using disperse Blue 79 dye in the presence and absence of ultrasound waves. In this work, the effect of some important parameters such as particle size, pH and effect of ultrasonic time on dye durability and adsorption behavior of disperse Blue 79 dye were evaluated. Under ultrasonic irradiation, the optimization conditions were achieved by PTT amount (0.1 g), irradiation time (15 min), contact time (120 min) at temperature (80 °C), pH = 6. The results showed that the ultrasonic time 15 min was chosen as an optimal time for nano-dye solution fabrication. Our results reveal that in pH higher than 6, the disperse dyes was degraded and the negative effect of alkaline environment on the adsorbent hydrolysis was specified. The achieved thermodynamics parameters values and the adsorption isotherms from the experiment suggests that the adsorption kinetics of the disperse Blue 79 dye on PTT is in accordance with a pseudo second-order kinetic model. The some important isotherms including Freundlich, Nernst, Temkin and Langmuir equations were used to determine the adsorption isotherm and results show that the Nernst isotherm has a good correlation coefficient. Thermodynamic evaluation showed that Gibbs free energy was found to be negative, indicating that the process is spontaneous. In addition, the positive value of enthalpy, signifying that the process is endothermic, and the negative entropy, indicating less activity in the interface. The particle size of disperse Blue 79 dye in the presence of ultrasound waves is smaller than those in the absence of ultrasound waves. Due to the polyester nature of the adsorbent, the adsorption was performed through diffusion mechanism between the fibers, and by diffusion increasing the adsorption is improved.