Influence of Ultrasound on the Adsorption, Diffusion and Kinetics of Leather Dyeing Process: Mechanistic Insight

Abstract

Leather is a natural porous material, which is composed of a three-dimensional weave of tanned collagen fibre bundles. This paper studies the influence of power ultrasound on the adsorption and kinetics of leather dyeing process. Dyeing experiments have been carried out using ultrasound (150 W, 33 kHz) and compared with that of static control dyeing process. The data of dye uptake in leather have been analysed using Freundlich and Langmuir adsorption isotherms. Intra Particle diffusion model has been employed to calculate Intra particle diffusion rate constant and Boundary Layer effect. Diffusion coefficient (D) of dye through leather matrix has also been calculated. Kinetics of leather dyeing process has been studied through pseudo first and second order rate equation. The Freundlich constant (K_f), Langmuir parameter (Q_m), Intra Particle diffusion rate constant (K_d) Apparent Diffusion coefficient (D) and Pseudo First order kinetic constant, K₁ have been calculated to be 18.67 mg/g, 50 mg/g, 0.006 min^-1, 1.89 * 10^-6 cm²/s and 1.7 mg/g min^0.5 respectively for ultrasound assisted leather dyeing as compared to that of 0.1 mg/g, 26.67 mg/g, 0.733 min^-1, 0.19 * 10^-6 cm²/s and 0.003 mg/g min^0.5 respectively for control process. The results indicate that significant enhancement in adsorption capacity with more favorable dye adsorption as well as about 10- fold increase in Apparent Diffusion coefficient with significant reduction in boundary layer effect, improved kinetic parameters due to the use of ultrasound in leather dyeing as compared to control. Mechanisms for enhancement in Adsorption and Kinetic Parameters in leather dyeing due to the use of ultrasound have been presented and corroborate well with better dye penetration, color value and fastness properties. Therefore, the present study demonstrates that the use of ultrasound in leather dyeing helps both in adsorption of dyes as well as diffusion process through the leather matrix.