Dyeing Mechanism of Wool and Silk with Extract of Allium Cepa

Abstract

Silk and wool fabrics were dyed with the colorant extracted from Allium cepa. Dyeing experiments were carried out varying temperature and pH. Colour uptake and colour fastness have been investigated. It was seen that pH of 3 and temperatures of 80 and 90 °C are the ones that produced the best results in wool and silk, respectively. Such results have been used to investigate the dyeing kinetics and the dyeing process at equilibrium through adsorption isotherms. The kinetic study showed that the pseudo second order equation is the one that best represents the kinetic mechanism of dyeing both fabrics, which is related to the chemisorption process as the rate-controlling step. The equilibrium data for wool and silk fabrics were easily adjusted to the Langmuir-Freundlich model indicating the significant contribution of chemisorption process in a monolayer followed by a multilayer physisorption.