Adsorption properties of direct dyes on viscose/chitin bicomponent fiber: evaluation and comparison with viscose fiber

Abstract

Two direct dyes were applied for dyeing the viscose/chitin bicomponent fiber, whose chitin component can provide functionalities and enhanced dyeing properties. Dyeing rates, adsorption isotherms and mechanisms, electrolyte and dye concentration dependence on dye adsorption, as well as dye desorption from dyed fiber, were investigated in comparison with dyeing system of regular viscose fiber. Higher adsorption and lower desorption of dyes occurred for viscose/chitin fiber. The viscose/chitin fiber showed great dye adsorption capability even at a low salt dosage providing environmental benefits for dyeing process. The rates of dye uptake by viscose/chitin fiber were faster and followed the pseudo-second-order kinetic model. Dye adsorption isotherms were closely correlated to the dual Langmuir–Nernst model consisting of site-specific and non-site-specific interactions between dyes and fibers; moreover, the Langmuir adsorption was predominant in total adsorption, and this predominance was more obvious for viscose/chitin fiber. The characteristics of above dye adsorption on viscose/chitin fiber resulted mainly from its partially deacetylated chitin component, which can reduce the negative charge density of the fiber and provide more site-specific dyeing sites.