A study on the adsorption of Direct Red 81 on pre-treated cotton fabric

This paper describes modeling of the dyeing process of pretreated cotton fabric. The cotton fabric is scoured, bleached, and then dyed in a solution of inorganic electrolyte and direct dye Direct Red 81. Cotton belongs to natural cellulose fibers, which are most often dyed with direct, reduction, reactive dyes, etc. Direct dyes are used for dyeing cellulosic fibers due to the simplicity of the dyeing process, the use of a smaller amount of electrolyte, achieving a lighter shade, low cost, etc. Dyeing was performed at 90?C at different times and initial concentrations of direct dye. The adsorption process is widely used and practiced in the processes of pretreatment, dyeing, purification, etc. It represents one of the most effective and promising techniques supported by easy, technically feasible and economical processes. One of the important adsorption factors is the adsorption isotherm, which explains the phenomena and interactions between adsorbent and adsorbate. In this study, three adsorption isotherm models (Langmuir, Halsey and Freundlich) were used to analyze the adsorption of direct dye on cotton fabric. The presence of multilayer adsorption in the pores resulted in a higher value of the coefficient of determination of the Halsey model compared to other models.