Effect of Ultraviolet Irradiation on Thermodynamic, Kinetic ‎and Adsorption Isotherm of Direct dye onto Cellulose ‎Acetate Fabric

Cellulose acetate fibers do not inherently have an affinity for direct dyes. One ‎of the methods to create affinity for this type of dye is saponification of ‎cellulose acetate fibers, which converts some acetate groups to hydroxyl ‎groups. However, the alkaline wastewater from saponification is a high ‎concentration alkaline wastewater. Therefore, other techniques should be ‎investigated to create hydrophilic groups on the surface of these fibers. In this ‎research, cellulose acetate fibers were first exposed to ultraviolet radiation and ‎then chemical and dyeing properties were investigated.SEM micrographs ‎showed that UV pretreatment makes fiber surface rough and porous.‎‏ ‏Moreover, FT-IR results showed that acetyl groups decreased after UV ‎treatment. Meanwhile, increasing irradiation time led to an increase in color ‎strength and fastness properties. Thermodynamic parameters showed that UV ‎treated fabric had higher affinity for direct dye in comparison to untreated ‎fabric. Freundlich isotherm was found the best model to describe the ‎adsorption of direct dye onto both untreated and UV treated cellulose acetate ‎fabrics. However, UV treated fabric showed higher adsorption capacity in ‎comparison to untreated fabric.‎