Cationization of cotton with ovalbumin to improve dyeing of modified cotton with cochineal natural dye

Natural dyeing of cotton is commonly associated with the use of metallic mordants, which are related to harmful effects on the environment and human health. For this reason, more environmentally sustainable processes should be investigated. In this work, cotton was cationized with ovalbumin by cross-linking in order to improve its dyeing with natural cochineal dye. Different pretreatments with chitosan, synthetic cationizer, and metal mordants were also carried out at different dyeing pH values. The best dyeing results were obtained at pH 3 at 55celcius on fiber pretreated by padding with a liquor concentration of 150 g L-1 ovalbumin and 90 g L-1 cross-linker. This cationization of ovalbumin by cross-linking was confirmed by Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, changes in the isoelectric point of the fabrics, and scanning electron microscopy. The kinetic study showed that the pseudo second-order model best represented the experimental data, indicating that the dyeing can be controlled by the chemisorption process. The equilibrium data were easily adjusted by the Langmuir model, indicating the formation of a dye monolayer in the cationized cotton. The thermodynamic study indicated that dye adsorption was spontaneous and exothermic. The cationized fabric with ovalbumin presented low wash fastness, good light fastness, and increase in tensile strength and crease recovery, with a decrease of hydrophilicity when compared with other treatments. Thus, ovalbumin is a viable and eco-friendly alternative in the dyeing of cotton with cochineal.