Ultrasound-assisted extraction of vegetable dyes and mordants from wool dyed with Curcuma longa and Reseda luteola

Abstract

With the increasing demand to reduce the use of synthetic dyes, driven by environmental and health concerns, natural dyes are emerging as a promising alternative. Their environmental friendliness and sustainability are consistent with the global move towards greener practices in various industries, including textiles. However, the widespread adoption of natural dyes has also exposed their vulnerability to adulteration and fraudulent practices. As demand for natural dyes continues to grow, addressing these challenges is essential to ensuring the integrity and authenticity of naturally dyed fibers. This paper aims to establish a mild extraction method for the dye, mordant and wool in naturally dyed fabrics. Wool dyed with a mixture of Reseda luteola and Curcuma longa, was subjected to extraction using various additives, including HCl, acetic acid, NaOH, citric acid, formic acid and EDTA. In this study, two extraction techniques - heating and ultrasound extraction - were compared. The effect of the geometry of the extraction reactor was first studied, then the optimized conditions were applied to different solutions and reagents. Characterization of the wool fabric was carried out using SEM and FTIR, while HPLC and LC/MS were applied to identify dye markers. In addition, ICP analysis was used to characterize the metallic mordant involved in the dyeing process. The results demonstrated that ultrasound allowed an efficient extraction of dyes from wool under mild conditions. This study highlights the potential of ultrasound as a valuable tool for non-destructive extraction in the analysis of dyed wool, providing a thorough characterization of dye, mordant and fiber components. The studied technique contributes significantly to the field of textile analysis, enabling accurate identification of naturally dyed fibers.