Enhancing silk dyeing with eco-friendly colorant extracted from Cassia fistula brown pods using green mordants

Abstract

This research project focuses on the extraction of the natural brown colorant, anthraquinone, from Cassia fistula pods using microwave radiation as a method for dyeing silk fabric. The colorant was isolated in aqueous and acidic mediums before and after microwave radiation for up to 6 min, and subsequently used for dyeing purposes. To achieve new and diverse hues, environmentally friendly chemical mordants (iron salt, aluminum salt, and tartaric acid) and biological mordants (red sumac, pomegranate, and hulela zard) were applied in varying quantities (ranging from 0.5g to 2.5g per 100 mL). Colorfast shades were developed by employing these mordants before and after the dyeing process on silk fabric. The dyeing variables essential for shade development before and after mordant application were determined through the utilization of central composite design for statistical analysis. The results indicated that the optimal conditions for irradiating both silk and extract were 6 min, while dyeing the irradiated silk fabric should be conducted at 75 °C for 45 min using 30 mL of extract irradiated at a pH of 3, with a salt concentration of 1.5g/100 mL. The optimized dyeing conditions also showed maximum level of colorfastness properties of 5 for light, 5 for wash, 5 for dry rubbing and 4/5 for wet rubbing. As a result, the extraction of anthraquinone from Cassia fistula pods using microwave radiation has the potential to be effective and ecologically benign, allowing for the creation of bright and colorfast hues on silk fabric. The results support the development of novel and sustainable dyeing techniques in the textile sector.