Macadamia integrifolia: A New Source of Natural Dyes for Textile Colouration

Valorization of bio-colorants extracted from Hypercium scabrum L. plant for sustainable and ecological coloration of wool yarns

Recently, natural dyes are being explored all over the world as safer and highly sustainable bio-based alternatives to synthetic dyes. Agricultural wastes and plant by-products are the most commonly explored alternatives with dual benefits of waste reclamation and sustainable dye production with extra value-adds. Hypercium scabrum plant contains interesting bio-dye molecules with high flavonoids and tannin contents. The present study aims at exploring the potential of H. scabrum plant extract to color wool textiles with a focus on sustainable bio-dye production and fastness properties. The extracted bio-dye was quantitatively (for total phenolic (2.733 mg per CE/g) and total flavonoid (1.140 mg per GAE/g) content using the Folin-Ciocalteu method) and qualitatively (UV-Vis, FT-IR, and EDX) characterized. The effect of dyeing parameters like pH (2-8), temperature (60-90 °C), dry-weight content of plant material as a dye (25-150% o.w.f.), and dyeing time (15-120 min) on color strength (K/S) values were assessed. Color fastness assays showed good resistance to light, washing, and rubbing. The effect of artificial aging (Xenon arc lamp) on the color strength of dyed wool yarns under different exposure times (0-48 h) was explored. The highest color fading occurred in control dyed samples with a first-order rate constant of 131.57 h-1 and a half-life period of 5.26 x 10-3 h. Color difference (ΔE) values suggested that mordanted samples showed less fading compared to control dyed samples at equal times of Xenon exposure. Additionally, the dyed samples were washed in double distilled water, tap water, and 4 g/L NaCl solution to check their effects on the corresponding K/S values while 4 g/L NaCl solution mimics the real conditions of perspiration. Maximum color leaching occurred in 4 g/L NaCl washing with a first-order rate constant of 11.57 min-1. Cost analysis of the dye extraction and dyeing procedure revealed that the process is sustainable and economical. Thus, the use of H. scabrum whole plant can provide a clean, economical, and sustainable source of alternative natural dyes that can be used to substitute synthetic analogs.

Sustainable fashion: eco-friendly dyeing of wool fiber with novel mixtures of biodegradable natural dyes

Natural materials, especially natural colorants, have achieved global prominence and might be regarded as an environmentally beneficial alternative to hazardous synthetic dyes. The color limitation of natural dyes hinders their application in textiles. The present work aims to prepare more color shades of wool yarns via dyeing with ternary natural dye mixtures without adding mordants. In this study, a sustainable dyeing approach for wool yarn was evaluated with three natural dyes, madder red (MR), gardenia blue (GB), and gardenia yellow (GY), by following an industrial dyeing procedure in the absence of a mordant. In the beginning, a preliminary assessment of dye stabilities was carried out, and it was found that the three natural dyes were sensitive to temperature and acid (degradation tendency). Then, the dyeing behavior was systematically evaluated, including a single natural dye, a binary natural dye mixture, and a ternary natural dye mixture. The results of wool yarn dyeing with a single natural dye show that the dye exhaustion percentage (E%) of MR, GY, and GB was in the ranges of 78.7-94.1%, 13.4-44.1%, and 54.8-68.5%, respectively. The dyeing results of wool yarns dyed with binary and ternary natural dye mixtures (a color triangle framework of dyed wool yarn) were characterized by colorimetric values (L*, a*, b*, C*, h, and K/S), and are presented to enlighten various colorful shades. Finally, color uniformity and colorfastness tests confirmed the vital contribution of natural dyes toward wool yarn coloration. Particularly, colorfastness to washing confirmed the stability of natural dyes with reference to the lower amount of dyes released into the effluent, which is beneficial for the environment. Overall, this study provides a good background for enhancing the industrialization trend of natural dyes by modulating their dyeing scheme.

Extraction of Natural Dye from Aerial Parts of Argy Wormwood Based on Optimized Taguchi Approach and Functional Finishing of Cotton Fabric

The aerial parts of the Argy Worm Wood (AWW) plant have been used in different Chinese foods as a colorant and a taste enhancer for a long time. Despite its application as a food colorant, it has rarely been considered for the coloration of textiles. Keeping in mind the variation in color strength due to the change in phytochemical contents by seasonal change and other variables, the extraction of AWW aerial parts was optimized using the Taguchi method. Optimization was performed on the basis of total phytochemical contents (phenols, flavonoids, and tannins) in the extracted solutions. For this purpose, two different solvent systems, namely sodium hydroxide/water (NaOH/water) and ethanol/water (EtOH/water), were applied through a simple aqueous extraction method at varying levels of solvent concentration, and extraction temperature and duration. Maximum phytochemicals yield of 21.96% was obtained using NaOH/water system with 9 g/L NaOH/water at 85 °C for 20 min and 25.5% with 75% aqueous ethanol at 85 °C for 40 min. Optimized extracts were characterized by UV-Vis and FTIR spectrophotometry, which showed the presence of multiple phytochemicals in the extracts. The dyeing temperature and time were also optimized. Dyed cotton fabrics showed medium to high colorfastness to washing and excellent antibacterial and UV radiation absorption properties. The effect of pre-mordanting with salts of iron and copper was also studied on the color fastness properties. Cotton fabrics dyed with two different solvent system extracts displayed various shades of brown with NaOH/water, and green with aqueous ethanol with and without pre-mordanting. The present study provides the textile industry with a promising source of functional bio-colorant and a value-adding approach for the AWW plant industry.