Ultrasonic Assisted Environmentally Friendly Extraction of Natural Dyes From Beta vulgaris for the Coloration of Silk Fabric Using Different Mordants

Abstract

Considering the indispensability of environmental protection, the utilization of natural ingredients as sustainable and eco‐friendly alternatives to synthetic dyes in fabric dyeing is of great significance. Betacyanins are naturally sourced pigments of red‐violet color that have the propensity to be fixed to mordanted substrates with reasonable permanency. In this study, the betacyanins sourced from beetroot (Beta vulgaris) were used to dye pre‐mordanted silk fabrics employing ultrasonication. In addition, a comparative analysis of the effects of five different mordants such as orange‐peel extracts, lemon peel extracts, tannic acid, ferrous sulfate, and alum on the color strength and fastness of beetroot‐dyed silk fabrics was presented in this research. For the characterization of the extracted dye, undyed, dyed, and mordanted silk fabric, infrared spectroscopy was performed. To observe the interaction of extracted dye and silk fabric, scanning electron microscopy was also accomplished. The outcomes of the characterization validated the successful extraction of dyes from beetroot and dyeing silk fabric with it. The values of color intensity (K/S), CIE L* a* b*, and CIE L* c* h* were measured using a reflectance spectrophotometer. At the same time, dry and wet rubbing and lightfastness ratings of dyed silk fabrics were determined according to the ISO standards. When 5% (o.w.f.) ferrous sulfate was used in pre‐mordanting, the ratings of colorfastness to wash, rub, and light ranged from 4 to 4/5, and the K/S value of the final sample was 4.88, which is higher than the K/S values of any other dyed samples. In contrast, the performance of 5% (o.w.f.) lemon peel extracts as a mordant was remarkably higher than orange peel extracts and even better than alum and tannic acid to some extent. The beetroot‐dyed silk fabric pre‐mordanted with 5% lemon peel exhibited a K/S value of 4.32, and the overall colorfastness rating ranged from 3/4 to 4/5. In conclusion, beetroot extracts hold the promise of being utilized as a sustainable replacement for environmentally harmful synthetic dyestuff in silk dyeing. Furthermore, in silk dyeing with beetroot extract, lemon peel extract is a potent alternative to ferrous sulfate as a mordant.