Ecological dyeing of Woolen yarn with Adhatoda vasica natural dye in the presence of biomordants as an alternative copartner to metal mordants

Introduction of natural dyes into modern dye houses is very promising green chemistry concept which should be popularized more and more to reduce the dependency of wool dyeing on some toxic and non-biodegradable synthetic dyes (Azo and benzidine dyes). In the present study, an attempt has been made to investigate the possibility of wool dyeing with Adhatoda vasica extract as a natural dye. A beautiful color palette of shades of varied hue and tone were obtained by using different mordants. The effect of various metal salts (ferrous sulphate, alum and stannous chloride) and natural tannin extracts (gallnut, pomegranate peel and babool bark) as mordants on color and fastness properties of dyed wool samples was comparatively evaluated. Dyeing experiments were performed with and without mordants, using pre-mordanting technique. The color of dyed woolen yarn was investigated in terms of CIELab (L*, a* and b*) and K/S values; and fastness properties were determined as per ISO and AATCC standard test methods. As confirmed by exhaustion studies, a substantial portion of metal salts remained in residual mordant baths. The results of using biomordants for wool dyeing were comparable with that of the metallic mordants in terms of color strength and fastness characterisctics. Biomordants produced quite different color gamuts as expected from a mordant and thus offer full potential to replace metal salts in wool dyeing. (C) 2016 Elsevier Ltd. All rights reserved.