Sustainable one-bath natural dyeing of cotton fabric using turmeric root extract and chitosan biomordant

Abstract

Metal mordanting is a common method for improving the dyeability and fastness of natural dyes. However, residual toxic metal ions discharged into wastewater can lead to adverse environmental effects. In this study, we designed an eco-friendly dyeing process for cotton fibers using the natural dye curcumin and biomordant chitosan (CS). To this end, aqueous turmeric root extract was applied along with CS biomordant to cotton fabrics using a one-bath dyeing process. CS was added to the dyebath at two different stages: at the start of dyeing and after reaching the dyeing temperature. The dyeing properties of the dyed samples, including the color strength, color coordinates, levelness, and color fastness to washing, were investigated. Mordant addition at the dyeing temperature produced a higher color strength on cotton fabrics than mordant addition at the start of dyeing. The CS-mordanted samples showed a color strength comparable to that of the metal-mordanted sample and retained the characteristic color of curcumin. In addition, CS mordanting improved the wash fastness of the fabric dyed with turmeric root extract by 1.0–1.5. Overall, the results suggest that the one-bath process of dyeing cotton fabrics using turmeric root extract and CS biomordant could be a sustainable alternative to conventional dyeing with metal mordanting.