Recyclable Reactive Dyeing of Wool Fabrics in Environmental Friendly Non-Aqueous Medium for a more Sustainable Textile Industry

Abstract

Reactive dyeing of wool fabrics in non-aqueous green solvents was investigated with the aim to cut effluent discharge via dyebath reuse. Hydrolysis of reactive dyes is the major obstacle for recycle and reuse of the spent dye bath. In the current work, 10 non-nucleophilic solvents were screened based on their Environmental, health, and safety (EHS) profile to be used as the dyeing media. Dimethyl sulfoxide (DMSO) and dimethyl carbonate were chosen for their favorable EHS score. ATR-IR, SEM and XRD analysis had revealed DMSO pretreatment induced appreciable morphological and structural changes wool fabrics, leading to enhanced dyeability. DMC was used in combination with DMSO to facilitate dye adsorption as a poor solvent for the dyes. The effect of dyeing temperatures, dyeing time, and DMC content on final depth of shade was investigated. Covalent fixation and ionic fixation were determined for the solvent-dyed wool fabric using a pyridine-stripping procedure and compared to that of an aqueously-dyed control. The results showed that about 30% higher covalent fixation was achieved in non-aqueous system, which leads to higher depth of shade (ΔK/S = 1.3-4.9), enhanced color build up properties and better colorfastness (0.5-1 grade). A multi-cycle repeated dyeing sequence involving the recovered solvents and dyes was demonstrated to give consistently high shade buildup and colorfastness. The recyclable dyeing procedure developed in the current study provides an alternative to effluent treatment in reduction of pollutant discharge for a more sustainable textile industry.