Sustainable Chemistry Method to Improve the Wash-off Process of Reactive Dyes on Cotton

Abstract

Reactive dyes are extensively used for coloration of cellulosic fibers because of their excellent wash fastness (stability to washing with aqueous detergent solutions), which arises from covalent bond formation between dye and fiber. However, up to 40% of the dyestuff may hydrolyze in the dyeing process; this hydrolyzed dye has affinity for the fiber via hydrogen bonding and van der Waals interactions, but is not covalently bonded and as such exhibits poor wash fastness. Accordingly, these reactive dyeings require a multistep “wash-off” process after dyeing, involving various aqueous rinses and washings, in order for the dyeing to achieve the characteristic very high wash fastness. Wash-off and subsequent effluent treatment can account for up to 50% of the total cost of reactive dyeing and consumes significant amounts of water and energy; from a sustainable chemistry and engineering perspective, consumption of water and energy are arguably the biggest issues in textile dyeing. Existing and developmental d...