Solvent-based stripping method for dyed cellulosic textiles

Abstract

The post-consumer textile waste may contain several dyes, and it is difficult to predict the type of dye present in it. The chemistry of dyes and their bonding with textiles are not similar; therefore, colour can be stripped off using a specific method pertaining to a specific dye-fibre combination. However, the common decolourisation method will be highly sought-after to solve such limitations. The present investigation deals with the combined stripping of cellulosic textile materials dyed with Direct, Reactive, Vat and Sulphur dyes, followed by optimisation. Sodium hydroxide and sodium hydrosulphite were used as stripping agents together with a solvent and water mixture during the process of stripping. The optimised recipe obtained was 20 g/l sodium hydroxide and 20 g/l sodium hydrosulphite at 90 °C for 20 min with a 50/50 water/DMSO (Dimethylsulphoxide) ratio. It has been found that solvent-based and conventional stripping perform equally well on direct and reactive dyed fabrics. However, conventional stripping cannot remove vat and sulphur dyes. Contrarily, the same colours showed greater than 90% stripping efficiency in solvent-based procedures.