Salt-free reactive dyeing of cotton fibers in a ternary solvent system with different reactive dye chemistries

Reactive dye chemistry plays a crucial role in the dyeing of cotton fibers. Herein, to provide insight on the adaptability of salt-free reactive dyeing for sustainable environmental development, the effect of dye chemistry on the dyeing properties of cotton fibers in the proposed ethanol-carbon tetrachloride-water (EtOH-CCl4-H2O) ternary solvent system was investigated in detail. Twelve commonly used reactive dyes were selected as representative dyes and applied to cotton yarns based on their reactive groups, chromophores, and number of sulfonate groups. Compared with the conventional aqueous dyeing method, the studied copper phthalocyanine (CuPc) dyes and azo dyes showed enhanced dyeing performances in the EtOH-CCl4-H2O (55:40:5) mixture, except for the investigated anthraquinone dyes. Dyeing results of cotton yarns indicated that the studied CuPc dyes and azo dyes are suitable dye categories for dyeing cotton in the EtOH-CCl4-H2O mixture. This study may offer a theoretical strategy for the industrial-scale production of cotton fibers using the developed solvent-assisted dyeing technology. The organic solvents recovery will be carried out in the future study.