Abstract:

Objective Dyeing silk fabrics with reactive dyes typically requires significant amounts of water and inorganic salts, which poses environmental challenges. Isoalkanes, which are non-toxic, colorless, and odorless environmentally friendly solvents, offer a promising alternative for sustainable dyeing processes. This study optimized the dyeing parameters and investigated the dyeing kinetics and thermodynamics of reactive dyes in isoalkane-based systems.
Method In order to investigate the feasibility of dyeing silk fabrics with reactive dyes in a non-aqueous medium and to achieve an environmentally friendly dyeing process, a single-factor experiment was conducted to optimize the dyeing conditions for silk fabrics. The dyeing kinetics of reactive dyes on silk fabric in isoalkanes were analyzed using pseudo-first-order and pseudo-second-order kinetic models, while the thermodynamic characteristics were examined using Nernst, Langmuir, and Freundlich isotherm models. Additionally, the color fastness of fabrics dyed in isoalkanes was compared with those dyed in water bath.
Results The use of isoalkane medium for dyeing silk habotai fabric with Reactive Red 195 significantly reduced water consumption. The influences of dyeing temperature, dyeing time, bath ratio, sodium carbonate concentration, and liquid-carrying rate were systematically studied. The optimal dyeing conditions were determined as dyeing temperature of 80 ℃, dyeing time of 40 min, bath ratio of 1∶40, sodium carbonate of 14 g/L, and liquid-carrying rate of 100% after pre-padding with sodium carbonate. Under these conditions, the fabric achieved the highest K/S value, the best levelness, and the highest fixation rate. The dyed silk fabric exhibited color fastness comparable to that of water bath dyeing, with superior wet rubbing fastness. The dyeing adsorption process of Reactive Red 195 on the silk fabric followed the pseudo-second-order kinetic model. The adsorption behavior was consistent with both the Langmuir and Freundlich isotherms, indicating that the dye could bind to the fiber through both chemical (covalent bonding) and physical (Van Der Waals forces, hydrogen bonding) interactions.
Conclusion A novel, water-saving method for dyeing silk fabrics with reactive red 195 using isoalkanes as a non-aqueous medium was proposed. Under optimized conditions (80 ℃, 40 min, bath ratio 1∶40, 14 g/L sodium carbonate, 100% liquid-carrying rate), the dyed fabric achieved the highest K/S value, optimal levelness, and maximum fixation rate. The adsorption process followed pseudo-second-order kinetics and conformed to both Langmuir and Freundlich isotherms, indicating dual chemical-physical interactions. Compared with the conventional water bath dyeing, the isoalkane system reduced water consumption by 90%-95%, while enabling near-zero wastewater discharge through solvent recycling (>90% recovery). Additionally, suppressed dye hydrolysis in the non-aqueous medium improved dye utilization efficiency. The dyed fabrics exhibited comparable color fastness and superior wet rubbing resistance. This approach demonstrates significant potential for sustainable textile manufacturing by integrating water-energy conservation, environmental compatibility, and industrial feasibility.

Key words: isoalkane, water-less dyeing, silk fabric, reactive dye, dyeing performance, dyeing kinetics