Sustainable silk dyeing in a silicon non-aqueous dyeing system with Reactive Red 195: salt-free and less alkali

Abstract

Conventional dyeing processes usually generate a huge amount of wastewater, and in general, silk dyeing with reactive dyes using large amounts of salt and alkali has a great environmental impact. Herein, a green approach for a new dyeing system involving silk fabric dyed with reactive dyes in a silicon non-aqueous dyeing system without salt was reported. The optimal dyeing parameters of silk fabric dyed in this green dyeing system without alkali were 90°C for 75 minutes and with alkali were 70°C for 75 minutes, and the Reactive Red 195 exhibited good dye permeability, superior exhaustion, high fixation rate, and good dyeing depth, indicating the high utilization of dye and less effluent discharge. The color fastness of silk fabric dyed in the silicon non-aqueous dyeing system was comparable to silk fabric dyed in the conventional water bath. In addition, the fixation rate and K/S value were improved by the addition of 0.4% (o.w.f) NaHCO₃, which cannot be obtained in a conventional water bath, and all silk fabrics showed better tensile strength dyed in the green dyeing system. Therefore, the sustainable green dyeing method with a silicon non-aqueous system achieved a salt-free, less alkali or alkali-free, and simple process, which has the potential to solve the problems of wastewater, high salt, and high alkali in conventional dyeing processes.