A novel efficient method for eco-friendly deep dyeing of wool yarns by extracted madder dyes in the presence of additives

Zinc sulfate and magnesium sulfate were used as additives to provide an effective simultaneous mordanting and dyeing process (meta mordant) for wool yarns with madder dyes extracted by ultrasound. In the dyeing procedure, aluminum sulfate and ferrous sulfate were used as mordants. A response surface methodology (RSM) experimental design was used to optimize the dyeing technique. Results showed that the highest color strength of dyed samples was achieved at 105-110 min at 1:30 ratio of aluminum sulfate to zinc sulfate, 1:10 ratio of aluminum sulfate to magnesium sulfate, and pH of 2.5-3. It was observed that the dyeing of yarns with extracted dye and ferrous sulfate could be carried out without using additives. The color properties of dyed yarns using the novel approach were compared to samples dyed using the conventional method (pre-mordant). The findings revealed that dyed samples using the novel approach had the same or greater color strength as dyed samples using the pre-mordant procedure. L* , a* , and b* of the dyed yarns by extracted dyes and aluminum sulfate in the presence of magnesium sulfate were approximately the same with yarns dyed by the pre-mordant method. Also, the color fastness properties of dyed samples by meta mordant method were acceptable in terms of wash, light, and rub fastnesses. Nearly similar or better color stability was achieved compared to the common method. In this respect, a novel efficient one bath method was introduced for deep dyeing of wool yarns with extracted madder dyes which can decrease the negative environmental impacts such as pollutants, water consumption, and energy in comparison to other conventional methods.