A novel approach towards green extraction of environmentally friendly anthraquinone based natural dye from amaltas fruits for leather coloration

The research highlights the extracting of natural dyes from the amaltas brown pods of Cassia fistula and their application on the coloration of leather. Herein, a series of experiments was conducted to optimize the dyeing parameters, and it was found that the maximum color yield was achieved using the conditions of 3.5 pH, 0.5 g/100 mL salt concentration, 40 min dyeing time with a temperature of 50 °C. It was also observed that the using bio-mordant provided the more sustainable shades when 0.5 % madder was used. On the other hand, the 0.5 % of Fe as a chemical mordants also shown higher color strength for the dyed leather sample. As a result, post-mordanting with 0.5 % madder (bio-mordant) and 0.5 % Fe (chemical mordant) gave excellent colorfastness ratings (washing 5, light fastness 5). The characterizations using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy also revealed that there were no alternations of chemical structure when the microwave radiation was applied before dyeing. The main color components found in the amaltas brown pods was anthraquinone, which was responsible for producing color shades during the leather dyeing using Cassia fistula extraction. Therefore, this research provides the alternative of synthetic dyes for the coloration of leather which can one of the environmentally friendly sustainable approaches in the leather industry.