Valorization of the leaves of fennel (Foeniculum vulgare) as natural dyes fixed on modified cotton: A dyeing process optimization based on a response surface methodology

Dyes obtained from different natural sources have emerged as an important alternative to synthetic dyes due to their negative ecotoxicological effects on the environment. In this study, natural colourant from the leaves of fennel (Foeniculum vulgare) was valorized in the dyeing of cationized cotton fabrics. The influence of the main dyeing conditions (dye bath pH, dyeing temperature, and dyeing duration) on the performances of this dyeing process was studied. The dyeing performances of this process were appreciated by measuring the colour yield (K/S) and the fastness properties of the dyed samples. A surface design with the help of Minitab 15 software was used for optimization of the dyeing process and evaluation of interaction effects of different operating parameters. The optimum conditions for dyeing process were found to be pH of 8.22, dyeing temperature of 99.83 °C and dyeing duration of 59.38 min. In addition, it was found that the dye bath of cationized cotton with Croscolor DRT absorbed polyphenols compounds and reduced the Biological Oxygen Demand COD and BOD5 of the dyeing bath.