Sustainable wool fibers dyeing using henna extract in non-aqueous medium

Dyeing processes usually consume a large amount of water and toxic chemicals, thus inducing environmental pollution. Therefore, we have designed here an eco-friendly process of dyeing wool fibers using natural dyes extracted from henna leaves in decamethyl cyclopentasiloxane. In this process, traditional hazardous metallic mordants and heavy metal salts were substituted by safe chitosan to pretreat wool fibers. Decamethyl cyclopentasiloxane was used to reduce the consumption of the high amount of water needed in traditional dyeing. Chitosan-treated and untreated samples were dyed with different henna extract/decamethyl cyclopentasiloxane suspensions at 40 °C, 60 °C, 80 °C and 90 °C. Results showed that dye uptake, fixation rate and apparent color depth of the samples dyed in henna extract/decamethyl cyclopentasiloxane suspensions were higher than water-based dyed samples. The dye uptake of samples dyed using our system reached 80–98%, as compared with 70–75% for water-based dyed samples; accordingly, the color strength and fixation rate were increased.