Green Process for Indigo Dyeing: Effect and Modeling of Physico-chemical Parameters Using Statistical Analysis

Textile Industries use different chemicals in indigo dyeing processes. Interest in eco-friendly processing in the textile industry has recently increased because of a larger awareness of environmental issues. For the case of indigo dyeing process, the reducing agent conventionally used is the - environmentally unfavourable – sodium dithionite, which will be replaced in this study with an ecological reducing agent called acetol that is also known as hydroxyacetone. In this paper, measurements of the redox potential at various experimental conditions were carried out in a dyeing bath, where acetol is the reducing agent of indigo. Moreover, an unconventional but eco-friendly indigo dyeing process of cotton was investigated. The effects of: reduction duration, dyeing duration, reduction temperature, alkalinity and the amount of indigo on the performances of this dyeing process were studied, and the dyeing results were evaluated by measuring the colour yield parameter (K/S) of the dyed samples at 660 nm. Finally, a factorial design was employed for the experimental plan; mathematical model equation and statistical analysis were derived by computer simulation applying the least squares method using Minitab 15.