Rhamnolipid (RL) microbial biosurfactant-based reverse micellar dyeing of cotton fabric with reactive dyes: A salt-free and alkali-free one-bath one-step approach

The viability of reverse micelles, using rhamnolipid (RL) microbial biosurfactant as the building block, for dyeing of cotton fabrics with reactive dyes has been studied. This novel and sustainable dyeing system not only can achieve salt-free, but also alkali-free under optimised dyeing parameters. Experimental results reveal that RL-based reverse micellar dyeing system can be achieved in one-bath one-step dyeing approach, which is environmentally friendly, time and energy saving, with better colour yield, lower reflectance when compared with conventional water-based dyeing system. RL-dyed samples can obtain comparable colour levelness, washing and rubbing fastness to water-dyed samples. No significant chemical damage of cotton fibre surface was observed from scanning electron microscopic (SEM) investigation. The dye-encapsulated reverse micelle was justified as spherical-like morphology from transmission electron microscopic (TEM) observation. The outcome of the study validates the potential and applicability of RL, as a substitute of synthetic surfactant, in non-aqueous reactive dyeing of cotton fabrics.