Limonene biosolvent-based non-aqueous dyeing medium for salt-free and alkali-free rhamnolipid (RL) biosurfactant reverse micellar dyeing of cotton fabric with reactive dyes

The feasibility of using different forms of limonene biosolvents as dyeing medium in rhamnolipid (RL) biosurfactant-based reverse micellar dyeing system for cotton fabrics is investigated, with different dyeing profiles. Experimental results reveal that limonene-dyed fabrics can achieve generally higher colour yield than water-dyed fabrics while samples dyed by one-step dyeing method could obtain higher colour yield, but poorer relative unlevelness index (RUI) values when compared with samples dyed by two-step method. The CIE L*a*b* value and reflectance of water-dyed and limonene-dyed samples were examined. The pH value of aqueous and non-aqueous dye liquor was measured. SEM images of limonene-dyed cotton fabrics and TEM images of reverse micelle morphology were evaluated. Washing and crocking fastness of the dyed samples were also assessed. The resulting evidence validate that limonene is feasible for reverse micellar reactive dyeing of cotton fabric with the use of RL biosurfactant and it can be one of the alternative solvents, making the dyeing process more natural, more biodegradable and environmentally more sustainable.