Microwave-assisted sustainable exploration of cocklebur leaves (Xanthium strumarium L.) as a novel source of distinct yellow natural colorant for dyeing cotton fabric.

During current times, the use of bio-colorants attained public acceptance as a sustainable alternative to synthetic ones which in turn reduced the environmental contamination. The present study focused on the green, safe, and clean technology for the resurgence of natural colorant from cocklebur (Xanthium strumarium L.) leaves and their application to cotton fabric. Natural colorants were extracted by employing an eco-friendly microwave-assisted extraction process using an aqueous and alkaline medium. Dyeing of cotton fabric was carried out using irradiated and unirradiated cotton fabric with irradiated and unirradiated natural dyes of cocklebur leaves. The results of extraction experiments revealed that 4 min microwave-assisted alkaline extract exhibited significantly outstanding color strength onto microwave-treated cotton fabric compared to aqueous one. Further to investigate the optimum dyeing conditions for cotton fabric, various dyeing variables such as dyeing time, dyeing temperature, dye concentration, and exhausting agent were monitored and found a superior result using a dye concentration of 45 ml, for dyeing cotton fabric at 75 °C for 50 min in the presence of 4 g/100 ml of table salt. For improvement in color strength and color fastness properties, the effects of various bio-mordants, such as eucalyptus bark, acacia bark, turmeric rhizome, and onion shells, and chemical mordants (aluminum and copper) on dyed cotton fabric were also evaluated. It was also observed that cotton fabric dyed with alkaline extract of cocklebur leaves using bio-mordants as pre-mordants (4% acacia, 4% eucalyptus, 2% onion) and post-mordants (3% onion, 3% eucalyptus, 4% acacia) exhibited the highest color strength and various hues with acceptable colorfastness properties against light, washing, and rubbing in comparison to chemical mordants. The ISO standard for fastness also revealed that bio-mordanting has enhanced the rating from good to excellent in comparison to chemical mordants. The results provide ample scope for the extraction of yellow natural dye from the cocklebur leaves for eco-friendly coloration of fabrics using bio-mordants.