Laccase-Catalyzed the Polymerization of Portulaca Oleracea L. Extract as a Precursor for Ecological Dyeing of Pure Cotton Fabric

The integration of natural dyes and biomass-based dyeing auxiliaries holds huge potential to address the environmental sustainability challenges, which the textile industry encounters. This research employed Portulaca oleracea L. extract as a natural dye, utilizing laccase as a catalyst for polymerizing the dye, thereby creating a precursor that enhances its eco-friendly dyeing attributes on cotton fabrics. The initially exhibited suboptimal direct dyeing performance on cotton fabrics, resulting in a faint yellow hue and a K/S value of 0.66. However, following laccase catalysis, the depth of color on the dyed fabric significantly increased, with a K/S value reaching 4.41, and the dye uptake rate increased from 14.54% to 33.69%. The resulting dyed fabric exhibited excellent fastness to soap washing, light, and rubbing, all scoring above levels 4 to 5. Analysis of dyeing kinetics and adsorption models indicated that the dyeing process was consistent with both the pseudo-first-order and pseudo-second-order kinetic models, suggesting physical and chemical bonding between the precursor and the fiber. Further investigations employing ultraviolet spectrum analysis, matrix-assisted laser desorption/ionization time of flight mass spectrometry, and gas chromatography-mass spectrometer revealed the fundamental composition of the natural dye, the molecular weight, and structural characteristics of the precursor, substantiating that the catalytic mechanism involves laccase-catalyzed oxidation. Additionally, the dyed cotton yielded an ultraviolet protection factor value of 230 and a long-lasting herbal fragrance, accurately identified by an electronic nose. These results confirm the viability of intensifying fabric color using the laccase-catalyzed system. This technique significantly expands the environmental applications of its extract.