Nano-engineered lignin from Rubia tinctorum L. waste: A breakthrough in sustainable UV-protective textile coatings

Revolutionizing textile waste valorization, this study transforms Rubia tinctorum L. biomass residues into high-performance functional materials through an innovative circular bioeconomy. The optimization of an organosolv process using response surface methodology enabled the extraction of high-purity lignin (97.3 %) from dye extraction waste, achieving a remarkable 53.83 % yield under optimal conditions (75 % organic acid, 0.1 solid-liquid ratio, 2.8 h extraction time). Comprehensive characterization such as Scanning electron microscopy (SEM), thermogravimetric analysis (TG), Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), and Nuclear magnetic resonance (NMR) confirmed the exceptional purity of the extracted lignin, containing minimal saccharide (2.129 %) and protein (0.28 %) impurities. Converting this lignin into nanoparticles via ultrasound technology represents a breakthrough for advanced textile applications. The application of these nanoparticles to wool fabrics in combination with traditional mordants (tannin and alum) and Rubia tinctorum L. dye created a dual-functional coating with outstanding UV protection (UPF 96) and significant antimicrobial properties against S. aureus and E. coli. This novel approach achieves superior fabric protection and establishes a sustainable closed-loop system by upcycling waste into value-added products. This scalable strategy for transforming textile industry waste into high-performance nanomaterials, pioneers new horizons for sustainable textile functionalization.