Valorization of Sulfonated Kraft Lignin as a Natural Dye for the Sustainable Dyeing of Wool Fabrics: Effect of Peroxide Oxidation

Lignin is an abundant and complex biopolymer with inherent color but has only a few applications. It has the potential to replace synthetic acid dyes for the coloration of wool fibers in brown shades, as traditional dyeing with acid dyes produces toxic effluent needing costly treatment. In this work, the valorization of sulfonated lignin was explored by using it as a natural dye for the coloration of wool fabrics alone and with hydrogen peroxide (H2O2). The dyed fabrics were characterized by reflectance and diffuse reflectance spectroscopies to assess the color yield and ultraviolet (UV) protection performance, respectively. The dyed fabrics exhibited reasonably good color yield and satisfactory colorfastness to washing (Grade 3/4), which improved to Grade 4 by the oxidation treatment with H2O2. The scanning electron microscopy (SEM) images show that when fabrics are dyed alone with lignin, deposition of lignin particles is visible on the fiber surface, but with hydrogen peroxide, no deposition of lignin is visible on the fiber surface, and the color strength of the fabric became almost double. The UV light transmission through the fabric decreased from 6.73 and 13.23% at 311 and 365 nm to 2.19 and 5.23%, respectively. The attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra of the dyed fabrics showed increased absorption of lignin sulfonate by the fabric, suggesting depolymerization of lignin by H2O2 to smaller macromolecules easing absorption into the wool fiber. Lignin sulfonate could be a cheap and sustainable alternative to harmful synthetic dyes for producing brown shades on wool fabric

Sustainable Ultrasound-Assisted Ultralow Liquor Ratio Dyeing of Wool Textiles with an Acid Dye

Conventional wool dyeing is an energy-hungry process as the dyeing is carried out at boil using a high liquor ratio. It can be energy efficient if dyeing can be carried out at low temperatures or if the liquor ratio can be reduced. Ultralow liquor ratio dyeing (materials to liquor ratio of 1:5) is advantageous as it considerably reduces consumption of auxiliary chemicals and energy in dyeing. However, at that low liquor ratio dye molecules form agglomerates causing low dye-uptake and uneven dying. In this work, the feasibility of using ultrasound in conjunction with a range of textile auxiliaries for the prevention from dye agglomeration has been investigated for the dyeing of wool with an acid dye. Three ultrasonic baths with different ultrasonic power were used to investigate the effect of ultrasonic power on dyeing performance. It was found that citric acid in conjunction with ultrasound prevented the formation of dye agglomeration in a dyebath and also produced deeper shades and uniform dyeings compared to the dyeing without ultrasound. The depth of shade increased with an increase in ultrasound power. The application of ultrasound did not cause any loss in tensile strength of the fabric, suggesting there was no fiber damage. The developed technique could be used in the textile industry to make wool dyeing even more sustainable than it is at present

Wound Dressing Based on Silver Nanoparticle Embedded Wool Keratin Electrospun Nanofibers Deposited on Cotton Fabric: Preparation, Characterization, Antimicrobial Activity, and Cytocompatibility

Wool keratin (WK) protein is attractive for wound dressing and biomedical applications due to its excellent biodegradability, cytocompatibility, and wound-healing properties. In this work, WK-based wound dressings were prepared by depositing WK/poly(vinyl alcohol) (PVA) and silver nanoparticle (Ag NP)-embedded WK/PVA composite nanofibrous membranes on cotton fabrics by electrospinning. Ag NPs were biosynthesized by reduction and stabilization with sodium alginate. The formed Ag NPs were characterized by ultraviolet–visible and Fourier transform infrared (FTIR) spectroscopy, and their size was determined by transmission electron microscopy and image analysis. The formed Ag NPs were spherical and had an average diameter of 9.95 nm. The produced Ag NP-embedded WK/PVA composite nanofiber-deposited cotton fabric surface was characterized by FTIR and dynamic contact angle measurements, and the nanofiber morphologies were characterized by scanning electron microscopy. The average diameter of the nanofibers formed by 0.1% Ag NP-embedded WK/PVA solution was 146.7 nm. The antibacterial activity of the surface of cotton fabrics coated with electrospun composite nanofibers was evaluated against the two most common wound-causing pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. The cotton fabric coated with 0.1% Ag NP-embedded WK/PVA nanofibers showed very good antibacterial activity against both pathogens, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay results showed good cytocompatibility against L-929 mouse fibroblast cells. However, the increase in Ag NP content in the nanofibers to 0.2% negatively affected the cell viability due to the high release rate of Ag ions. The results achieved show that the developed wound dressing has good potential for wound healing applications

Broadening Color Shade of Dyed Wool Fibre with Binary and Ternary Natural Plant Dye Combinations

A limited selection of natural dyes’ color impedes the development of textile dyeing with natural plant dyes. Inspiring by the conventional coloration of textiles with a combination of three synthetic dyes generally, the present work is to investigate the broadening color shade of dyed wool fiber with ternary natural dye combinations of madder red (MR), gardenia yellow (GY), and gardenia blue (GB) without mordants in a decamethylcyclopentasiloxane (D5) medium. The wool yarn was wetted in an aqueous solution of pH 3 to own a 300% pickup rate, followed by immersion in a D5 medium containing 2% of alcohol ethoxylate (AEO-3) and solid natural dyes at 90°C for 90 min for coloration. The colorfastness to washing was achieved at a 4–5 for fading and a 5 rating for staining for all colors. The XRD patterns and TGA analysis confirmed that the dyeing procedure did not affect the crystallinity nature and stable thermal tendency. SEM images and cross-sections showed that the dyeing procedure did not damage the morphological structure of the wool fiber surface, and the dyes were evenly distributed. Finally, many color shades of dyed fibers were prepared with various dyes’ ratios.</p