Investigation of the Possibilities of Wool Fiber Surface Modification with Copper Selenide

Towards zero-waste processes: Waste wool derivatives as phosphate adsorbents and auxiliaries for textiles' natural dyeing

The textile industry is a pillar of the manufacturing sector worldwide, but it still represents a significantly polluting production sector since it is energy-, water- and natural resource-intensive. Herein, waste wool that did not meet the technical requirements to be used for yarns and fabrics was recovered first to prepare materials for wastewater remediation, specifically for phosphate removal. The wool underwent an alkaline treatment, eventually saturated with FeCl3 and then left at room temperature or thermally treated to induce crosslinking/stabilisation, obtaining adsorbent panels. The main characterisation findings concerned the impact of alkaline treatment on morphology and structure; additionally, the samples with iron displayed a behaviour attributable to a crosslinking effect operated by Fe3+. Batch experiments showed that only samples with iron were efficient in phosphate adsorption, with a high removal percentage obtained in a wide pH range. Adsorption isotherms and kinetics were investigated, suggesting a complex system of interactions. Moreover, during the alkaline treatment necessary to prepare such wool-derived adsorbent panels, a significant amount of wool hydrolysates left in the solution was produced. These substances, in view of zero-waste procedures, were isolated and re-employed as dyeing auxiliaries. Preliminary results demonstrated that the wool hydrolysates enabled the dyeing of cotton with natural dyes, which is generally a tricky process.

Keratin from Animal By-Products: Structure, Characterization, Extraction and Application-A Review

Keratin is a structural fibrous protein and the core constituent of animal by-products from livestock such as wool, feathers, hooves, horns, and pig bristles. This natural polymer is also the main component of human hair and is present at an important percentage in human and animal skin. Significant amounts of keratin-rich animal tissues are discarded worldwide each year, ca. 12 M tons, and the share used for keratin extraction and added-value applications is still very low. An important stream of new potential raw materials, represented by animal by-products and human hair, is thus being lost, while a large-scale valorization could contribute to a circular bioeconomy and to the reduction in the environmental fingerprint of those tissues. Fortunately, scientific research has made much important progress in the last 10-15 years in the better understanding of the complex keratin architecture and its variability among different animal tissues, in the development of tailored extraction processes, and in the screening of new potential applications. Hence, this review aims at a discussion of the recent findings in the characterization of keratin and keratin-rich animal by-product structures, as well as in keratin recovery by conventional and emerging techniques and advances in valorization in several fields.

Keratin/Copper Complex Electrospun Nanofibers for Antibacterial Treatments: Property Investigation and In Vitro Response

The frontiers of antibacterial materials in the biomedical field are constantly evolving since infectious diseases are a continuous threat to human health. In this work, waste-wool-derived keratin electrospun nanofibers were blended with copper by an optimized impregnation procedure to fabricate antibacterial membranes with intrinsic biological activity, excellent degradability and good cytocompatibility. The keratin/copper complex electrospun nanofibers were multi-analytically characterized and the main differences in their physical-chemical features were related to the crosslinking effect caused by Cu2+. Indeed, copper ions modified the thermal profiles, improving the thermal stability (evaluated by differential scanning calorimetry and thermogravimetry), and changed the infrared vibrational features (determined by infrared spectroscopy) and the chemical composition (studied by an X-ray energy-dispersive spectroscopy probe and optical emission spectrometry). The copper impregnation process also affected the morphology, leading to partial nanofiber swelling, as evidenced by scanning electron microscopy analyses. Then, the membranes were successfully tested as antibacterial materials against gram-negative bacteria, Escherichia coli. Regarding cytocompatibility, in vitro assays performed with L929 cells showed good levels of cell adhesion and proliferation (XTT assay), and no significant cytotoxic effect, in comparison to bare keratin nanofibers. Given these results, the material described in this work can be suitable for use as antibiotic-free fibers for skin wound dressing or membranes for guided tissue regeneration.

Modification of wool fibre's structural properties as a cheap adsorbent for the elimination of Cr6+ and Rhodamine6g dye from aqueous solution

Wool, a naturally occurring biopolymer made up of amino acids, is employed as an adsorbent for both modified and unmodified forms of the dyes rhodamine6G (R6G) and Cr6+. The two-step procedure of (i) ring opening polymerization (ROP) and (ii) condensation reaction was used to modify the structure of wool fibre. Both the ROP and the condensation provide steric free chain expanding groups as well as adsorption-improving groups. The FT-IR spectrum, which showed peaks about 1725 and 1630 cm-1 corresponding to the CO and CN stretchings, respectively, confirmed the structural modification. By detecting a slight hump at 8.5 ppm, 1H NMR was able to validate the later functional group. DSC, TGA, FE-SEM, EDX, and water contact angle (WCA) were also used to characterize it. With the aid of a UV-visible spectrophotometer, the quantitative adsorption of both Cr6+ and R6G by modified and unmodified Wool fibre was monitored. For the adsorption of Cr6+ and R6G, the pseudo first order and pseudo second order kinetics were used. The multilayer coating of adsorbate onto adsorbent was confirmed by the Langmuir adsorption isotherm. Thermodynamic parameters were calculated and compared to values found in the literature.

Effect of Reducing Agent on Characteristics and Antibacterial Activity of Copper-Containing Particles in Textile Materials

Textile materials modified with copper-containing particles have antibacterial and antiviral properties that have prospects for use in healthcare. In the study, textile materials were saturated with copper-containing particles in their entire material volume by the absorption/diffusion method. The antibacterial properties of modified textile materials were confirmed by their inhibitory effect on Staphylococcus aureus, a Gram-positive bacterium that spreads predominantly through the respiratory tract. For the modification, ordinary textile materials of various origins and fiber structures were used. Technological conditions and compositions of modifying solutions were established, as well as the most suitable textile materials for modification. To assess the morphological and physical characteristics of copper-containing particles and the textile materials themselves, X-ray diffraction, a scanning electron microscope, and an energy-dispersive X-ray spectrum were used. In modified textile samples, XRD data showed the presence of crystalline phases of copper (Cu) and copper (I) oxide (Cu2O). On the grounds of the SEM/EDS analysis, the saturation of textile materials with copper-containing particles depends on the structure of the textile materials and the origins of the fibers included in their composition, as well as the modification conditions and the copper precursor.

Effect of Copper Selenide Modification on the Conductivity of PA6, PA66, PAN, and PES Fibers

Textile production has been steadily increasing for a few decades and, as a result, the amount of industrial textile waste is also increasing. This waste can be reused as raw material to produce new functional composites. Such materials can be used for special purposes with varying combinations of physical and chemical properties by using polymers modified with thin semiconductive or electrically conductive layers of binary inorganic compounds. In this paper, a study of the possibilities of altering the properties of synthetic fiber conductivity by modification with copper selenide is presented. A two-step adsorption/diffusion method was used for the copper selenide layer forming on the surface of the fibers. The treatment process was repeated cyclically. To evaluate the morphological properties of Cu_xSe treated fibers, scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) were performed. The study showed that the chosen modification method is more suitable for PA and PAN fibers. Dense layers of copper selenides were successfully formed on their surface, which significantly reduced their electrical resistance.