A review: can waste wool keratin be regenerated as a novel textile fibre via the reduction method?

Abstract

In the mid-twentieth century, natural fibre shortages spurred research into regenerated protein fibres, including research into regenerated wool keratin. Although these materials were soon displaced by outperforming synthetic fibres, today's global shifts towards an eco-friendlier, more environmentally aware, sustainable fashion industry have increased interest into such materials. This paper discusses the theory behind chemically recycling wool (keratin) from textile waste via a mixed solvent system that employs reduction, one of the several possible methods, and then wet spinning of a blended keratin solution to create a novel filament. The scope is to create a high value product that could help close the loop of the wool textile industry. Chemical wool recycling is suggested as a complementary process to the already existing mechanical wool recycling methods, as it can be used for materials that cannot be processed mechanically. It is generally recognised that regenerated wool keratin has poor mechanical stability and if used for textile production would most likely exist in blends with other materials and require post-processing to improve performance. These novel materials could displace some of the currently dominant fibres on the textile market and therefore help mitigate some the negative environmental impacts of the fashion industry, provided they meet ecofriendly credentials in their manufacture and end-of-life. The chemical principles outlined herein can be in many cases applied to other keratinaceous waste streams such as non-edible animal products (horns, hooves), feathers and, importantly, other (non-textile) sources of wool.

Bioinspired Processing of Keratin into Upcycled Fibers through pH-Induced Coacervation

“…Growing concerns about the shortage and nonsustainability of resources have stimulated research to replace petrochemical plastics with bio-based materials. Proteins from natural resources have attracted much attention as green materials for various applications, including coatings, packaging, adhesives, cosmetics, and fibers, due to their excellent biocompatibility and good mechanical properties. − Keratin, abundantly available through extraction from wool, feathers, and hair, is a particularly promising candidate to substitute oil-derived synthetic products. − However, most keratin waste from the textile and poultry industry currently ends up in landfills and is not recycled. To change this and to make full use of keratin-based natural resources, new extraction and processing strategies are needed.…”

“…Keratin extraction from wool and feathers has been extensively studied in the past. − During the extraction process, inter- and intramolecular interactions (mostly hydrogen bonds and disulfide bonds) need to be broken to facilitate the dissolution of keratin. − More specifically, disulfide bonds can be reduced to thiol groups by reducing agents such as 2-mercaptoethanol, dithiothreitol (DTT), and sodium bisulfite, while hydrogen bonds can be disrupted by lithium bromide (LiBr), sodium dodecyl sulfate (SDS), and ionic liquids. However, the pure keratin obtained upon removal of these agents (e.g., by dialysis) is highly hydrophobic and has a low solubility both in water and most organic solvents.…”

“… 1 − 6 Keratin, abundantly available through extraction from wool, feathers, and hair, is a particularly promising candidate to substitute oil-derived synthetic products. 7 − 9 However, most keratin waste from the textile and poultry industry currently ends up in landfills and is not recycled. To change this and to make full use of keratin-based natural resources, new extraction and processing strategies are needed.…”

Biomimetic synthesis of 2D ultra-small copper sulfide nanoflakes based on reconfiguration of the keratin secondary structure for cancer theranostics in the NIR-II region

“…[26][27][28][29] Intermediate filaments can be organized into a coiled structure (7 nm in diameter) due to its hierarchical structures. 30 The WK molecule, which is composed of the a-helix structure, not only provides the binding sites for metal ion coordination but is important due to the secondary structural metastability of the protein. 31,32 Due to hydrogen bonding in the peptide chain, the structure of wool fibers can maintain the stability of the spiral shape.…”

Zwitterionic keratin coating on silk‐Laponite fibrous membranes for guided bone regeneration

“…Wool keratin is one of the natural zwitterionic polymers. Keratin is the largest intermediate filament group with at least 30 different protein chains and specific physicochemical properties (Lebedytė & Sun, 2021). Wool keratin is characterized by negatively charged carboxylate and positively charged amino groups.…”