From textile waste to sustainable biomaterials: the role of ionic liquids and deep eutectic solvents in protein-based textile waste valorization

Abstract

The 2030 Agenda aims to create strategies based on circular economy while addressing economic, environmental, and social issues. In this context, implementing a sustainable bioeconomy for waste valorization is indispensable for the appropriate development of society. Although vital to global socioeconomic development, the textile industry is one of the most environmentally harmful sectors due to its reliance on non-renewable resources, high energy consumption, and significant waste generation. In response to these challenges, this critical review addresses sustainable strategies for the valorization of protein-based textile waste, specifically silk and wool, emphasizing the potential of ionic liquids (ILs) and deep eutectic solvents (DESs) as alternative and efficient solvents for protein recovery. The proteins from silk and wool can be efficiently recovered and reused through upcycling strategies in various value-added applications. This approach strengthens a sustainable bioeconomy focused on waste recovery and valorization, which is essential for balanced and environmentally responsible socioeconomic development. Based on their relevance, this review discusses the chemical and structural properties of the proteins present in silk and wool, namely fibroin, sericin, and keratin, as well as conventional and advanced recycling methods. It further discusses the mechanisms of protein dissolution in ILs and DESs, highlighting their efficacy in selectively dissolving these target biomacromolecules while preserving structural integrity and functionality. This review also presents recent advances in upcycling these proteins into high-value materials, including biomedical scaffolds, hydrogels, films, and nanostructures. Furthermore, a SWOT analysis is shown to critically assess the current potential and limitations of IL and DES-based approaches to recycle protein-rich textile waste, identifying strengths such as process selectivity and structural preservation, as well as challenges related to cost, scalability, and environmental impact.