Improved Mechanical Recycling of Cellulose Fibres and the Co-Production of Nanocellulose: A Biochemical Approach to Textile Waste Management

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Abbreviations: SEM: Scanning electron microscopyXRD: X-ray diffractionNCC: Nanocellulose crystalsAbstractWhilst synthetic fibre recycling has been established, the recycling of cotton is still far behind the expected recycling rates (1). Mechanical recycling can help to combat this issue. However, the high frictional actions in mechanical recycling which shorten and degrade the quality of waste fibres, places restrictions on the use of the method (2).Consequently, mechanical recycling can only offer semi-closed loop solutions whereby a small number of waste fibres, with adequate lengths, are combined with virgin fibres to produce new yarns. To maintain the lengths of waste fibres during shredding thereby increasing the number of suitable extracted fibres, the frictional forces must be reduced. This can be achieved by reducing inter-yarn friction within the textile, loosening it and therefore reducing the shredding force.Environmentally friendly cellulase-enzyme treatments have previously been shown to reduce the shear rigidity of fabrics (3) and assist in the refining of pulp by lowering the shredding force (4). These enzymes have also been used to produce high-strength NCCs from cotton waste, however, the current methodologies suffer from low yields (5). This study investigates the feasibility of cellulase as a pre-treatment to mechanical recycling, decreasing the inter-yarn friction of woven cotton fabric and co-producing NCCs that can be used as a reinforcing textile coating. The treatments reduce friction by reducing contact points between fibres and loosening the structure. Keywords: Mechanical recycling, enzymes, textile waste, Nanocellulose, Textile coating, frictional forcesResearch question: Can a cellulase enzyme treatment be used as a pre-treatment to mechanical recycling?Research aims: This project seeks to investigate the effect of enzyme treatments on the inter-yarn friction of woven cotton fabric during mechanical shredding.Objectives:1. To optimize the enzyme treatment to reduce the combing force and inter-yarn friction of cellulose-based textiles.2. To isolate long fibres from mechanical shredding of treated textiles.3. To produce a methodology to extract enzyme produced Nanocellulose crystals (NCCs) from the reaction solution.4. To coat cellulose fibres with enzyme derived NCC and quantify the mechanical properties.Approach: The student will be conducting laboratory work to treat cellulose-based textiles e.g., cotton, lyocell and/or viscose with a cellulase enzyme solution. The textiles will then be characterized using several laboratory techniques, such as XRD and SEM, to understand the effects of enzyme treatment on the structure and morphology of the textile. Changes in the shear properties will also be measured using mechanical tests such as bias extension tests and combing tests. The student will measure the lengths of treated fibres after mechanical shredding to assess the success of the treatments in maintaining fibre lengths.Novel engineering and/or physical sciences content: High-value NCC production integrated into enzyme-assisted mechanical recycling of textile waste.