The valorization of discarded clothing offers significant economic, social, and environmental benefits by repurposing waste and presents a major opportunity to reduce landfill burden while providing an alternative to virgin raw materials. This thesis explores the potential of discarded garments as a source of cellulose nanomaterials (CNMs).

Sulfated cellulose nanocrystals (SCNCs) were extracted from cotton, polyester/cotton, and acrylic/cotton blends via sulfuric acid hydrolysis, with simultaneous recovery of the synthetic fibers. The properties of the highly pure extracted SCNCs were comparable to those from virgin cotton, despite the presence of textile dyes. A life cycle assessment (LCA) revealed a reduced environmental footprint for SCNC production using clothing rather than wood pulp as a feedstock.

An alternative route for CNC extraction was developed: citric acid esterification and partial hydrolysis followed by mechanical fibrillation. This yielded citrated cellulose nanocrystals (CitCNCs) with carboxyl and citrated surface moieties, high crystallinity, a needle-like morphology, and a surface charge of 0.9 mmol g⁻¹. The LCA identified the use of citric acid as the environmental hotspot for optimization, highlighting the importance of such assessments for guiding sustainable development from the laboratory scale.

The versatility of cotton garments was explored by oxidizing them with NaClO and catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxy/NaBr, yielding TO-Cotton with a surface charge of 1.4 mmol g⁻¹. The NaClO also degraded the cotton fabric dyes. TO-Cotton was treated in two ways to generate distinct CNMs. First, it was hydrolyzed with hydrochloric acid to obtain carboxylated cellulose nanocrystals (TCNCs) with an average surface charge of 1.1 mmol g⁻¹ and a morphology similar to that of SCNCs. Second, TO-Cotton was mechanically fibrillated to yield carboxylated cellulose nanofibrils (TO-CNFs).

To investigate the influence of textile functionalization on the final properties of CNFs, cotton garments were cationized using (2,3-epoxypropyl)trimethylammonium chloride to form Cat-Cotton, which was further fibrillated to yield Cat-CNFs. Both Cat-CNFs and TO-CNFs showed high surface charge (>0.9 mmol g⁻¹), small cross-section (<10 nm), and high aspect ratio (>35). TO-CNFs were formed in higher yields and with a greater surface charge compared to Cat-CNFs. However, the Cat-CNFs possessed a higher aspect ratio and maintained colloidal stability over a wider pH range. Both CNFs were used to prepare nanopapers and foams, whose mechanical properties depended on the type of CNF.

All three CNC types (SCNCs, CitCNCs, and TCNCs) were used to prepare anisotropic foams in combination with xanthan gum (XG). These foams exhibited minimal shrinkage after freeze-drying, high alignment, and excellent thermal stability. The CNC type influenced the foam properties: SCNC foams had the lowest water uptake, pristine CitCNC foams exhibited the best mechanical properties, and the incorporation of XG significantly enhanced the mechanical properties of TCNC foams.

This thesis demonstrates the feasibility and potential of using post-consumer cotton fabrics as a feedstock for CNM production, indicating the versatility of the resulting CNMs in various applications.