I urval från Stockholms universitets publikationsdatabas

• Citrated cellulose nanocrystals from post-consumer cotton textiles

  2023. Maria-Ximena Ruiz-Caldas (et al.). Journal of Materials Chemistry A

  Artikel

  We propose a new method for the extraction of cellulose nanocrystals (CNCs) from post-consumer cotton textiles through surface functionalization followed by mechanical treatment. Cotton-based textiles were esterified using an 85 wt% solution of citric acid at 100 degrees C, then further fibrillated in a microfluidizer. The final product, citrated cellulose nanocrystals (CitCNCs), was a dispersion of needle-like nanoparticles with high crystallinity. Up to 78 wt% of the cotton fabric was converted to CitCNCs that exhibited higher yields and a higher surface group content than CNCs extracted through H2SO4 hydrolysis, although CitCNCs showed a broader size distribution and decreased thermal stability. Experimental data supported by DFT calculations showed that the carboxyl groups on the CitCNC surface are bonded to cellulose by mono or diester linkages. An early-stage life cycle assessment (LCA) was performed to evaluate the environmental impact of using discarded textiles as a source of cellulose and analyze the environmental performance of the production of CitCNCs. Our work showed a significant reduction in the environmental burden of CNC extraction using post-consumer cotton instead of wood pulp, making clothing a good feedstock. The environmental impact of CitCNC production was mainly dominated by citric acid. As a proof of concept, around 58 wt% of the citric acid was recovered through evaporation and subsequent crystallization, which could reduce climate impact by 40%. With this work, we introduce a catalyst-free route to valorize textiles with the extraction of CitCNCs and how conducting LCA in laboratory-scale processes might guide future development and optimization.

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• Cellulose Nanocrystals from Postconsumer Cotton and Blended Fabrics: A Study on Their Properties, Chemical Composition, and Process Efficiency

  2022. Maria-Ximena Ruiz-Caldas (et al.). ACS Sustainable Chemistry and Engineering 10 (11), 3787-3798

  Artikel

  From manufacturing to disposal, the textile industry faces multiple challenges to achieve sustainability and reduce its environmental impact. This work investigates the properties and composition of cellulose nanocrystals (CNCs) extracted from clothing waste made of cotton fibers. We isolated CNCs from cotton, polyester/cotton, and acrylic/cotton waste fabrics through acid hydrolysis with sulfuric acid. A yield of 51-62 wt S4, ( co tt on basis) was obtained, and nearly all the polyester and acrylic libers contained in the initial fabrics were recovered in a convenient shape that could allow easier recycling. CNCs extracted from the selected fabrics showed high purity, similar structural, physical, and chemical characteristics, and their properties were comparable to those extracted from virgin sources, although their surface chemistry and elemental composition slightly differed. The chemical components in the waste fabrics and the extracted CNCs were evaluated through a nontarget chromatographic-mass spectrometric screening strategy. Both the recycled textiles and the CNCs contained hundreds of compounds common in postconsumer textiles, including some with health and environmental concerns. However, our initial findings show that their concentrations in the CNCs are negligible. Our results provide insights into the challenges associated with the use of cotton waste textiles for the extraction of cellulose nanoparticles, and into the potential applications of the extracted nanomaterials.

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• Water Filtration Membranes Based on Non-Woven Cellulose Fabrics: Effect of Nanopolysaccharide Coatings on Selective Particle Rejection, Antifouling, and Antibacterial Properties

  2021. Blanca Jalvo (et al.). Nanomaterials 11 (7)

  Artikel

  This article presents a comparative study of the surface characteristics and water purification performance of commercially available cellulose nonwoven fabrics modified, via cast coating, with different nano-dimensioned bio-based carbohydrate polymers, viz. cellulose nanocrystals (CNC), TEMPO-oxidized cellulose nanofibers (T-CNF), and chitin nanocrystals (ChNC). The surface-modified nonwoven fabrics showed an improvement in wettability, surface charge modification, and a slight decrease of maximum pore size. The modification improved the water permeance in most of the cases, enhanced the particle separation performance in a wide range of sizes, upgraded the mechanical properties in dry conditions, and showed abiotic antifouling capability against proteins. In addition, T-CNF and ChNC coatings proved to be harmful to the bacteria colonizing on the membranes. This simple surface impregnation approach based on green nanotechnology resulted in highly efficient and fully bio-based high-flux water filtration membranes based on commercially available nonwoven fabrics, with distinct performance for particle rejection, antifouling and antibacterial properties.

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• 3D printed polylactic acid (PLA) filters reinforced with polysaccharide nanofibers for metal ions capture and microplastics separation from water

  2023. Natalia Fijoł (et al.). Chemical Engineering Journal 457

  Artikel

  The need for multifunctional, robust, reusable, and high-flux filters is a constant challenge for sustainable water treatment. In this work, fully biobased and biodegradable water purification filters were developed and processed by the means of three-dimensional (3D) printing, more specifically by fused deposition modelling (FDM).

  The polylactic acid (PLA) – based composites reinforced with homogenously dispersed TEMPO-oxidized cellulose nanofibers (TCNF) or chitin nanofibers (ChNF) were prepared within a four-step process; i. melt blending, ii. thermally induced phase separation (TIPS) pelletization method, iii. freeze drying and iv. single-screw extrusion to 3D printing filaments. The monolithic, biocomposite filters were 3D printed in cylindrical as well as hourglass geometries with varying, multiscale pore architectures. The filters were designed to control the contact time between filter’s active surfaces and contaminants, tailoring their permeance.

  All printed filters exhibited high print quality and high water throughput as well as enhanced mechanical properties, compared to pristine PLA filters. The improved toughness values of the biocomposite filters clearly indicate the reinforcing effect of the homogenously dispersed nanofibers (NFs). The homogenous dispersion is attributed to the TIPS method. The NFs effect is also reflected in the adsorption capacity of the filters towards copper ions, which was shown to be as high as 234 and 208 mg/gNF for TCNF and ChNF reinforced filters, respectively, compared to just 4 mg/g for the pure PLA filters. Moreover, the biocomposite-based filters showed higher potential for removal of microplastics from laundry effluent water when compared to pure PLA filters with maximum separation efficiency of 54 % and 35 % for TCNF/PLA and ChNF/PLA filters, respectively compared to 26 % for pure PLA filters, all that while maintaining their high permeance.

  The combination of environmentally friendly materials with a cost and time-effective technology such as FDM allows the development of customized water filtration systems, which can be easily adapted in the areas most affected by the inaccessibility of clean water.

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• Automated thermal desorption-gas chromatography/mass spectrometry for screening of hazardous chemicals in cotton and cotton blend garments – analytical challenges

  Tim Åström (et al.).

  The global production of textiles involves large amounts of health-hazardous chemicals, constituting possible health risks since residues usually remain in the finished garments. An analytical method based on automated thermal desorption (ATD) coupled online to GC/MS for screening of several classes of toxic chemicals in synthetic garments was recently published by us. In the present study, the ATD-GC/MS methodology is further extended to cotton and cotton blend materials. 

  Different textile materials with a high content of cotton were found to exhibit large variations in adsorption strength for many chemicals frequently detected in textiles. This was shown to influence the thermal desorption efficiency strongly in ATD-GC/MS. By using absolute response factors from appropriate internal standards spiked directly onto the textile samples, the effects of these differences could be minimized. In this way, accurate quantification was made possible regardless of textile composition, and quantification of native textile chemicals in garments made with the ATD-GC/MS method agreed well with an offline method based on solvent extraction and GC/MS analysis.

  The ATD-GC/MS method has now been shown to be applicable for quantitative screening of around 75% of [UN1] [TÅ2] all the textiles on the retail market. The simplified quantification method makes it suitable for screening many samples. For all textile chemicals and fibre materials investigated, the method limits of detection, using only 20 mg of textile, is at least 100 times lower than the current EU regulation for quinoline and several toxic arylamines.

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• Trash to treasure: 3D printing of waste-based polycotton composite for the production of water filters and commodity products

  Varvara Apostolopoulou Kalkavoura (et al.).

  The recycling of polycotton without separating its constituents for high-performance applications has not yet been fully investigated. In this study, we propose a simple and efficient method involving one-pot, 2, 2, 6, 6 – tetramethylpiperdine-1-oxyl (TEMPO) - oxidation of post-consumer polycotton textile waste followed by lenient mechanical fibrillation. Successful chemical modification of the polycotton waste was confirmed by the Fourier-transform infrared (FT-IR) spectroscopy measurements, in which the presence of carboxyl groups introduced during the TEMPO-oxidation was observed. Moreover, the waste-based pellets were single-screw extruded into 3D printing filaments, which were further processed via desktop Fused Deposition Modelling (FDM) 3D printer.

  FDM processing was carried out without hindrance. The textile-based filament was used for the fabrication of a variety of high surface-finish quality models, which presented diverse geometries and porosity architectures. The versatility of the developed 3D printed models was demonstrated through both, their potential to be utilized as fashion accessories, and by evaluating their performance in water treatment applications. Taking advantage of the introduction of negatively charged carboxylic groups onto the polycotton-based materials, which was expected to facilitate the electrostatic interactions with positively charged species, the 3D printed filters were tested for removal of cationic dye methylene blue (MB) from water in a batch adsorption study. The adsorption followed Langmuir model, with a maximim adsorption capacity of 3 µmol/g. 

  Overall, this work presents a novel approach for the upcycling of polycotton waste into functional filament suitable for a variety of 3D printing, and further, engineering applications. The development of composite filaments and their mechanical and adsorption properties pave the way for future research within valorisation of textile-based waste.

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• Is it possible to completely dry cellulose?

  2025. Aleksandar Y. Mehandzhiyski (et al.). Carbohydrate Polymers 365

  Artikel

  Cellulose nanocrystals (CNCs) are widely used in advanced materials due to their unique mechanical and physicochemical properties. However, their interactions with water, particularly in the context of drying, remain poorly understood. The presence of bound water in CNC poses challenges for processing, storage, and applications sensitive to moisture. In this study, we combine molecular simulations and experimental drying investigations to assess the extent of water retention in both native and TEMPO-CNC under different thermodynamic conditions. Our results demonstrate that while native CNCs can be fully dried under low pressure (≤1 mbar) and elevated temperature (110 °C), TEMPO-CNC retain a significant amount of water (1–7 wt%) due to electrostatic interactions between water molecules and the charged surface carboxylic groups and the sodium counter-ions. These findings provide fundamental insights into the drying behavior of functionalized nanocellulose and highlight the importance of considering residual bound water in applications requiring moisture-sensitive performance.

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• Multimodal structural humidity-response of cellulose nanofibril foams derived from wood and upcycled cotton textiles

  2025. Agnes Åhl (et al.). Carbohydrate Polymers 357

  Artikel

  We have produced foams from cellulose nanofibrils from upcycled cotton (upCNF) and wood (wCNF) through unidirectional (UIT) and multidirectional ice-templating (MIT) and investigated the structural humidity response through in-situ WAXS, SAXS, and micro tomography (μCT) between 10 and 95 % relative humidity (RH). The upCNF and wCNF WAXS patterns displayed a shape- and position shift as the RH was increased, with a compression in the (200) direction and an elongation in the (004) direction. The average separation distance extracted from the 1D SAXS patterns revealed no significant change for the upCNF foams regardless of RH and processing route, while a significant increase was observed for the wCNF foams. The μCT measurements of the upCNF foams showed a slight shift in macropore distribution towards larger pores between 50 and 80 % RH which can be attributed to the weakening and partial disintegration of the pore wall as more moisture is introduced. The humidity-induced structural alterations of the upCNF foam were significantly lower compared to the wCNF foams, confirming our claim of upCNF being more moisture resistant than wCNF foams.

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• Anisotropic foams derived from textile-based cellulose nanocrystals and xanthan gum

  2024. Maria-Ximena Ruiz-Caldas (et al.). Carbohydrate Polymers 338

  Artikel

  The upcycling of discarded garments can help to mitigate the environmental impact of the textile industry. Here, we fabricated hybrid anisotropic foams having cellulose nanocrystals (CNCs), which were isolated from discarded cotton textiles and had varied surface chemistries as structural components, in combination with xanthan gum (XG) as a physical crosslinker of the dispersion used for foam preparation. All CNCs had crystallinity indices above 85 %, zeta potential values below -40 mV at 1 mM NaCl, and true densities ranging from 1.61 to 1.67 g center dot cm(-3). Quartz crystal microbalance with dissipation (QCM-D) measurements indicated weak interactions between CNC and XG, while rheology measurements showed that highly charged CNCs caused the XG chains to change from an extended to a helicoidal conformation, resulting in changes the in viscoelastic properties of the dispersions. The inclusion of XG significantly enhanced the compression mechanical properties of the freeze-casted foams without compromising their thermal properties, anisotropy, or degree of alignment. CNC-XG foams maintained structural integrity even after exposure to high humidity (91 %) and temperatures (100 degrees C) and displayed very low radial thermal conductivities. This research provides a viable avenue for upcycling cotton-based clothing waste into high-performance materials.

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• Discarded Textiles as an Underexplored Source of Cellulose Nanomaterials: Processing, Properties, and Applications in Lightweight Materials

  2024. Maria-Ximena Ruiz-Caldas.

  Avhandling (Dok)

  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.

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• In Situ Functionalisation and Upcycling of Post-Consumer Textile Blends into 3D Printable Nanocomposite Filaments

  2024. Varvara Apostolopoulou Kalkavoura (et al.). Advanced Sustainable Systems 8 (9)

  Artikel

  The linear lifecycle of the textile industry contributes to the enormous waste generation of post-consumer garments. Recycling or repurposing of post-consumer garments typically requires separation of the individual components. This study describes a novel and facile chemo-thermo-mechanical method for producing extrudable pellets, involving one-pot, 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of post-consumer polycotton textiles, followed by mild mechanical treatment, all without isolating the constituents of the polycotton blend. The oxidized blend with high cellulose and carboxylate content of 1221 ± 82 mmol COO− per kg of cotton, is pelletised into a masterbatch and further in situ extruded into nanocomposite filaments for 3D printing. The carboxyl groups introduced on the polycotton-based filters enable cotton fibrillation into nanoscaled fibers during mechanical treatment and extrusion resulting to a variety of functional and high surface-finish quality models, including filters and fashion accessories. The electrostatic interactions with positively charged species, such as methylene blue (MB), facilitate their adsorption from water while exhibiting promising adsorption capacities. The adsorption of MB follows the Freundlich model and depends on the printed porosity of the filter. A “trash to treasure” concept for textile waste is further corroborated through the use of the developed 3D printing filament into commodity products.

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• The fate of hazardous textile pollutants in an upcycling process for post-consumer garments

  2024. Tim Åström (et al.). Cleaner Engineering and Technology 22

  Artikel

  The environmental impact is a strong incentive for the development of upcycling processes for textile waste. However, toxic chemicals may occur in both brand-new textiles and post-consumer garments, and the chemical transfer in such routes is important to investigate. The present study applied non-target screening and quantification with liquid chromatography/mass spectrometry to follow the fate of hazardous chemicals from post-consumer polycotton garments to a new material, cellulose nanocrystals, in a chemical upcycling utilizing strongly acidic conditions. The majority of hazardous chemicals detected within the process were found to be transferred to a residual of polyester material and not to the enriched cellulose. However, phthalates were found to be mainly attached to the cellulose nanocrystals. The detected total concentration, in this case, was below 5 μg/g, at least 200 times lower than the limit set by the European Union. This indicates the importance of monitoring and controlling the phthalate content in the starting material of the process, i.e., the post-consumer garments. The chemical release into the process waste effluent could be estimated based on water solubility data for chemicals under the applied conditions. Three compounds, the water-repellent substance perfluorooctanesulfonic acid and the dyes Crystal Violet and Victoria Pure Blue, were almost entirely transferred into the process waste effluent. Although the levels detected were very low in the present pilot process, their presence eventually indicates the need for wastewater purification at further upscaling, depending on the exposure and dose in relation to toxicological relevant thresholds.

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• The influence of drying routes on the properties of anisotropic all-cellulose composite foams from post-consumer cotton clothing

  2024. Carina Schiele (et al.). Nanoscale 16 (30), 14275-14286

  Artikel

  Biopolymer-based functional materials are essential for reducing the carbon footprint and providing high-quality lightweight materials suitable for packaging and thermal insulation. Here, cellulose nanocrystals (CNCs) were efficiently upcycled from post-consumer cotton clothing by TEMPO-mediated oxidation and HCl hydrolysis with a yield of 62% and combined with wood cellulose nanofibrils (CNFs) to produce anisotropic foams by unidirectional freeze-casting followed by freeze drying (FD) or supercritical-drying (SCD). Unidirectional freeze-casting resulted in foams with aligned macropores irrespective of the drying method, but the particle packing in the foam wall was significantly affected by how the ice was removed. The FD foams showed tightly packed and aligned CNC and CNF particles while the SCD foams displayed a more network-like structure in the foam walls. The SCD compared to FD foams had more pores smaller than 300 nm and higher specific surface area but they were more susceptible to moisture-induced shrinkage, especially at relative humidities (RH) > 50%. The FD and SCD foams displayed low radial thermal conductivity, and the FD foams displayed a higher mechanical strength and stiffness in compression in the direction of the aligned particles. Better understanding how drying influences the structural, thermal, mechanical and moisture-related properties of foams based on repurposed cotton is important for the development of sustainable nanostructured materials for various applications.

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• Unlocking the potential of post-consumer garments as a source of nanocellulose

  2024. Maria-Ximena Ruiz-Caldas, Varvara Apostolopoulou Kalkavoura, Aji P. Mathew. Cell Reports Physical Science 5 (2)

  Artikel

  Discarded garments contribute to an environmental crisis worldwide, prompting the development of new strategies for recycling and upcycling. In this work, we present the extraction of nanocellulose from textiles as an underexplored route for upcycling textile garments made of cotton. We summarize the current state of textile waste management worldwide, discuss strategies for extracting nanocellulose from cotton -based textiles, and outline the associated challenges and outlooks in this field. We further aim to highlight the opportunities and advantages of using cotton as a nanocellulose source and stimulate further research in this area.

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• Upcycling Textile Waste into Anionic and Cationic Cellulose Nanofibrils and Their Assembly into 2D and 3D Materials

  2024. Maria-Ximena Ruiz-Caldas (et al.). ChemSusChem

  Artikel

  Extracting high-performance nanomaterials from waste presents a promising avenue for valorization. This study presents two methods for extracting cellulose nanofibrils (CNFs) from discarded textiles. Post-consumer cotton fabrics are chemically treated through either cationization with (2,3-epoxypropyl)trimethylammonium chloride or TEMPO/NaBr-catalyzed oxidation, followed by fibrillation to produce Cat-CNFs and TO-CNFs, respectively. Molecular models indicate variations in the effective volume of each grafted group, influencing the true densities of the functionalized fibers. Significant differences in the morphology of the CNFs arise from each functionalization route. Both CNF types exhibit high surface charge (>0.9 mmol g⁻¹), small cross-sections (<10 nm), and high aspect ratios (>35).

  TO-CNFs have a higher surface charge, whereas Cat-CNFs exhibit a higher aspect ratio and greater colloidal stability across a broader pH range. Cat-CNFs exhibit cross-sections at the elementary fibril level, highlighting the steric impact of the grafted surface groups on fibrillation efficiency. Nanopapers from these CNFs demonstrate high optical transmittance and haze, whereas anisotropic foams show mechanical properties comparable to foams made from wood-based CNFs. This work highlights the potential of post-consumer cotton textiles as a CNF source and the impact of chemical treatment on the properties of the fibers, CNFs, and resulting lightweight materials.

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