| 1. |
- Fijoł, Natalia, 1994-
(author)
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3D printing of Green Water Purification Filters : Design towards Sustainable and Scalable Biocomposite Materials
- 2023
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Doctoral thesis (other academic/artistic)abstract
- The globally escalating water pollution and water scarcity necessitates the development of efficient and sustainable water treatment technologies. This thesis investigates the feasibility of utilizing renewable and waste materials in the form of green composites for the fabrication of water purification filters via Fused Deposition Modelling (FDM).The first system studied within this thesis is based on the biobased thermoplastic polymer - polylactic acid (PLA), which serves as a composite matrix that is reinforced and functionalized with an array of green materials including fish-scale extracted hydroxyapatite (HAp), 2,2,6,6 – tetramethylpiperdine-1-oxyl (TEMPO) - oxidized cellulose nanofibers (TCNF), chitin nanofibers (ChNF), and bioinspired metal-organic framework – SU-101. All the developed PLA-based biocomposites exhibited great design flexibility and excellent printability, leading to the development of high surface-finish quality water purification filters of various geometries and porosity architectures. The developed filters successfully removed various contaminants from water. High capability for removal of metal ions from both, model solutions (reaching removal capacity towards Cu2+ ions of 208 mg/gNF and 234 mg/gNF for ChNF/PLA and TCNF/PLA filters, respectively, compared to only 4 mg/g for PLA filters), as well as from an actual mine effluent, reaching removal efficiency towards i.a. Mn2+ ions of over 50 % was demonstrated. Moreover, the developed TCNF/PLA and ChNF/PLA filters successfully removed microplastics from laundry effluent with over 70 % separation efficiency. The PLA-based biocomposite filters surface-functionalized with SU-101 were also suitable for the removal of cationic dye, methylene blue (MB), from water with removal efficiencies of over 40 %.The second composite system explored the possibility of using post-consumer polycotton textile waste as a functional entity for the polyethylene terephthalate glycol (PETG) matrix, for the fabrication of 3D printing filaments, which can be further processed into highly functional water purification filters by the FDM. The conducted TEMPO-mediated oxidation of the polycotton garments introduced negatively charged carboxylic groups onto the 3D printing filament’s surface and consequently, onto the 3D printed structures, yielding filters suitable for removal of cationic dyes, such as MB, from water.Apart from being evaluated for their ability to remove various contaminants from water, the filters have been subjected to a series of tests to assess the homogeneity of the filler dispersion in the polymer matrix as well as the filters’ permeability and mechanical stability. The high throughput character of the filters was demonstrated, as e.g., for the HAp/PLA filters the calculated flux reached 2x106 Lm-2h-1bar-1. The reinforcing impact of the nanospecies on the polymer matrix in the gradient porosity filters was investigated and so, it was shown that the addition of ChNF and TCNF fibers into PLA increases their Young’s modulus value from 550.7 ± 2.8 MPa, to 622.7 ± 1.6 MPa and 702.9 ± 5.4 MPa, respectively. Moreover, the lifespan of the filters was assessed by subjecting them to an accelerated ageing procedure in water, which have shown that the TCNF/PLA and ChNF/PLA filters could serve up to eight and five months, respectively, while maintaining their functionality and good mechanical performance. Furthermore, the study revealed that the filters are indeed biodegradable, as after prolonged exposure to water at elevated temperatures, they have fully disintegrated.Overall, the obtained results demonstrate the feasibility of combining renewable and recycled materials with 3D printing technology to create water purification filters suitable for the removal of a wide variety of contaminants from water.
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| 2. |
- Herrera Vargas, Natalia
(author)
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Processing and properties of nanocomposites based on polylactic acid, chitin and cellulose
- 2017
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Doctoral thesis (other academic/artistic)abstract
- The production of bio-based and biodegradable nanocomposites has gained attention during recent years for environmental reasons; however, the large-scale production of these nanocomposites still poses challenges. The objective of this work has been to prepare bio-based and biodegradable nanocomposites via liquid-assisted extrusion and to gain a deeper understanding of the process and the relationship between the process, composition, structure and properties. Extrusion is a common industrial process and thus, the development of this technique for the preparation of bionanocomposites can promote the commercialization of these materials in future.In this work, nanocomposites based on polylactic acid (PLA), cellulose nanofibers (CNF), cellulose nanocrystals (CNC), and chitin nanocrystals (ChNC) with varying nanomaterial content were prepared via liquid-assisted extrusion using a plasticizer as a dispersing and processing aid. This process consists of dispersing the nanomaterial in a liquid composed of water, a plasticizer and/or a solvent, and then feeding this suspension directly into the extruder during the process. To be able to carry out this process successfully, parameters such as the amount of liquid, the liquid feeding rate or the water-to-solvent ratio, among others, should be taken in account.CNF and ChNC were produced from banana rachis waste and crustacean waste, respectively, whereas CNC were available as a commercial product. Glycerol triacetate (GTA) and triethyl citrate (TEC) were used as plasticizers, dispersing and processing aids. The effects of the liquids used during extrusion, the plasticizers and the nanomaterials in the PLA properties were studied. Furthermore, the effects of the cooling rate during the compression molding and the solid-state drawing on the properties of the PLA nanocomposites were investigated. Additionally, the effect of ChNC on the processing and properties of blown films was evaluated.The results presented in this work demonstrated that the use of water and a solvent during the liquid-assisted extrusion did not decrease the molecular weight of the PLA. It was also found that the feeding of nanomaterials in aqueous or aqueous/solvent suspension resulted in PLA micro-composite with lower mechanical properties than PLA. However, when a nanomaterial was fed together with a plasticizer, its dispersion and distribution into the PLA were progressively improved with increasing plasticizer content. The plasticized PLA nanocomposites showed improved properties compared to their respective counterpart without nanomaterials when the plasticizer content was ≥7.5 wt%. Furthermore, it was demonstrated that the properties of PLA can be tailored through the composition of the nanocomposite or during the processing. It was observed that the modification of PLA with only plasticizer in high amounts (20 wt%) resulted in enhanced elongation at break and toughness but it had negative effects on the thermal and mechanical properties; however, the incorporation of nanomaterials minimized these effects. The addition of a small amount of nanomaterial (1 wt%), either CNF, CNC or ChNC, to plasticized PLA resulted in enhanced mechanical properties. It was also demonstrated that the cooling rate during compression molding and the solid-state drawing significantly affected the crystallinity of the PLA nanocomposites and, thus, their final properties. The fast cooling rate during compression molding resulted in more flexible and transparent materials than when a slow cooling rate was used, and as a result, PLA films with different mechanical properties were obtained. The drawing of the PLA/CNF nanocomposite at a drawing temperature slightly above the Tg, a high draw speed and at the highest drawing ratio, resulted in the highest mechanical properties. It was also found that the increased toughness after adding CNF to the plasticized PLA or after drawing the PLA/CNF nanocomposite, was attributed to the occurrence of massive crazing effect as a result of the presence of CNF and its effect on the crystallinity and/or on the spherulite growth. Finally, 6 kg of plasticized PLA nanocomposite with 5 wt% of ChNC was prepared and used as a masterbatch to produce bio-nanocomposite blown films. The nanocomposite material showed easier processability during the film-blowing process when compared with the reference material without nanocrystals. In addition, the nanocomposite blown films exhibited higher tear and puncture strength, lower fungal activity and lower electrostatic attraction properties, which are favorable in packaging applications. In conclusion, this thesis shows that the liquid-assisted extrusion process is an excellent approach for producing PLA nanocomposites using cellulose and chitin nanomaterials. The results indicated that the addition of these nanomaterials, together with a plasticizer and further processing, can result in PLA nanocomposites with varied properties that can be used for packing applications. It was also shown that the processing technique presented can be a step forward for the large-scale production of bionanocomposites.
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| 3. |
- Zhu, Chuantao, 1984-
(author)
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Nanocellulose and Its Biohybrids for Water Purification : Atomic Force Microscopy as a Tool to Probe Surface Properties and Interactions
- 2018
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Doctoral thesis (other academic/artistic)abstract
- Nanocellulose has been explored extensively in recent years as an adsorbent due to its promising performance in the removal of charged contaminants from water. In this thesis, various atomic force microscopy (AFM) techniques are used to understand the surface characteristics and specific interactions of nanocellulose with water contaminants (heavy metal ions and dyes) and nanoscale entities (Graphene Oxide (GO) and Graphene Oxide nanocolloids (nanoGO)), and explain the mechanisms related to adsorption, metal ion clustering, self-assembly and mechanical reinforcement.AFM probes functionalised with microscale and nanoscale celluloses were used as colloidal probes to study specific surface interactions with heavy metal ions and dyes in the aqueous medium. This approach enabled quantitative measurements of the adhesion force between nanocellulose and the water pollutants under in situ conditions by direct or in-direct methods. Adhesion forces, including the piconewton range, were measured, and the forces depended on the surface groups present on the nanocellulose.AFM imaging in dry and/or wet conditions was successfully used to investigate the adsorption, self-assembly, morphology and mechanical properties of nanocellulose and its bio-hybrids. The self-assembly, the metal nanolayer and the nanoclusters on the surface of nanocellulose and its biohybrids after adsorption were confirmed and explained by advanced microscopy, spectroscopy and computational modelling.The adhesion and stiffness measurement of single nanocellulose fibers using in situ PeakForce Quantitative Nanomechanical (PF-QNM) characterization confirmed the adsorption of metal ions on the surface in the liquid medium. PF-QNM mapping of the freestanding biohybrid membranes also revealed the enhanced modulus of the biohybrid membrane compared with the TEMPO(2,2,6,6-tetramethylpiperidine-1-oxylradical)-mediated oxidation nanofibers (TOCNF) membrane, which explained the hydrolytic stability and recyclability of these membranes.The established methodology, which combines advanced microscopy with spectroscopy and modelling techniques, can be extended to other biobased macromolecular systems to investigate the adsorption behaviour and/or surface interactions in bio nanotechnology.
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| 4. |
- Aguilar Sánchez, Andrea, 1987-
(author)
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Nanopolysaccharide coatings for functional surfaces in water-treatment materials : From mechanisms to process scalability
- 2022
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Doctoral thesis (other academic/artistic)abstract
- In this thesis, materials from renewable resources were used to develop functionalized surfaces for water treatment. The work is thus inspired by, and contributes to, the United Nations sustainable goals of: (i) clean water and sanitation, (ii) climate action, (iii) responsible consumption and production, (iv) life below water, and (v) partnerships for the goals.Nanopolysaccharides, most specifically nanocellulose and nanochitin, are great candidates for functional and renewable materials for multiple applications, including the treatment of water and wastewater. This thesis focused on the formulation of different types of nanopolysaccharide-based coatings to enhance the performance of commercially available membranes and cellulose fabrics. We developed a simple waterborne layer-by-layer cellulose nanocrystals (CNC) and TEMPO-oxidized cellulose nanofibrils (T-CNF) coating for commercially available membranes. By changing the surface and pore structure of the membrane, the coating tuned which substrates could pass through the membrane, improved antifouling performanced, and when derived from T-CNF, it was harmful to bacterial colonization. Considering the observed T-CNF’s effect on bacteria, we developed a chemically crosslinked T-CNF/Poly(vinyl) alcohol (PVA) coating with outstanding antibiofouling performance, ion adsorption/rejection combined with size exclusion, and with dimensional and pH stability. Furthermore, we used a surface-impregnation approach based on bio-based nanotechnology which resulted in highly efficient, with improved mechanical properties, and fully bio-based high-flux water filtration membranes using commercially available nonwoven fabrics. Membranes with coatings prepared from CNC, chitin nanocrystals (ChNC) and T-CNF separated particles in the size range of bacteria and viruses, and those prepared from also T-CNF showed high microplastic filtration efficiency. Moreover, membrane coating based on ChNC and T-CNF had outstanding antibacterial properties.Overall, we demonstrated that nanopolysaccharide coatings on membranes could provide a significant reduction in organic fouling and biofilm formation while enabling the adsorption of ions and separation of microplastics. In the case of biofilm formation, the functional group and surface charge of the different nanopolysaccharides determined the effect over bacteria, indicating that surfaces could be tailored against microbes. In addition, we directly compared the effect of the different nanopolysaccharides of interest (CNC, T-CNF, ligno-celullose nanocrystals (L-CNC), and ChNC) on bacterial viability and biofilm formation, and found a great difference between the different types of nanocellulose and a different mechanism for nanochitin. Thorough, none of the nanopolysaccharides displayed cytotoxic effects while in indirect contact with the bacterial cells. Nevertheless, T-CNF, ChNC and L-CNC showed a cytostatic effect on bacterial proliferation. Furthermore, the nanomechanical properties of the bacterial cells and interacting forces between the nanopolysaccharides and Escherichia coli (E. coli) were affected when in direct contact with the nanopolysaccharide surfaces.Lastly, we upscaled one of our coating processes, demonstrating that the method could be easily implemented at an industrial level. The impact of this thesis relies on the effectiveness of the coatings, the different types of functionalities observed, the demonstrated fast implementation at an industrial scale, and the potential to extrapolate this technology to other applications.
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| 5. |
- Sultan, Sahar, 1987-
(author)
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Nanocellulose based 3D printed hydrogel scaffolds for cartilage and bone regeneration : Tuning of composition, pore structure and functions
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Biobased-materials with customized scaffolds have played a prominent role in the success of tissue engineering (TE). Cellulose nanomaterials (CNM) isolated from the abundant biopolymer, cellulose, is explored in this thesis for TE engineering due to its versatile properties such as biocompatibility, high specific strength, surface functionality and water retention capacity. Hydrogel formation capability of CNM at low concentrations (1–2 wt%) and shear thinning behavior has facilitated its use in 3-dimensional (3D) printing as a fabrication technique for 2-dimensional (2D) and 3D scaffolds. This technique offers 3D scaffolds with tailored, controlled and complex geometries having precise micro and macro scaled structures. The current work focuses on CNM-based 3D printed hydrogel scaffolds with tuned composition and pore structure for cartilage and bone regeneration. Design of CNM hydrogel formulations with suitable rheological properties, hydrogel inks capable of ex-situ crosslinking, print resolution during printing due to swelling and mechanical and dimensional stability of the printed scaffolds in moist environment are key challenges that were addressed.Inspired by the hierarchical and gradient nature of natural tissues 3D printed hydrogel scaffolds with gradient pore structure and composition are reported for the first time with focus on cellulose nanocrystals (CNC) and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-oxidized cellulose nanofibers (TOCNF) based hydrogel ink printing for advanced and functional scaffolds.CNC-based hydrogel ink was used to 3D print uniform and gradient porous cubic scaffolds for cartilage regeneration. This work highlighted the importance of nozzle movement to obtain high resolution scaffolds with higher z-axis. The anisotropic rigid CNC aligned themselves along the printing direction due to the shear induced orientation that was quantified between 61–76%. To obtain adequate mechanical properties (0.20–0.45 MPa) suitable for cartilage regeneration, the hydrogel ink solid content was increased almost two-fold (5.4 wt% to 9.9 wt%) while exhibiting and mimicking the viscoelasticity of natural cartilage tissues. To improve the bioactivity of the CNC-based 3D printed scaffolds, a surface treatment through dopamine coating was performed. This coating enhanced the hydrophilicity and capability of 3D printed scaffolds to bind bioactive molecules such as fibroblast growth factor (FGF-18) for soft TE scaffolds.Surface functionality of TOCNF was utilized to fabricate functional hybrid scaffolds (CelloZIF-8) through one-pot in- situ synthesis of Metal-Organic frameworks (MOFs) with varied ZIF-8 loadings (30.8–70.7%). The inherent porosity of the ZIF-8 was used for loading and stimuli-responsive (pH-dependent) releasing of drug molecule such as curcumin. The developed CelloMOF system was extended to other MOFs (MIL-100) and drugs (methylene blue). The shear thinning property of TOCNF was reserved after MOFs hybridization and was used to 3D print porous scaffolds with excellent shape fidelity. In Cello-Apatite, TOCNF was also used as template for in-situ synthesis of hydroxyapatite (HAP) where the HAP loading was 67 wt% to mimic the bone composition. In an attempt to address both cartilage and bone regeneration, a biphasic osteochondral 3D printed hydrogel scaffold has been introduced with tuned composition, pore structure and mechanical properties.The work presents a sustainable, cost effective and scalable approach for TE using biobased and toxic free water-based formulations using low temperature processes that are extendable to other biomaterials as well as to other applications, such as water treatment.
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