3D printing of Green Water Purification Filters: Design towards Sustainable and Scalable Biocomposite Materials

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 Cu 2+ ions of 208 mg/g NF and 234 mg/g NF 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. Mn 2+ 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,