Membranes are a robust, reliable and economical technology. However, polymeric membranes are manufactured from polymeric and organic solvent sources derived from petrochemical sources. The high volatile organic compounds (VOC) emissions of the organic solvents and the non-recyclability of the polymers often question the membrane manufacture sustainability. The main goal of this dissertation is the preparation of polymeric membranes for liquid separation through more sustainable processes. We report here the green preparations of hollow fibers, thin-film composite and integrally skinned asymmetric membranes. An important part of the work is represented by the development of cellulose hollow fibers from ionic liquid solutions, avoiding strong alkali or harsh solvents. By tuning the manufacturing process, we prove that the membranes can be used for different applications such as oil-water separation, protein separation via ion-exchange chromatography and solvent purification via organic solvent nanofiltration. The main advantages of using cellulose to prepare hollow fiber membranes are the biodegradability of the polymer and the intrinsic chemical stability. Another significant milestone of this work is replacing volatile solvents such as hexane during the thin-film composite membrane manufacture. As green alternative solvents, we decided to use naturally extracted oleic acid and decanoic acid. Due to their low costs and volatility, they represent a valid alternative for industrial membrane preparation through the interfacial polymerization process. The membranes prepared with this process were used for solvent resistant nanofiltration. Finally, by using ionic liquids as solvents, we improved the manufacturing sustainability polytriazole asymmetric membranes synthesized in the lab.

The polyolefins production is the largest among all types of plastics given their thermal and chemical stability and low cost, which allows them to be used in a wide variety of products worldwide, including polypropylene (PP) and polyethylene (PE) membranes. However, the small percentage of polyolefins being recycled compared to the enormous amount produced has led to severe environmental pollution issues. In addition, the traditional polyolefin membrane fabrication methods utilize mostly toxic non-renewable solvents such as xylenes at high temperatures, causing further negative environmental impact. The objective of this study is to propose a greener alternative for polyolefins in general and in particular for membrane fabrication. For this, two bio-based solvents (α-pinene and Dlimonene) were proposed to dissolve PP and LDPE, and the resulting films and membrane properties were studied. Hydrophobic PP microporous membranes were obtained by thermally induced phase separation from pristine commercial polymers and plastic waste. They were applied for water-in-toluene emulsion separation. The water rejection was above 95% for membranes fabricated from dope solutions containing 25% pristine PP and 30% waste PP heated at 130°C, suggesting that they could be used in oil spill recovery operations. This work aims to contribute to the implementation of more sustainable practices in the membrane industry.

The fabrication of electrospun nanofibers has sparked great interest in both academia and industry owing to their unique properties, such as a high surface area to volume ratio, porosity, interconnected porous structure, or controllable fiber morphology. They are highly desired in numerous application areas such as filtration, biotechnology, and energy storage. Cellulose acetate is an ester of cellulose, one of the most abundant natural polymers, that is biodegradable, non-toxic, and has good stability. Electrospinning of cellulose acetate has received significant interest in a broad spectrum of applications, including membranes and air filters, drug-delivery systems, scaffolds for tissue engineering, sensors, and batteries. The electrospinning of cellulose acetate predominantly suffers from the use of toxic and hazardous solvents, which makes the final products less suitable for application in biosystems. In this work, the sustainable electrospinning of cellulose acetate has been shown using renewable-based green solvents, dimethyl carbonate, and cyclopentanone. A binary system consisting of these solvents has been applied. The addition of green salts and biosurfactants substantially improved the spinnability of the cellulose-based solutions. Altering the composition of the solvents allowed tuning of the fiber texture from highly porous to smooth fiber morphology. The thermal analysis revealed that the polymer’s thermal behavior had not been influenced by the salt in nanofibers. Incorporating additives into the polymer matrix resulted in enhanced mechanical properties of nanofibers. Uniform cellulose acetate-based porous nanofibers from green solvents and additives could be successfully fabricated, which has not been reported yet. Based on the reported advantageous properties of electrospun CA nanofibers, it may serve as a possible green and biodegradable porous support layer in thin-film composite membranes replacing the conventional fossil-derived polymeric membrane supports.

The recycling of materials from waste electrical and electronic equipment (WEEE) is of great concern today, as increasing public awareness and the implementation of recent legislations have created a situation where industries need to 1) comply with the environmental regulations and 2) fulfil producers’ responsibility initiatives. In this context, the work described in this thesis investigates the applications of new leaching solvents, the ionic liquids (ILs), to recycle two materials, copper and decabromodiphenylether (DBDE), which are common in WEEE. A total of 18 ILs, methylimidazolium (MIM) and methylpyridinium (MPy) based, were prepared using a microwave-assisted method. These ILs were selected to allow characterisation of performance with respect to three parameters: hydrophobicity of the cation, polarity of a terminal functional group in the cation side chain, and the type of aromatic ring, in order to identify their effects on the solubility and extraction processes. All ILs were successfully characterised by IR spectroscopy, mass spectrometry and NMR. Hydrophobicity was measured by HPLC, and the retention factors compared to logP values predicted from Molinspiration. High correlation (>88%) was observed, which indicated that the predicted logP values were representative of the real hydrophobicity of the cation. Copper metal was not significantly dissolved in any of the ILs, and performance was therefore assessed with the dissolution of CuO. The dissolution tests were conducted at 70°C for ten minutes and the resultant solutions analysed for Cu by using atomic absorption spectroscopy. A short side chain and the presence of a strongly polarised functional group at the terminal position were required to achieve maximum dissolution. Furthermore, the short chain methylimidazolium system was better than methylpyridinium for dissolving CuO. Consequently, 1-(2-cyanoethyl)-1-methylimidazloium bromide was found to be the best solvent and dissolved 75.5 mg of Cu in one g of IL. High impact polystyrene (HIPS), containing 4.4% of DBDE, was prepared in order to test the extraction abilities of various non-substituted ILs. The extraction of DBDE from the polymer was conducted at 90°C for 2 h 45 min. The results indicated that high hydrophobicity was required to achieve the maximum extraction of DBDE, however, the percentage extraction remained very low (<10%). The low extraction was attributed to the fact that only the DBDE present on the outer surface of the polymer was extracted during the process. In spite of being more hydrophobic, MPy-based systems did not dissolve as much as MIM-based systems because they were more viscous. The high viscosity value actually hindered the diffusion process and ultimately reduced the extraction of DBDE. The effects of different factors on the extraction process were evaluated and the maximum extraction was achieved by using 1-octyl-3-methylimidazolium bromide at 110 °C. The results described in this thesis have identified and quantified the link between the structures of the ILs and extraction efficiencies in relation to their potential use for recovery of CuO and DBDE from WEEE. The recommendations for future work have also been identified. The results obtained in this work, however, have contributed to increase the knowledge about the properties of ILs and can be used in future research to design a large scale recycling process.

Les nanocelluloses connaissent un fort développement depuis ces dernières décennies et font l’objet de nombreuses études menées par les industriels et/ou consortiums académiques. Cette étude s’insère dans le cadre d’un projet européen (SUNPAP) visant à l’industrialisation des nanofibrilles de cellulose (NFC). La présente thèse fait l’état de nouveaux procédés de modification chimique de surface des NFC dans une optique de chimie verte. Plusieurs stratégies ont été développées telle que l’emploi de liquides ioniques comme solvant de réaction (décrit comme solvants verts) ou l’utilisation d’une nanoemulsion en phase aqueuse permettant le greffage de surface des NFC. Dans le but d’étudier l’impact de ces modifications chimiques, les substrats ainsi traités ont été par la suite utilisés dans diverses applications. Ainsi, des bionanocomposites ont pu être produits, l’impact sur l’introduction de NFC (modifiées ou non) dans du papier a également été étudié. Une étude sur les propriétés antibactériennes et la biodégradabilité des NFC modifiées est également proposée. Une caractérisation approfondie des NFC vierges et modifiées a été réalisée. Des techniques puissantes et innovantes ont été utilisées pour caractériser ces substrats tels que l’XPS (X-ray Photoelectron Spectroscopy) ou encore la SIMS (Secondary Ion Mass Spectrometry). Toutes ces modifications, applications et caractérisations proposées constituent une avancée et des perspectives prometteuses dans le monde des nanocelluloses. / Nanocelluloses know a strong interest since last decades and they are the subject of many studies led by industrials and / or academic consortia. This study is a part of a European project (SUNPAP) for the industrialization of nanofibrillated cellulose (NFC). This thesis is the state of new methods for the chemical surface modification of NFC with a view of green chemistry. Several strategies have been developed such as the use of ionic liquids as reaction solvent (described as green solvents) or the use of an aqueous medium in order to graft the surface of NFCs. Thus, the treated substrates were then used in various applications. Also, bionanocomposites were produced, the impact of the introduction of NFC (modified or not) in paper sheets has also been studied. A study on the antibacterial properties and biodegradability of modified NFC is also proposed. Several characterizations of neat and modified NFC were performed. Powerful and innovative techniques have been used to characterize these substrates such as XPS (X-ray Photoelectron Spectroscopy) or SIMS (Secondary Ion Mass Spectrometry). All these chemical modifications, applications and characterizations are offered promising prospects in the world of nanocelluloses.