Membrane separation technologies have been rapidly developed and deployed in the last few decades in light of its high energy efficiency. Thin film composite (TFC) membranes have exhibited great potential because of the unique composite structure and flexibility in individual layer modification for targeted organic solvent nanofiltration (OSN). However, the full life cycle of traditional TFC membrane fabrication has remained unsustainable as non-biodegradable petroleum-based substrates and hazardous solvents were employed during the interfacial polymerization (IP) process. Therefore, bio-resourced materials and green solvents are highly desirable during the membrane fabrication. In this dissertation, we developed green TFC membranes that exhibit comparable OSN performance comparable to conventional petroleum-based materials.
To understand the effect of the selection of materials, we screened multiple natural biobased polymers, including polylactic acid and cellulose acetate, were used as the biodegradable support. Different preparation methods such as electrospinning and phase inversion were employed to fabricate the green supports. Followed by enzymatic biodegradation of the supports to achieve a closed sustainable life loop of membrane technology.
Genipin–priamine, dialdehyde starch–priamine, algal aqueous extract–trimesoyl chloride and chitosan–2,5-furandicarboxaldehyde were tested as the reactive pairs for TFC membrane fabrication. While dopamine–priamine was employed for green nanofilm preparation. Cross-linking mechanisms were investigated via various characterizations including fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and solid state nuclear magnetic resonance.
Green solvents, including eucalyptol and p-cymene, were studied as the organic media. This know-how was further explored by investigating the correlation between the OSN performance and the nature of the biobased material. To validate the sustainability of the IP systems, a comprehensive sustainability assessment was carried out, where quantitative comparisons among the toxicity and expense of the solvents and chemicals are necessary for a detailed understanding of the selection of materials and processing routes. This study paves the path towards greener TFC membrane development.