Mist based interfacial polymerization technique for graphene oxide modified thin film composite nanofiltration membrane

• Main Author: Seah, Mei Qun
• Format: Thesis
• Language: English
• Published: 2022
• Subjects: TP Chemical technology
• Online Access: http://eprints.utm.my/id/eprint/101623/1/SeahMeiQunPSChe2022.pdf; http://eprints.utm.my/id/eprint/101623/; http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:150691

Among the major issues faced by thin film composite membrane used in nanofiltration (NF) application are the fouling behaviour and the trade-off effect between water permeability and salt rejection. This study aimed to develop a new type of nanomaterials-modified thin film nanocomposite (TFN) membrane with enhanced surface characteristics by employing a new interfacial polymerization (IP) technique based on the mist method. Particularly, the objectives of this work are to investigate the effects of different mist-based interfacial polymerization conditions on the polyamide (PA) selective layer properties of membranes, to evaluate the impacts of plasma-enhanced chemical vapour deposition (PECVD)-modified graphene oxide (GO) interlayer on the characteristics of TFN membrane made of optimized mist-based IP conditions, and to investigate the influences of organic solution temperature during IP process on the properties of GO-modified TFN membrane for NF applications. The results show that in addition to forming thinner and looser PA structure, the piperazine (PIP) solution required in the mist-based IP (MIP) reaction was significantly reduced, i.e., 17 times lower than conventional IP. The microdroplet dispersion approach in MIP could form a higher crosslinked PA due to the high polymerization interface, besides forming a higher free volume selective layer due to the disruption in the PA repeat structure. The newly developed membrane could achieve 9.08 L/m2 hbar pure water permeability (PWP) and 97.2% Na2SO4 rejection coupled with complete flux recovery rate. Following this, a new TFN membrane incorporating GO was fabricated using the developed MIP technique. GO was surface-functionalized using greener PECVD approach to improve its dispersibility. Compared to the control GO, acrylic acid-modified GO (AA/GO) was able to improve PWP of TFN membrane by 6.6%, reaching 11.34 L/m2 hbar. Its PWP was also higher compared to TFC membrane (~25% enhancement) owing to enhanced membrane hydrophilicity coupled with formation of thin yet highly crosslinked PA upon AA/GO incorporation. By varying the temperature of organic solvent (0 to 55 °C) during IP, the TFN 0 membrane with the thinnest and smoothest PA layer was able to be produced, recording 12.14 L/m2 hbar PWP, 93% Na2SO4 rejection and 16% NaCl rejection. This membrane with the smoothest surface aided in its low protein adsorption, demonstrating great antifouling potential. Meanwhile, the TFN 55 membrane achieved a water-salt permselectivity ratio of 11.0, which was found to be >2 folds compared to the commercial NF3 membrane (4.88) owing to its enhanced crosslinking. Both TFN 55 and TFN 0 membrane showed great short-term (12 h) stability and retained more than 95% of the AA/GO nanosheets after a 5-day agitation period. Overall, the mist-based IP fabrication of TFN membrane at low temperature can overcome the limitations of the conventional IP technique to produce a smooth and defect-free TFN membrane with improved filtration performance and reduced protein adsorption.