Development of novel electrospun nanofibrous scaffold with nanomaterials for target adsorption in different applications

• Main Author: Lim, Huai Xun
• Other Authors: Wang Rong
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Chemical engineering; Engineering::Nanotechnology
• Online Access: https://hdl.handle.net/10356/170617
• Institution: Nanyang Technological University

With the concerning rise in pollution of waters threatening the critical sources of clean water, tremendous amounts of efforts had been put into the research and development of water treatment technologies, inexhaustive of conventional municipal water treatment, to ion-exchange, electrolysis or biological treatment, membrane technology is one of the most energy efficient processes to remove targeted solutes from water. Amongst the removal techniques, which includes separative membranes or chemical treatment, physical adsorption is one of the cheapest while requiring low energy input to operate. To address the water crisis and tackling the shift to energy reliance, this thesis aims to amalgamate the two energy efficient technologies, namely membranes and adsorption together, to synergistically enhance the targeted removal from various systems. The thesis presents a novel nanofibrous membrane scaffold with nanomaterials for the adsorption of compound of interest. With the highly porous electrospun nanofibers scaffold, permeability can be very high while operating in a low-pressure environment. The overlapping layers and interwoven nanofibers provide the scaffold to space out and hold the nanomaterials responsible for the targeted removal. In the beginning, we first announced the successful fabrication of the novel nanofibrous membrane scaffold by alternating electrospinning process and pneumatically spraying the adsorbents into a multi-layered membrane scaffold. The membrane scaffold was investigated for their anionic dye removal in aqueous systems and performed beyond expectations, demonstrating up to 8808 Lm-2h-1bar-1 water permeability at 2 psi with exceptional >99% dye removal capability for anionic dyes in aqueous systems. The membrane scaffold was further evaluated for its stability and regenerative capability through multiple acid-alkaline flushes and showed excellent reversion of adsorption performance with little signs of degradation. To further expand the application and showcase the versatility of the novel nanofibrous membrane scaffold, we challenged the novel nanofibrous membrane scaffold to target solutes removal in organic solvent systems. The critical selection and synthesis of chemically stable adsorbents paved the way to the eventual combination into the hierarchical multi-layered nanofibrous membrane scaffold. The membrane scaffolds delighted with amazing anionic and cationic dye removal from organic solvent system, achieving up to 99% dye removal rates in IPA and delivering processing capacities of up to 60 L m-2 h 1 of IPA at a low operating pressure of 0.04 bar. The study illustrated the many possibilities to creatively choose adsorbents to specifically target solutes in focus and be chemically robust to be stable even in harsh conditions. In the last part of this thesis, we explored dehumidification with the novel nanofibrous membrane scaffold. In spite of initial limited moisture adsorption, the preliminary results were encouraging and prompts for further examination. Super adsorptive polymers were selected, and the corresponding results gave direction to propel towards super hydrophilic polymeric membrane with a high-capacity adsorbent, with possibility to transform into a hydrogel for significant moisture capture. In conclusion, the thesis developed a novel nanofibrous membrane scaffold with nanomaterials, highlighting its versatility and adaptability to rationally select the materials required for the adsorption and removal of targeted compound of interest and be conscious on the required chemical stability and mechanical strength of chosen materials to the environment or condition it is set to perform in. Therefore, with the successful use cases of novel nanofibrous membrane scaffold with nanomaterials, this work contributes to the development of nanofibrous membrane fabrication technology by showcasing the versatility in the electrospinning process. This thesis also facilitates potential practical application of adsorptive nanofibrous membranes in different systems, especially in harsh organic solvent systems for the removal of low molecular weight solutes.