Hierarchically structured polymeric membranes with interconnected pores: design, application and scale-up production
File(s)
Author(s)
Peng, Hao
Type
Thesis or dissertation
Abstract
Porous membranes prepared through phase inversion have revolutionised membrane technology, making it economically viable to produce polymeric membranes in large quantities, and enabling the development of water treatment technologies using membranes as energy-saving separators. However, these membranes have been limited in their efficiency due to low permeance and sieving ability. In this thesis, significant innovations were made to produce high-permeance porous membranes with well-defined, interconnected porosities based on the combined crystallisation and diffusion (CCD) method.
The thesis begins with mechanistic studies to understand the influence of driving force on skin layer formation in CCD membranes. The insights gained led to the development of a first-of-its-kind NIPS-CCD membrane, bridging CCD and non-solvent induced phase separation (NIPS) to produce a nanostructured skin layer with continuous microporosity in a single cast PES membrane. This membrane exhibited 50-fold higher water permeance than PES NIPS membranes. Then, an innovative membrane fabrication technique was introduced, inspired by surface melting phenomenon observed during the CCD process, to achieve the highest pure water permeance in PVDF membranes to date and enable separate control of pore size on both membrane surfaces. In parallel, leveraging the continuous porosity of the CCD structure, covalent organic framework (COF) crystals were grown onto the microchannels of PVDF CCD membranes, yielding a composite adsorbent capable of rapidly removing emerging contaminants under gravity-driven filtration. Finally, a prototype membrane casting machine was developed to enable the continuous casting of CCD and NIPS-CCD membrane morphologies, demonstrating the adaptability of CCD-based membrane manufacturing processes for large-scale industrial mass production.
The thesis begins with mechanistic studies to understand the influence of driving force on skin layer formation in CCD membranes. The insights gained led to the development of a first-of-its-kind NIPS-CCD membrane, bridging CCD and non-solvent induced phase separation (NIPS) to produce a nanostructured skin layer with continuous microporosity in a single cast PES membrane. This membrane exhibited 50-fold higher water permeance than PES NIPS membranes. Then, an innovative membrane fabrication technique was introduced, inspired by surface melting phenomenon observed during the CCD process, to achieve the highest pure water permeance in PVDF membranes to date and enable separate control of pore size on both membrane surfaces. In parallel, leveraging the continuous porosity of the CCD structure, covalent organic framework (COF) crystals were grown onto the microchannels of PVDF CCD membranes, yielding a composite adsorbent capable of rapidly removing emerging contaminants under gravity-driven filtration. Finally, a prototype membrane casting machine was developed to enable the continuous casting of CCD and NIPS-CCD membrane morphologies, demonstrating the adaptability of CCD-based membrane manufacturing processes for large-scale industrial mass production.
Version
Open Access
Date Issued
2023-04
Online Publication Date
2024-06-30T23:01:30Z
2024-08-15T09:17:37Z
Date Awarded
2023-07
Copyright Statement
Creative Commons Attribution NonCommercial ShareAlike Licence
Advisor
Li, Kang
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)