Abstract
Increasing awareness of the widespread presence and multitude of persistent micropollutants in freshwater sources worldwide is a cause of growing public concern. In addition to regulating their production and consumption, water treatment is an important step in removing micropollutants from the water cycle. One method to advance water treatment towards micropollutant removal is pressure-driven filtration, using specifically designed nanofiltration (NF) membranes based on polyelectrolyte multilayers (PEMs). Currently, a lack of clear design rules limits this highly versatile method of fabricating membranes. Optimisation of membrane design is further complicated by the multitude of process-related factors that influence the overall separation performance in water treatment applications. In this work, transport processes through PEMs were studied to develop a better understanding of the relations between membrane fabrication, structure and performance. In addition, the influences of process scale, operating conditions and solution composition on NF performance were investigated to pave the way for rational membrane design.
The outline of this thesis is as follows. Chapter 1 gives the motivation for this work and places it in its scientific context by introducing the reader to the fundamentals (and state-of-the-art) of NF and PEMs (for NF). Chapter 2 focuses on mass transfer resistances in the water phase of hollow fiber NF membranes at both laboratory and commercial scale. In Chapter 3, a theoretical model considering a pore size distribution inside the PEM is used to characterise PEM NF membranes and predict the retention of uncharged solutes. The following Chapter 4 examines the sensitivity of filtration performance of PEM NF membranes towards solution pH. Chapter 5 studies the removal of micropollutants by PEM NF membranes in the presence of salt at concentration ratios resembling real applications. Chapter 6 uses a theoretical transport model to investigate the structure and performance of asymmetric PEM NF membranes (composed of two PEM systems). Finally, Chapter 7 summarises the research findings and drawn conclusions of this thesis, and provides an outlook on the remaining challenges and opportunities of PEMs as building blocks for NF membranes.
The outline of this thesis is as follows. Chapter 1 gives the motivation for this work and places it in its scientific context by introducing the reader to the fundamentals (and state-of-the-art) of NF and PEMs (for NF). Chapter 2 focuses on mass transfer resistances in the water phase of hollow fiber NF membranes at both laboratory and commercial scale. In Chapter 3, a theoretical model considering a pore size distribution inside the PEM is used to characterise PEM NF membranes and predict the retention of uncharged solutes. The following Chapter 4 examines the sensitivity of filtration performance of PEM NF membranes towards solution pH. Chapter 5 studies the removal of micropollutants by PEM NF membranes in the presence of salt at concentration ratios resembling real applications. Chapter 6 uses a theoretical transport model to investigate the structure and performance of asymmetric PEM NF membranes (composed of two PEM systems). Finally, Chapter 7 summarises the research findings and drawn conclusions of this thesis, and provides an outlook on the remaining challenges and opportunities of PEMs as building blocks for NF membranes.
| Original language | English |
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| Qualification | Doctor of Philosophy |
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| Award date | 7 Jul 2023 |
| Place of Publication | Enschede |
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| Print ISBNs | 978-90-365-5686-6 |
| Electronic ISBNs | 978-90-365-5687-3 |
| DOIs | |
| Publication status | Published - 7 Jul 2023 |