This thesis is based on three publications in peer-reviewed journals with the addition of an introduction and literature review section, presenting in Journal Format (formerly referred to as Alternative Format) set by The University of Manchester. The aim of this thesis is the design and preparation of polymer composite membranes for organic solvent nanofiltration (OSN) with improved properties through nanoengineering. Although the development of the field is rapid, challenges still exist such as long-term operational stability and unfavourable separation performance. In my thesis work, two methods were proposed and carried out in order to test the hypotheses that through nanoengineering, the challenges mentioned above could be alleviated. I have made mixed matrix OSN membranes by incorporating graphene oxide flakes into polybenzimidazole matrix. In order to enhance the interactions between the two components and thus the stability of the membranes, hydroxylated polybenzimidazole was synthesized by N-benzylation and was added as the third component of the membrane, which acted as the anchoring points for crosslinking by using a chemical crosslinkers. This modification strategy led to membranes with improved properties including greatly enhanced permeance due to incorporation of graphene oxide and increased membrane stability in solvents due to crosslinking. I have also made OSN membranes with coatings from biophenols through oxidant-promoted polymerisation. A systematic study was carried out to examine the effects of various biophenol coatings towards the properties of a series of polymer membranes. Biophenol coatings were thought to fine-tune the separation performance of the membranes through adjustment of membrane pore size. Biophenols also improved the solvent resistance of the membranes possibly due to strengthened bonds between the crosslinked biophenols and the polymer membranes. I have also finished a project where quartz crystal microbalance was used to establish a screening platform for chelation-based calcinosis treatments. This project was done during my first year of PhD, which allowed me to be acquainted with a range of materials characterisation techniques that were proved to be extremely useful for the OSN projects that were carried out later on. Moreover, albeit not being included in this thesis, I also participated in two other projects during my PhD that led to publications: one was in the field of OSN and the other was related with quartz crystal microbalance. In conclusion, although being a combination of a main project and some side experiments, my thesis is mainly focusing on OSN membranes. Two kinds of nanoengineering methods have been proven to improve the separation properties and solvent stabilities of OSN membranes. These methods also have good potentials for developing other membrane processes such as desalination and gas separation.
Nanoengineered Polymer Composite Membranes for Organic Solvent Nanofiltration
Fei, F. (Author). 1 Aug 2019
Student thesis: Phd