Development of 2D Nanomaterials Based Membranes for Nanofiltration Applications

Abstract

The main aim of this work was to develop new membranes based on 2D nanomaterials, such as boron nitride (BN) and molybdenum disulphide (MoS2) for potential nanofiltration applications. The exfoliation and membrane preparation processes for all the materials were optimised, with the goal to obtain high retention, high-performance membranes for water purification.. New materials were also introduced into the membranes to produce new composite membranes with enhanced properties. Initially, BN was exfoliated in three different solvents, NMP, IPA and water and the product was used to make membranes for water filtration, using dyes as an example of water contaminants. The membranes obtained by exfoliation in water showed great retention performances for different sized molecules. BN was thermally oxidised and the material was exfoliated and used to make membranes. Exfoliated BNOx was also fully characterised and any differences with BN and BNOx were noted. The membranes were tested for separation of dyes for water treatment as well as for sugar separation using saccharides of different sizes. Moreover, the BNOx was functionalised using glucose as well as glutaraldehyde and other sugars, to try to improve the properties of the membranes as well as to introduce cross-linking between the layers of the nanosheets to improve their stability. Once the membranes had been optimised, BN and BNOx were mixed with different nanomaterials to improve their properties. LDHs flakes were mixed with BNOx with the aim to make the membranes reusable, due to the photodegradation properties of the LDHs. These membranes were optimised, and studies were conducted on the photodegradation and quantification of the products to understand the mechanism and kinetics of the process. Fe3O4 nanoplates were used in order to introduce magnetic properties into the BN membranes. These membranes were optimised for dye retention as well as magnetic separation. Tests using Evans Blue showed superior dye retention. The capacity of the membranes for magnetic separation was also tested. Finally, the effect of introducing a 1D nanomaterial in the form of carbon nanotubes (CNTs) into the BN-based membranes was also studied. BN and CNTs were exfoliated in three different solvents and their performances for retaining Evans Blue were tested. Finally, another material, MoS2, was tested to produce membranes. These membranes were tested for selected dye retention. The material was functionalised with chiral molecules and enantiomeric separation was attempted. Two of the main materials of this work, MoS2 and BNOx were mixed to produce composite membranes that were also tested for dye retention. Overall, this work has contributed to the further development of functionalised 2D BN and MoS2 based nanomaterials, corresponding membranes and their applications in separation and nanofiltration technologies.