Advanced functional metal organic frameworks-reinforced membranes for enhanced microplastic fouling mitigation

Author Identifier

Mitra Golgoli

https://orcid.org/0000-0002-4005-3719

Date of Award

2024

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Doctor of Philosophy

School

School of Engineering

First Supervisor

Masoumeh Zargar

Second Supervisor

Mehdi Khiadani

Third Supervisor

Tushar Kanti Sen

Fourth Supervisor

Michael Johns

Abstract

The increasing presence of microplastics (MPs) in aquatic environments has caused considerable concerns. Wastewater treatment plants (WWTPs) are recognized as major sources of MP discharge, underscoring the urgent need for improved techniques to efficiently remove MPs. Although polymeric membranes are effective for this purpose, fouling remains a primary challenge. Therefore, understanding the contribution of MPs to membrane fouling is crucial for developing efficient membrane-based MP removal techniques. Forward Osmosis (FO) emerges as a promising solution due to distinct advantages. Its energy efficiency aligns with minimal hydraulic pressure requirements. Furthermore, implementing FO in WWTPs, with seawater as the draw solution, could reduce the energy requirements for the draw solution recovery. This technology not only prevents entrance of MPs to the environment but also addresses other micro-contaminants affecting aquatic ecosystems.

Successful implementation and utilization of FO systems relies on advanced FO membranes exhibiting high water permeability, low reverse salt flux (RSF), and robust resistance to fouling. Although FO experiences less severe membrane fouling compared to the other filtration techniques, attributed to its low or absent hydraulic pressure operation, fouling still contributes to the reduction of FO membranes’ performance. Additionally, MPs have been identified as emerging foulants in water treatment systems, diminishing the membranes’ efficiency and lifespan. Therefore, the presence of MPs in the effluent of WWTPs can exacerbate fouling and impair FO efficiency. Furthermore, simultaneous presence of MPs and other fouling agents can synergistically increase fouling, emphasizing the need to consider MP fouling when designing sustainable membranes. One of the main approaches to improve performance and antifouling behaviour of membranes is the integration of nanomaterials into the membrane structure.

Metal-organic frameworks (MOFs) are novel porous materials composed of inorganic metal ions connected by organic linkers. MOFs are gaining significant attention in membrane development due to their distinct characteristics such as their high surface area, porosity, and holding both organic and inorganic attributes. The organic linkers in MOFs enhance their compatibility with organic polymers. That facilitates the non-covalent bonding of MOFs with the polymer structure and makes them more favourable for the integration with polymeric membranes compared to purely inorganic additives. However, the integration of MOFs in water treatment membranes is less explored than in gas separation membranes.

This thesis introduces innovative strategies for incorporating advanced materials into thin-film composite (TFC) FO membranes targeting improved performance and antifouling properties of membranes, considering MPs as potential emerging foulants. Different materials namely MIL-53, UiO-66-NH2, MWCNT/UiO-66-NH2, and zwitterion/UiO-66-NH2 were synthesized and characterized using advanced techniques such as X-ray diffraction (XRD), Fouriertransform infrared spectroscopy (FTIR), dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis. These materials were then integrated into TFC FO membranes, which were characterized using SEM, FTIR, XRD, atomic force microscopy (AFM), streaming potential and contact angle measurements. Subsequently, membrane performance and fouling behaviour against MPs and organic foulants were assessed. This work contributes valuable insights into the development of advanced membranes resistant to MPs fouling.

DOI

10.25958/tstx-sh73

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