Preparation of Thin-Film Nanocomposite Membranes Based on Metal-Organic Frameworks (Mofs) and Study of their Performance in Forward Osmosis (Fo) Process

Bayrami, Arshad | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54330 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagherzadeh, Mojtaba
  7. Abstract:
  8. The forward osmosis (FO) process is a high potential emerging membrane process in the seawater desalination and contaminated water treatment fields. One of the main challenges facing this process is the weak separation (high reverse solute flux, low water flux, and insufficient selectivity) and antifouling performances of its membranes. Various sections of this study focus on the development of FO membranes and their performance improvement. For this purpose, thin-film composite membranes with the same combination of polyethersulfone/polyamide (PES/PA) have been used to investigate the effect of metal-organic frameworks (MOFs) introduction on their performance. The support layer in all cases is PES, prepared through the phase inversion process and does not contain any nanofiller. The modification process takes place in the polyamide layer via dispersing the desired nanoparticles in the aqueous monomer solution required to form this active layer. The identification and characterization of the synthesized nanoparticles and membranes were carried out by using several analysis techniques namely FT-IR, PXRD, FE-SEM, EDS, HR-TEM, BET, AFM, water contact angle measurement, and zeta potential. The selected MOFs for this purpose include UiO-66-(F)4, UiO-66-NH2, MIL-125-NH2, ZIF-8, MIL-53-NH2 (Al), and MIP-202 (Zr). These compounds possess outstanding features of stability in water, pores with smaller window size compared to hydrated ions of NaCl salt, good compatibility with the polymer layer compared to pure inorganic compounds, high hydrophilicity (except ZIF-8), availability, low-cost metal center (especially Al and Ti), high porosity, and contain amino functional groups suitable for the post-synthesis modification process (UiO-66-NH2, MIL-125-NH2, MIL-53-NH2 (Al) and MIP-202 (Zr)). The results show that the insertion of nanofillers affects water permeability, selectivity, and antifouling properties of the modified membranes by altering the hydrophilicity, morphology, charge, thickness, and roughness properties of the PA active layer. While modification of the intended MOFs by graphene quantum dots (such as GQDs and His-GQDs) and zwitterionic amino acid compounds (like cysteine and aspartic acid) improves membranes performances many times over (in terms of desalination, antifouling, and metal ions removal). The main reasons for choosing these compounds as MOF modifiers are: their good compatibility with the polyamide layer, the presence of diverse hydrophilic functional groups in their structures, the adsorption ability of metal ions with the help of these functional groups, and zwitterionic pairs in them (amino acids). The results of this study indicate that MOFs and their modified/functionalized analogs (if needed) are one of the most potent and promising additives in the field of forward osmosis membranes due to their unique structure and properties
  9. Keywords:
  10. Forward Osmosis ; Amino Acid ; Graphene Quantum Dots (GQDs) ; Fouling ; Nanocomposite Membrane ; Desalination ; Metal-Organic Framework ; Polyether Sulfone ; Thin-film Composite Membrane ; Metal Ions Removal

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