NANOCELLULOSE MEMBRANES VIA LAYER-BY-LAYER ASSEMBLY

Date

2024-3-26

Author

Aydın, Onur Kaan

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Membrane filtration is a cost-effective alternative to traditional separation processes and is diversely applied in treating aqueous streams. While organic solvents may be purified via membrane filtration, many common membrane materials are dissolved by organic solvents. Membranes were manufactured from cellulose for the investigation of their separation performance in aqueous environment as well as in Organic Solvent Ultrafiltration and Nanofiltration (OSU, OSN) applications. Integrally Skinned Asymmetric (ISA) cellulose acetate membranes were prepared via Nonsolvent Induced Phase Separation (NIPS) and chemically treated to form cellulose membranes of tunable charge. The membranes were tested in water, methanol (MeOH), dimethylformamide (DMF), and dimethylsulfoxide (DMSO). The Pure Solvent Permeabilites (PSP), dye rejections and Molecular Weight Cut-Off (MWCO) values were evaluated. Moreover, nanocellulose materials were synthesized, characterized and applied as Layer-by-Layer (LbL) coatings to cellulose ISA support membranes to improve the separation performance without significantly compromising PSP. The chemical and liquid crystal properties of these materials were studied. LbL self-assembled nanocellulose or nanocellulose / polyelectrolyte coatings were deposited onto the membranes. LbL modified membranes were tested under equivalent conditions and compared with the unmodified membranes. The Layer-by-Layer modified membranes were stable in the solvents tested for up to a week as evidenced by constant PSP and MWCO values. The separation performance was improved based on MWCO values (5-6kDa vs. 15kDa in water, 17-18kDa vs. >35kDa in MeOH, 3-5kDa vs. 8kDa in DMSO, 2-4kDa vs. 18kDa in DMF). The membranes were found to be significantly negatively charged and could reject small molecules based on their charge (complete rejection of Rose Bengal (RB) in water, up to 95% RB rejection in MeOH). Consequently, the membranes were found to be promising for the separation of aqueous and organic solutions.

Subject Keywords

membrane, cellulose, nanocrystal, ultrafiltration, nanofiltration

URI

https://hdl.handle.net/11511/109194

Collections

Graduate School of Natural and Applied Sciences, Thesis