Membrane fabrication VIA shear induced deposition and chemical stabilization of cellulose nanocrystals

Date

2023-8

Author

İçten, Berk Can

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This study shows membrane preparation using cellulose nanocrystals and their chemical crosslinking. Membrane preparation with colloids like cellulose nanocrystals is expected to lead to tuneable membrane structures which would have narrow pore size distribution. AgNO3 and KPS (potassium persulfate were used for crosslinking for TEMPO (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation CNCs (cellulose nanocrystals). For 2 hours reaction, particle size was found to be stabilized with stabilization of turbidity. Additionally, 0.08 % KPS and 0.36 % AgNO3 were found to be optimal crosslinker concentrations for the membrane application. Membrane preparations were done with crossflow deposition of TEMPO CNC suspensions on a porous support with or without addition of NaCl in suspension during deposition. These layers were stabilized with AgNO3 and KPS crosslinking. Membranes prepared with suspensions not containing any salt were stable for up to 1 week in ethanol solution and 2 days of continuous filtration experiments. It was also observed that the membrane rejection is partly caused by Donnan exclusion. To reduce internal stress in the membrane and prevent cracking, 100 mM NaCl was added to the TEMPO CNC suspension, which increased the stability of the layer where 5 days of continuous filtration did not change the membrane performance, and higher than 95% blue dextran (5 kDa) rejection was observed for the membrane. Additionally, salt addition led to the formation of cholesteric self assembly on the TEMPO CNC layer. This layer showed visible wavelength Bragg’s reflection in wet state where the pitch length decreased to ultraviolet range which could only be observed with scanning electron microscopy.

Subject Keywords

TEMPO Cellulose Nanocrystal, Cholesteric Liquid Crystal, Ultrafiltration, Crossflow, Crosslinking

URI

https://hdl.handle.net/11511/105298

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Graduate School of Natural and Applied Sciences, Thesis