Cellulose ultrafiltration membranes for separation of nanoparticles from organic solvents

Date

2023-9-11

Author

Özçelik, Feyza

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Membrane processes for concentration and solvent exchange in nanoparticle synthesis are attractive due to low energy consumption and easy integration into a continuous process. Fouling of membranes with nanoparticles can differ with the surrounding solvents medium due to changing interactions of particles in these media. Obtaining insight on fouling mechanism in organic solvent ultrafiltration is crucial for the use of this application. In this study, the cake layer formations of native and hydrophobized silica nanoparticles are examined in water, isopropyl alcohol, dimethylformamide and ethanol during ultrafiltration by cellulose membranes to observe the effect of solvents and hydrophobicity of particles on fouling. Concentration and diafiltration experiments are conducted to increase the nanoparticle concentration and to change the solvent. By particle size, permeance and turbidity analyses, cake layer properties such as thickness, porosity and resistance are calculated. With native particles the highest cake resistance is observed in water, the least in dimethylformamide. The highest cake resistance in water is consistent with the least porous cake structure calculated using the Kozeny-Carman equation. With hydrophobized particles, the highest cake resistance is observed in dimethylformamide, the least cake resistance is observed in water. The highest cake resistance in dimethylformamide is consistent with the thickest cake at 200μm. Hydrophobized particles formed substantially higher cake resistance than native particles by the increased particle-particle interaction. In diafiltration experiments, hydrophobized and native particles both created insignificant cake resistance during transition from isopropyl alcohol to ethanol and dimethylformamide where tangential flow was effective in redispersing particles to the bulk. In water, the fouling resistance was more severe than other solvents which reveals the effect of medium in cake formation. Consequently, organic solvent ultrafiltration is a promising method in concentration and solvent exchange of nanoparticles which display different fouling behaviors in different organic solvents.

Subject Keywords

Organic solvent ultrafiltration, Membrane fouling, Silica nanoparticles, Diafiltration, Surface interactions

URI

https://hdl.handle.net/11511/105936

Collections

Graduate School of Natural and Applied Sciences, Thesis