Membrane fouling is a common and serious issue in ultrafiltration (UF), caused by clogging and aggregation of proteins and other biomolecules in the feed stream. The irreversible fouling would result in the reduction of filtration efficiency, especially in polymeric membranes, and require higher energy for filtration. Many approaches have been demonstrated that can mitigate the membrane fouling problem.  These approaches include the increase in surface hydrophilicity, enhanced electrostatic repulsion between the foulants and membrane, and tailored surface roughness and pore size. In this study, we investigated if nanocellulose-based membranes could reduce the fouling tendency for ultrafiltration of wasted water with negatively charged contaminants. This is because nanocellulose particles have both hydrophilic and hydrophobic components and negative surface charges. In specific, we examined the factors of surface charge density, roughness, hydrophilicity, membrane pore size, and supporting substrates on the fouling tendency. The chosen membranes were prepared by coating of TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl) oxidized cellulose nanofibers (CNF) on three substrates: highly negatively charged electrospun polyacrylonitrile (PAN) substrate, slightly negatively charged cellulose acetate (CA) substrates, and non-charged cellulose filter papers. All membranes exhibited high permeation flux (33 LMH - 61 LMH) under low pressure (0.1 psi) with high rejection rate (90% - 99%) in the cross-flow filtration tests, using bovine serum albumin (BSA) as a model protein. The fouling results indicate that the combined effect of negative charge and hydrophilicity on the CNF surface has significantly reduced the fouling tendency of the membranes, while the membrane pore size, roughness and supporting substrates have less impact on the fouling property but they greatly influence the permeation flux and rejection ratio.

Improving the fouling resistance of nanocellulose membranes for ultrafiltration

2019 Fall National Meeting

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