Robust, Small Diameter Hydrophilic Nanofibers Improve the Flux of Ultrafiltration Membranes

Abstract

In this study, we systematically investigated the flux performance of ultrafiltration (UF) membranes functionalized with randomly-accumulated nanofibers. By electrospinning nanofibers from hydrophobic polysulfone (PSf) and hydrophilic cellulose (CL), we were able to explore the role that bulk nanofiber (NF) layer thickness, individual NF diameter, and intrinsic chemistry have on composite membrane flux. Additional parameters that we systematically tested include the molecular weight cut-off (MWCO) of the base membrane (10, 100, and 200 kDa), flow orientation (cross-flow versus dead-end), and the feed solution (hydrophilic water versus hydrophobic oil). Structurally, the crosslinked PSf nanofibers were more robust than the CL nanofibers, which lead to the PSfNF-UF membranes having a greater flux performance. To decouple the structural robustness from the water affinity of the fibers, we chemically modified the PSf fibers to be hydrophilic and indeed, the flux of these new composite membranes featuring hydrophilic crosslinked nanofibers were superior. In summary, the greatest increase in flux performance arises from the smallest diameter, hydrophilic nanofibers that are mechanically robust (crosslinked). We have demonstrated that electrospun nanofiber layers improve the flux performance of ultrafiltration membranes.

Optimizing the Packing Density and Chemistry of Cellulose Nanofilters for High-Efficiency Particulate Removal

“…Cellulose nanofilters were successfully fabricated using electrospinning, and to explore the role of chemistry on filter performance, we also performed two surface chemical modifications. First, to manufacture the base material, we electrospun cellulose acetate nanofilters and using an alkaline treatment regenerated them into pure cellulose . The FTIR spectra of the as-spun cellulose acetate and regenerated cellulose are provided in Figure .…”

“…The procedure used to electrospin cellulose was based on the literature where cellulose acetate is electrospun and regenerated into cellulose nanofibers . Cellulose acetate (2.25 g) was mixed with 15 mL of acetone (15% w/v) for 24 h at 20 rpm using an Arma-Rotator A-1 (Bethesda, MA) in ambient conditions.…”

“…The procedure used to electrospin cellulose was based on the literature where cellulose acetate is electrospun and regenerated into cellulose nanofibers. 37 Cellulose acetate (2.25 g) was mixed with 15 mL of acetone (15% w/v) for 24 h at 20 rpm using an Arma-Rotator A-1 (Bethesda, MA) in ambient conditions. The solution was loaded into a 5 mL Luer-Lock tip syringe capped with an 18gauge needle, which was then mounted on a PHD Ultra syringe pump (Harvard Apparatus, Plymouth, PA).…”

Nanopatterning Reduces Bacteria Fouling in Ultrafiltration

“…A custom-build cross-flow cell (channel dimensions of 28 mm long, 17 mm wide, and 1.5 mm deep, and an active area of 5.44 cm 2 ) equipped with 17 mil low-foulant spacer and a permeate carrier (Sterlitech), was used to evaluate the pure water permeance of the pristine and patterned membranes. All tests were conducted at a flow rate of 50 mL min –1 enabled by a reciprocating pump (Eldex Laboratories Incorporated, Napa, CA) followed by a dampener (Cat Pumps, Minneapolis, MN) .…”

Sodium Chloroacetate Modified Polyethyleneimine/Trimesic Acid Nanofiltration Membrane to Improve Antifouling Performance

“…In addition, the modification failed to change the molecular weight cut-off (MWCO) of the PEI/TMA membrane (SI, Figure S1). It could be believed that the increased flux was mainly caused by the hydrophilic surface and the neutralization of chargeability [34,35]. In the modification process, the increase in water flux was positively correlated with hydrophilicity (Figure 4).…”