Nanofibrous Microfiltration Membrane Based on Cellulose Nanowhiskers

Abstract

A multilayered nanofibrous microfiltration (MF) membrane system with high flux, low pressure drop, and high retention capability against both bacteria and bacteriophages (a virus model) was developed by impregnating ultrafine cellulose nanowhiskers (diameter about 5 nm) into an electrospun polyacrylonitrile (PAN) nanofibrous scaffold (fiber diameter about 150 nm) supported by a poly(ethylene terephthalate) (PET) nonwoven substrate (fiber diameter about 20 μm). The cellulose nanowhiskers were anchored on the PAN nanofiber surface, forming a cross-linked nanostructured mesh with very high surface-to-volume ratio and a negatively charged surface. The mean pore size and pore size distribution of this MF system could be adjusted by the loading of cellulose nanowhiskers, where the resulting membrane not only possessed good mechanical properties but also high surface charge density confirmed by the conductivity titration and zeta potential measurements. The results indicated that a test cellulose nanowhisker-based MF membrane exhibited 16 times higher adsorption capacity against a positively charged dye over a commercial nitrocellulose-based MF membrane. This experimental membrane also showed full retention capability against bacteria, for example, E. coli and B. diminuta (log reduction value (LRV) larger than 6) and decent retention against bacteriophage MS2 (LRV larger than 2).

A review on electrospun bio-based polymers for water treatment

“…In the case of MF, the infusion of the whiskers resulted in a reduction of the mean pore size with a narrower distribution than the electrospun PAN nanofibrous membrane. In comparison with the commercial membrane GS0.22 made of nitrocellulose and acetyl cellulose ester, the water flux cellulose nanowhiskerbased membrane was better because of the difference in porosity (>80% versus 52%) [144]. The mechanical properties were improved with Young's modulus and tensile strength values of 375±15 and 14.3±0.4 MPa, respectively, compared to the unmodified membrane (226±20 and 8.5±0.3 MPa) which was still higher than the commercial membrane with a tensile strength of 5.6±0.3 MPa.…”

“…The adsorption capacity was 16 times higher for the cellulose nanowhiskers-based membrane. The cellulose nanowhiskers as a thin barrier layer in TNFC displayed superior performance compared to the commercial known membranes [144]. The hydrophilicity, large surface area to volume ratio and the surface charges of the cellulose nanowhiskers played a significant role in improving the rejection and flux of the membrane.…”

“…Cellulose nanowhiskers can be extracted from their abundant source (cellulose) by mechanical and chemical means [141,144]. The high aspect ratio, high crystallinity, easy functionalization, and large surface areas make the nanowhiskers the next generation of wastewater treatment nanomaterials.…”

“…The modulus and tensile strength were significantly increased from 0.4 to 4.3 GPa and and from 4.6 to 34.9 MPa, respectively. An antibacterial TNFC membrane was developed by including chitin nanowhiskers as barrier layer onto electrospun PAN nanofibres (as a mid-layer on top of a PET nonwoven support) [144]. The flux permeation was Figure 11.…”

“…TNFC membranes have been one of the growing subjects in water filtration, because of the performance displayed by these materials since the introduction of electrospun nanofibres as one of the sub-layers. Several researchers found that the coating of these TNFC with cellulose nanowhiskers imparts significant hydrophilicity and mechanical properties to the membrane [144,[149][150][151][152]. The thin top-layer coating enhanced the rejection and flux.…”