Polar molecule filtration using charged cellulose nanofiber membrane on the nanoporous alumina support for high rejection efficiency

Abstract

In this study, we propose a charged cellulose nanofiber membrane on nanoporous alumina support (c-CNFNA), which consists of eco-friendly materials for polar molecule filtration. The CNFs were extracted from the cell walls of a tree and oxidized by TEMPO ((2,2,6,6-Tetramethylpiperidin-1-yl)oxyl) to exhibit a negative charge on its surface. The nanoporous alumina support (NAS) with high aspect ratio was fabricated by anodic aluminum oxidation process and chemical wet etching process. The charged CNFs were coated on the NAS surface for fabrication of c-CNFNA, and negatively-charged polar molecules would be rejected by the equivalent charge of c-CNFNA. To investigate the polar molecule rejection performance of c-CNFNA, a polar molecule solution was injected into the surface of c-CNFNA. Rejection efficiency was calculated by measuring the concentration of the output solution, and hydraulic resistance was calculated from the pressure loss and flow rate. The results show that the rejection efficiency of c-CNFNA is 88–99% in the first rejection. In the second rejection, for almost all cases, approximately 100% rejection efficiency was achieved.