Synthesis and Characterization of a High Flux Nanocellulose-Cellulose Acetate Nanocomposite Membrane.

Nancy Li,Benjamin Hsiao,Hongyang Ma,Pejman Hadi,Harold Walker,Xiangyu Huang,Mengying Yang,Jackie Zheng

doi:10.3390/membranes9060070

Nancy Li, Benjamin Hsiao + Show 6 more

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https://doi.org/10.3390/membranes9060070

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Abstract

Despite the advantages of membrane processes, their high energy requirement remains a major challenge. Fabrication of nanocomposite membranes by incorporating various nanomaterials in the polymer matrix has shown promise for enhancing membrane flux. In this study, we embed functionalized cellulose nanofibers (CNFs) with high aspect ratios in the polymer matrix to create hydrophilic nanochannels that reduce membrane resistance and facilitate the facile transport of water molecules through the membrane. The results showed that the incorporation of 0.1 wt % CNF into the polymer matrix did not change the membrane flux (~15 ) and Bovine Serum Albumin (BSA) Fraction V rejection, while increasing the CNF content to 0.3 wt % significantly enhanced the flux by seven times to ~100 , but the rejection was decreased to 60–70%. Such a change in membrane performance was due to the formation of hydrophilic nanochannels by the incorporation of CNF (corroborated by the SEM images), decreasing the membrane resistance, and thus enhancing the flux. When the concentration of the CNF in the membrane matrix was further increased to 0.6 wt %, no further increase in the membrane flux was observed, however, the BSA rejection was found to increase to 85%. Such an increase in the rejection was related to the electrostatic repulsion between the negatively-charged CNF-loaded nanochannels and the BSA, as demonstrated by zeta potential measurements. SEM images showed the bridging effect of the CNF in the nanochannels with high CNF contents.

Highlights

Despite the unique advantages of membranes for water purification, the high energy demand of the separation process remains a challenge
We developed a facile method for the preparation of a cellulose nanofibers (CNFs)-embedded nanocomposite membrane, which consisted of cellulose acetate as the polymer matrix and the CNF as the filler to create nanochannels for preferential water flow
Saito et al measured the CNF width using the transmission electron microscope (TEM) and atomic force microscope (AFM) and demonstrated that wood cellulose had a width of 3.6 ± 0.3 nm by TEM and 2.6 ± 0.3 nm by AFM, whereas tunicate cellulose showed a width of 13.5 ±

Summary

Introduction

Despite the unique advantages of membranes for water purification, the high energy demand of the separation process remains a challenge. High pressures are required to generate sufficient flux through conventional polymeric membranes which are hydrophobic in nature and have low affinity for water molecules [1]. In addition to challenges related to the hydrophobicity of the membranes, their porosity, mostly prepared by nonsolvent-induced phase separation, is relatively low due to the instantaneous solvent-nonsolvent exchange and fast polymer precipitation. These two intrinsic membrane characteristics – comparatively low hydrophilicity and low porosity – lead to low water flux at a given applied pressure

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