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. 2019 Apr 18;11(4):712.
doi: 10.3390/polym11040712.

Anisotropic Cellulose Nanofibers/Polyvinyl Alcohol/Graphene Aerogels Fabricated by Directional Freeze-drying as Effective Oil Adsorbents

Lijie Zhou  1 , Shengcheng Zhai  2 , Yiming Chen  3 , Zhaoyang Xu  4
Affiliations

Anisotropic Cellulose Nanofibers/Polyvinyl Alcohol/Graphene Aerogels Fabricated by Directional Freeze-drying as Effective Oil Adsorbents

Lijie Zhou et al. Polymers (Basel). .

Abstract

Under the current situation of frequent oil spills, the development of green and recyclable high-efficiency oil-absorbing aerogel materials has attracted wide attention from researchers. In this study, we report a high-strength, three-dimensional hydrophobic cellulose nanofiber (CNF)/polyvinyl alcohol (PVA)/graphene oxide (GO) composite aerogel with an anisotropic porous structure, which was fabricated by directional freeze-drying technology using anisotropically grown ice crystals as a template, followed by hydrophobic treatment with a simple dip coating process. The prepared composite aerogel presented anisotropic multi-level pore microstructures, low density (17.95 mg/cm3) and high porosity (98.8%), good hydrophobicity (water contact angle of 142°) and great adsorption capacity (oil absorption reaching 96 times its own weight). More importantly, the oriented aerogel had high strength, whose compressive stress at 80% strain reached 0.22 MPa and could bear more than 22,123 times its own weight without deformation. Therefore, the CNF/PVA/GO composite aerogel prepared by a simple and easy-to-operate directional freeze-drying method is a promising absorbent for oil-water separation.

Keywords: cellulose nanofibers; directional freeze-drying; graphene; oil absorption; polyvinyl alcohol.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic representation of (a) the directional freeze-drying method; (b) the non-directional freeze-drying method and (c) the refrigerator freeze-drying method. Cellulose nanofiber (CNF); polyvinyl alcohol (PVA); graphene oxide (GO).
Figure 2
Figure 2
Schematic showing experimental process of the samples.
Figure 3
Figure 3
Macroscopic pictures and microstructures of aerogels formed by different freeze-drying methods. (a), (d) and (g) are macro photographs of d-MCPGA, r-MCPGA, n-MCPGA, respectively; (b) vertical section of d-MCPGA; (c) cross section of d-MCPGA; (e–f) internal SEM image of r-MCPGA; (h) vertical section of n-MCPGA; (i) cross section of n-MCPGA.
Figure 4
Figure 4
FTIR spectra of (a) CNFs, (b) GO, (c) PVA, (d) CNF/PVA/GO and (e) TMCS /CNF/PVA/GO aerogels.
Figure 5
Figure 5
XRD patterns of (a) CNFs, (b) PVA, (c) GO, (d) CNF/PVA/GO and (e) TMCS/CNF/PVA/GO aerogels.
Figure 6
Figure 6
Compressive behavior of aerogels (d-MCPGA, r-MCPGA, n-MCPGA) prepared by different freeze-drying methods consisting of CNFs, PVA and GO.
Figure 7
Figure 7
Comparison of the compressive strength of different materials [49,50,51,52,53].
Figure 8
Figure 8
(a) Ultra-light cylindrical d-MCPGA supported by young leaves; (b–d) the pre, middle and post processes of the d-MCPGA supporting a 500 g mass load.
Figure 9
Figure 9
Water contact angle of (a) CPGA, (b) d-MCPGA, (c) r-MCPGA and (d) n-MCPGA.
Figure 10
Figure 10
Removal of corn oil (dyed with Sudan red) from the water surface using MCPGA.
Figure 11
Figure 11
Absorption capacity of MCPGA (d-MCPGA, r-MCPGA, n-MCPGA) for different oils and organic liquids.
Figure 12
Figure 12
The absorption capacity of MCPGA (d-MCPGA, r-MCPGA, n-MCPGA) to adsorb (a) pump oil; (b) engine oil and (c) corn oil as a function of time.
See this image and copyright information in PMC

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