(595f) Nanodisperse Organic/Inorganic Hybrid Membranes for Efficient Bioalcohol Pervaporation

Organic/inorganic
hybrid membranes have been proposed as promising materials for pervaporation in
bioalcohol production.^[1-4] However, achieving a uniform dispersion
of nano-inorganic fillers in the polymer matrix is a primary challenge in the
advancement of hybrid membranes.^[5-7] Herein, we proposed two
effective approaches to overcome nanoparticle (including porous MOF and
nonporous silicon oxide) agglomeration during hybrid
membrane formation. The first way is to prepare a homogeneous, nanodisperse
MOF/polymer membrane by repeated immersion of a supporting membrane in a dilute
MOF/polymer suspension and subsequent removal of defects using a concentrated
polymer solution. To improve the nanoscale dispersion of MOF, the nascent MOF
suspension was directly dispersed in a polymer solution without drying. This
procedure avoids aggregation and re-dispersion of MOF nanoparticles after
forming the powder. Analyses confirmed that such strategy effectively
diminished aggregation between nanoparticles and led to the formation of a
well-dispersed MOF/polymer membrane (see Fig. 1). The ZIF-8/PDMS hybrid
membrane exhibited a high separation factor (52.81) and high flux (2800.5 g m^-2
h^-1) in the separation of 5.0 wt.% n-butanol¨Cwater solution
(80 °C) (see Fig. 2). Besides, we performed sonication-enhanced in situ
assembly to obtain a hybrid membrane with high degree of dispersion of silicon
oxide nanoparticles. Characterizations suggested that through ultrasonic
cavitation during assembly of the hybrid membrane, this method could effectively
avoid nanoscale agglomeration and in turn uniformly disperse SiO₂ nanoparticles
within the polymer matrix (see Fig. 3). The prepared organic/inorganic hybrid
membrane has a higher hydrophobicity and higher performance. For example, the
contact angle of SiO₂/PDMS hybrid membrane increased from 135.5° to
146.3º, and the separation factor for the pervaporation of 5 wt.% ethanol/water
mixture increased from 7.3 to 12.5. Furthermore, this method could also be used
to prepare a well-dispersed ZIF-8/PDMS hybrid membrane with higher performance
in the pervaporation of alcohol/water mixtures. These results further suggest
that in situ assembly via sonication is a promising approach to improve the
dispersion of inorganic fillers and thus the membrane performance. As nanoscale
dispersion of inorganic nanoparticles in the polymer matrix is one of the most
difficult and important issues in the preparation of high performance hybrid
membranes, these strategies we proposed above may contribute to the design and
assembly of various hybrid membranes and thus extend the use of these membranes
to different uses.

Keywords:
Organic/inorganic hybrid membrane, Nanoscale dispersion, Sonication-enhanced in
situ assembly, Pervaporation, Alcohol/water mixture

References

[1]
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[2]
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[3]
H. Yan, J. Li, H. Fan, S. Ji, G. Zhang and Z. Zhang, Sonication-enhanced in
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[4]
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[6]
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Figure
1. Surface SEM images of suspension-dispersed ZIF-8/PDMS nanohybrid membrane

Figure 2.
Pervaporation performance in the recovery of butanol from aqueous solutions
reported in previous studies and in our study

Figure 3.
Surface SEM images of the in situ sonication assembled SiO₂/PDMS
nanohybrid membrane