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Janus Graphene Oxide Sponges for High-Purity Fast Separation of Both Water-in-Oil and Oil-in-Water Emulsions
journal contribution
posted on 2017-05-08, 15:48 authored by Jongju Yun, Fakhre Alam Khan, Seunghyun BaikMembrane separation
of oil and water with high purity and high permeability is of great
interest in environmental and industrial processes. However, membranes
with fixed wettability can separate only one type of surfactant-stabilized
emulsion (water-in-oil or oil-in-water). Here, we report on Janus
graphene oxide (J-GO) sponges for high purity and high permeability
separation of both water-in-oil and oil-in-water emulsions. Millimeter-scale
reduced GO sponges with a controlled pore size (11.2 or 94.1 μm)
are synthesized by freeze drying, and the wettability is further controlled
by fluorine (hydrophobic/oleophilic in air) or oxygen (hydrophilic/oleophilic
in air) functionalization. J-GO sponges are prepared by the fluorine
functionalization on one side and oxygen functionalization on the
other side. Interestingly, the oil wettability of oxygen-functionalized
surface turns into an oleophobic surface when immersed in water, which
is explained by Young’s theory. This effect is further used
in the separation of both water-in-oil and oil-in-water emulsions
by changing the flow direction. The purity of the separated oil and
water is very high (≥99.2%), and the permeability is more than
an order of magnitude greater than those of the other Janus membranes
reported. J-GO sponges can be reused with an excellent repeatability,
demonstrating feasibility in practical applications.