Stable Superwetting Meshes for On-Demand Separation of Immiscible Oil/Water Mixtures and Emulsions

Oil–water
separation is of great importance for the treatment of oily wastewater,
including immiscible light/heavy oil–water mixtures, oil-in-water,
or water-in-oil emulsions. Recently, interfacial materials (especially
filtration membranes) with special wettability have been broadly developed
to solve the environmental problems by virtue of their advantages
in energy saving, high flux, and good selectivity. However, the given
wetting property (superhydrophilicity or superhydrophobicity) and
pore size and poor stability of filtration membranes limit their widespread
applications, which is far from meeting a wide variety of oil-polluted
water. Here polypyrrole-coated meshes with underwater superoleophobicity
and underoil superhydrophobicity as well as controllable pore size
were prepared by adopting cyclic voltammetry. It is found that the
surface micro/nanohierarchical structures play a critical role in
the formation of underwater superoleophobicity and underoil superhydrophobicity.
HCl is advantageous to the construction of highly rough surface rather
than H2SO4 and H3PO4.
The obtained filtration membranes can be used for the on-demand separation
of oil–water mixtures, showing outstanding stability in harsh
conditions, such as high temperature (80 °C), low temperature
(0 °C), salt (0.5 M NaCl), and acid (1 M HCl), except for alkali
(1 M NaOH).