In Situ Redox Strategy to Fabricate Superhydrophobic Sponges for Efficient Oil–Water Separation

In this work, a superhydrophobic MnO2@AF-MWCNTs@PDMS@Melamine
sponge (S-MMP@MS) with highly efficient oil–water separation
was prepared. MnO2 nanoparticles were loaded onto melamine
sponges through the in situ redox reaction between AF-MWCNTs and KMnO4. To further enhance the hydrophobic properties of the modified
sponges, a nontoxic polydimethylsiloxane (PDMS) glue layer was fixed
on the sponges by dip-coating. The S-MMP@MS demonstrated excellent
superhydrophobicity (with a water contact angle of 156.8°), a
high adsorption capacity (54.3–136.7 g/g), and excellent recyclability
(50 times of the adsorption–extrusion cycle). In addition to
immiscible oil–water mixtures, the modified sponges can separate
water-in-oil emulsions and oil-in-water emulsions with equal effectiveness
(the separation rate exceeded 99.0%). Furthermore, the modified sponges
can maintain stable superhydrophobicity in simulated complex marine
environments, including acidic environments, alkaline environments,
corrosive conditions, different temperatures, and mechanical compression.
The superhydrophobic melamine sponges are expected to be a potential
material for oil spill treatment due to their excellent oil–water
separation efficiency, reusability, environmental suitability, and
mechanical stability.