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 degrees), 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.