Nanoparticle-decorated and poly(dimethyl siloxane)-modified superhydrophobic melamine sponge for efficient oil/water separation

A superhydrophobic and superoleophilic sponge (MS/UIO-66(F4)/RGO/PDMS) was fabricated by decorating the skeleton of a melamine sponge (MS) with UIO-66(F4) nanoparticles and reduced graphene oxide (RGO) nanosheets layer by layer, and then hydrophobic modification with polydimethylsiloxane (PDMS). The composition, morphology, thermal stability, and wettability of the modified sponge were characterized, and its oil/water separation application was investigated. Characterization results reveal that compared with the hydrophilic pure MS, the fiber surface of the prepared sponge becomes rough and demonstrates remarkable super-hydrophobicity with a water contact angle of 153.5°. The modified sponge can efficiently separate water-in-diesel emulsion (flux of 3665 L· m−2 · h−1) and multiple stratified oil-water mixtures via the auxiliary device with a separation efficiency above 98.3%, which has no significant change after 25 cycles. The modified sponge can absorb oils or organic solvents 48–100 times higher than its weight, with a stable absorption capacity after 20 cycles. Moreover, it can be applied in handling flammable oils, showing good flame retardancy. Considering it also possesses excellent chemical stability, extreme environmental stability (resistance to high/low temperature, UV irradiation and load-bearing) and mechanical durability under harsh conditions, the modified sponge is a promising candidate in the field of oily wastewater treatment.