A novel hierarchical hollow SiO2@MnO2 cubes reinforced elastic polyurethane foam for the highly efficient removal of oil from water

- The composite PU foam was synthesized by a facile one-step foaming technology.
- Hierarchical hollow SiO2@MnO2 cubes enhanced adsorption capacity of foam.
- The composite PU foam selectively adsorb and continuously remove water from oil.
- The composite PU foam showed excellent elasticity and recyclability.
- The composite PU foam could be reused for at least ten cycles.

Oil-polluted water has become a worldwide problem due to ever-increasing industrial oily wastewater as well as the frequent oil spill accident. A superior oil adsorbing material capable of separating oil-water mixtures efficiently, especially with a high oil adsorption capacity and mechanical strength, is urgently desired. Here, we report a novel strategy of preparing composite foams with hierarchical porous structures for effective oil/water separation and selective oil adsorption. The composite polyurethane foam is synthetized by a facile one-step foaming technology, which uses hierarchical hollow SiO2@MnO2 cubes to modify the inner structures of composite polyurethane foam. The incorporation of hierarchical hollow SiO2@MnO2 cubes into the foam could not only improve the morphologies, specific surface areas and hydrophobic properties but also enhance the adsorption capacity and mechanical properties. The as-prepared composite PU foam is put into the oil/water mixture to adsorb oils, and the adsorbed oils can be recovered simply by squeezing oil from composite PU foam. The resulting composite PU foam exhibits high oil adsorption capacity, high selectivity and oil adsorption capacity for carbon tetrachloride was measured to be 31.6 g/g. Also, the composite PU foam shows excellent elasticity and the height of the composite PU foam decreased from 100% to 94% after 30 compressing-releasing cycles. Furthermore, the as-prepared composite PU foam exhibits the high reusability and durability by being reused for oil-water separation for 10 cycles without losing its hydrophobicity, which makes it a good candidate for industrial oil-polluted water treatments and oil spill cleanup.

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