Oil/Water Separations from Nanosized Superhydrophobic to Microsized under-Oil Superhydrophilic Dust

Dust, which can be seen almost everywhere in real life, often dirties the building, car, cloth, and so on. Humans have come up with many ideas to wash it out for a cleaner world. While in the point of material researchers, dust is composed of particles in different scales. In this work, for the first time, we try to make full use of the dust to separate various types of oil/water mixtures, recycling the waste materials. The tiny dust particles mixed with polydimethylsiloxane could realize superhydrophobicity. The superhydrophobic dust coating was spray-coated onto glass, sponge, and steel net substrates and achieved self-cleaning, oil absorption, and immiscible heavy oil/water separation, respectively. The tiny dust particles and a kind of organic binder adhered on the steel net. The membrane was superamphiphilic in air and superoleophobic under water and separated immiscible light oil/water mixtures efficiently. The larger dust particles could be stacked to form a dust layer. This layer was underoil superhydrophilic and quickly separated the surfactant-stabilized water-in-oil emulsion. Dust with different simple treatments could separate various types of oil/water mixtures only under gravity.