To handle serious oil spills, many strategies have been proposed to design novel materials for oil-water separation. In particular, conventional oil-water separation processes with superhydrophobic-superoleophilic materials are easily fouled by adsorbed oils thus resulting in the quick decrease of flux and separation efficiency. However, superhydrophilic and underwater superoleophobic materials have shown advantages in overcoming the above mentioned problems. In this paper, we developed a facile method for fabricating an underwater low adhesive hydrogel-coated functionally integrated device. Due to its superhydrophilicity and underwater superoleophobicity, the separation of oil from oil-water mixtures was achieved by allowing water to permeate through. The separation efficiency for various oils was above 98%, and for dichloromethane even reached 99.5%. Furthermore, the as-prepared device can be cycled 6 times and still had a high separation efficiency. In addition to the underwater oil-repellent and water-absorbing capabilities, the as-prepared device exhibited also magnetic properties and it can float easily on dichloromethane. Hence, by simply moving the device using a magnet, the device can absorb the floating water from the dichloromethane, thereby purifying the oil underneath. It is expected that superhydrophilic and underwater superoleophobic oil-water separation materials will achieve industrial scale production and be used for oily wastewater treatment in the near future.
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