Abstract
Materials with stimulus-responsive wettability are increasingly attracting attention due to their potential applications in oil-water separation and oil spill treatment. In this work, a pH-responsive filter paper was rapidly fabricated by facile solution immersion, which was modified by a mixture of SiO 2 nanoparticles and octadecylamine (ODA)-modified TiO 2. The resultant filter paper exhibited its superhydrophobicity and superoleophilicity in the air when the solution pH was greater than 6.0, while it transformed superhydrophilic and underwater superoleophobic when the solution pH was less than 2.0. The as-prepared filter paper was applied to the controllable separation of complex oil/water/oil ternary mixtures, demonstrating its pH stimulus-responsiveness. More importantly, both immiscible oil-water mixtures and different kinds of oil-in-water emulsions were effectively separated with their separation efficiencies more than 99%, respectively. The typical CCl 4-in-water emulsion maintained a separation efficiency of around 99% even after 25 cycles, indicating its excellent durability for the as-prepared filter paper. The developed method can provide new ideas for the design of smart materials for oily wastewater treatment.