Three-dimensional adsorbent with pH induced superhydrophobic and superhydrophilic transformation for oil recycle and adsorbent regeneration.

With the development of research on superwettability materials, superhydrophobic and superoleophilic materials show superior separation ability in oil-water separation due to their excellent oil-water selectivity. However, due to the super wetting ability of the oil to the material, it is difficult to clean and reuse after adsorbing the oil spill. Therefore, how to realize the complete regeneration of superhydrophobic and superoleophilic materials is still a worldwide problem. In this paper, the controlled adsorption-desorption process of oil and the complete regeneration of materials are realized by pH induced superwettability transformation. We fabricate a pH-responsive oil-water separation sponge by a method of simply impregnating the carboxyl and alkyl group modified SiO2 nanoparticles on the surface of melamine sponge (MS) skeleton, which can change the wettability from superhydrophobicity and superhydrophilicity through protonation and deprotonation in different pH solutions. The experiment results indicate that the sponge is superhydrophobic and superoleophilic in acid and neutral solution, and can adsorb oil in water. While in basic solution, it becomes superhydrophilic and underwater superoleophobic, which can release the adsorbed oil. With the help of a vacuum pump, we can use this wettability transition to achieve a continuous oil adsorption and desorption process. These findings offer a new preparation method of regenerative 3D adsorption materials like MS in oil-water separation.