Lei Tang

The oil dewetting self-cleaning performance is the most effective method to solve viscous oil pollution. The surface composition has a positive correlation with the property, and oil droplets tend to desorb on highly hydrophilic surfaces, but the influence of surface microstructure is more complex. Herein, we prepared a variety of surface structures with different morphologies and parameters, and performed the same surface modification to ensure compositional homogeneity. By testing the oil dewetting performance, combined with structural characteristics and wettability characterization, we found that the surface microstructure has two modes of action: promotion and inhibition, and the final effect depends on the relative strength. The former comes from the amplifying effect of the structure on the wettability. And the latter refers to the hindering effect of the structure on the movement of oil droplets. For the same morphology, the promoting effect is positively correlated with roughness, but there is no analogy between different morphologies. Due to the semi-open morphology, extremely strong hydrophilicity, and large oil droplet permeability resistance, the nanoparticle-deposition and the honeycomb structure exhibit excellent crude oil pollution cleaning performance and crude oil-water separation ability. This study can not only provide two kinds of structures for crude oil treatment in practice, but also help us deeply understand the structure-activity relationship between surface morphology and oil dewetting performance in theory, and lay a solid foundation for the further optimal structure design.

Responsive smart surfaces with controllable wettability have a high potential application in self‐cleaning and oil‐water separation. In this work, a new and simple method is reported to fabricate a pH‐responsive superwettability surface. And the self‐cleaning performance from air to water after oil contamination in a dry state is studied. Wettability regulation can be achieved by controlling the ratio of carboxyl groups with protonation or deprotonation state in acid or basic solutions. Rough surface with 40% carboxyl content (X_COOH = 0.4) shows the most significant response. The surface is superoleophilic underwater after wetted in acid solution in advance but superoleophobic underwater with basic solution pre‐wetted. Oil desorption can be achieved under the superoleophobic state to realize the self‐cleaning effect on a rough surface with a complex process. The dynamic self‐cleaning process can be achieved by changing the pH value of the solution. This pH‐responsive surface also has a good self‐cleaning effect for the common water and solid pollutants. Moreover, a smart separation system with the ability to realize selective oil‐water separation under two different states is prepared. It is believed that the results reported could broaden the understanding of self‐cleaning systems and open a new perspective in controlling wettability.

Superhydrophilic self-cleaning surface can perfectly deal with oil pollution, which cannot be realized by superhydrophobic surface. This research is designed to study the mechanism of wetting behavior of superhydrophilic coating with different function groups and guide to design stable self-cleaning surface. We prepare several hydrophilic coatings including nonionic, ionic and zwitterionic coatings to investigate their self-cleaning performance underwater when they have been polluted by oil in dry state. The chemical composition, surface roughness, static and dynamic wettability, underwater oil adhesive force and swelling degree of the coatings are studied to explore their oil dewetting mechanism. The results indicate that the wettability of the coating to water and oil is the key factor to determine the self-cleaning performance. The smooth 3-Sulfopropyl methacrylate potassium salt (SA) anionic coating shows the best self-cleaning performance even be polluted by heavy crude oil in dry state in air. It is also found that in dry state the rough hydrophilic anionic surface will lock up the oil in the structures and then lose its self-cleaning ability underwater, while oil droplet can detach from the smooth coating surface quickly. Meanwhile, the superhydrophilic and underwater superoleophobic SA anionic surface also exhibits excellent anti-fogging and oil-water separation performance.