Yaoxia Yang

A prewetting induced underwater superoleophobic or underoil (super) hydrophobic waste potato residue-coated mesh for selective efficient oil/water separation

Oil/water separation has recently become a worldwide challenge due to expanding industrial oily wastewater and frequent oil spill accidents. The development of a low-cost, biobased, and environmentally friendly material has been attempted to treat environmentally sensitive water pollution caused by oils. Herein, prewetting induced underwater superoleophobic or underoil (super) hydrophobic waste potato residue coated-mesh (PRCM) without any further chemical modification was demonstrated for the first time for selective oil/water separation, which was fabricated by spraying waste potato residue powders (PRP) and waterborne polyurethane (PU) mixtures on a stainless steel mesh. After the PRCM is prewetted with water, water can be removed from the light oil/water mixture by gravity with high separation efficiency. On the other hand, heavy oil can be removed from the oil/water mixture by gravity via the heavy oil prewetted PRCM. The as-prepared PRCM showed a high separation efficiency of above 96.5% for a series of light or heavy oil–water mixtures. In addition, the PRCMs maintained a high separation efficiency of over 98.0% and a stable recyclability even after 40 separation cycles for a kerosene–water mixture. Furthermore, the as-prepared PRCM exhibited excellent environmental stability under a series of harsh conditions that were used for the separation of mixtures of oil and various corrosive materials, including strong acidic, alkaline and salt aqueous solutions.

Facile Spray-Coating Process for the Fabrication of Tunable Adhesive Superhydrophobic Surfaces with Heterogeneous Chemical Compositions Used for Selective Transportation of Microdroplets with Different Volumes

In this paper, tunable adhesive superhydrophobic ZnO surfaces have been fabricated successfully by spraying ZnO nanoparticle (NP) suspensions onto desired substrates. We regulate the spray-coating process by changing the mass percentage of hydrophobic ZnO NPs (which were achieved by modifying hydrophilic ZnO NPs with stearic acid) in the hydrophobic/hydrophilic ZnO NP mixtures to control heterogeneous chemical composition of the ZnO surfaces. Thus, the water adhesion on the same superhydrophobic ZnO surface could be effectively tuned by controlling the surface chemical composition without altering the surface morphology. Compared with the conventional tunable adhesive superhydrophobic surfaces, on which there were only three different water sliding angle values: lower than 10°, 90° (the water droplet is firmly pinned on the surface at any tilted angles), and the value between the two ones, the water adhesion on the superhydrophobic ZnO surfaces has been tuned effectively, on which the sliding angle is controlled from 2 ± 1° to 9 ± 1°, 21 ± 2°, 39 ± 3°, and 90°. Accordingly, the adhesive force can be adjusted from extremely low (∼2.5 μN) to very high (∼111.6 μN). On the basis of the different adhesive forces of the tunable adhesive superhydrophobic surfaces, the selective transportation of microdroplets with different volumes was achieved, which has never been reported before. In addition, we demonstrated a proof of selective transportation of microdroplets with different volumes for application in the droplet-based microreactors via our tunable adhesive superhydrophobic surfaces for the quantitative detection of AgNO3 and NaOH. The results reported herein realize the selective transportation of microdroplets with different volumes and we believe that this method would potentially be used in many important applications, such as selective water droplet transportation, biomolecular quantitative detection and droplet-based biodetection.