•An extremely simple accumulated method was used to treat multiform pollutant.•The WSPs showed excellent separation capacity and high flux for oil/water mixture.•The WSPs displayed outstanding capacity of dynamic adsorption for organic dyes.Functional materials with superwetting property have been extensively used for wastewater treatment. Here, walnut shell powders (WSPs) were accumulated into a layer to separate oil/water mixtures and adsorb organic dyes, avoiding the complex process involved in the fabrication of traditional superhydrophobic or underwater superoleophobic filtering membranes. By making use of the underwater superoleophobicity and low adhesion to oils, the pre-wetted WSPs layer can be used for gravity driven oil/water separation with ultrahigh separation efficiency. Furthermore, the WSPs exhibited excellent adsorption property to the organic dyes including methylene blue, rhodamine B and crystal violet. Finally, the WSPs are agricultural residue to environment, and using it for water remediation not only is a good way to treat water pollution, but also can reduce the pressure to the environment. We believe that such multifunctional material will be an effective approach for separating oil/water separation and adsorbing organic dyes pollution in practical applications.Download high-res image (113KB)Download full-size imageMultifunctional water remediation was achieved by WSPs layer, including separating oil/water mixtures and adsorbing organic dyes.

•Underwater superoleophobic TiO2 mesh was fabricated by a facile spray-coating process.•The mesh was used to separate a series of oil from water with the separation efficiency up to 99.0%.•The mesh can be reused more than 40 times with the separation efficiency still above 97.5%.The removal of oil and organic pollutants from water is highly desired because of the frequent oil spill accidents and increase of industrial oily wastewater. Here, underwater superoleophobic TiO2 coated mesh was fabricated through spraying TiO2 nanoparticles and polyurethane mixtures onto stainless steel mesh. The underwater superoleophobic TiO2 coated mesh was then used to separate water from oil/water mixtures, where only the water permeates through the mesh while the oil is repelled on the mesh. In addition, the separation efficiency of the coated mesh is as high as 99.0%. Furthermore, the TiO2 coated mesh still maintained high separation efficiency over 97.5% and stable recyclability after 40 separation cycles. Thus, such superhydrophilic and underwater superoleophobic TiO2 coated mesh is a very potential material for the application of oil spill cleanup and industrial oily wastewater remediation.The underwater superoleophobicTiO2 coated meshes can separate oil from water with the separation efficiency up to 99.0%.

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.Keywords: heterogeneous chemistry; selective transportation; spray-coating; superhydrophobic surfaces; tunable adhesion;