Robust superhydrophilic and underwater superoleophobic membrane optimized by Cu doping modified metal-organic frameworks for oil-water separation and water purification

Preparation of Superhydrophobic/Superoleophilic Nitrile Rubber (NBR) Nanocomposites Contained Silanized Nano Silica for Efficient Oil/Water Separation

To achieve oil/water separation using both absorption and filtration regardless of the oil/water density relationship, the super-hydrophilic/underwater super-oleophobic graphene oxide coated melamine sponge (GO@MS) and super-hydrophobic/super-oleophilic reduced graphene oxide coated melamine sponge (rGO@MS) were prepared via dip-coating of graphene oxide (GO) sheets onto melamine sponge (MS) and subsequent chemical reduction, respectively. The structures of the GO@MS and rGO@MS were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectra, and X-ray diffraction (XRD). Both GO@MS and rGO@MS can preserve their original wettability in harsh environments containing acidic, alkaline, saline, and hot waters. The GO@MS and rGO@MS show excellent capability for selective absorption of water and oil respectively, with high capacities of 72.3–136.5 g g −1 and excellent recyclability. The compressed GO@MS and rGO@MS also exhibit high separation efficiency of about 99% and ultra-high permeation flux above 1.62 × 10 5 L m −2 h −1 for separating different oil/water mixtures containing light and heavy oils through filtration driven by gravity, respectively. Furthermore, a bidirectional separation setup assembled with the compressed GO@MS and rGO@MS was constructed, which demonstrates high efficiency for continuously separating different oil/water mixtures of any oil density. • We report a simple way to fabricate graphene-based sponges with reverse wettability. • The GO@MS and rGO@MS show high capacity and recyclability for selective absorption. • Both sponges exhibit superior performance for oil/water separation through filtration. • A bidirectional separation setup was assembled for continuous oil/water separation. 

Graphene-based melamine sponges with reverse wettability for oil/water separation through absorption and filtration

Selective superantiwetting/superwetting nanostructured ZnO/CuO mesh membrane was constructed using a facile method. The ZnO/CuO coated mesh exhibited switchable wettability from superhydrophobic to superhydrophilic properties using annealing treatment at high temperatures. The field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses were applied for characterization. The wettability was determined by water/oil static contact angle (W/OCA) and contact angle hysteresis (CAH). The coated mesh showed superhydrophobic properties without any post-treatment with a water contact angle of 161.2° ± 1.5° and contact angle hysteresis of 4.2° ± 1°. The wettability of the surface was altered to superhydrophilicity in air and underwater superoleophobicity (OCA of 162° ± 2°) after annealing at high temperatures. Evaluation of wetting stability confirmed that the ZnO/CuO surfaces exhibited long-term stability of superwetting properties towards the water after exposure to ambient air due to creating high oxygen vacancies amounts after annealing treatment compared to the ZnO coating. The prepared nanostructured surface was considered to isolate the oil/water mixtures. The results proved that the coated meshes could be applied effectively to separate oil/water mixtures with excellent separation efficiency (> 99.9%) and good flux (above 2000 L m −2 h −1 ) regardless of oil density, even in harsh conditions. • A ZnO-CuO surface with switchable wettability was fabricated for oil-water separation. • The wettability of the surface remained stable up to two months of exposure to ambient air. • High concentration of oxygen vacancies is responsible for the superhydrophilic long-term stability. • The separation performance of meshes was excellent in oil/corrosive solutions. 

Selective superantiwetting/superwetting fluorine-free nanostructured ZnO/CuO mesh membrane for efficient separation of oil/water mixture: Oxygen vacancy-dependent wetting stability studies

Ying Zhou

Papers

Metal mesh-based special wettability materials for oil-water separation: A review of the recent development