Zhanjian Liu,Ping Wang,Jing Jing,Meiling Li,Yuxin Fu,Xiguang Zhang,Huaiyuan Wang
Superwetting oil-water separation membranes are effective materials for treatment of wastewater containing emulsified oil, but the problem of membrane pollution remains a huge challenge during its long-term operation. In this study, we successfully developed a superhydrophilic/underwater superoleophobic membrane using a simple phase separation method. The fabrication process involved three key steps: (1) surface hydroxylation of pristine PVDF using NaOH etching to generate active hydrogen bonds and hydroxyl groups, (2) acrylic acid (AA) grafting onto the hydroxylated PVDF surface to introduce carboxyl functionalities, and (3) in-situ chelation of needle-like ZnO onto the AA-grafted matrix. The synergistic effect of the surface needle-like ZnO and the hydration layer endowed the PVDF-OH/AA@ZnO membrane with an outstanding oil-water separation efficiency of n-hexane up to 99.68 %, and higher than 98 % for various emulsions (e.g. kerosene, petroleum ether, chloroform, and dichloromethane) under gravity. Moreover, compared with the basement membrane, the tensile strength of the modified membrane increased from 106.21 kPa to 153.84 kPa, indicating its excellent mechanical properties under strong external forces. The PVDF-OH/AA@ZnO membrane demonstrated exceptional recycling performance, with a separation efficiency above 97.25 % after five cycles, and exhibited anti-fouling capability with simple water rinsing used to remove surface oil residues. Overall, this study provides a scalable strategy for the design of superhydrophilic/underwater superoleophobic separation membranes for the practical treatment of oily wastewater.
Jin Wang,Qiong Du,Jiashuang Luan,Xuanbo Zhu,Jinhui Pang
Membrane separation has been considered to be the most effective decontamination method for oily waste water. The most significant point of membrane separation is the resistance against membrane fouling. Fabricating hierarchical architectures on the membrane surface is an available approach to improving its anti-fouling property. In this study, ZnO nanoneedles were successfully anchored onto surface-sulfonated poly(ether-ether-ketone) (PEEK) felt via UV/ozone cleaning and hydrothermal synthesis. The modified felt (PEEK-f-Z) showed much better anti-fouling properties and far higher rejection height (33 cm) than the unmodified felt (17 cm) with a separation efficiency up to 99.99%. The enhanced separation properties could be attributed to the stronger water locking capability of the hierarchical architectures on the surface. Furthermore, benefiting from the great chemical stability of PEEK substrates and ZnO nanoneedles, the as-prepared membrane exhibited admirable solvent resistance, mechanical strength, and thermal stability. As a result, PEEK-f-Z could even separate immiscible organic liquids with different polarities and collect hot water from the oil/water mixture, promising to be used under severe conditions.
Superhydrophobic surfaces (SHS) have potential application prospects in many fields for the lotus effect. The microdroplet self-propelling effect is a newly discovered mechanism of SHS phenomena, which provides more possibilities for SHS applications. In this study, the ZnO-nanoneedle array was designed and constructed by an electrodeposition method. Based on surface characterization and analysis, the nucleation, growth, and merging process of SHS surface droplets under simulated condensation conditions were studied. The correlation between the surface microstructure and the jumping behavior was established, and the self-propelling mechanism was analyzed from an energy perspective. Based on electrochemical data, the contribution of self-propelling behavior to the atmospheric corrosion protection performance of SHS was analyzed, which confirms that the droplet self-propelling behavior, as a new SHS atmospheric corrosion protection mechanism, has potential applications in atmospheric corrosion protection in the future.
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