Boosting Demulsification and Antifouling Capacity of Membranes via an Enhanced Piezoelectric Effect for Sustaining Emulsion Separation.

Traditional superwettable membranes for demulsification of oil/water emulsions could not maintain their separation performance for long because of low demulsification capacity and surface fouling during practical applications. A charging membrane could repel the contaminants for a while, the charge of which would gradually be neutralized during the separation progress. Here, a superhydrophilic piezoelectric membrane (SPM) with sustained demulsification and antifouling capacity is proposed for achieving prolonged emulsion separation, which is capable of converting inherent pulse hydraulic filtration pressure into pulse voltage. A pulse voltage up to -7.6 V is generated to intercept the oil by expediting the deformation and coalescence of emulsified oil droplets, realizing the demulsification. Furthermore, it repels negatively charged oil droplets, avoiding membrane fouling. Additionally, any organic foulants adhering to the membrane undergo degradation facilitated by the generated reactive oxygen species. The separation data demonstrate a 98.85% efficiency with a flux decline ratio below 14% during a 2 h separation duration and a nearly 100% flux recovery of SPM. This research opens new avenues in membrane separation, environmental remediation, etc.

Metformin-Induced Epigenetic Toxicity in Zebrafish: Experimental and Molecular Dynamics Simulation Studies.

The increased detection of many prescription drugs in aquatic environments has heightened concerns of their potential ecotoxicological effects. In this study, the effects of metformin (MEF) exposure on tissue accumulation, gene expression, and global DNA methylation (GDM) in zebrafish were investigated. The toxic mechanism of MEF exposure was simulated by molecular dynamics (MD) to reveal any conformational changes to DNA methyltransferase 1 (DNMT1). The results showed MEF accumulation in the gills, gut, and liver of zebrafish after 30 days of exposure, and the bioaccumulation capacity was in the order of gut > liver > gills. After a 30 day recovery period, MEF could still be detected in zebrafish tissues in groups exposed to MEF concentrations ≥ 10 µg/L. Moreover, the liver was the main site of GDM, and the restoration of GDM in the liver was slower than that in the gut and gills during the recovery period. Furthermore, MEF could induce the abnormal expression of CYP3A65, GSTM1, p53, and DNMT1 genes in the liver due to the formation of hydrogen bonds between MEF and the protein residues of those genes. The MD simulation allowed for the mechanistic determination of MEF-induced three-dimensional (3D) conformational changes and changes to the catalytic activity of DNMT1.

Directional Self-Transportation of Droplets on Superwetting Wedge-Shaped Surface in Air and Underliquid Environments.

The directional self-transportation of droplets has aroused great attention in microfluidic systems. However, most reported surfaces are mainly designed for driving water droplets to move in air, displaying low adaptability in complex environments. This work presents a wedge-shaped surface with multiple superwettability, i.e., superhydrophilicity/superoleophilicity and underwater superoleophobicity/underoil superhydrophobicity, fabricated by electrodeposition of a metal-organic framework on a copper sheet. This surface exhibited excellent performance for driving droplet self-transportation, regardless of the droplet type (water or oil) and environmental media (air or underliquids). In air, the wedge-shaped surface with wedge angle of 9.2° could move droplets of water and dodecane up to 24.5 mm and 17.9 mm, respectively. The movement of water droplet under dodecane, however, dropped from 24.5 mm to 22.1 mm, while the dodecane droplet underwater increased from 17.9 mm to 20.3 mm in moving displacement, indicating the underliquid environment is in favor of manipulation of oil droplets. Furthermore, the droplet convergence, transportation, and separation were achieved on the well-designed multiple wedge tracks in air with a total movement distance up to 60.0 mm. The test of micro-oil droplets collecting under water demonstrated that a sponge with two wedges has 2.1 times the oil droplet collection capacity over that of the sponge only, providing a new strategy for efficient treatment of the micro-oil droplets contaminated water.

Designing Robust Superhydrophobic Materials for Inhibiting Nucleation of Clathrate Hydrates by Imitating Glass Sponges.

Superhydrophobic surfaces are suggested to deal with hydrate blockage because they can greatly reduce adhesion with the formed hydrates. However, they may promote the formation of fresh hydrate nuclei by inducing an orderly arrangement of water molecules, further aggravating hydrate blockage and meanwhile suffering from their fragile surfaces. Here, inspired by glass sponges, we report a robust anti-hydrate-nucleation superhydrophobic three-dimensional (3D) porous skeleton, perfectly resolving the conflict between inhibiting hydrate nucleation and superhydrophobicity. The high specific area of the 3D porous skeleton ensures an increase in terminal hydroxyl (inhibitory groups) content without damaging the superhydrophobicity, achieving the inhibition to fresh hydrates and antiadhesion to formed hydrates. Molecular dynamics simulation results indicate that terminal hydroxyls on a superhydrophobic surface can inhibit the formation of hydrate cages by disordering the arrangement of water molecules. And experimental data prove that the induction time of hydrate formation was prolonged by 84.4% and the hydrate adhesive force was reduced by 98.7%. Furthermore, this porous skeleton still maintains excellent inhibition and antiadhesion properties even after erosion for 4 h at 1500 rpm. Therefore, this research paves the way toward developing novel materials applied in the oil and gas industry, carbon capture and storage, etc.

Janus sand filter with excellent demulsification ability in separation of surfactant-stabilized oil/water emulsions: An experimental and molecular dynamics simulation study.

Developing efficient separation materials for surfactant-stabilized oil/water emulsions is of great importance while significantly challenging. In this work, a sand filter with Janus channels was prepared by simply mixing superhydrophilic and superhydrophobic quartz sand in a mass ratio of 1:1. Due to the imbalanced force of droplets in those Janus channels, better separation performance under gravity was achieved for both surfactant-stabilized oil-in-water and water-in-oil emulsions than the superhydrophilic or superhydrophobic sand filter alone. It also received high flux (1080.13 L m-2 h-1 for dichloroethane-in-water emulsion and 1378.07 L m-2 h-1 for water-in-dichloroethane emulsion) and high separation efficiency (99.80% for dichloroethane-in-water emulsion and 99.98% for water-in-dichloroethane emulsion). Molecular dynamics based computational work and experimental studies revealed that the Janus channels of mixed sand layer exhibited greater interaction energy with emulsion droplets for more efficient adsorption, resulting in better demulsification capability and separation performance. The as-prepared Janus sand filters retained excellent separation performance after 50 cycles of the stability test. Together with the needs on only cheap and easily accessible raw materials and its environmentally friendly preparation method, this Janus sand filtration process exhibits its great potential for the separation of surfactant-stabilized oil/water emulsions.