High Separation Flux Research Articles

Efficient separation of viscous emulsion through amphiprotic collagen nanofibers-based membrane

Separating viscous emulsions remains a critical challenge since the existing porous sieving membranes suffer from severe pore blocking caused by low liquidity of viscous emulsion. We here develop amphiprotic millimeter-scale collagen nanofibers-based (MCN) membrane for efficient separation of viscous emulsions. The MCN membrane features a free-standing 3D network of self-assembled millimeter-scale collagen nanofibers, which enables capillary effect-induced efficient liquid transport, allowing the separation of viscous emulsion to proceed at a low pressure of 0.3 bar. The MCN membrane enables successful separation of a variety of viscous emulsions (77.3–200.0 mPa•s), which are unable to separate by commercial single-sided poly tetra fluoroethylene (PTFE) and single-sided polyvinylidene fluoride (PVDF) sieving membranes. High separation flux (1582 L m−2 h−1 bar−1) and separation efficiency (99.97%) are simultaneously achieved. The MCN membrane also shows good anti-fouling properties and recycling capability.

Bi-functional composite foam with hierarchical structure for efficient separation of emulsified mixtures consisting of oil and water

Seeking of novel materials with special wettability is highly demanded for efficient separation of emulsified mixtures. In this study, carbonized melamine foam modified with cobalt hydroxide nanosheets was fabricated by a two-step route consisting of thermal pyrolysis and controlled chemical precipitation. The developed material exhibited a superamphiphilicity in air, and a controlled superoleophobic or superhydrophobic performance in various liquid conditions. By utilizing these properties, the composite foam was used as a bi-functional material to separate various oil-water emulsions. The results demonstrated that the developed material, solely using gravity without external stimulus, had the capability to separate not only the surfactant-stabilized oil-in-water emulsions with a high separation flux, but also the water-in-oil ones with remarkable oil purity. The facile method for the material preparation, high separation merit and excellent anti-fouling property of material provided a new candidate for the separation of emulsion systems.

An underwater superoleophobic nanofibrous cellulosic membrane for oil/water separation with high separation flux and high chemical stability.

Oil spills and an increasing demand for the treatment of industrial oily wastewater are driving the need for continuous large-scale oil/water separation processes. Herein, we report a nanofibrous cellulosic membrane (NFC membrane) for the continuous high-flux separation of large amounts of oil/water mixtures. The NFC membrane was fabricated using wet electrospinning, a facile yet effective method for stacking nanofibrous membranes with uniform porous structures on a substrate. Owing to its cellulosic nature, the membrane showed excellent underwater superoleophobicity along with robust chemical stability and was able to separate oil/water mixtures at efficiencies exceeding 99%. Repetitive oil/water separations could be performed using a single membrane, during which the oil content in the filtrate remained extremely low (<29 ppm). The nanofibrous membrane exhibited a fine porous structure that was interconnected throughout the membrane, resulting in a high oil intrusion pressure (>30 kPa) that allowed not only gravity-driven but also pressure-driven separation of oil/water mixtures. The separation flux reached 120 000 L m-2 h-1 during pressure-driven separations, which is a very promising feature for actual applications such as the large-scale treatment of industrial oily wastewater.