Although we have seen a lot of materials designed to remove oil from water, many of them will soon become saturated and must be discarded. However, a new reusable membrane developed by scientists at Kobe University in Japan solves the problem by rejecting oil rather than simply absorbing it. The bottom of the membrane’s positive charge is made of tiny polyketone fibers. The substrate is very porous, making it easy for water to flow through.
On one side of the substrate, a negatively charged silicon dioxide coating is applied. The layer is only 10 nanometers thick and super-oily, which means it can repel oil. In addition, because it has the opposite charge to the substrate, they are pulled together through the electrostatic attraction process.
Once silicon dioxide is placed in upstream-facing flowing water, the membrane is reported to be able to repel 99.9% of the oil droplets, even if it is only 10 nanometers in diameter. Moreover, while oil does accumulate on the surface of the membrane (which can be collected for reuse or disposal), it is not actually absorbed by the material, so it can be removed quickly and easily.
In laboratory tests, a 1-square-meter film was able to treat 6,000 liters of oily sewage in less than an hour. In addition, the material shows resistance to a variety of acidic, alkaline, solvent and salt solutions.
Now researchers hope that once further developed, the technology could be used in applications such as the removal of offshore oil spills and wastewater treatment.
The paper on the study, led by Matsuyama Hideto and Professor Yoshioka Tomohisa, was recently published in the journal Journal of Materials Chemistry A.