Media New Atlas reported that the world’s oceans are now threatened not only by large chunks of plastic waste, but also by tiny “microplastic” particles, many of which come in the form of fibers that are dropped by synthetic fibers when washed. A new system uses sound waves to help capture these fibers from the source.
Because scientists have previously developed filters, this has helped filter microfibres from wastewater discharged from washing machines. Such filters usually have to be cleaned or replaced, but their holes do allow particularly small fibers to pass through.
Taking these limitations into account, researchers at Shinjuku University in Japan designed a so-called body sound wave (BAW) system. It starts with a central stream of plastic fiber-rich wastewater and is then diverted into three separate channels. In the upper reaches of the fork point, a sound wave is applied from either side of the central stream using a piezoelectric device, creating a stationed sound wave in the middle. The fibers gather within the wave and are then all taken away along the middle channel – clean, plastic-free water flows down the two side channels. This means that clean water can enter the sewer system, while large amounts of fiber water can be collected for processing (this is likely to involve evaporating water and then collecting fibers).
In laboratory tests, the BAW device was found to capture 95% of PET (polyphenyl ethylene) fiber and 99% nylon 6 fiber. However, the fiber separation process must be accelerated before the system can go into production, as it currently takes a long time to get out of the washing machine.
The paper on the study, led by Hiroshi Moriwaki and Professor Yoshitake Akiyama, was recently published in the journal Sensors and Actuators B: Chemical.