A team of researchers from Shinshu University has developed a microplastic (PM) harvesting device based on non-recirculating sequential acoustic separation, which provides 105-fold PM enrichment, science news site EurekAlert reports April 15, citing the press service of the University.
The results of the study of the device’s performance are presented in the article “A device to collect microparticles of various sizes using four consecutive acoustic separations: work to prevent the release of microplastics”, published in the journal Separation and Purification Technology.
Microplastics (PM) are plastic debris particles less than 5mm in size, which have recently created a serious environmental problem on Earth. Microplastics come from sun-degraded plastic waste from landfills, synthetic fiber waste from laundromats, and cosmetic microspheres.
All of them adsorb and release harmful chemicals that pollute the environment. According to experts, by 2050, the volume of PM in the oceans may exceed the volume of fish. Therefore, the collection and disposal of PM from water are of crucial importance for the environment.
The traditional method for removing PM from water is filtration through screens. In this case, the filtered PM needs to be deleted manually, which requires a lot of work and time. At the same time, the screens are easily clogged, which requires frequent and quite expensive maintenance, and they also let through particles smaller than their holes.
To rule out these problems, a research team led by Professor Yoshitake Akiyama of the Department of Mechanical and Robotics Engineering, Department of Textile Science and Technology, Shinshu University, has developed a highly enriched microfluidic device for 10–200 µm MP.
The microfluidic device is a micrometer-sized channel system that uses acoustic focusing to collect MF. The acoustic device generates ultrasonic waves that transport the PM to the center of the fluid flow, enriching it, that is, increasing the amount of PM collected.
Currently existing microfluidic devices require multiple liquid recirculation for high PM enrichment. Therefore, Akiyama’s team developed a new design for such a device.
“The proposed microfluidic device, developed based on a hydraulic-electric analogy, has three 1.5mm-wide microchannels connected via four 0.7mm-wide triple connections in series. The MPs are aligned at the center of the mid-microchannel using a massive acoustic wave with a resonant frequency of 500 kHz. As a result, a 3.2-fold MF enrichment should occur at each junction, leading to an overall device enrichment of 105-fold.said Professor Akiyama.
Therefore, MPs are collected in the middle branch of the ternary junctions and the remaining fluid without MP is removed from other branches.
The scientists evaluated the performance of the MP collection device by measuring the overall collection rate of microparticles with a diameter of 5, 10, 15, 25, 50 and 200 microns. For all microparticles except 5 µm, which were too small for acoustic control, the collection level exceeded 90%.
The experiment showed that some plastic microparticles slow down and clog the walls of the device’s microchannels with the force of acoustic radiation, so the researchers decided to introduce prefiltration into the cleaning process and improve 2D ultrasound focusing.
“This proposed microfluidic device based on acoustic approach can efficiently, rapidly and continuously collect microparticles from 10 to 200 µm without recirculation after pre-filtering larger particles through a mesh. It can be installed in washing machines, factories and other sources of MF to effectively remove various sizes of MF from domestic and industrial wastewater. This will prevent the release of PM into the environment.”– Professor Akiyama gave a description of the new device.
Source: Rossa Primavera
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