Researchers Filter Microplastics From Water Using Acoustics

Microplastics caused by washing machines are hard to remove from the ocean.
Donna Fuscaldo

Microplastics are the scrouge of environmentalists and scientists because of how hard they are to be removed from the environment.

The leading ways have limitations that prevent them from being effective on a mass scale. But researchers at Shinshu University devised a new method that gathers microplastics in water using acoustics. 


Laundry machine microplastics aplenty in oceans

The research was spurred on when Professor Hiroshi Moriwaki from Shinshu University's Faculty of Textile Science and Technology wanted to know if there was a way to get microplastics out of the water applying engineering principles. Associate Professor Yoshitake Akiyama teamed up with Moriwaki to devise a way.

Focusing on the huge amount of microplastics in the ocean caused by laundry machines, the researcher created a device that collects microplastic and microplastics fibers by using piezo vibrations.

The researchers chose to focus on washing machine microplastics because laundry machines discharge around ten thousand fibers per one 100 liter washing cycle, according to the scientists. Add the chemical fibers the clothes are made of in the mix and small pieces of microplastic fibers come off in the washing machine. According to the researchers its impossible to capture and filter out the microplastics which is why they're focused there. 

Based on the length, diameter, and compressibility of the microplastic, the scientists used acoustics as a force to push the debris to the center of the three-channel device. Two side channels push out clean water while the microplastic fibers were pushed into the middle. The scientists used the piezo element to create an acoustic wave. 

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More channels needed for it to work in the real world 

"Different types of microplastics have different types of densities, bulk modulus, and compressibility which makes for a different acoustic contrast factor (ACF)," the researchers explained in a release highlighting the work. "By choosing the width of the microchannel to be half of the wavelength in water, the particles are encouraged to gather in the middle of the tube. It took about 0.7 seconds for the particles to be focused in this way."

In order for this method to be used in real-world applications the researchers said multiple channels in serial and parallel with different diameters need to be added to capture all the different microplastics found in water. 

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