Microplastics are receiving a lot of attention lately due to its difficulty in removal from the environment.
Sieves and filtrations are currently the predominant way to capture microplastics in water. However, this is impractical because filters clog easily and regularly need to be cleaned or replaced.
Another issue is that it has been impossible to collect anything smaller than 0.3mm, the size of the mesh plankton net pore diameter. This is unfortunate because the majority of microplastics causing havoc are smaller than that, with unknown effects on the eco and biosystems.
A promising new method to collect such microplastics has been devised using acoustics to gather them in water. A bulk acoustic wave (BAW) device was designed and fabricated that channels microplastics, gathering them in the middle channel while water flows out the two side channels. The idea for this study came about when Professor Hiroshi Moriwaki, specializing in environmental analysis at the Faculty of Textile Science and Technology at Shinshu University asked Associate Professor Yoshitake Akiyama, first author of the study (known for unique approaches to solving long standing problems *link to inkjet for cryopreservation*) if there was a way to tackle microplastics in water from an engineering standpoint.
The researchers focused in on the fact that one of the biggest sources of microplastics in our oceans are from laundry machines. A typical laundry machine discharges about ten thousand fibers per one 100 liter washing cycle. Many of our clothes are made of chemical fibers, and tiny pieces of microplastic fibers break off in the washing machine. Wastewater treatment plants are currently unable to capture microplastics.
The researchers decided to create a device that collects microplastics and microplastic fibers by piezo vibrations. By using acoustics at a force and amplitude appropriate for the length, diameter and compressibility of the microplastic, debris collects in the middle of a three channel device. The two channels on the side expels clean water while the microplastic fibers gather in the middle, having been acoustically focused utilizing the piezo element to create the acoustic standing wave. Different types of microplastics have different types of densities, bulk modulus and compressibility which makes for a different acoustic contrast factor (ACF). 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.
The researchers ran into trouble when preparing microplastics for the experiment. It was difficult to create microplastics of appropriate size. At first they tried to use a blender to chop up the fibers to the same length but the plastic fibers would not cut up. By asking colleagues in the Textile department the researchers found out about the Kanehara Pile manufacturer who kindly provided them with materials necessary for research.
For the experiment, a formula was devised to calculate the best acoustic focusing to target microplastic fibers Nylon 6, PET, and polystyrene microparticles. Collection rates were very high, 95% for PET and 99% for Nylon 6 when not accounting for minimal particles that stuck to the walls. The hydrodynamic force aligns the fibers so the BAW device avoids clogging. The particles were tracked using motion-analysis software. For future improvements, the surface of the microchannels could be produced by using methods to minimize roughness and discourage sticking.
Refinements needed for real world applications and scalability is to use multiple channels in serial and parallel with different diameters and force to capture all types of microplastics. By adding multiple channels (7 trifurcated, which means 3 to the power of 7) a 100 liters of laundry water can effortlessly be concentrated into 50mL, which would make it easy to throw away or burn. The study used concentrations of microplastic fibers of the maximum expected in real world applications.
Current limits to implementations are that the draining process would take a long time. With this study, PS beads 15?m in diameter were captured, and in theory, the minimum size of PS beads capable of being captured by this BAW device are 4.3?m. Smaller beads could be captured with modifications to the BAW device. Most microplastics in waste water has a diameter of 10?m and length of 2 to 200?m. The BAW device can successfully capture such microplastics. Further developments in acoustofluidics are needed to capture nanoplastics smaller than 100nm in diameter.
Go deeper with Bing News on:
- Steph Shep Is a Climate 'Activist' for the Kardashian Generationon March 31, 2020 at 5:00 pm
But, she says, there are ways to make laundry day less of an environmental burden, like using a Guppyfriend Washing Bag or a Cora Ball to capture said microplastics. I bought the Cora Ball. I was ...
- The Pirates of Puntland: Practical, Legal and Policy Issues in the Fight Against Somali Piracyon March 22, 2020 at 5:00 pm
New U.S. Military Orders and Government Policy in the Fight Against Somali Piracy Result in First Capture of Suspected Pirates by U.S. Forces Last month, for the first time since the U.S. Navy's ...
- Bandit safe among hills, reports sayon March 19, 2020 at 5:00 pm
EL PASO, TEXAS — Reported hemmed in among the canyons of the Guerrero mountains, Francisco Villa is believed to be surrounded today by several Carranzista columns and the American expedition ...
- DOE awards $84M for 18 carbon-capture projectson March 4, 2020 at 4:00 pm
What do you think about this particular story? Your feedback will go directly to Science X editors.
- Squirrels are now using plastic to build nests, shocking photos showon February 26, 2020 at 12:34 pm
Upon seeing the squirrel exhibit "odd" behavior of going through the plastic scraps it was carrying before scurrying off, Jacobs knew he had to capture ... 236,000 tons of microplastics, pieces ...
Go deeper with Google Headlines on:
Go deeper with Bing News on:
Microplastics in water
- Fast fashion speeding toward environmental disaster, report warnson April 7, 2020 at 8:00 am
Study highlights industry failures and calls for shift in consumer attitudes ...
- To Study a Problem That’s Everywhere, They’re Getting Creativeon April 6, 2020 at 4:16 pm
Dimitri Deheyn’s lab has become a hub of novel research on the microfibers found in our waterways and even the air we breathe.
- Everyone Needs This Emergency Water Filter at Homeon April 5, 2020 at 4:12 am
Those hollow fibers are only 0.2 microns in diameter, so contaminants like bacteria and protozoa, chemicals, or particulates like dirt and microplastics are unable to pass through. Hollow fibers ...
- Merino wool could be a solution for global microplastics problemon March 31, 2020 at 5:05 pm
New Delhi, March 31 (IANSlife) Merino wool does not contribute to the issue of microplastics in oceans, a new study has revealed ... In this latest study, researchers compared the biodegradability of ...
- Seven Simple Ways To Reduce Your Plastic Footprint (And Why You Should Care)on March 30, 2020 at 5:57 pm
Plastic pollution is a very real and burgeoning threat to our health and environment. Here's how you can cut down your increasing reliance on plastic, according to zero-waste experts.