Professor Tizazu Mekonnen’s research group has engineered a new method of capturing microplastics in water systems with 90 per cent efficiency. The approach is customizable, inexpensive, easy to produce, and uses no toxic ingredients, making it promising for commercial and residential use.
Microplastics are ubiquitous and found in every corner of the planet. The problem is so prevalent that microplastics are also found in our bodies. A study from the National Institute of Health found microplastics can even be found in breast milk and can come from unexpected sources like your laundry.
“Our clothes are mostly a mix of Polyethylene terephthalate (PETs) in the form of polyester and cotton or pure polyester. When you pull out the dryer filter, you can see how much fiber it captures. Those are all microplastics and that filter can capture only a portion of it,” says Mekonnen.
Due to the high-speed spinning washing machines release even more microplastics, sending them into wastewater systems.
Mekonnen utilized his chemical engineering expertise to design a gravity‑driven filtration column using 3D‑printed disk filters made from PLA, a biodegradable polymer to capture microplastics.
The research group which included MASc student Ethan Crawford, created a three-step process. First, the geometry of the 3D printed disk filters are designed with a one‑millimeter offset pattern, forcing water to go through the grid pattern, creating maximum contact between the filter and the flowing water, termed torture geometry.
Then they added water‑soluble polymer into the PLA before printing. After printing, this polymer is washed away, leaving behind nano‑ to microscale pores. These pores increase the surface area and create spaces where microplastics can lodge.
The third step is coating a thin layer of pressure sensitive adhesive that enhances capture without blocking the pores.
A cross-sectional drawing of the 3D printed filter design
“Then we stack them together forming layers of filters. We studied from 8 to 20 stacked filters together. Using 20 stacked filters, we removed 90 per cent of the microplastics which is very high compared to the incumbent technology, which can achieve 55 to 70 per cent,” says Mekonnen, a Canada Research Chair in Sustainable Multiphase Polymers.
Larger microplastics were captured almost completely, while particles smaller than ten micrometers were more difficult to trap. Figuring out how to trap that 10 per cent is the next step in this research.
This technology could potentially be integrated into household drinking water systems or industrial water treatment plants, since current methods like activated carbon are only partially effective at removing microplastics.
The study, 3D-printed, flow-through water filters for microplastic capture: The effect of surface porosity, column height, and pressure-sensitive adhesives on removal efficiency was recently published in the journal of Separation and Purification Technology.