This surprising technology could remove microplastics from drinking water

The future of water filtration technology sounds bright.

Microplastics detected.

Microplastics are everywhere, in water, soil, and even in our own bodies, and researchers are still unsure how they affect our health. Worse yet, microplastics are incredibly difficult to get rid of. But recently, scientists have come up with a new solution from a surprising source—sound.

A team of researchers has developed a new method for cleaning microplastics from water using high-frequency sound waves. Unlike previous ultrasonic filtration techniques, their method can theoretically remove both large and small microplastic particles in a unique two-step process, making plastic-contaminated water safe to drink. The results were presented today at a meeting of the American Chemical Society.

Microplastics are defined as any plastic debris smaller than 5 millimeters in diameter. They often come from larger pieces of trash, like water bottles, Styrofoam cups, or even acrylic paint, as they break down in the environment. For years, no one paid much attention to these tiny pieces of plastic. But in 2004, a landmark study by marine ecologist Richard Thompson documented their presence on 17 different beaches. Since then, they’ve turned up everywhere researchers have looked: in soil, in the ocean, and even in our bodies. “[Scientists] have found microplastics in human blood samples,” says Menake Piyasena, an analytical chemist at New Mexico Tech and co-author of the study. “So this is going to have a huge impact in the future.”

Scientists still don’t have a clear picture of what all that plastic means for human health, but it’s probably not good. Microplastics have been linked to everything from inflammation to fertility problems to cancer, although it’s still unclear how the tiny polymer fragments might cause these conditions. But that said, since 2019, microplastics have been deemed a major concern (and a potential public health emergency) by the World Health Organization.

Currently, most microplastics removed from water are captured using filters. But these devices tend to clog; they need to be removed, cleaned, or replaced regularly, which can quickly become costly on a large scale. Piyasena and his lab wanted to find a way to remove microplastics without filters. And they found one: ultrasound.

The new water washing technology is based on a technique that Piyasena calls “acoustic focusing.”

“That means using sound waves to concentrate or condense particles within a certain perimeter,” Piyasena says. In this case, it’s helpful to think of sound not as soft music or a conversation, but as waves of force at ultrasonic frequencies, above the range of human hearing. When applied inside a confined area, like a steel pipe, these waves push small particles together—think of the way a speaker might bounce around grains of sand on a beach.

Piyasena’s team isn’t the first to use ultrasound to remove plastic waste from water. Last year, a group of researchers based in Indonesia tested an “sonic scrubber” that was able to remove up to 95% of tiny microplastic particles from freshwater samples (the system proved much less effective in saltwater). Unlike Piyasena’s study, however, this group only tested plastic fragments smaller than 180 micrometers wide. They assumed that larger pieces would behave in a similar way—but Piyasena and his co-authors found that this wasn’t necessarily the case.

“The larger [the plastic] is, the more likely it is to concentrate in some ways,” Piyasena said. When suspended in pure freshwater, all sizes of microplastics agglomerated in the middle of the tube as the researchers increased the ultrasound volume, allowing clean water to flow out of the side tubes. But when they added detergent or fabric softener to the water, larger microplastics (between 180 and 300 micrometers in diameter) began to agglomerate on the sides of the channel. In this case, the water in the middle tube remained clean, while the sides remained contaminated with plastic.

To ensure that all sizes of plastic were removed, the team developed a two-step water purification cycle that first removed microplastics, then slightly larger plastics. This way, they were able to remove 82 percent of the larger particles and more than 70 percent of the smaller ones.

But before they can deploy the system in the real world, the researchers will need to do some more testing. For example, “we only tested it in one water source,” Piyasena says. But the concentration of salt or other dissolved minerals can affect the density of the water, which changes how the microplastics flow through it. If they want to effectively clean up all different densities of water, the team will need to be able to predict how the microplastics will react.

Source: https://baoquocte.vn/cong-nghe-dang-ngac-nhien-nay-co-the-loai-bo-vi-nhua-khoi-nuoc-uong-284522.html