Eliminate microplastics

Eliminate microplastics
Eliminate microplastics

Microplastics, tiny and difficult-to-degrade fragments of textile fibers, water bottles and other synthetic products, have found their way into the air, water and soil around the world. Now, new research published in ACS Applied Materials & Interfaces has shown a way to induce their decomposition, at least in water, using even smaller microrobots. When added to water along with hydrogen peroxide, these bacteria-sized devices attach to microplastic particles and begin to break them down.

The microrobots in question are metallic, have the shape of a four-pointed star and are covered with magnetic particles. Exposure to visible light causes its electrons to absorb energy and react with water and hydrogen peroxide in a process called photocatalysis. As a result, the robots move. “They cover a much larger area than could be covered with a static technique,” explains Martin Pumera, a researcher at the Prague University of Chemistry and Technology and co-author of the study. When the microrobots attach themselves to the plastic, photocatalysis also produces charged molecules that break the chemical bonds of the plastic molecules, similar to how a jeweler cuts the links of a bracelet.

The researchers tested the microrobots with four types of plastic. Within a week, all four had begun to degrade, losing between 0.5 and 3 percent of their mass. In another experiment, microrobots propelled themselves through a small channel. A tiny magnet was used to collect the devices, which dragged up to 70 percent of the microplastic particles with them.

Pumera plans to release future versions of the robots into the sea to attach to microplastics, then retrieve the devices for reuse. However, according to Win Cowger, a plastics pollution expert at the University of California, Riverside who was not involved in the study, such devices are likely only to be useful in closed systems, such as those used to treat drinking water or sewage. The expert points out that current robots can adhere to substances other than plastic, and that it may not be safe to release large amounts of them into the water. To solve both problems, Pumera’s team is testing microrobots made from other materials, which could also work without hydrogen peroxide.

“The work is undoubtedly very interesting, but more research is needed to make it a truly viable, attractive technique capable of dealing with the enormous scale of the problem,” say Peter Edwards and Sergio González-Cortés, chemists at the University of Oxford outside the study. In the past, both researchers have proposed using microwave radiation to break down plastic waste. For now, Cowger concludes, “the best way to remove microplastics from the environment is to prevent them from getting there.

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