Tiny Magnetic Coils Used to Remove Microplastics From Water

(CN) – A study released Wednesday in the scientific journal Matter offers a biotechnological strategy for purifying microplastics in water systems before the contaminants can enter bodies of water and threaten the health of marine and human life.

Researchers used “tiny coil-shaped carbon-based magnets” to convert microplastics in wastewater into nontoxic substances that can help algae, a source of biofuel, grow.

“The most interesting discovery in this research is that we find the degradation products can be used as the carbon sources for algae growth, which may provide a new opportunity for integration of this approach with biotechnology for purification and reutilization of plastic contaminants,” Shaobin Wang, University of Adelaide chemical engineering professor and senior author, said in an interview.

Less than one-fifth an inch in diameter, microplastics are tough to gather for industrial water treatment. They stay in water systems for decades, releasing pollution from the chemicals used in their manufacture – and more.

“In rivers and oceans, microplastics can be uptaken by the microorganisms and accumulated via the food net to eventually poison or harm the health of ocean animals in diverse ways,” Wang said. “Using this technique, we can effectively decompose the microplastics.”

Concerns over plastic pollution often focus on bags and bottles that find their way to oceans, but hard-to-see microplastics are being detected in sick and dead fish and seabirds.

Decomposition of the microplastics is a chain reaction in which their long molecules get broken into bits that dissolve in water. In this study, researchers laced carbon nanotubes with nitrogen to speed the process – and make it cleaner.

“Our research group has been working on nanocarbon materials for several years,” Wang said.

Like a cross between a spring and a honeycomb, a carbon nanotube maximizes the surface area where chemical reactions take place. By lacing the “springs” with nitrogen, researchers boosted the creation of reactive oxygen species.

And the magnetism? Researchers buried a bit of manganese below the surface of the springs as a way to stop leaching. The springs became magnets.

“Having magnetic nanotubes is particularly exciting,” said project co-leader Xiaoguang Duan in a statement, “because this makes it easy to collect them from real wastewater streams for repeated use in environmental remediation.”

Until now, reactive oxygen species usually have been produced with heavy metals, such as iron, which are not suited for use in a marine environment because they create their own pollution. The chance to bypass those issues, speed decomposition, and also feed algae, a source of biofuel, would be super green.

In this study, researchers concentrated on microplastics sent down drains from rinse-off cosmetics. In further study, they want to test others.

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