Best of 2019: Extracting microplastic from water using magnets

Originally published on 11 August

Irish teenager Fionn Ferreira developed a method to remove microplastic from water using strong magnets.

Microplastics are plastic particles of less than 5mm in diameter. Large pieces of plastic all eventually break down into microplastic, posing a threat to marine life. Unfortunately, because of the small size, it is nearly impossible to filter it out.

Ferreira was inspired by an article written by Arden Warner, in which non-toxic iron oxide (magnetite) was used to clean up oil spills. Ferreira used this method to extract microplastics of the 10 most common types of plastic by adding oil to a suspension containing a known concentration of microplastics. The microplastics migrated into the layer of oil. Ferreira then added magnetite powder, which binds itself to the oil and plastic. The plastic/oil/magnetite mixture, now a ferrofluid (a liquid that becomes strongly magnetised in the presence of a magnetic field), could then be removed with strong magnets.

Ferreira estimated that he would be able to remove 85 per cent of microplastics using this method, a number that was confirmed in two different counting tests.

Ferreira later found that the use of oil does not increase the amount of particles captures, meaning that there is no need for using it.

“There is no doubt that the most effective way to reduce microplastic pollution in oceans is to use less plastics and ensure that plastics used can be recycled and separated to prevent them from entering our wastewater, but the reality is that more and more of the products we use contain plastics and potentially degrade into microplastics before entering our wastewater,” Ferreira says. “This project only forms the very beginning of this extraction idea which has never been conducted before. Further research needs to be carried out to investigate the efficacy of various grades of magnetite, different types of magnetic systems, methods for separating the waste and the design of a system that could be introduced into treatment centres.”

Ferreira’s project earned him first place in the Google Science Fair this year.