Turning Pollution into Power: Microplastics become Batteries

TLDR: Microplastics are turned into battery materials using a wastewater treatment process and heat

The length of my posts has gotten away from me in recent weeks. My goal is for you to be able to open my email, read the content in a few minutes, and understand a cutting-edge piece of science.

That works best with shorter pieces. From now on, I’m going to aim for posts you can get through and understand in ~5 minutes. I’d love to hear your thoughts on post length/detail: if you have any, put them in this survey.

Microplastics contaminate everything around you, including your drinking water and the rain. They’re a large problem that won’t go away on their own.

Today’s authors figured out how to remove microplastics from water and turn them into a functional battery part. This is a great example of upcycling, or turning waste into a new product.

Plastic waste is a big environmental problem. We’ve all heard it, but recently it’s been highlighted even more due to the discovery of microplastics.

Over time, plastic pieces break down into smaller bits that are a lot harder to purify. These pieces get into our air, drinking water (looking at you plastic water bottles), and even our rain. When these pieces get small enough they’re called microplastics.

Microplastics are everywhere.

They’re a problem we can’t avoid. So, we have to figure out ways to remove them from the environment and our drinking supply. Ideally, we do this while turning them into something useful.

This is exactly the problem this week’s authors addressed. They separated out microplastics from water using iron ions. Then, they processed the iron-microplastic particles into coated iron nanoparticles to use in a battery.

They used a wastewater treatment process called electrocoagulation to separate the microplastics. In electrocoagulation, electric currents suspend iron ions in a water solution containing microplastics.

These iron ions then attach to the microplastics and cause the microplastics to lose their charge. Without a charge keeping them apart, the microplastic pieces all clump together.

Once the charge on the microplastics is gone, they bunch together into larger pieces. These large pieces still have iron particles attached to them. This is convenient since iron is strongly magnetic. With the iron attached, the microplastics can be simply pulled out of the water using a magnet.

After they’re separated with the magnet, the iron-coated microplastics are processed into useable battery components.

Heating the iron-coated microparticles at 500ºC caused the plastic portions to degrade. The left-over plastic formed a carbon shell around the iron nanoparticles, highlighted in red below.

People have tried similar iron-based particles as anodes in batteries before with little success. The biggest two problems were:

1. The iron particles changed size as the battery charged/discharged leading to a short battery lifetime.

2. The particles just weren’t that conductive.

Introducing the carbon shell from the microplastics fixed both of these issues.

The shell served as a restraint on the particle size. With the shell, the particles couldn’t get much larger. The shell also improves the contact between the iron particles and the other battery components, increasing their conductivity into a useful range.

This paper hits 2 birds with 1 stone: microplastic purification and new battery tech.

They use a common wastewater treatment process to purify microplastics from water. Then they take the resulting particles and turn them into useful battery materials. This way, they’re taking harmful waste and transforming it into a valuable material.

See you next week for more science,

Neil

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