Blog Post 2: Every Answer Leads to More Questions

Hello Iron Oxide connoisseur!

At this point, you’re probably wondering how this fancy rust will help me clean microplastics from water. Still sounds pretty crazy, huh?

This week we’ll be doing a Proof of Concept.

The following process was developed by Fionn Ferreira, the winner of the 2019 Google Science Fair. Through my Senior Project, we will be adapting his scientific method into a prototype that can be used to automate the process.

Here’s the basic idea:

1. Given a solution of microplastics and water, add a drop of oil (vegetable oil preferred) and mix thoroughly.
2. Since both oil and most microplastics are hydrophobic while the water is hydrophilic, the microplastics will clump within the oil (“like mixes with like”).
3. To collect the oil, mix in an equal volume of magnetite to the solution. The magnetite will become suspended within the oil, creating a weak ferrofluid within the water.
4. Use a magnet to collect the ferrofluid from the water. Several passes may be needed, depending on the strength of the magnet.

Take a look here for a video demonstration of the process.

Crazy still?

Although the current process visibly reduces the cloudiness of the water by removing the microplastics, I still have so many questions! What is the optimal ratio of magnetite to oil in the ferrofluid? Does the order of steps matter? Can I combine the oil and magnetite beforehand while still preserving the method’s effectiveness at cleaning up microplastics? Can I recycle the spent ferrofluid? How long does the cleaning process take? Can I make it faster? And the biggest question of all: How will I automate this?

I’m still refining my understanding of using magnetite and oil for microplastic removal. This week, I’ve narrowed my reading down from general textbooks to recent research papers and literature reviews. Some of my questions are being answered (use a 1:1 ratio between magnetite and oil in the ferrofluid by volume for a 97% collection rate!); others won’t be until I get my hands on the supplies I’ve ordered for my upcoming prototype.

If you come back next week, we’ll be moving on to planning and prototyping–join me for Hack-A-Blender!

See you then!