26 Jun Removing the Needle from a Haystack: A Magnet for PFAS Removal

Nebojša Ilić (ESR13)

Hello again! In my previous blog post, I introduced you to a family of chemicals (PFAS) that have been around since the 1960s and proven to be harmful in the late 1990s. These “forever chemicals” have been accumulating in the water bodies all around us continuously for decades. They are resistant to biodegradation and slip through most conventional water treatment technologies and eventually end up in our glass of water. Even though the concentrations vary from country to country, we can say with certainty that they are present absolutely everywhere.

So how do you conceptualize a solution to remove these chemicals from water sources if they are so resistant?

Well, nature functions in an elegant and unaggressive manner. The world around us is alive thanks to a lot of different chemical reactions that together make up a complex network. A network where each member of the ecosystem has a specific role to play. This is why man-made materials are sometimes not “recognizable” by nature. There has simply not been enough time to adapt. Fun fact: it took 60 million years for bacteria to start degrading trees!

PFAS, due to their chemical nature, fall under the category of these resistant compounds. There have been recent developments in getting nature to clean up our mess. We are still a long way from applicable solutions though.

That’s why if we want to remove PFAS from water, we should start by considering the following:

1. Almost no compound is immune to high temperatures;

2. Every chemical has properties that we can use to our advantage.

With this in mind, I have set out on two different paths to try and design a system for PFAS removal.

The first approach uses ultrasound in a very crafty manner, and has been one of the more promising treatment methods in the last years.

The ultrasound creates very tiny bubbles in water due to pressure differences that the sound waves create. These bubbles eventually collapse and form very high temperatures in many small areas of water. They are so tiny that even though the temperatures at these collapse sites achieve up to 3500°C, the water itself is just a few degrees warmer at the end of the treatment than it was at the beginning.

The advantages of using this method are that it is a straightforward process and requires no chemicals or specific materials. The drawback is a very high energy consumption when running this process. Therefore, if we aim for a practical application in the future, we need to make it more efficient and price-competitive. We are trying to achieve this both through reactor design and through process optimization by looking in-depth into the mechanism behind the process.

The second path involves the use of a fascinating nanomaterial.

Based on previous experience and theoretical modelling, we are trying to come up with a new “version” of an exciting (nano)material (called MOF) that has been in the focus of chemists in the last years.

So why this material?

Due to how this nanomaterial is made, we can adjust its properties to work in our favor. Ideally, we want it to be resistant to water and incredibly stable. That way we can use it for a long time unlike commonly used materials which are replaced often.

By modifying the material properties, we can also achieve selective removal of PFAS from water. This is done by changing the chemical structure of the material’s surface to match the features of the chemical we want to remove.

This removal process is called adsorption, and the best part is – it occurs spontaneously without any need for energy! Plus, it allows us to remove contaminants at super low concentrations, which is for PFAS extremely relevant. You probably know the basics of how this process works from Barbara’s post about parking antibiotics in zeolites.

In other words, we are taking a big magnet with us to use in the search for the needle in our haystack.

The fight against PFAS is certainly not an easy task. Regardless, my goal is to dedicate time and energy into pursuing these two research directions that show a lot of promise. I am excited to work on a project that is a true representation of the possibilities how research can improve the world around us.