GoKawiilHumanity has littered the sky with the refuse of fossil fuel use, releasing enough CO 2 to change the planet’s climate. We are also chucking incredible sums of carbon in the form of plastics into landfills and into the environment around (and inside of) us. What if cleaning up one of these problems could also help clean up the other?
A new study led by Ruth Ebenbauer at Aarhus University experiments with this idea by upcycling discarded polystyrene into (part of) a material commonly used in carbon-capture systems.
Adding amines
This material is based on amines—a simple chemical group that conveniently acts like a sponge for CO 2 . An amine will grab CO 2 molecules when exposed to them, but let go of the CO 2 when heated or depressurized, leaving it ready to go again. The first “CO 2 scrubbers” tried in smokestacks used amines dissolved in water to do this, but solid amines are used in all kinds of carbon-capture systems now because they require less energy. These solid materials—often made into granules similar to the activated carbon in a water filter—have high surface area and high porosity, so the amines can efficiently partner up with CO 2 molecules.
Currently, these materials are all derived from fossil fuels. There are two components: the amine groups themselves, and something else that provides a structure for them to sit within. The research team’s idea was that polystyrene could be a great fit for that structural component. Polystyrene has been used for Styrofoam and for solid items like eating utensils or the clear portion of a CD case. Less than 1 percent of it is recycled in the US, while Europe manages a slightly less awful 10 percent.
The upcycling process has two chemical steps. The first attaches bromine atoms to aromatic rings in the polystyrene, using gold as a catalyst. The second step introduces a two-carbon form of amine (a common ingredient in a wide array of products) and a copper catalyst, which swaps amine groups in where the bromine atoms were.