New liquids can safely extract nanoplastics from water

US researchers have made substances that can extract nanoplastics from water.

The solvents, made from non-toxic components, could remove 98% of the tiny plastic particles from water in a lab environment.

The team has published its research in ACS Applied Engineering Materials.

 “Our strategy uses a small amount of designer solvent to absorb plastic particles from a large volume of water,” says corresponding author Gary Baker, an associate professor at the department of chemistry in the University of Missouri-Columbia.

The researchers tested 10 different solutions, each mixtures of “hydrophobic” materials – that is, substances which don’t mix with water, like oil.

All of these solvents were “eutectic”: when mixed together, they had lower melting points, meaning mixtures were more likely to be liquid at room temperature than pure samples.

Because plastics are made from hydrocarbons and are also hydrophobic materials, they are attracted to the solvents.

The researchers could mix their solvents with water, then allow the solvents to separate out and float to the surface. Then, they could use a pipette to remove them entirely from the water.

The researchers found that 3 of the mixtures worked most effectively: 2 were mixtures of a fatty acid called decanoic acid, and salts made from ammonium hydrocarbons and bromide, while the third was a mixture of menthol and a thyme extract called thymol.

“These solvents are made from safe, non-toxic components, and their ability to repel water prevents additional contamination of water sources, making them a highly sustainable solution,” says lead author Dr Piyuni Ishtaweera, who recently earned her doctorate at the University of Missouri-Columbia.

In the lab, the researchers tested their solvents on pieces of polystyrene sized from 100 nanometres to 1 micrometre, which is the upper bound on nanoplastic size.

The team is now interested in finding ways to scale the process up and eventually test it in lakes and oceans.

“Currently, the capacity of these solvents is not well understood,” says Baker.

“In future work, we aim to determine the maximum capacity of the solvent. Additionally, we will explore methods to recycle the solvents, enabling their reuse multiple times if necessary.”