Want fewer microplastics in your tap water? Try boiling it first

February 29, 2024

Contamination of water supplies with nano- and microplastics (NMPs), which can be as small as one thousandth of a millimeter in diameter or as large as 5 millimeters, has become increasingly common. Zhanjun Li, Eddy Zeng and colleagues wanted to see whether boiling could be an effective method to help remove NMPs from both hard and soft tap water. 
The researchers collected samples of hard tap water from Guangzhou, China, and spiked them with different amounts of NMPs. Samples were boiled for five minutes and allowed to cool. Then, the team measured the free-floating plastic content. Boiling hard water, which is rich in minerals, will naturally form a chalky substance known as limescale, or calcium carbonate (CaCO3). Results from these experiments indicated that as the water temperature increased, CaCO3 formed incrustants, or crystalline structures, which encapsulated the plastic particles. Zeng says that over time, these incrustants would build up like typical limescale, at which point they could be scrubbed away to remove the NMPs. 
In the tests, the encapsulation effect was more pronounced in harder water — in a sample containing 300 milligrams of CaCO3 per liter of water, up to 90% of free-floating MNPs were removed after boiling. However, even in soft water samples (less than 60 milligrams CaCO3 per liter), boiling still removed around 25% of NMPs. The researchers say that this work could provide a simple, yet effective, method to reduce NMP consumption.

From: EurekAlert!