Micro- and nanoplastics are found everywhere: in soil, water and air. Previously, researchers proposed many original options for removing these ubiquitous particles, but recently it turned out that people have been using one effective method for purifying drinking water from them since ancient times.
Experts in the field of biomedical engineering and the study of microplastics from Guangzhou Medical University and Jinan University (both in China) spoke about a long-familiar solution. Their experiment showed that boiling water with a high calcium content (also called hard water) removed more than 80 percent of microplastics from it.
For the study, published in the journal Environmental Science & Technology Letters, samples of tap water of varying hardness were taken in the Chinese city of Guangzhou. They added three types of plastic particles – polystyrene, polyethylene and polypropylene – ranging in size from 0.1 to 150 micrometers. Then the samples were boiled for five minutes, and then cooled and the content of plastic particles in the water was measured.
The fact is that during boiling in hard water saturated with minerals, insoluble calcium carbonate CaCO3 appears, in other words, scale. The researchers suggested that it could bind plastic particles and precipitate with them.
This is what happened in the experiment. The cleaning effect was most pronounced in samples with increased hardness, containing 300 milligrams of CaCO3 per liter. Boiling allowed to remove up to 90 percent of microplastic particles in the water. In soft water (less than 60 milligrams of CaCO3 per liter), boiling removed 25 percent of the added microplastics.
Thus, the researchers demonstrated that the task of purifying drinking water from microplastics is solved not only with the help of expensive modern filtration systems, but also with such a simple and time-tested method as boiling, which also provides disinfection.