New technique removes microplastics from seawater
doi:10.1038/nindia.2021.73 Published online 18 May 2021
A microfiltration process shows promise in removing microplastics – plastic particles less than 5 millimetres in size – from contaminated seawater1.
The process, developed by a research team from the Indian Institute of Technology in Guwahati, could potentially be used just before pumping seawater into salt pans, allowing production of plastic-free edible salts.
Microplastics from seawater often make their way into edible salts, making the salts potentially harmful to human health.
To find a way to remove such microplastics, the IIT scientists, led by Kaustubha Mohanty and S. Senthilmurugan, first identified the presence of microplastics in 12 Indian edible salts. They then made synthetic seawater, by dissolving microplastic-laden edible salts in deionised water.
The team, which also included Naveenkumar A. Yaranal, passed the synthetic seawater through a hollow-fibre membrane filter that contained hundreds of tiny straw-like tubes. Numerous micropores on the tubes trapped microplastics inside, letting plastic-free seawater flow out.
The filter, they report, was able to remove almost 99 per cent of the microplastics present in the seawater, without reducing its salt content. The filtered seawater could then be used to make plastic-free edible salts.
The filtration technique is cheap and easy to install. It can operate under low water pressure without needing any power.
In a separate study, the researchers showed that the filter could also remove drug-based micropollutants from water.
1. Yaranal, A. N. et al. Identification, extraction of microplastics from edible salts and its removal from contaminated seawater. Environ. Tech. Innovat. 21, 101253 (2021)