Researchers in Australia have developed a technique for removing microplastics from water sources using carbon nanosprings.
Microplastics are defined as tiny pieces of plastic debris that measure less than 5mm across. These microplastics originate from everyday consumer products such as clothes and facial cleansers and can have a radical effect on the environment and on human health.
In 2018, the WHO launched a health review after discovering microplastics in 90% of bottled water. The Guardian reported that “an analysis of 259 bottles from 19 locations in nine countries across 11 different brands found an average of 325 plastic particles for every litre of water being sold. In one bottle of Nestlé Pure Life, concentrations were as high as 10,000 plastic pieces per litre of water.”
Microplastics were also found in high concentrations in tap water and natural water sources. A study in the journal Groundwater showed that microplastics were found in limestone aquifers. About 25% of the global drinking water supply comes from these aquifers.
Many of the microplastics that aren’t directly ingested end up in the ocean where they contaminate marine life. As these animals are consumed, the hazardous waste moves back up the food chain.
The New Study
Researchers Xiaoguang Duan and Shaobin Wang from the University of Adelaide and Curtin University respectively, are tackling the problem of microplastic contamination using reactive oxygen species (ROS). The researchers produce ROS using manganese carbine nanocomposites, carbon nanotubes, and nitrogen.
A report by Physics World described the process. Tests are run on solutions containing microplastics using “ROS manganese carbide nanocomposites encapsulated in helical-shaped carbon nanotubes doped with nitrogen.” The tests include solutions containing microplastic beads from a facial cleanser.
The carbon nanotubes break down the molecules in the microplastics which enables the ROS to break down the sub-polymers into short chains. The resulting by-product is harmless and can dissolve in water.
The results of the study showed a significant reduction in microplastic contaminants. The ROS catalysts also contain manganese, making them magnetic. This means they can be separated from the treated solutions and recycled over and over.
Ecological Impact
The researchers also conducted tests on the by-products produced from the microplastic degradation. Their discoveries showed that not only were the resultant intermediates non-toxic, but they also enabled the growth of algae. The researchers tested the solutions to see how the algae (Chlorella vulgaris) fared and observed an increase in the density of the algae compared to the control test in pure water.
Xiaoguang Duan told Physics World: ‘the organic intermediates from microplastics might be digested by microorganisms to be transformed to other valuable products (such as sugars, proteins, and biofuels), so returning the carbons to nature.’
As the research continues, both Duan and Wang plan to develop more advanced strategies that can degrade different plastic types from solutions collected from rivers, oceans and sediment.
