Scientists at the Indian Institute of Science (IISc) have developed an eco-friendly hydrogel to remove microplastics, a new global pollutant, from water.
These small pieces of plastic waste can enter our bodies through drinking water and increase the risk of disease. They also pose a threat to the environment, occurring even in remote areas such as polar ice caps and deep ocean trenches, and posing a threat to aquatic and terrestrial life.
On the seabed alone, the amount of microplastics has tripled in the last two decades, says a team of researchers from the Institute of Environmental Science and Technology at the Autonomous University of Barcelona (ICTA-UAB) and the Department of Built Environment at Aalborg University.
This is how hydrogel works
This material has a unique interlocking polymer network that can bind pollutants and decompose them under the influence of ultraviolet rays. The research was published in the journal Nanoscale.
Scientists have already tried to remove microplastics using membrane filters. However, the membranes can become clogged with these small particles and thus become unstable. Instead, the IISc team led by Suryasarathy Bose, professor in the Department of Materials Science and Engineering, chose 3D hydrogels.
The new hydrogel developed by the research team consists of three different polymer layers (chitosan, polyvinyl alcohol and polyaniline) interwoven into an interpenetrating polymer network (IPN) structure.
The team filled this array with nanoclusters made of a material called copper-substituted polyoxometalate (Cu-POM).
These nanoclusters are catalysts that can break down microplastics using ultraviolet light.
The combination of polymers and nanoclusters created a long-lasting hydrogel capable of adsorbing and breaking down large amounts of microplastics.
Laboratory tests
Most microplastics are created through incomplete breakdown of household plastics and fibers. To simulate this in the lab, the team cut lids from food containers and other everyday plastic products to create the two most common types of microplastics found in nature: polyvinyl chloride and polypropylene.
“In addition to cleaning or eliminating microplastics, their detection is another important topic. Since these are very small particles, they cannot be seen with the naked eye.“, explains Sumi Dutta, lead author of the study and SERB National Postdoctoral Fellow at the Department of Materials Science and Engineering, in a statement.
To solve this problem, the researchers added fluorescent dyes to the microplastics to monitor how much the hydrogel absorbed and degraded under different conditions. “We test microplastic removal at different water pH values, different temperatures and different microplastic concentrations“explains Dutta.
The hydrogel proved to be very effective as it was able to remove about 95% and 93% of two different types of microplastics from the water at a near-neutral pH (around 6.5). The team also conducted several experiments to test the strength and durability of the material. They found that the combination of three polymers provided stability at different temperatures.
Hydrogel, an ecological and reusable material
“We wanted to create a material that was more ecological and reusable“explains Bose. The hydrogel can withstand up to five microplastic removal cycles without any significant loss of effectiveness.
Additionally, Bose points out that once the hydrogel is deactivated, it can be reused as carbon nanomaterials that can remove heavy metals such as hexavalent chromium from contaminated water.
In the future, the researchers and colleagues want to develop a device that can be used to remove microplastics from various water sources on a large scale.
With information from: https://www.iagua.es/
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