New Hydrogel Material Removes Microplastics From Water
Scientists have developed a new 3D hydrogel material that can adsorb – and degrade – large volumes of microplastic.
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Researchers have developed a new multi-layered hydrogel material that can effectively capture microplastics from contaminated water and break them down when exposed to ultraviolet (UV) light.
The new material is a more sustainable alternative to traditional membrane filters, the researchers say, as the hydrogel can be reused up to five times. It is also possible to upcycle the material into carbon nanomaterials once it is retired.
The material was developed by scientists at the Indian Institute of Science and has been described in a new paper published in Nanoscale.
Using multi-layered hydrogels for water treatment
Microplastics have spread to cover almost the entire globe – from polar ice caps to deep ocean trenches. This accumulation of microplastics in our environment is an issue that is currently the subject of much research by environmental scientists. Still, the full impacts of microplastic pollution on our health are not yet fully understood.
In an attempt to limit human microplastic exposure, many water treatment plants will try to filter out microplastics through coagulation and then pass the water through a membrane filter. While this removal strategy is effective at filtering out microplastics, the membranes themselves can easily become clogged or fouled by these tiny particles.
In search of a more sustainable way to remove microplastics from water, researchers at the Indian Institute of Science have been investigating the use of multi-layered hydrogels. Their newly unveiled hydrogel material consists of three unique polymer layers – chitosan (CS), polyvinyl alcohol (PVA) and polyaniline (PANI) – that are intertwined together to form an “interpenetrating polymer network” (IPN) architecture.
“PVA contributes to the hydrogel's mechanical strength, flexibility, and water retention capacity, attributed to its high hydrophilicity and biocompatibility,” the researchers wrote in the new Nanoscale paper. “Additionally, PVA provides abundant hydroxyl functional groups for cross-linking and hydrogel formation. Conversely, CS, derived from chitin, is another excellent candidate for hydrogel formation due to its biocompatibility, biodegradability, and antimicrobial properties.”
This IPN matrix was then infused with nanoclusters of copper substitute polyoxometalate (Cu-POM). These nanoclusters act as catalysts when exposed to UV light, promoting the photocatalytic degradation of any microplastics captured within the hydrogel structure.
Hydrogel removes more than 93% of microplastic
The team tested out their new hydrogel material by submerging it in water samples spiked with a pre-prepared microplastic powder and microplastic fragments generated by grinding waste food containers. To assist with analysis, the microplastic particles were stained with a fluorescent dye so that they could be detected through fluorescence spectroscopy.
Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) mapping were also used to assess the structure of the hydrogel and the adsorption of any microplastics.
“We checked the removal of microplastics at different pH levels of water, different temperatures, and different concentrations of microplastics,” said Soumi Dutta, first author of the study and a post-doctoral fellow in the Indian Institute of Science’s Department of Materials Engineering.
The hydrogel appeared to be very efficient at microplastic removal – removing between 93-95% of the two types of microplastic in the prepared water samples at a near-neutral pH.
Physical materials testing also demonstrated that the hydrogel was durable and remained stable across a wide range of temperatures.
Repeated testing showed that the hydrogel remained effective for microplastic capture and removal for up to five treatment cycles. Once the hydrogel was fully spent, the researchers were also able to upcycle the material via hydrothermal processing to form carbon quantum dots – a useful nanomaterial that can also be used to remove heavy metal contamination from water.
“We wanted to make a material that is more sustainable and can be used repetitively,” said research team leader Suryasarathi Bose, a professor of materials engineering at the Indian Institute of Science.
For now, this new hydrogel material has only been demonstrated at a small scale in the laboratory setting. But moving forward, the researchers say they are planning to develop a device using this material that can be deployed at much larger scales to help with industrial microplastic clean-up.
Reference: Dutta S, Misra A, Bose S. Polyoxometalate nanocluster-infused triple IPN hydrogels for excellent microplastic removal from contaminated water: detection, photodegradation, and upcycling. Nanoscale. 2024;16(10):5188-5205. doi: 10.1039/D3NR06115A
This article is a rework of a press release issued by the Indian Institute of Science. Material has been edited for length and content.
