West Wake News

Researchers at North Carolina State University have demonstrated a new system that actively removes microplastics from water in a single cycle. The study, published in the journal Advanced Functional Materials, suggests this method could advance efforts to cleanse oceans and other bodies of water of tiny plastics that pose risks to human health and the environment.

"The idea behind this work is: Can we make the cleaning materials in the form of soft particles that self-disperse in water, capture microplastics as they sink, and then return to the surface with the captured microplastic contaminants?" said Orlin Velev, S. Frank and Doris Culberson Distinguished Professor of Chemical and Biomolecular Engineering at NC State and corresponding author of the paper.

The research utilizes soft dendritic colloids—hierarchically-branched particles known for their ability to adhere to surfaces—which can be crafted from various polymers. According to Velev and Ph.D. student Haeleen Hong, these particles' adhesive nature enables them to attract microplastics even in wet and salty environments like ocean water.

"The cleansing particles in this research are made from chitosan, a biodegradable polymer originating from chitin, which comes from processed shellfish waste," Velev explained. He noted that using environmentally safe materials derived from marine sources enhances sustainability.

These colloids take on a pellet shape when dried over a water-repellent surface. Upon entering water, they disperse to capture microplastics. Researchers add eugenol oil to part of each pellet as a dispersant.

"This oil makes the pellets move in the water by the so-called 'camphor boat effect,' decreasing the surface tension on one side of the pellet and driving it forward. This allows our microcleaners to spread out across a larger area, capturing microplastics as they move and descend," Hong stated.

To return to the surface, these microcleaners include magnesium particles that react with water to create bubbles. A gelatin coating delays this reaction, allowing more time for capturing microplastics before surfacing.

"As the gelatin dissolves, the magnesium generates bubbles and the microcleaners rise, bringing the captured plastics particles to the surface in a dense, scummy mixture," Hong added. The paper indicates these particles can collect microplastics for up to 30 minutes before being skimmed off once they reach the surface.

"Potentially, the collected scum can be bioprocessed into more chitosan, which can then be used to create more microcleaners in order to capture more microplastics," Velev mentioned. Further investigations are needed for scaling up this process.

Former NC State Ph.D. student Rachel Bang co-authored alongside current Ph.D. student Lucille Verster. The research received funding support from National Science Foundation grants EFMA-2029327, CMMI-2233399, and DMR-2243104.