Plants used to filter microplastics out of water

Could plants be the answer to the looming threat of microplastic pollution? Scientists at The University of British Columbia’s (UBC) BioProducts Institute have found that if you add tannins — natural plant compounds that make your mouth pucker if you bite into an unripe fruit — to a layer of wood dust, you can create a filter that traps virtually all microplastic particles present in water.

Microplastics are tiny pieces of plastic debris resulting from the breakdown of consumer products and industrial waste. Keeping them out of water supplies is a huge challenge, according to Dr Orlando Rojas, the institute’s scientific director, who noted one study which found that virtually all tap water is contaminated by microplastics.

“Most solutions proposed so far are costly or difficult to scale up,” Rojas said. “We’re proposing a solution that could potentially be scaled down for home use or scaled up for municipal treatment systems. Our filter, unlike plastic filters, does not contribute to further pollution as it uses renewable and biodegradable materials: tannic acids from plants, bark, wood and leaves, and wood sawdust — a forestry by-product that is both widely available and renewable.”

For their study, published in the journal Advanced Materials, scientists at the BioProducts Institute and their collaborators analysed microparticles released from popular tea bags made of polypropylene. They found that their method, dubbed ‘bioCap’, trapped from 95.2% to as much as 99.9% of plastic particles in a column of water, depending on plastic type. When tested in mouse models, the process was found to prevent the accumulation of microplastics in the organs.

Rojas noted that it is difficult to capture all the different kinds of microplastics in a solution, as they come in different sizes, shapes and electrical charges. “There are microfibres from clothing, microbeads from cleansers and soaps, and foams and pellets from utensils, containers and packaging,” he said. “By taking advantage of the different molecular interactions around tannic acids, our bioCap solution was able to remove virtually all of these different microplastic types.

While the experiment remains a lab set-up at this stage, the team is convinced that the solution can be scaled up easily and inexpensively once they find the right industry partner. Rojas concluded, “We’re thrilled that the BioProducts Institute’s multidisciplinary collaboration has brought us closer to a sustainable approach to combat the challenges posed by these plastic particles.”

Image caption: UBC postdoctoral researcher Dr Tianyu Guo is part of a team that developed a wood dust-based filter for removing microplastics from water. Image credit: UBC Forestry/Jillian van der Geest.