Okra, fenugreek extracts remove most microplastics from water, study shows

Researchers at Tarleton State University in Texas have found that substances behind the slimy strings from okra and the gel from fenugreek seeds trap microplastics better than a commonly used synthetic polymer.

It’s fair to say that both okra and fenugreek are among the more exotic foodstuffs in the world. Okra is a flowering plant in the mallow family native to East Africa that’s used in the cuisines of many countries; fenugreek seeds, also known as methi seeds, are small, brown seeds from the fenugreek plant, which is part of the legume family. Beyond that, the two substances have never had anything in common – until now.

According to U.S. researchers at Tarleton State University, in Stephenville, Tex., okra and fenugreek extracts can attract and remove up to 90 per cent of microplastics from ocean water, freshwater, and groundwater, providing a biodegradable and nontoxic alternative to conventional water treatment – specifically to polyacrylamide, which is a synthetic polymer derived from acrylamide.

Microplastics are tiny plastic particles, smaller than five millimeters, that contaminate the environment by breaking down from larger plastic objects, intentionally manufactured microbeads in personal care products, and microfibres shed by clothing. These particles are found in water, food, and even the air we breathe, posing potential risks to human health and ecosystems.

Rajani Srinivasan, an associate professor of chemistry at Tarleton, and his colleagues have been exploring nontoxic, plant-based approaches to attract and remove contaminants from water. In one set of lab experiments, they found that polymers from okra, fenugreek, and tamarind stick to microplastics, clumping together and sinking for easy separation from water.

To create the plant-based solutions, the researchers extracted gel from fenugreek seeds and polymers from sliced okra and placed them into separate containers of water overnight. They then removed the plant extracts, dried them into powders, and mixed the plant extracts with microplastic contaminated water. They determined that one gram of either powder in one litre of water trapped microplastics the most effectively – specifically, dried okra removed 67 per cent of microplastics in one hour, while the fenugreek extract removed 93 per cent.

Shifting to a real-world application, the researchers then tested the plant extracts on real microplastic-polluted water. They collected samples from waterbodies around Texas and brought them to the lab. The plant extract removal efficiency changed depending on the original water source: Okra worked best in ocean water (80 per cent), fenugreek in groundwater (80 to 90 per cent), and the 1:1 combination of okra and fenugreek in freshwater (77 per cent). The researchers hypothesize that the natural polymers had different efficiencies because each water sample had different types, sizes, and shapes of microplastics.

Polyacrylamide is currently used to remove contaminants during wastewater treatment, but the researchers say that okra and fenugreek extracts could serve as biodegradable and nontoxic alternatives.

“Utilizing these plant-based extracts in water treatment will remove microplastics and other pollutants without introducing additional toxic substances to the treated water, thus reducing long-term health risks to the population,” Srinivasan said.