Extracts of okra and other slimy plants commonly used in cooking can help remove dangerous microplastics from wastewater, scientists said Tuesday.
The new research was presented at the spring meeting of the American Chemical Society, and offers an alternative to the synthetic chemicals currently used in treatment plants that can themselves pose risks to health.
“In order to go ahead and remove microplastic or any other type of materials, we should be using natural materials which are non-toxic,” lead investigator Rajani Srinivasan, of Tarleton State University, said in an explainer video.
Srinivasan’s past research had examined how the goo from okra and other plants could remove textile-based pollutants from water and even microorganisms, and she wanted to see if that would equally apply to microplastics.
Typical wastewater treatment removes microplastics in two steps.
First, those that float are skimmed off the top of the water. These however account for only a small fraction, and the rest are removed using flocculants, or sticky chemicals that attract microplastics into larger clumps.
The clumps sink to the bottom and can then be separated from the water.
The problem is that these synthetic flocculants, such as polyacrylamide, can break down into toxic chemicals.
They tested chains of carbohydrates, known as polysaccharides, from the individual plants, as well as in combination, on various microplastic-contaminated water, examining before and after microscopic images to determine how many particles had been removed.
They found that polysaccharides from okra paired with those from fenugreek could best remove microplastics from ocean water, while polysaccharides from okra paired with tamarind worked best in freshwater samples.
Overall, the plant-based polysaccharides worked just as well or better than polyacrylamide. Crucially, the plant-based chemicals are both non-toxic and can be used in existing treatment plants.