In a new study by Tarleton State University scientists, okra and/or fenugreek extracts attracted and removed up to 90% of microplastics from ocean water, freshwater and groundwater.
Srinivasan et al. demonstrated that plant-based polysaccharides showed better microplastic removal efficiency than polyacrylamide, which is commercially used for water treatment. Image credit: Srinivasan et al., doi: 10.1021/acsomega.4c07476.
Microplastics are new, emerging contaminants that are becoming detrimental to aquatic environments on a global scale.
These water-insoluble, solid polymers less than 5 mm in size originate from the fragmentation of large plastic litter or environmental emissions.
These new emerging pollutants not only cause physical harm but also serve as a substrate for other contaminants that adhere to and/or are adsorbed in microplastics.
Consumption of these fine particles by organisms may lead to bioaccumulation and bioamplification.
Conventional wastewater treatment using inorganic and organic polymeric flocculants is nonbiodegradable and toxic to ecosystem.
Dr. Rajani Srinivasan and colleagues at Tarleton State University 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 extract the sticky plant polymers, they soaked sliced okra pods and blended fenugreek seeds in separate containers of water overnight.
They then removed the dissolved extracts from each solution and dried them into powders.
Their analyses showed that the powdered extracts contained polysaccharides, which are natural polymers.
Initial tests in pure water spiked with microplastics showed that: (i) one gram of either powder in a quart (one liter) of water trapped microplastics the most effectively; (ii) dried okra and fenugreek extracts removed 67% and 93%, respectively, of the plastic in an hour; (iii) a mixture of equal parts okra and fenugreek powder reached maximum removal efficiency (70%) within 30 minutes; (iv) the natural polymers performed significantly better than the synthetic, commercially available polyacrylamide polymer used in wastewater treatment.
The researchers tested the plant extracts on real microplastic-polluted water.
They collected samples from water bodies 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%), fenugreek in groundwater (80-90%), and the 1:1 combination of okra and fenugreek in freshwater (77%).
The scientists 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 okra and fenugreek extracts could serve as biodegradable and nontoxic alternatives,” they said.
“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,” Dr. Srinivasan said.
The team’s work was published in the journal ACS Omega.
_____
Rajani Srinivasan et al. 2025. Fenugreek and Okra Polymers as Treatment Agents for the Removal of Microplastics from Water Sources. ACS Omega 10 (15): 14640-14656; doi: 10.1021/acsomega.4c07476
