Fenugreek and Okra Polymers as Treatment Agents for the Removal of Microplastics from Water Sources

Microplastics 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. Plant-derived polysaccharides can provide a highly efficient, nontoxic, and ecofriendly substitute to synthetic flocculants. The microplastic removal efficiency of polysaccharides derived from fenugreek, okra, and the combination of okra and fenugreek in the ratio of 1:1 was studied in simulated and water samples collected from various sources under bench-scale laboratory conditions. Water samples used for the study were collected from surface, ocean, and groundwater sources. A combination of optical microscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy was used to study the microplastic removal efficiency of the plant-derived polysaccharides. ζ-Potential measurements and scanning electron microscopy were used to confirm the mechanism and capture of microplastic from water samples. The effect of varying polymer concentrations and contact time was also studied. The best concentration was found to be 1 g/L, with fenugreek showing the best microplastic removal in 30-60 min as the optimum contact time. It was found that fenugreek was the most efficient with an ∼89% microplastic removal from groundwater samples. A combination of okra and fenugreek was the most efficient for freshwater samples with an ∼77% microplastic removal. For the ocean water, okra showed the best removal efficiency of ∼80%. The mechanism of microplastic removal using plant-based polysaccharides as flocculant was found to be bridging. Both experimental and statistical analyses demonstrated that plant-based polysaccharides showed better microplastic removal efficiency than polyacrylamide, which is commercially used for water treatment.