Natural coagulants (Moringa oleifera and Benincasa hispida) based removal of microplastics

Abstract

The presence of small-sized (<5 mm) plastic particles, called microplastics (MPs), in the environment, including aquatic bodies, air, soil, and bodies of living beings, is a cause of significant concern to the entire world. These MPs can contaminate drinking water sources, move up the food chain, and release toxic substances that could pose a threat to human health. Therefore, there is an urgent need to develop methods for removing MPs from the environment to protect present and future generations. The coagulation-flocculation sedimentation (CFS) process (using synthetic chemicals) has emerged as a fundamental method for treating MPs in water because of its economy, high efficiency, and ease of use. However, the xenobiotic nature of such compounds, coupled with their adverse health effects, calls for the development of sustainable solutions. This is the first study to report the effectiveness of plant-based natural coagulants in removing MPs from water and their comparison against synthetic coagulants. Two natural coagulants, Benincasa hispida (BH) and Moringa oleifera (MO), were investigated and have shown comparable MP removal efficiencies to commonly used synthetic coagulant: alum. The CFS approach resulted in 83.73 ± 1.41% (100 mg L^–1 dosage) and 86.99 ± 1.41% (150 mg L^–1 dosage) MP removal efficiencies for BH and MO, respectively, while alum resulted in 86.58 ± 1.22% removal (50 mg L^–1 dosage). Further, FTIR analysis has revealed that these MPs are composed of high-density polyethylene (HDPE), and SEM imaging has shown their shapes as spherical, rod-like and irregular. The results of the present study show that plant-based natural materials can be used for MP removal, thus yielding a sustainable and cost-effective process.