Exploring potential of pearl millet (Pennisetum glaucum) and black-eyed pea (Vigna unguiculata subsp. unguiculata) as bio-coagulants for water treatment

Plant-based natural coagulants can act as potential alternatives to most of the commonly used chemical coagulants. Not only plant-based coagulants have been found to be eco-friendly but also they can generally be classified as non-toxic and produce less sludge in comparison with chemical coagulants. In this study, the coagulation potential of crude extract from seeds of Pearl millet (Pennisetum glaucum) and Black-eyed pea (Vigna unguiculata subsp. unguiculata) was evaluated using lab-prepared samples having initial turbidity of 200 ± 5 NTU. Response surface method was used for the design of experiments while statistical analysis was also applied on the experimental results obtained. The obtained results revealed that pearl millet and black-eyed pea can effectively remove turbidity and produce water with a turbidity of less than 5 NTU. The statistical analysis revealed that pH was a more significant parameter as compared with coagulant dose. Pearl millet and black-eyed pea performed best in a pH range of 2–4 and 4–6, respectively. Fourier transform infrared spectroscopy and scanning electron microscopy were employed on coagulants and flocs formed. Mechanism of coagulation for pearl millet was found to be adsorption due to the carboxyl group and adsorption due to hydrogen bonding for black-eyed pea.