Toward green technology: a review on some efficient model plant-based coagulants/flocculants for freshwater and wastewater remediation

Abstract

Plant-based coagulants/flocculants are foreseen to be a major progress in water treatment technology owing to their safety, biodegradability and availability, unlike synthetic chemical water refiners such as Al, Fe salts and organic polymers claimed to cause threats to our ecosystem either via their residues in the treated waters or due to their generated toxic sludge. Further, the increasing global awareness about environmental issues is acting as a driving force behind the interest toward the use of green resources as valuable products for water treatment. Substitution of synthetic coagulants/flocculants by such natural materials can not only minimize ecosystem damages and threats, but would also foster the way toward an era of clean technology and a sustainable environment. The present paper reviews works on the most efficient model plant-based coagulants/flocculants, moringa seeds, cactus pads, okra seed pods and mango kernels, via highlighting their effectiveness in treating a variety of waters. This review focuses also on the extracting processes used for their preparation, on the type of their active compounds as well as on water pollutant removal mechanisms. Among the four known coagulation–flocculation phenomenon, both polymer bridging and charge neutralization were assumed to be the main predominant mechanisms of bio-coagulants/bio-flocculants toward water contaminant removal. Further, this paper sheds light on where future works should head aiming to stress on the exploitation of green materials in water remediation. We believe that this review can provide an immediate platform for scientists to intensify their research on more efficient natural products to be used in water processing for the sake of a safer environment.