Chitosan biopolymer in industrial wastewater treatment

Population growth, rapid urbanization and industrialization are increasingly contaminating existing fresh water sources with various pollutants, including heavy metals, toxic organic matter, and making them unavailable for human and industrial use. Physicochemical methods constitute the most important class of separation processes, which play a decisive role in the field of wastewater treatment. These mainly include processes that use both physical and chemical reactions/interactions to effect the desired separation. Various processes such as coagulation/flocculation, extraction, reactive separation, oxidation and cavitation belong to this important class. Coagulation and flocculation are now widely used processes in water treatment. These methods facilitate the removal of fine particles suspended in the liquid by forming well-defined aggregates that can quickly settle out of the water. Recently, there has been increased interest in using natural, biocompatible, and non-toxic polymers, chitosan, as flocculant aids, rather than synthetic polymers, to improve coagulation/flocculation processes. The increasing knowledge of structural analysis and chemical modifications enables the use of the natural coagulant's chitin and chitosan in a newer way for the human welfare. The abundant free amino groups on the chitosan backbone protonated in acidic medium behave as a typical cationic polyelectrolyte and hence due to its properties, efficient charge neutralization and bridging effects, the chitosan acts as an outstanding anticoagulant with good coagulation and flocculation performance. Chitosan, a natural water coagulant/flocculant with the ability to reduce turbidity, color and clay particles, is successfully used in water treatment mainly to remove organic residues, suspended solids, amino acids and dyes