Chitosan and carboxymethylchitosan as high turbidity water biocoagulants

Abstract

Biocoagulants emerges as a promising technology in water treatment, in order to exploit renewable and biodegradable materials. The present work aims to study the coagulant action of chitosan and carboxymethylchitosan on water with very high turbidity (above 300 NTU), contrasting the physicochemical results with those obtained for aluminum sulphate. Carboxymethylchitosan was produced by the Williamson’s ethers synthesis and characterized by potentiometric titration, FTIR and 1H-NMR. The coagulant tests were performed using synthetic water in a Jar-test equipment, through the induction of high and low velocity gradients, followed by sedimentation. The results showed turbidity and color removal efficiencies above 99% for the biocoagulants, by applying dosages much lower than those used for aluminum sulphate; the volume of sedimentable solids obtained at the end of the water treatment process was much lower when chitosan and carboxymethylchitosan were used as coagulants (reduction of 25% when compared to aluminum sulphate). In summary, carboxymethylchitosan is a non-toxic, renewable, biodegradable material with high efficiency as a coagulant for waters with very high turbidity, showing promise for in natura applications.