Synthesis of Novel Amphoteric Chitosans as Flocculants and Research on the Flocculation

This study focused on chemical modification of chitosan to improve its flocculation effects in wastewater treatment process.Based on Mannichi-type reaction of the amino groups of chitosan,formaldehyde and phenolic compound, sulfonic groups were introduced into chitosan and three kinds of amphoteric chitosan derivatives with different degree of substitution of sulfate groups were prepared.IR and NMR spectra confirmed that the new chitosan derivatives have a benzoxazine structure.For removal of turbidity from kaolin suspensions,the flocculation effect of the products varies with dosage,pH and ionic strength,and an optimum value can be obtained in an appropriate flocculation condition.The flocculation effect of the modified chitosans is much better than that of the chitosan controls.The turbidity removal rate reached to about 100%when the sulfated chitosan with DS of 0.8 was used.