Natural polymer flocculant has an extensive application prospect in water treatment because of its flocculation

non-toxicity and biodegradability. However

its flocculation effect is not ideal due to the lack of charge and poor solubility. It needs to be modified

such as etherification

graft copolymerization and so on. Various functional groups are introduced into its molecular chain to improve its flocculation or its charge

adsorption and sterilization. This paper summarizes the usual natural polymer based modified flocculants such as starch

chitosan

cellulose and lignin according to different modification methods

and summarizes the research progress of modified natural polymer based flocculants in China and abroad in recent years. At the same time

the preparation process of natural polymer based flocculant is briefly described

and the research direction of natural polymer based flocculant is prospected.