PFS - carboxymethyl potato starch composite flocculant and preparation and application

The invention relates to a polymeric ferric sulfate-carboxymethyl potato starch composite flocculant. The flocculant is complexed by polymeric ferric sulfate and carboxymethyl potato starch, wherein the weight ratio of Fe in polymeric ferric sulfate to carboxymethyl potato starch is 1:3-3:1. The invention also discloses a preparation method of the flocculant and an application of the flocculant in the COD wastewater treatment. After the composite flocculant prepared from carboxymethyl potato starch is introduced in polymeric ferric sulfate, the defect that the molecular chain of the inorganicflocculant is short can be overcome, the damage of the residues generated in the flocculation process of polymeric aluminum and the synthetic macromolecular flocculant can be avoided; and the charge neutralization capability can be fully utilized, the flocculant has high-effect functions of bridging and net capturing and tiny particles in wastewater can be removed through sweeping, thus the removal efficiency can be increased.