Polyamidine-based flocculant as well as preparation method and application thereof

The invention provides a polyamidine-based flocculant as well as a preparation method and application thereof. The preparation method comprises the following steps: 1), adding N-vinylformamide, acrylonitrile and an initiator into an aqueous carboxymethylcellulose solution, and reacting at 40-60 DEG C for 1-5 hours; 2), adding inorganic strong acid into liquid obtained in the step 1), and reactingfor 1-5 hours while stirring; 3), heating liquid obtained in the step 2) to 80-100 DEG C, and amidinizing for 1-2 hours while stirring; 4), adding ethanol into liquid obtained in the step 3) to separate out a precipitate from the liquid, wherein the ethanol is added until no new precipitate is separated out; 5), performing suction filtration on a mixture obtained in the step 4), and drying the obtained precipitate; 6), extracting the dried precipitate by an extracting solution, and drying residues to obtain the polyamidine-based flocculant. The polyamidine-based flocculant can reduce secondarypollution on water, is mo