Method for preparing flocculant for treating papermaking black liquor by using waste collagen

The invention discloses a method for preparing a flocculant for treating papermaking black liquor by using waste collagen. The method comprises the following steps of: soaking waste scurf in water at room temperature; adding protease and performing enzymolysis at the temperature of between 45 and 50 DEG C; performing stirring reaction under the condition of the pH of between 4.0 and 4.5 and the temperature of between 70 and 90 DEG C; cooling to the temperature of between 50 and 60 DEG C, adding a cationization agent for stirring reaction when the pH is between 8.0 and 8.5, and filtering, washing, drying, and crushing to prepare the flocculant. The flocculant prepared by the method of the invention achieves a larger adsorption ratio surface area, and can be more widely combined with hydroxyls, sulfo groups and the like of hemicellulose and lignin in the papermaking black liquor so as to promote soluble pollutants in the black liquor to be separated, adsorbed and precipitated, and thus, the overall treatment efficiency of the black liquor is improved and a treatment period of the black liquor is shortened greatly. In the invention, the price of raw materials is low, the preparation process is simple, the operability is high, the promotion is easy, the production cost is low, and thus, the method has a good market prospect.