The invention discloses a method for preparing a double-acid ferro-aluminum flocculating agent, which relates to a process for preparing the double-acid ferro-aluminum flocculating agent by using
calcium aluminate powder. The method comprises the following steps of: taking the
calcium aluminate powder of which the particle size is smaller than 60 meshes, putting the
calcium aluminate powder into a
hydrochloric acid solution in a part
mass ratio of the
hydrochloric acid solution to the calcium aluminate powder of 3-5:1, reacting the two materials at a temperature of 98 DEG C for 1 to 1.5 hours, standing the mixture for 30 minutes, and then taking a supernatant to obtain AlCl3 liquid; adding
ferrous sulfate to the mixture in a part
mass ratio of the calcium aluminate powder to the
ferrous sulfate of 9-11:1 at a temperature of between 80 and 90 DEG C, dropwise adding a
sodium hydroxide solution of which the concentration is 0.5 mol / L into the mixture after 15 minutes, dropping oxyful into the mixture in a part
mass ratio of the
ferrous sulfate to the oxyful of 1:1-1.5 when the basicity is 30 to 40 percent, stirring the mixture continuously for 15 to 20 minutes, and then curing the mixture at a temperature of between 50 and 60 DEG C for 12 hours to obtain a
liquid product of the double-acid ferro-aluminum flocculating agent; and
drying the
liquid product of the double-acid ferro-aluminum flocculating agent to obtain a double-acid ferro-aluminum
solid product. Tests show that in the
solid product, Al2O3 is over 30 percent, the total iron is over 1 percent, the insoluble substances is less than 1 percent, and other indexes accord with the national standards. The method has a simple process and a low cost, and the prepared product has a good coagulation effect and high economic and
social benefits.