Method for reducing zinc content in precipitated iron slag in zinc hydrometallurgy process

The invention belongs to the technical field of hydrometallurgy, and discloses a method for reducing the content of zinc in precipitated iron slag in the zinc hydrometallurgy process. Zinc calcine pretreated by a cationic surface active agent, iron-rich seed crystals pretreated by an anionic surface active agent and an additive are added into an iron-containing zinc sulfate solution for iron removal reaction, and then iron-rich slag and zinc-rich slag are separated through reselection. And the iron-rich slag is further subjected to hydrothermal treatment to obtain iron precipitation slag with very low zinc content. The surface active agent is used for increasing the property difference between the surface of the zinc calcine and the surface of iron precipitation particles, so that iron is not attached to the surfaces of zinc-rich particles as much as possible in the iron precipitation process; the iron-rich particles are used as template seed crystals in the iron precipitation process, so that iron can be att