Magnetic separation method and separation system for rainwater containing heavy metals

The invention discloses a magnetic separation method and separation system for heavy metal-containing rainwater, and the separation method comprises the following steps: adding alkali liquor into the heavy metal-containing rainwater for reaction to obtain first reaction liquid; respectively adding polymeric ferric sulfate and magnetic seeds into the first reaction solution for reaction to obtain a second reaction solution; respectively adding aluminum sulfate and polyacrylamide into the second reaction solution for reaction to obtain a third reaction solution; and carrying out solid-liquid separation on the third reaction liquid to obtain rainwater containing magnetic sludge and having up-to-standard heavy metal content. The method comprises the following steps: settling heavy metals in rainwater by using alkali liquor to reduce the hardness of the rainwater, adding polymeric ferric sulfate and magnetic seeds to make precipitates have magnetism and make arsenic in the rainwater precipitate, then adding alumin