Preparation method of dense medium for treating wastewater containing multiple pollutants

The invention discloses a preparation method of a heavy medium for treating wastewater containing multiple pollutants, which comprises the following steps: firstly, carrying out sulfuric acid pickling on nonferrous mine acid wastewater treatment bottom slag to obtain a stock solution containing Fe, Al and Mn metal ions, and controlling the mass ratio of the nonferrous mine acid wastewater treatment bottom slag to garnet to saw wood powder to a gelling agent to be (3-6): (1-2): (1-2): 1; the preparation method comprises the following steps: preparing a raw solution, adjusting the pH value of the raw solution, stirring and infiltrating to obtain an infiltrating solution, adding a reducing agent which is hydroxylamine, sodium borohydride or potassium borohydride in a ratio of 0.02-0.2 kg/L to the infiltrating solution for modification, filtering to obtain a filter cake as a precursor, granulating the precursor, drying, roasting and cooling to obtain the heavy medium for treating wastewater containing multiple po