Abstract: In this study, the magnetic separation of a historical steel slag tailings dump in Yunnan wastaken as the object of study, and the properties of the steel slag tailings were analyzed. In this experiment, four leaching solutions with different acidity were used to carry out a 42-day dynamic leaching ex-periment to analyze the leaching release of Fe, Zn and Cd, and a release model was established. The re-sults showed that the pl value of the tailings leachate was higher in the initial stage of leaching, and de-creased rapidly after reaching the maximum , and kept stable in the later stage. Under the same pH value , the smaller the size of tailings is, the earlier the peak concentration of each metal appears. The dis-solution order of Fe ion concentration is as follows: acidic solution > neutral solution > weak acidic solution. The leaching of Zn is different. The leaching of Zn was higher in the early stage of leaching.reached the lowest value in about 9 days, and the concentration peak appeared again in 21 days to 27days. When the concentration of OH"in solution increased, the concentration increased slightly. Thedissolution of Cd showed a dynamic change, showing a rapid release of intermittent process. The dynamic process of the leaching of the three metals can well describe with the quadratic regression equation andthe DoseResp equation. But for Fe, the correlation coefficient R’ of the DoseResp equation is higher thanthat of the quadratic regression equation.

Key words: steel slag, simulated acid rain, heavy metals, leaching