Abstract: Heavy metal Cu and Cd in waste acid residue were solidified/stabilized by magnesium slag.Toxicity leaching experiment that mixed different concentrations of Cu and Cd with the mixer of waste acid residue and magnesium slag was carried out.The contents of Cu and Cd were tested by ICP and the phase changes of the slag were tested by XRD.Results showed that: The highest mass concentrations of Cu and Cd in leaching solution were 0.52 mg/L and 0.32 mg/L respectively when the leaching agent was nitric acid with volume fraction of 1%~5%.The maximum mass concentrations of Cu and Cd were 3.06 mg/L and 2.9 mg/L respectively with 1%~3% sulphuric acid as the leaching agent.The effect that magnesium slag solidified/stabilized Cu and Cd in waste acid residue was significant.With the addition of magnesium slag the phase of mixed slag had not changed，but the intensity of the diffraction peaks had changed.

Key words: magnesium slag, waste acid residue, solidification/stabilization, toxic leaching