Leaching of Lead from Geopolymer Prepared by Waste Acid Residue

The waste acid residue is limestone neutralized slag in the preparation of acid with pyrometallurgical exhaust in lead production enterprises. There are many hazardous heavy metals in the slag, such as lead, mercury, cadmium, arsenic, etc. It is difficult to remove them from the waste acid residue. The leakage of the heavy metals will gradually get into the groundwater and the soil, contaminate the surrounding environment. However, the waste acid residue can be used to prepare geopolymer in order to solidify the toxic elements. The present experiment aimed to investigate the leakage rate of lead from the geopolymer made by the waste acid residue. The samples were lixiviated by a mixture of sulfuric and nitric acid, with the mass ratio of sulphuric acid/ nitric acid 2:1. The ratio of liquid to solid was 10:1. And the geopolymer was oscillated for 18 hours on the turnover oscillation. The leaching of lead under influence of acidic rainfall and then entering into the environment was simulated. The lead in the supernatant of leaching solution under different conditions was analyzed. And the result showed that lead can be well solidified in the geopolymer made by the waste acid residue.