Study on dissolution of heavy metals from lead and zinc smelting waste acid slag
The heavy metal-containing waste acid slag generated in the lead and zinc smelting industry poses a considerable environmental risk.And at the same time it is also a resource.The purification of the calcium sulfate matrix is the first step for the downstream resource utilization of the slag.In this work,a comprehensive phase and composition analysis was carried out on the waste acid slag,and the distribution characteristics of the heavy metals and calcium sulfate in the slag were obtained.Then the effects of heating time,temperature and sulfuric acid concentration on the leaching rate of key elements such as Fe,Zn,As,Pb,Cd,and Sb were studied,and the dissolution rule of these key elements in acid medium was systematically explored.What's more,based on the general relationship between the crystal phase of calcium sulfate and the water activity and temperature,the effects of the phase transition as a result of the water activity regulation at atmospheric pressure or the hydrothermal environment in acidic medium on the dissolution of the metals were studied.The results showed that the effect was ideal when the heating time was 2 h,the heating temperature was 80 ℃,and the concentration of sulfuric acid was 1.0 mol/L.And the leaching rates of As,Zn,Sb,Cd,and Fe under the optimal conditions were all over 95％,with the leached CaSO4·2H2O residue showing smooth surface and in flake and rod mixed morphologies.Reducing the activity of water in the medium and hydrothermal conditions can promote the rotation of calcium sulfate.The dissolution of heavy metals in or between the crystal lattices of calcium sulfate can be further enhanced,assisted by the crystal transformation.As a consequence,the strengthened dissolution technology based on the crystal transformation of calcium sulfate is an effective way to purify the calcium sulfate matrix deeply.
smelting waste acid slagsulfuric acid mediumdissolution of heavy metalscrystal transformation of calcium sulfate
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NSTL
万方数据
维普
