铅锌冶炼污酸渣中重金属溶出研究

Study on dissolution of heavy metals from lead and zinc smelting waste acid slag

铅锌冶炼行业产生的重金属污酸渣对环境风险大,但同时也是一种可利用资源,硫酸钙基体净化是其资源化利用的第一步。本工作对污酸渣开展了全面的矿相解析,获得了污酸渣中重金属与硫酸钙的嵌布规律,并系统研究了加热时间、加热温度及硫酸浓度对污酸渣中Fe, Zn, As, Pb, Cd, Sb等关键元素浸出率的影响,系统探究了这些元素在酸性介质中的溶出规律,且基于硫酸钙晶相与介质水活度、温度的一般规律,开展了硫酸介质中常压下水活度调控致相转和高温水热致相转对元素溶出的影响。结果表明,加热时间为2 h、加热温度为80℃及硫酸浓度为.01 mol/L时效果较为理想,且在此优化溶出条件下,污酸渣中As, Zn, Sb, Cd, Fe的浸出率均可达95%以上,浸出残渣为表面光滑的薄片状和棒状的二水硫酸钙晶相;降低介质中水的活度和水热条件能够促进硫酸钙的相转,借助硫酸钙形态或晶型的转化,可进一步强化硫酸钙晶格内或晶间重金属的溶出。基于硫酸钙转晶的金属强化溶出技术是硫酸钙渣基体深度净化的有效手段。

The heavy metal-containing waste acid slag generated in the lead and zinc smelting industry posessaconsiderable 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 CaSO_(4)·2H_(2)O 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.