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首页> 外文期刊>RSC Advances >Selective leaching of lead from lead smelter residues using EDTA
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Selective leaching of lead from lead smelter residues using EDTA

机译：使用EDTA的铅冶炼残留物选择性浸出铅

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Ethylenediaminetetraacetic acid (EDTA) has been widely used as an effective reagent for removal of lead from soil because of its high lead extraction efficiency caused by the high thermodynamic stability of the Pb( II )–EDTA complex. In this study, EDTA was used as a lixiviant for recovery of lead from residues (matte and slag) of secondary lead smelter plants. The residues were composed mainly of iron (34–66 wt%) and lead (7–11 wt%). Leaching parameters (EDTA concentration, pH, temperature, liquid-to-solid ratio and leaching time) were optimized. The optimum leaching efficiency was achieved when leached for 1 h at room temperature using 0.05 mol L ~(?1) EDTA at a liquid-to-solid ratio of 5 mL g ~(?1) . At such conditions, 72 to 80% of lead and less than 1% of iron were leached from both matte and slag. The high selectivity towards lead with minimal co-dissolution of iron is a major advantage since it reduces the chemical consumption and simplifies the downstream processes. Although the stability constants of the complexes Fe( III )–EDTA, Fe( II )–EDTA and Pb–EDTA are all large (log? K _(S) 25.1, 14.33 and 18.04, respectively), the leaching of iron was most likely limited by its presence in insoluble phases such as iron oxides, sulfides and silicates in the residues. 100% leaching of lead was achieved by a multi-step leaching process where the leaching residues were contacted three times by a fresh EDTA solution. To recover EDTA, first iron was precipitated as iron hydroxide by raising the pH of pregnant leach solution (PLS) above 12.6 using sodium hydroxide, followed by precipitation of lead as lead sulfide by adding ammonium sulfide. The recovered EDTA was successfully reused two times for leaching without significant changes in leaching yields.
机译：乙二胺四乙酸（EDTA）已广泛用作用于从土壤中除去铅的有效试剂，因为它具有高热力学稳定性引起的PB（ii）-edTA复合物的高热力稳定性引起的。在这项研究中，EDTA被用作来自二次铅冶炼厂植物的残留物（遮罩和炉渣）的铅的唇振。残留物主要由铁（34-66wt％）和铅（7-11wt％）组成。优化了浸出参数（EDTA浓度，pH，温度，液体至固体比和浸出时间）。当在室温下使用0.05mol L〜（α1）EDTA以5mL g〜（α1）的液体与固体比在室温下浸出1小时时，实现了最佳的浸出效率。在这样的条件下，从遮罩和渣中浸出72至80％的铅和少于1％的铁。由于铁的最小共同溶解的引线的高选择性是主要优势，因为它降低了化学消耗并简化了下游过程。虽然复合物Fe（III）-EDTA，Fe（II）-EDTA和PB-EDTA的稳定常数都大（Log？K _（）分别为25.1,14.33和18.04），最多的铁浸出可能受到其在不溶性阶段的存在的限制，例如氧化铁，硫化物和残留物中的硅酸盐。通过多步浸出过程实现100％铅，其中通过新鲜EDTA溶液接触浸出残留物三次。为了回收EDTA，通过使用氢氧化钠提高12.6的妊娠浸出溶液（PL）的pH，将第一铁作为铁氢氧化铁沉淀，然后通过加入硫化铵作为铅硫化物沉淀。回收的EDTA成功地重复使用了两次浸出，而无明显改变浸出产量。

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