Hydrometallurgical recovery of zinc from industrial hot dipping top ash  

从工业热浸镀锌灰中湿法回收锌

作　　者：Ewa RUDNIK Ewa RUDNIK(Faculty of Non-ferrous Metals,AGH University of Science and Technology,Al.Mickiewicza 30,30-059 Cracow,Poland)

机构地区：[1]Faculty of Non-ferrous Metals,AGH University of Science and Technology,Al.Mickiewicza 30,30-059 Cracow,Poland

出　　处：《Transactions of Nonferrous Metals Society of China》2020年第8期2239-2255,共17页中国有色金属学报（英文版）

基　　金：the Project No.POIR.01.01.01-00-0032/16 in the frame of Smart Growth Operational Programme 2014-2020 financed by the National Centre for Research and Development(Poland)。

摘　　要：Top ash from hot-dip galvanizing plant was investigated as a source of secondary zinc to be returned to galvanizing bath.The waste material contained 63%Zn as metallic,oxide and hydroxychloride phases.It was leached in H2SO4 solutions(20%and 25%)at various bath loadings(100-300 g/L).Leaching behaviors of zinc,manganese,iron and chloride ions were investigated.A few strategies of iron elimination from leaching liquors were examined.Flocculant addition was harmful for subsequent filtration of iron precipitates due to increased viscosity of solution,while a combination of zinc oxide and calcium carbonate for rising pH resulted in the formation of dense suspension unenforceable to separate from zinc sulphate solution.Zinc electrowinning was carried out at different pH(from-0.5 to 2.8)using a range of current densities(3-10 A/dm^2).Optimal conditions for pure metal recovery were:leaching in 20%H2SO4 solution at zinc ash content 100-150 g/L,Fe2O3·xH2O precipitation using H2O2 and CaCO3,zinc electrowinning at pH of 0.1-1.0 at 3-6 A/dm2.Correlations between pH and free H2SO4 concentration in electrolyte solutions were also discussed.pH-acid concentration dependence for zinc electrolyte was between experimental and calculated curves for pure H2SO4 solutions,while the curve was shifted towards lower pH if ferric ions were in the solution.研究热浸镀锌厂的锌灰,使之可以作为二次锌资源返回镀锌槽。这种废料中含有63%的锌,锌以金属、氧化物和羟基氯化物相存在。在各种浸出槽负荷(100~300 g/L)下于H2SO4溶液(20%,25%)中浸出锌灰,研究锌、锰、铁和氯离子的浸出行为。考察几种从浸出液中除铁的方法。添加絮凝剂对后续的铁沉淀物过滤有害,因为会导致溶液黏度增大;氧化锌与为了提高pH值而加入的碳酸钙结合,形成高密度的悬浊液,无法从硫酸锌溶液中分离出来。在不同的pH值(-0.5~2.8)下进行锌电积,电流密度范围为3~10 A/dm^2。从锌灰中回收纯金属的最佳条件如下:用20%的硫酸浸出,浸出槽负荷100~150 g/L,用H2O2和CaCO3沉淀出Fe2O3·xH2O,在pH 0.1~1.0、电流密度3~6 A/dm2的条件下进行电积锌。还讨论电解液中pH与游离H2SO4浓度之间的关系。锌电解液的pH-酸浓度曲线介于纯H2SO4溶液的实验曲线与计算曲线之间;如果溶液中存在铁离子,则曲线向低pH方向移动。

关 键 词：top ash ZINC LEACHING PURIFICATION ELECTROWINNING recycling 

分 类 号：TF813[冶金工程—有色金属冶金]