Microwave assisted chloride leaching of zinc plant residues

[摘要] Microwave (MW) assisted chloride leaching was studied to remove valuable and heavy metals from two zinc plant residues, i.e. goethite sludge and Zn-leach product. For both materials, NaCl leaching parameters, such as temperature, NaCl concentration, leaching time and addition of acid, were optimized. For goethite sludge, the best efficiencies for Cu (45-47 %), Pb (83-90 %), and Zn (47-58 %) extraction, with a minimal dissolution of matrix elements, were obtained at 200 degrees C, 300 g/L NaCl and L/S 10. At short leaching times (5 min) the maximal leachability of Cu and Zn was reached, while at longer leaching time (60 min) the Pb extraction increased to 90 +/- 1%. Zn leaching was limited due to the presence of stable franklinite (ZnFe2O4). NaCl (280 g/L) leaching of Zn-leach product required the addition of 1 M HCl to improve metal leaching to Ag 52 +/- 3 %, Bi 83 +/- 1 %, Cd 82 +/- 4 %, Sb 39 +/- 1 %, Zn 71 +/- 2 % at 200 degrees C, L/S 10 for 30 min. Consequently, matrix dissolution was enhanced. Metal associations in Zn-leach product were statistically investigated. The environmental impact of the MW leached materials was evaluated by a one stage leaching test, which showed a significant overall reduction in heavy metal leachability compared to untreated materials.

[发布日期] 2020-11-05

[关键词] Microwave leaching;Chloride leaching;Zinc plant residues;Zinc;Copper;Lead;Bismuth;Antimony;Silver;Cadmium