Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran.
Waste Manag. 2013 Nov;33(11):2354-63. doi: 10.1016/j.wasman.2013.07.017. Epub 2013 Aug 5.
A novel hydrometallurgical process was proposed for selective recovery of Cu, Ag, Au and Pd from waste printed circuit boards (PCBs). More than 99% of copper content was dissolved by using two consecutive sulfuric acid leaching steps in the presence of H2O2 as oxidizing agents. The solid residue of 2nd leaching step was treated by acidic thiourea in the presence of ferric iron as oxidizing agent and 85.76% Au and 71.36% Ag dissolution was achieved. The precipitation of Au and Ag from acidic thiourea leachate was investigated by using different amounts of sodium borohydride (SBH) as a reducing agent. The leaching of Pd and remained gold from the solid reside of 3rd leaching step was performed in NaClO-HCl-H2O2 leaching system and the effect of different parameters was investigated. The leaching of Pd and specially Au increased by increasing the NaClO concentration up to 10V% and any further increasing the NaClO concentration has a negligible effect. The leaching of Pd and Au increased by increasing the HCl concentration from 2.5 to 5M. The leaching of Pd and Au were endothermic and raising the temperature had a positive effect on leaching efficiency. The kinetics of Pd leaching was quite fast and after 30min complete leaching of Pd was achieved, while the leaching of Au need a longer contact time. The best conditions for leaching of Pd and Au in NaClO-HCl-H2O2 leaching system were determined to be 5M HCl, 1V% H2O2, 10V% NaClO at 336K for 3h with a solid/liquid ratio of 1/10. 100% of Pd and Au of what was in the chloride leachate were precipitated by using 2g/L SBH. Finally, a process flow sheet for the recovery of Cu, Ag, Au and Pd from PCB was proposed.
提出了一种从废印刷电路板（PCB）中选择性回收 Cu、Ag、Au 和 Pd 的新型湿法冶金工艺。在 H2O2 作为氧化剂的存在下，通过两个连续的硫酸浸出步骤，超过 99%的铜含量被溶解。第 2 步浸出的固体残渣用酸性硫脲处理，以铁作为氧化剂，实现了 85.76%的 Au 和 71.36%的 Ag 溶解。使用不同量的硼氢化钠（SBH）作为还原剂，研究了从酸性硫脲浸出液中沉淀 Au 和 Ag。第 3 步浸出后固体残渣中的 Pd 和残留金用 NaClO-HCl-H2O2 浸出体系浸出，研究了不同参数的影响。通过增加 NaClO 浓度至 10V%，可以提高 Pd 和特别是 Au 的浸出率，进一步增加 NaClO 浓度的影响可以忽略不计。通过增加 HCl 浓度从 2.5 增加到 5M，可以提高 Pd 和 Au 的浸出率。Pd 和 Au 的浸出是吸热的，升高温度对浸出效率有积极影响。Pd 的浸出动力学相当快，30 分钟后完全浸出了 Pd，而 Au 的浸出需要更长的接触时间。在 NaClO-HCl-H2O2 浸出体系中浸出 Pd 和 Au 的最佳条件为 5M HCl、1V% H2O2、10V% NaClO，在 336K 下浸出 3h，固液比为 1/10。使用 2g/L SBH，可将氯化浸出液中 100%的 Pd 和 Au 沉淀。最后，提出了从 PCB 中回收 Cu、Ag、Au 和 Pd 的工艺流程。
