Western Australian School of Mines: Minerals, Energy and Chemical Engineering, Curtin University, WA 6102, Australia.
Western Australian School of Mines: Minerals, Energy and Chemical Engineering, Curtin University, WA 6102, Australia; Mining and Metallurgical Engineering, Asyut University, Asyut 71515, Egypt.
Waste Manag. 2021 Apr 15;125:87-97. doi: 10.1016/j.wasman.2021.02.033. Epub 2021 Mar 5.
Waste printed circuit boards (WPCBs) constitute a hazardous material with up to 40 different metals, including numerous many heavy metals and environmentally harmful metals. Most hydrometallurgical processing approaches use high concentrations of toxic reagents and generate significant amounts of harmful effluents. This research investigates the use of cyanide-starved glycine solution containing no free cyanide in the leachate to extract precious metals from WPCBs, with most of copper and base metals pre-removed by upstream glycine-only leaching. Under the optimised conditions, 90.1% Au, 89.4% Ag and 70.1% Pd were extracted together with 81.0% Cu and 15.0% Zn. The extraction of other base metals remained low at 8.3% for Al and <5% for Pb, Ni, Co, Fe and Sn, indicating a fairly good selectivity of the leaching system. By comparing with stoichiometric and intensive cyanidation, the cyanide-starved glycine system showed comparable or better performance on precious metals extraction, but cyanide use was reduced by >70% whereas the glycine can be reused. Analysis indicates that with an initial cyanide dose of 250 ppm, the leaching solution was starved of cyanide after 4 h with no free cyanide, which minimises safety and health risks significantly compared with traditional intensive cyanidation ([CN] > 3500 ppm). Glycine and cyanide dose, pH, and particle size dominated leaching kinetics, while staged addition of cyanide did not enhance the extractions. A significant (70-90%) reduction in required cyanide use and cyanide-bearing effluents can be achieved while performing polymetallic metal removal and allowing reagent recycling.
废弃印刷电路板 (WPCB) 构成了一种危险物质，其中含有多达 40 种不同的金属，包括许多重金属和对环境有害的金属。大多数湿法冶金处理方法使用高浓度的有毒试剂，并产生大量有害的废水。本研究探讨了在浸出液中使用不含游离氰化物的氰化物饥饿甘氨酸溶液从 WPCB 中提取贵金属，其中大部分铜和贱金属通过上游仅甘氨酸浸出预先去除。在优化条件下，90.1%的 Au、89.4%的 Ag 和 70.1%的 Pd 与 81.0%的 Cu 和 15.0%的 Zn 一起被提取。其他贱金属的提取率仍然较低，Al 为 8.3%，Pb、Ni、Co、Fe 和 Sn 均<5%，表明浸出体系具有相当好的选择性。与化学计量和强化氰化相比，氰化物饥饿甘氨酸体系在提取贵金属方面表现出相当或更好的性能，但氰化物用量减少了>70%，而甘氨酸可以重复使用。分析表明，在初始氰化物剂量为 250ppm 的情况下，浸出溶液在 4 小时后就会出现氰化物饥饿状态，没有游离氰化物，与传统强化氰化相比，这大大降低了安全和健康风险([CN]>3500ppm)。甘氨酸和氰化物剂量、pH 值和粒度控制着浸出动力学，而分步添加氰化物并不能提高提取率。在进行多金属金属去除并允许试剂回收的同时，可以显著减少所需氰化物用量和含氰废水。
