Xiong Zhenfeng, Huang Ying, Li Yonghua, Sheng Changdong, Sun Liwei, Ma Jing, Chi Baoyan, Tan Jiali, Tang Xiong, Zha Rong, Zhan Xinhua
Waste Treatment & Resource Recycle Laboratory, Department of Environmental Science and Engineering, School of Energy and Environment, Southeast University, Nanjing 210096, PR China; Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China.
Waste Treatment & Resource Recycle Laboratory, Department of Environmental Science and Engineering, School of Energy and Environment, Southeast University, Nanjing 210096, PR China; Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, PR China.
J Hazard Mater. 2024 Dec 5;480:136255. doi: 10.1016/j.jhazmat.2024.136255. Epub 2024 Oct 22.
A large amount of gold in electronic waste (E-waste) is not properly recovered owing to the absence of efficient and safe leaching methods. Herein, we proposed the concept of 'water-soluble organic Au leaching' and created a new water-soluble organic leaching agent, WS NBS-DMF, by dissolving millimolar amounts of N-bromosuccinimide (NBS) and dimethylformamide (DMF) in water. Under mild conditions (25 ℃, pH 7.0), WS NBS-DMF achieved a 94.9 % leaching efficiency of Au for waste printed circuit board (WPCB) with limited leaching of base metals. The potent bromine radical (Br•) and ligands significantly contributed to Au complexation and oxidization via in situ bromine generation and radical initiation from WS NBS-DMF. The bidirectional hydrogen-bond effect of DMF facilitated the in situ bromine generation. Two Au(I) complexes ([AuBr] and [(NHS)AuBr]) and an Au(III) complex ([(NHS)AuBr]) were confirmed as the Au leaching products by spectroscopy and mass spectrometry. Furthermore, reciprocal σ-donations between the Au center and ligands in the bonding orbitals enhanced the stability of the Au complexes, thereby promoting efficient Au leaching. Comparing with other leaching methods, this study of WS NBS-DMF provides a safe, economic and eco-friendly technique for efficient and selective gold recovery from e-waste.
由于缺乏高效且安全的浸出方法，电子废弃物（电子垃圾）中的大量金未能得到妥善回收。在此，我们提出了“水溶性有机金浸出”的概念，并通过将毫摩尔量的N-溴代琥珀酰亚胺（NBS）和二甲基甲酰胺（DMF）溶解于水中，创制了一种新型水溶性有机浸出剂WS NBS-DMF。在温和条件（25℃，pH 7.0）下，WS NBS-DMF对废弃印刷电路板（WPCB）中金的浸出效率达到94.9%，同时贱金属的浸出量有限。强氧化性的溴自由基（Br•）和配体通过WS NBS-DMF原位生成溴及引发自由基反应，对金的络合和氧化起到了显著作用。DMF的双向氢键效应促进了原位溴的生成。通过光谱学和质谱分析确认，两种Au(I)配合物（[AuBr]和[(NHS)AuBr]）以及一种Au(III)配合物（[(NHS)AuBr]）为金的浸出产物。此外，金中心与配体在成键轨道间的相互σ-电子给予作用增强了金配合物的稳定性，从而促进了金的高效浸出。与其他浸出方法相比，本研究中的WS NBS-DMF为从电子垃圾中高效、选择性回收金提供了一种安全、经济且环保的技术。
