Wang Ruixue, Fan Guoliang, Zhang Chenglong
School of Resources and Environmental Engineering, Shanghai Polytechnic University, No. 2360 Jinhai Road, Shanghai 201209, People's Republic of China; Shanghai Collaborative Innovation Centre for Waste Electrical and Electronic Equipment Recycling, Shanghai Polytechnic University, No. 2360 Jinhai Road, Shanghai 201209, People's Republic of China.
School of Resources and Environmental Engineering, Shanghai Polytechnic University, No. 2360 Jinhai Road, Shanghai 201209, People's Republic of China; Shanghai Collaborative Innovation Centre for Waste Electrical and Electronic Equipment Recycling, Shanghai Polytechnic University, No. 2360 Jinhai Road, Shanghai 201209, People's Republic of China.
Waste Manag. 2024 Apr 15;178:351-361. doi: 10.1016/j.wasman.2024.02.043. Epub 2024 Mar 1.
The traditional hydrometallurgy technology has been widely used to recover precious metals from electronic waste. However, such aqueous recycling systems often employ toxic/harsh chemicals, which may cause serious environmental problems. Herein, an efficient and environment-friendly method using a deep eutectic solvent (DES) mixed system of choline chloride-ethylene glycol-CuCl·2HO is developed for gold (Au) recovery from flexible printed circuit boards (FPCBs). The Au leaching and precipitation efficiency can reach approximately 100 % and 95.3 %, respectively, under optimized conditions. Kinetic results show that the Au leaching process follows a nucleation model, which is controlled by chemical surface reactions with an apparent activation energy of 80.29 kJ/mol. The present recycling system has a much higher selectivity for Au than for other base metals; the two-step recovery rate of Au can reach over 95 %, whereas those of copper and nickel are < 2 %. Hydrogen nuclear magnetic resonance spectroscopy (HNMR) and density functional theory (DFT) analyses confirm the formation of intermolecular hydrogen bonds in the DES mixed system, which increase the system melting and boiling points and facilitate the Au leaching process. The Au leaching system can be reused for several times, with the leaching efficiency remaining > 97 % after five cycles. Moreover, ethylene glycol (EG) and choline chloride (ChCl) act as aprotic solvents as well as coordinate with metals, decreasing the redox potential to shift the equilibrium to the leaching side. Overall, this research provides a theoretical and a practical basis for the recovery of metals from FPCBs.
传统的湿法冶金技术已被广泛用于从电子废物中回收贵金属。然而，这种水相回收系统通常使用有毒/苛刻的化学物质，这可能会导致严重的环境问题。在此，开发了一种使用氯化胆碱-乙二醇-CuCl·2H₂O的深共熔溶剂（DES）混合体系从柔性印刷电路板（FPCBs）中回收金（Au）的高效且环境友好的方法。在优化条件下，金的浸出率和沉淀率分别可达到约100%和95.3%。动力学结果表明，金的浸出过程遵循成核模型，该过程由化学表面反应控制，表观活化能为80.29 kJ/mol。本回收系统对金的选择性远高于其他贱金属；金的两步回收率可达95%以上，而铜和镍的回收率<2%。氢核磁共振光谱（HNMR）和密度泛函理论（DFT）分析证实了DES混合体系中分子间氢键的形成，这提高了体系的熔点和沸点，并促进了金的浸出过程。金的浸出体系可重复使用多次，五次循环后浸出效率仍>97%。此外，乙二醇（EG）和氯化胆碱（ChCl）既作为非质子溶剂，又与金属配位，降低了氧化还原电位，使平衡向浸出方向移动。总体而言，本研究为从FPCBs中回收金属提供了理论和实践基础。
