EARTH

[3901-12-09] Evaluation of Metal Leaching Efficiency from Waste Printed Circuit Boards by Inorganic Acid

○Zhenfeng Xiong¹, Ying Huang¹, Kemei Zhou², Dong Zhang¹, Juan Bao², Yuxue Qiu¹, Huaping Yu¹, Zifei Sun¹ (1. Southeast University, 2. Nanjing Water Affairs Group Company Limited)

Chairman: Kyoungkeun Yoo （Korea Maritime and Ocean University）, Naoki Hiroyoshi (Hokkaido University)

Keywords:Leaching, Golden finger, Precious metals;, Nitric acid, Aqua regia

Production of waste electronic and electrical equipment (WEEE) has increased significantly in recent years. Therefore, the recycling of these E-wastes especially the waste printed circuit boards (WPCB) is very important for resource recycle. It is found that precious metals from WPCB can be extracted effectively by hydrometallurgical method, but interference from other potential competing metals may affect the extraction efficiency of precious metals (i.e. Au). For further extraction and separation, leaching method using nitric acid and aqua regia has great advantages to separate Au from most other metals in WPCB. In this study, two-step leaching process was employed to leach metals from WPCB. Three kinds of WPCB samples were used: whole WPCB board, golden finger part and board besides golden finger. Leaching efficiencies of metals from these three parts with different nitric acid concentration were studied. Metal contents of leaching liquor were characterized by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The results show that the Au concentration of the golden finger part is 3 times of that of the whole WPCB board. Competing metals such as Ni and Fe have lower mass fraction in the whole WPCB board compared with that in the golden finger. However, Cu shows a higher proportion in the golden finger part. It is found that Au can be effectively separated from most other metals by first nitric acid leaching with 8M concentration and the following aqua regia leaching. This is useful for increasing the Au proportion in the leaching liquor and can positively influence the following Au recycling efficiency.