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Available online at www.sciencedirect.com Procedia Environmental Sciences 16 (2012) 560 – 568 The 7th International Conference on Waste Management and Technology Current status on leaching precious metals from waste printed circuit boards Yanhua Zhanga,*, Shili Liua, Henghua Xiea, Xianlai Zengb, Jinhui Lib aDongjiang Environmental Company Limited, Shenzhen 518057, China bSchool of Environment, Tsinghua University, Beijing 100084, China Abstract Current research on leaching precious metals from waste printed circuit boards (PCBs) in the world is introduced. In the paper, hydrometallurgical processing techniques including cyanide leaching, thiourea leaching, thiosulfate leaching, and halide leaching of precious metals are addressed in detail. In order to develop an environmentally friendly technique for recovery of precious metals from Waste PCBs, a critical comparison of main leaching methods is analyzed based on three-scale analytic hierarchy process (AHP). The results suggest that thiourea leaching and iodide leaching make more possible to replace cyanide leaching. © 2012 Published by Elsevier B.V. © 2012 Selection and/or peer-review under responsibility of Basel Convention Coordinating Centre for Asia and the Pacific Selection and/or peer-review under responsibility of Basel Convention Coordinating Centre for Asia and the Pacific and National Center of Solid Waste Management, Ministry of Environmental Protection of China. and National Center of Solid Waste Management, Ministry of Environmental Protection of China. Open access under CC BY-NC-ND license. Key Words: waste printed circuit board; leaching; recovery; precious metals; analytic hierarchy process. 1. Introduction Nowadays, the amount of scrap materials generated in the process of molding and machining of printed circuit boards (PCBs) reach 100,000 tons every year in China. Taking into account PCBs from the large quantities of waste electrical and electronic products imported abroad and dismantling of end-of-life electrical and electronic equipments, each year more than 500,000 tons waste PCBs need to be treated in China mainland [1], which contain about 150,000 to 200,000 tons of metals. Table 1 gives examples of the metal composition of waste PCBs from literatures [2-15]. As can be seen from Table 1, metals contents of PCBs are varied in different literatures. The reason for this is that metals contents especially precious metals contents of PCBs are varied with age, origin and manufacturer. But even calculating with the minimum content of gold in Table 1, there will be 40 tons of gold in 500,000 tons of waste PCBs. * Corresponding author. Tel.: +86 755 2726 4217; fax: +86 755 2726 4217. E-mail address: zhyh@dongjiang.com.cn 1878-0296 © 2012 Selection and/or peer-review under responsibility of Basel Convention Coordinating Centre for Asia and the Pacific and National Center of Solid Waste Management, Ministry of Environmental Protection of China Open access under CC BY-NC-ND license. doi:10.1016/j.proenv.2012.10.077PDF Image | leaching precious metals from waste printed circuit boards
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