Metal recycling from waste memory modules efficiently and environmentally friendly by low-temperature alkali melts
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tal recycling from waste memory modules efficiently and environmentally friendly by low-temperature alkali melts 1
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ZHU MingWei , MA HaoBo , HE Jie , CHEN Bin , ZHANG LiLi , JIANG HongXiang , 2 2 SUN XiaoJun & ZHAO JiuZhou 1
School of Materials Science and Engineering, Shenyang Aerospace University, Shenyang 110136, China; 2 Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China Received March 9, 2020; accepted May 7, 2020; published online August 7, 2020
Recycling of waste electrical and electronic equipment has become an urgent global issue in recent years from the prospectives of resources recycling and environmental protection. In the present work, the recycling of waste memory modules (WMMs) through low-temperature alkali melts was investigated, based on the thermodynamic analysis of the nonmetallic reactions of brominated epoxy resin, glass fiber and memory chip with the molten mixed alkali. The effects of the reaction temperature and the ratio of alkali mixture on the removal rate of nonmetallic parts in WMMs were discussed under the condition of air atmosphere. The optimum process parameters were further confirmed by in-situ monitoring of the temperature during the whole reaction process. The mixtures with Cu, Fe and Ni as the main components were obtained after the treatment of WMMs in the molten alkali. These mixed metals were further separated into copper-rich and ferronickel-rich metals by physical magnetic separation. Moreover, the precious metals Au and Ag were enriched in Cu-rich alloys. This work provided an efficient and environment-friendly method for metal recycling from WMMs. metal recycling, waste memory module, molten alkali, precious metal Citation:
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Zhu M W, Ma H B, He J, et al. Metal recycling from waste memory modules efficiently and environmentally friendly by low-temperature alkali melts. Sci China Tech Sci, 2020, 63, https://doi.org/10.1007/s11431-020-1624-8
Introduction
With the rapid development of electronic manufacturing industry, a large amount of waste electrical and electronic equipment (WEEE) will be discarded due to the continuous updating of electronic equipment. Consequently, 0.6–1.5 million tons of waste printed circuit boards (WPCBs) are produced every year around the world, accounting for about 3% of the total electronic waste [1,2]. Metal resources are rich in the circuit boards which include not only common metals such as Cu, Fe, Ni, Sn and Zn, but also some rare precious metals like Au, Ag, Pt, Pd, Sb, etc. The grade of those precious metals in WPCBs is dozens to hundreds of
*Corresponding author (email: [email protected])
times higher than that in common minerals, which makes WPCBs so-called urban mines [3,4]. On the other hand, some toxic heavy metals such as Pb, Cd, Cr, also exist in WPCBs. In particular, the brominated epoxy resin in the circuit board contains a lot of halogen like chlorine and bromine. Therefore, incineration or simple burying of the electronic waste not only causes the waste of metal resources, but
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