Recovery of Metals from Discarded Integrated Circuits
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Recovery of Metals from Discarded Integrated Circuits Amit Barnwal 1 & Nikhil Dhawan 1 Received: 17 December 2019 / Accepted: 9 June 2020 # Society for Mining, Metallurgy & Exploration Inc. 2020
Abstract The present study reports a processing route to recover metals from integrated circuits of discarded random access memory (RAM) units containing ~ 66% printed circuit boards and ~ 33% integrated circuits. The integrated circuits are manually separated, grounded, classified, and subjected to water fluidization for the effective separation of metals. The significant separation was achieved via water fluidization, and the underflow fraction was magnetically separated. The magnetic fraction was thermally exposed in a muffle furnace, and the process optimization was carried out using a Box-Behnken statistical design. The detailed characterization at subsequent steps significantly aids the understanding of metal-plastic separation and enrichment. A concentrate containing 97% metals (Fe-59%, Ni-9.5%, Cu-7.7%, Sn-13.4%, Pb-5.6%, Ag-1.6%) with 96 wt% recovery can be recovered from discarded IC units. The process pursued is simple, adaptable, and environment-friendly, and the product can be used in conventional smelters. Keywords Integrated circuit . Fluidization . Magnetic separation . Iron . Nickel . Recovery
1 Introduction The composition complexity of printed circuit boards (PCBs) poses great difficulty for an appropriate recycling method. By 2020, electronic waste comprising old computers, laptops, mobile, and other electronic equipment will jump by ~ 500% in India compared to the year 2007 [1]. Integrated circuits (ICs) are a miniaturized electronic circuit on the surface of a thin substrate of semiconductor material [2]. Recycling of ICs present on RAM units is essential because of the presence of a mixture of metals such as iron (Fe), nickel (Ni), copper (Cu), tin (Sn), and silver (Ag). “ICs” possess small size, lightweight, with excellent performance, and are widely used in electronics such as tape recorders, televisions, computers, military communications, and remote control. ICs are tightly covered with mold resin comprising organic materials and often cause difficulty in metal recovery [3]. During pyrometallurgical processing, PCBs are reduced in size and burned at high temperature (900–1000 °C) with slag formation comprising nonmetallic matter [4, 5]. However, it produces hazardous dioxin, furans, lead, acidic fumes, and ashes with significant heavy metals. Discarded “PCBs” are recycled and treated by * Nikhil Dhawan [email protected] 1
Department of Metallurgical and Materials Engineering, Indian Institute of Technology IIT, Roorkee, Uttarakhand 247667, India
hydrometallurgy [1, 6, 7], pyrometallurgy [8, 9], bioleaching [10], mechanical [11, 12, 14], and combination of methods [15]. Most of the processes mentioned above are confined to lab-scale research, whereas the industrial processes include the smelting process. The release of acid fumes during acid leaching, degradation, and generation of to
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