Evaluating the optimal digestion method and value distribution of precious metals from different waste printed circuit b
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ORIGINAL ARTICLE
Evaluating the optimal digestion method and value distribution of precious metals from different waste printed circuit boards Mahdokht Arshadi1 · Soheila Yaghmaei1 · Alireza Esmaeili1 Received: 27 July 2019 / Accepted: 22 March 2020 © Springer Japan KK, part of Springer Nature 2020
Abstract Knowing the metal content of electronic waste is essential to evaluate metal recovery. Lack of a standard method for digestion of precious metals from electronic waste has resulted in difficulty in comparison to the efficiency of recovery. In this study, different precious metal digestion methods and economic value of precious metals from different types of waste printed circuit boards in different fraction sizes, including computer printed circuit boards, mobile phone printed circuit boards, television printed circuit boards, fax machine printed circuit boards, copy machine printed circuit boards, and central processing unit were examined. The optimal digestion method using aqua regia, hydrogen peroxide, hydrofluoric acid, and boric acid was adopted. The precious metal content was analyzed to answer what precious metals and types of printed circuit boards is prefer∑ ence. The results presented the following order of total value of precious metals ( Wti Prti ): central processing unit > Mobile phone > Copy > Fax > Computer > Television. Among the precious metals, gold and palladium were, respectively, attributed to the highest value distribution. The average values of the precious (gold and palladium) and all of the metals of electronic waste are about 19 and 21 times higher than the average cost of the world’s top ten mines. Keywords Waste PCBs · Acid digestion · Precious metal recycling · Value distribution
Introduction With the development of electronic instrument industry and consumer market in recent years, electronic waste (E-waste) has created a great concern worldwide and has a significant impact on the environment. The increase of E-waste is quite fast, and its generation rate is three times more than other solid municipal waste streams [1–3]. The global trend in E-waste goes upwards, and it estimates to be continued for a long time [4]. United States Environmental Protection Agency (EPA, 2004) estimated a mobile phone is held by the users for a period of 9–18 months [5]. The lifespan of personal computers between 1992 and 2005 decreased from 5 to 3 years [6]. It is estimated that approximately 72 million tons of E-waste was generated in 2017 worldwide [7]. E-waste embodies a vast range of electrical and electronic instruments generated from industries as well as homes, including laptops, tablets, MP3 players, computers, * Soheila Yaghmaei [email protected] 1
Chemical and Petroleum Engineering Department, Sharif University of Technology, Tehran, Iran
mobile phones, refrigerators, televisions, air conditioners, etc., [8]. It contains more than 1000 different elements, including wood, plywood, glass, concrete, ferrous metals, non-ferrous metals, plastics, rubber, ceramics, and other items [9].
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