Leaching of metastannic acid from e-waste by-products
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ORIGINAL ARTICLE
Leaching of metastannic acid from e‑waste by‑products Jovana Djokić1 · Branimir Jovančićević2 · Ilija Brčeski2 · Milisav Ranitović3 · Nataša Gajić3 · Željko Kamberović4 Received: 29 October 2019 / Accepted: 29 June 2020 © Springer Japan KK, part of Springer Nature 2020
Abstract Anode slime and tin precipitate as by-products of the electrorefining (ER) of non-standard anodes obtained after experimental smelting of waste electric and electronic equipment (e-waste), in addition to the base and precious metals, contains a significant amount of tin. Due to its presence as inert S nO2 hydrate (β metastannic acid) and its dissipation between slime and electrolyte, anode slime processing and metals valorization are difficult. This study aimed to investigate conditions under which efficient leaching of metastannic acid could be achieved to facilitate further metals valorization, especially precious metals. The investigation was performed using the by-products obtained from the ER of the non-standard Cu anodes produced by pyrometallurgical processing of e-waste. After detailed characterization of obtained products, the influence of various process parameters like temperature, acid concentration, leaching time, as well as the influence of reducing agent, sulfur compounds, and SnO2 hydration rate on leaching efficiency was investigated. It was found that efficiency of 99% can be achieved by leaching the desulfurized tin precipitate sample in 6 M HCl at 90 °C for 90 min with the addition of Mg powder. The application of the tin removal process, described in this paper, contributes to efficient material flow management. Graphic abstract
Keywords E-waste · Tin · Metastannic acid · Leaching · Anode slime
1
Branimir Jovančićević [email protected]
Innovation Centre of Faculty of Chemistry in Belgrade Ltd., University of Belgrade, Studentski trg 12‑16, 11000 Belgrade, Serbia
2
Ilija Brčeski [email protected]
Faculty of Chemistry, University of Belgrade, Studentski trg 12‑16, 11000 Belgrade, Serbia
3
Innovation Centre of Faculty of Technology and Metallurgy in Belgrade Ltd., University of Belgrade, Karnegijeva 4, 11000 Belgrade, Serbia
4
Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade, Serbia
* Jovana Djokić [email protected]
Milisav Ranitović [email protected] Nataša Gajić [email protected] Željko Kamberović [email protected]
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Introduction Due to the specific properties, tin is present in almost every e-device. In addition to the common conductive alloys such as bronze or brass, over 40% of produced tin is used in soldering alloys, and this figure tends to grow due to transition to the new lead-free soldering alloys containing more than 95 wt.% of this metal [1, 2]. In addition, e-waste generation is in constant increase, so tin share in this valuable secondary material is only growing. However, tin recovery from e-waste represents a huge technological challenge. According to literature, e
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