Investigation of waste PCB leach residue as a reducing agent in smelting processes

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2020-09-01
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Mcode
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Language
en
Pages
14
Series
Minerals Engineering, Volume 156
Abstract
The advancement in technology has resulted in the development of newer and improved electrical products. The older products are becoming obsolete and are discarded as waste at a continuously increasing trend. Printed circuit board (PCB) is the main focus of electronic waste recycling because of the inherently high value of contained metals such as gold and copper. Hydrometallurgical route, which is often used to recover the metals, does not take into account the non-metallic PCB fractions. These non-metallic fractions may end up in landfills or incinerated which leads to secondary pollution. In this work, the use of the leached PCB waste fraction as reductant in primary metal smelting operations and solid state reduction is investigated. Laboratory-scale experiments and thermodynamic modelling were performed to simulate solid state reduction of hematite (Fe2O3) using various blends of PCB and graphitic carbon. Differential Scanning Calorimeter (DSC) analysis of several samples were performed up to 1200 °C. Thermodynamic modelling was done using FactSage to predict the products of the hematite reduction below 1600 °C. The study showed that PCB residue might be used to partially replace the conventional reductants. The investigations revealed that at temperatures below 1000 °C, PCB reduces hematite to lower forms of iron oxide at a faster rate than that of graphite. The optimal blend contains about 20 wt% PCB residue which has the same reduction degree as graphite. Thermodynamic modelling of iron smelting was also performed using various blends of PCB and coal. The models showed that PCB residue might be used to partially replace the conventional reductants. The study revealed that in iron smelting, the optimal blend contains around 20 wt% PCB residue, with energy savings of 150 kWh/t of ore to achieve the same metal recovery.
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Keywords
Electronic waste, Hydrometallurgy, Printed circuit board, Pyrometallurgy, Reductant
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Citation
Attah-Kyei , D , Akdogan , G , Dorfling , C , Zietsman , J , Lindberg , D , Tesfaye , F & Reynolds , Q 2020 , ' Investigation of waste PCB leach residue as a reducing agent in smelting processes ' , Minerals Engineering , vol. 156 , 106489 . https://doi.org/10.1016/j.mineng.2020.106489