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Metals 2019, 9(3), 363; https://doi.org/10.3390/met9030363

High-Pressure Oxidative Leaching and Iodide Leaching Followed by Selective Precipitation for Recovery of Base and Precious Metals from Waste Printed Circuit Boards Ash

1
Graduate School of International Resource Sciences, Akita University, 1-1 Tegata-Gakuen machi, Akita 010-8502, Japan
2
Department of Metallurgy and Materials Engineering, Montana Technological University, 1300 West Park Street, Butte, MT 59701, USA
*
Authors to whom correspondence should be addressed.
Received: 1 March 2019 / Revised: 16 March 2019 / Accepted: 18 March 2019 / Published: 20 March 2019
(This article belongs to the Special Issue Leaching Kinetics of Valuable Metals)
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Abstract

This paper deals with the recovery of gold from waste printed circuit boards (WPCBs) ash by high-pressure oxidative leaching (HPOL) pre-treatment and iodide leaching followed by reduction precipitation. Base metals present in WPCB ash were removed via HPOL using a diluted sulfuric acid solution at elevated temperatures. Effects of potassium iodide concentration, hydrogen peroxide concentration, sulfuric acid concentration, leaching temperature, and leaching time on gold extraction from pure gold chips with KI–H2O2–H2SO4 were investigated. The applicability of the optimized iodide leaching process for the extraction of gold from the leach residue obtained after HPOL were examined at different pulp densities ranging from 50 g/t to 200 g/t. Results show that the removal efficiency was 99% for Cu, 95.7% for Zn, 91% for Ni, 87.3% for Al, 82% for Co, and 70% for Fe under defined conditions. Under the optimal conditions, the percentage of gold extraction from the gold chips and the residue of WPCBs was 99% and 95%, respectively. About 99% of the gold was selectively precipitated from the pregnant leach solution by sequential precipitation with sodium hydroxide and L-ascorbic acid. Finally, more than 93% of gold recovery was achieved from WPCB ash by overall combined processes. View Full-Text
Keywords: waste printed circuit board; gold; iodide; iodine; ascorbic acid; leaching; precipitation waste printed circuit board; gold; iodide; iodine; ascorbic acid; leaching; precipitation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Batnasan, A.; Haga, K.; Huang, H.-H.; Shibayama, A. High-Pressure Oxidative Leaching and Iodide Leaching Followed by Selective Precipitation for Recovery of Base and Precious Metals from Waste Printed Circuit Boards Ash. Metals 2019, 9, 363.

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