Abstract
This study presents an optimized leaching and electrowinning process for the recovery of copper from waste printed circuit boards including studies of chemical consumption and recirculation of leachate. Optimization of leaching was performed using response surface methodology in diluted sulfuric acid and hydrogen peroxide media. Optimum leaching conditions for copper were found by using 3.6 mol L−1 sulfuric acid, 6 vol.% hydrogen peroxide, pulp density of 75 g L−1 with 186 min leaching time at 20°C resulting in complete leaching of copper followed by over 92% recovery and purity of 99.9% in the electrowinning. Study of chemical consumption showed total decomposition of hydrogen peroxide during leaching, while changes in sulfuric acid concentration were minor. During recirculation of the leachate with up to 5 cycles, copper recovery and product purity remained at high levels while acid consumption was reduced by 60%.
Highlights
The revolution of information technology has led to rapidly increasing generation of waste electrical and electronic equipment (WEEE), with the annual global production of approximately 45 million metric tons in 2016
Havlik et al studied the combustion of printed circuit boards and found that metallic copper was oxidized to CuO at 900°C.8
Hydrogen peroxide was decomposed in 90 min during the leaching, while only minor changes were observed in the sulfuric acid concentration in each step
Summary
The revolution of information technology has led to rapidly increasing generation of waste electrical and electronic equipment (WEEE), with the annual global production of approximately 45 million metric tons in 2016. WEEE is a valuable secondary resource containing base and precious metals, with high economic prospects, but the heterogeneity of the material generates great challenges in waste treatment processes as well as in the recovery of metals. Printed circuit boards (PCBs) are the most valuable fraction of WEEE containing high concentrations of base metals, including up to 27 wt.% of copper, and high concentrations of precious metals including silver, gold, and palladium.[4]. Pretreated PCB material, with fine particle size (500–1000 lm), is commonly used for the leaching studies of metals.[12,13,14,15,16]
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