Pyrometallurgy coupling bioleaching for recycling of waste printed circuit boards
2022
Abstract The pyrometallurgy coupling indirect bioleaching strategy is proposed for the recycling of WPCBs to avoid the disadvantages of time-consuming, low processing power, and relatively low efficiency of conventional bioleaching. The results show that under the pulp density of 2.5% (w/v), the low content (0.26 wt.%) of Ni in the raw WPCBs is completely extracted by indirect bioleaching, while the release rate of a high content (24.52 wt.%) of Cu is only 46.9%. However, the calcination pretreatment significantly improves Cu release by indirect bioleaching, and 100% Cu extraction is attained from the 600 °C-treated WPCBs at the high pulp density of 5.0% due to the formation of tractable CuO. Conversely, the release of Ni is inhibited by calcination evidently, and the indirect bioleaching efficiency of Ni declines from 34.9% to 10.1% when the pulp density lifts from 2.5% to 10.0% because of the formation of NiO with lower kinetics of acid-dissolution. On the other hand, due to the complete removal of Cu and the formation of insoluble NiO, the toxicity and environmental risk analysis indicates that the bioleaching residue of the 600 °C-treated WPCBs at the pulp density of 5.0% is completely detoxified and can be reused as non-hazardous materials safely, while the combination of the calcination and indirect bioleaching significantly reduces the environmental risk associated with the WPCBs. These findings provide the theoretical basis for a perfect combined process of pyrometallurgy and bioleaching for tackling the WPCBs from a technological perspective.
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