Abstract
Bioleaching is a promising strategy to recover valuable metals from spent printed circuit boards (PCBs). The performance of the process is catalyzed by microorganisms, which the toxic effect of PCBs can inhibit. This study aimed to investigate the capacity of an acidophilic iron-oxidizing culture, mainly composed of Leptospirillum ferriphilum, to oxidize iron in PCB-enriched environments. The culture pre-adapted to 1% (w/v) PCB content successfully thrived in leachates with the equivalent of 6% of PCBs, containing 8.5 g L–1 Cu, 8 g L–1 Fe, 1 g L–1 Zn, 92 mg L–1 Ni, 12.6 mg L–1 Pb, and 4.4 mg L–1 Co, among other metals. However, the inhibiting effect of PCBs limited the microbial activity by delaying the onset of the exponential iron oxidation. Successive subcultures boosted the activity of the culture by reducing this delay by up to 2.6 times under batch conditions. Subcultures also favored the rapid establishment of high microbial activity in continuous mode.
Highlights
Printed circuit boards (PCBs) are the main processing unit for the electronic devices that have become essential to our daily lives in recent decades
Microbial Performance at Different Leachate Concentrations. These experiments performed in shake flasks aimed to characterize the bacterial performance of the adapted FeOB culture in PCB environments
A wide range of other metals was present in concentrations below 100 mg L−1
Summary
Printed circuit boards (PCBs) are the main processing unit for the electronic devices that have become essential to our daily lives in recent decades. The dissolution of metals assisted by microorganisms, known as bioleaching, is a biotechnological process that is established worldwide This technology is already applied at an industrial scale for the extraction of Au and Cu, and marginally for Ni, Co, and U, from primary ores (Rawlings and Johnson, 2007; Wassink and Asselin, 2019). It is attracting considerable attention for the extraction of metals from secondary sources such as mining waste, contaminated river sludge (Zhang et al, 2018), fly ash (Xu et al, 2014), batteries (Liu et al, 2020), and spent PCBs (Bryan et al, 2015, 2020; Guezennec et al, 2015; Isıldar et al, 2016; Wu et al, 2018; Hubau et al, 2020).
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