Double-stage continuous bioreactor for the bioleaching of printed circuit boards (PCBs) to recover metals with acidophilic micro-organisms

摘要

Nowadays, many studies focus on bioleaching methods for recovering metals from WEEE. The efficiency of this process is strongly dependent on the microorganisms and the design of the reactor since solid-liquid-gas mass transfer plays an important role. In the present study, comminuted spent printed circuit boards (PCBs) were bioleached into a double-stage continuous bioreactor. The first stage of the bioreactor was a bubble column in which the acidophilic consortium BRGM-KCC composed of Leptospirillum ferriphilum and Sulfobacillus benefaciens was used to oxidize iron(II) into iron(III). The resulting leaching solution was employed to leach the metals contained in PCBs under mechanical stirring in the second stage of the bioreactor. The use of two distinct stages avoids microbial growth inhibition by separating the reactor in which microbial growth occurs from the reactor in which metal leaching takes place. Such a double-stage reactor is therefore particularly performant to achieve high bioleaching efficiency.