Continuous removal and recovery of palladium in an upflow anaerobic granular sludge bed (UASB) reactor

Abstract

BACKGROUND: The aim of this study was to investigate the feasibility of utilizing a continuous-flow anaerobic granular sludge bed (UASB) reactor for the removal of palladium (II) from aqueous streams and the recovery of this precious metal as biogenic Pd(0). Anaerobic methanogenic granular sludge has been recently shown to reduce Pd(II) in the presence of a suitable electron donor leading to the formation of biomass-associated Pd(0). RESULTS:Two laboratory-scale UASB reactors were fed with ethanol or acetate, in order to compare their performance in terms of Pd removal and reduction. Pd(II) was added in two periods of increasing concentration, 5 mg Pd(II) L −1 and then 15 mg Pd(II) L −1 . Extensive removal of Pd (up to 99%), was attained in both reactors. X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analysis confirmed significant differences in the content of Pd(0) in the biomass, depending on the electron donor used. The main mechanisms of Pd(II) removal when acetate and ethanol were used as electron donor were biosorption and reduction to Pd(0) by biogenic H 2 released as fermentation product, respectively. CONCLUSIONS:The results obtained demonstrate that it is possible to apply a continuous process for Pd reduction and recovery using a methanogenic consortium. Scanning electron microscopySludge samples obtained from both reactors were prepared for scanning electron microscopy (SEM) by fixation in 2.5% glutaraldehyde for 30 min, washed with two changes in 0.1 mol L −1 PIPES wileyonlinelibrary.com/jctb

Immobilization of biogenic Pd(0) in anaerobic granular sludge for the biotransformation of recalcitrant halogenated pollutants in UASB reactors

“…Moreover, Suja and colleagues (Suja et al 2014) demonstrated that interaction between biogenic Pd(0) and aerobic granular sludge promoted the reduction of p-nitrophenol and Cr(VI). Our previous study demonstrated that it is possible to reduce Pd(II) to Pd(0) in UASB reactors using anaerobic granular sludge, which promoted its immobilization (Pat-Espadas et al 2015).…”

“…Moreover, the use of mixed microbial consortia can offer advantages over pure cultures including easy process control and low operational costs since operation in aseptic conditions is not necessary and consortia have the ability to adapt to minor changes in conditions and promote synergistic interactions (Alexander 1999;Mukred et al 2008;Rashamuse and Whiteley 2007). Furthermore, if a methanogenic consortia is provided with an adequate electron donor, it would promote Pd(II) reduction to Pd(0) via biogenic hydrogen produced from fermentation and this H 2 can be used to activate the catalyst once Pd(0) has already been produced; in this way, the process would be self-sustained (Pat-Espadas et al 2015). For that reason, the aim of this work was to develop a new option for the recovery of palladium from industrial streams based on the capacity of methanogenic granular sludge to reduce Pd(II) and to immobilize biogenic Pd(0) in the granular biomass.…”

Bio-Reclamation of Strategic and Energy Critical Metals from Secondary Resources

“…It has been observed that the microbial activity is helpful to generate an in situ reducing environment for metal ion reduction and the subsequent catalytic reactions as well [60][61][62]. Lenz et al [63] showed the important role of metal species in reduction potential and bacterial uptake efficiency.…”

“…Geobacter), biofilms, and granular sludge [60,64]. In a continuous recovery of palladium from granular sludge in an up-flow anaerobic bed reactor, Pat-Espadas et al [61] showed the practical feasibility of the bio-recovery. Using Serratia sp.…”

Considerations about recovery of critical metals using bio-metallurgy

“…Paladium has been obtained using diverse microorganisms and biofilms [23]. The platinium recovery by mixed culture has been demonstrated [24].…”