Abstract
Acid mine drainage (AMD) is a typical source of environmental pollution ascribing to its characteristics of high acidity and heavy metal content. Currently, most strategies for AMD treatment merely focus on metal removal rather than metal recovery. However, bioelectrochemical system (BES) is a promising technology to simultaneously remove and recover metal ions from AMD. In this study, both cupric ion and cadmium ion in simulated AMD were effectively recovered by BES inoculated with a novel exoelectrogen, Pseudomonas sp. E8, that was first isolated from the anodic electroactive biofilm of a microbial fuel cell (MFC) in this study. Pseudomonas sp. E8 is a facultative anaerobic bacterium with a rod shape, 0.43–0.47 μm wide, and 1.10–1.30 μm long. Pseudomonas sp. E8 can agglomerate on the anode surface to form a biofilm in the single-chamber MFC using diluted Luria-Bertani (LB) medium as an energy substrate. A single-chamber MFC containing the electroactive Pseudomonas sp. E8 biofilms has a maximum output voltage of 191 mV and a maximum power density of 70.40 mW/m2, which is much higher than those obtained by most other exoelectrogenic strains in the genus of Pseudomonas. Almost all the Cu2+ (99.95% ± 0.09%) and Cd2+ (99.86% ± 0.04%) in simulated AMD were selectively recovered by a microbial fuel cell (MFC) and a microbial electrolysis cell (MEC). After the treatment with BES, the high concentrations of Cu2+(184.78 mg/L), Cd2+(132.25 mg/L), and total iron (49.87 mg/L) in simulated AMD were decreased to 0.02, 0.19, and 0 mg/L, respectively. Scanning electron micrograph (SEM), energy dispersive X-ray spectrometry (EDXS) and X-ray diffraction (XRD) analysis indicate that the Cu2+ and Cd2+ in simulated AMD were selectively recovered by microbial electrochemical reduction as Cu0 (together with trace amounts of Cu2O) or Cd0 on the cathode surface. Collectively, data suggest that Pseudomonas sp. E8 has great potential for AMD treatment and metal recovery.
Highlights
Acid mine drainage (AMD) is a metal-rich acidic water occurring in abandoned, inactive, and active mining sites, around open-pit mining operations, and mine waste sites, which poses significant environmental and economic challenges to the mining industry [1]
AMD is primarily generated from multi-step oxidation processes when the mineral-containing sulfides are exposed to air and water, especially in the presence of chemolithotrophic acidophiles [2,3]
The novel exoelectrogenic strain used in this study was isolated from the anode of a microbial fuel cell (MFC), which was inoculated with the activated sludge from Xinkaipu Municipal Sewage Treatment Plant (Changsha, China) and fed with 20 mM sodium acetate
Summary
Acid mine drainage (AMD) is a metal-rich acidic water occurring in abandoned, inactive, and active mining sites, around open-pit mining operations, and mine waste sites, which poses significant environmental and economic challenges to the mining industry [1]. Passive treatments usually achieve precipitation by creating reduction conditions, using organic matter as alkaline agents to achieve sulfide metal precipitation, which include aerobic wetlands, composting reactors, and so on [13] These technologies require the continuous supply of a large quantity of chemicals and energy, and a high processing cost [14]. Those technologies have the drawbacks of either low remediation efficiency or producing new wastes (e.g., sludge, brines, and spent media) which require further treatment. E8 has great potential for AMD treatment and metal recovery
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