Simultaneous microbial and electrochemical reductions of vanadium (V) with bioelectricity generation in microbial fuel cells

Bibliometric analysis and systematic review of electrochemical methods for environmental remediation

Electrochemical methods are increasingly favored for remediating polluted environments due to their environmental compatibility and reagent-saving features. However, a comprehensive understanding of recent progress, mechanisms, and trends in these methods is currently lacking. Web of Science (WoS) databases were utilized for searching the primary data to understand the knowledge structure and research trends of publications on electrochemical methods and to unveil certain hotspots and future trends of electrochemical methods research. The original data were sampled from 9080 publications in those databases with the search deadline of June 1st, 2022. CiteSpace and VOSviewer software facilitated data visualization and analysis of document quantities, source journals, institutions, authors, and keywords. We discussed principles, influencing factors, and progress related to seven major electrochemical methods. Notably, publications on this subject have experienced significant growth since 2007. The most frequently-investigated areas in electrochemical methods included novel materials development, heavy metal remediation, organic pollutant degradation, and removal mechanism identification. "Advanced oxidation process" and "Nanocomposite" are currently trending topics. The major remediation mechanisms are adsorption, oxidation, and reduction. The efficiency of electrochemical systems is influenced by material properties, system configuration, electron transfer efficiency, and power density. Electro-Fenton exhibits significant advantages in achieving synergistic effects of anodic oxidation and electro-adsorption among the seven techniques. Future research should prioritize the improvement of electron transfer efficiency, the optimization of electrode materials, the exploration of emerging technology coupling, and the reduction in system operation and maintenance costs.

The biotechnological potential of the Chloroflexota phylum

In the next decades, the increasing material and energetic demand to support population growth and higher standards of living will amplify the current pressures on ecosystems and will call for greater investments in infrastructures and modern technologies. A valid approach to overcome such future challenges is the employment of sustainable bio-based technologies that explore the metabolic richness of microorganisms. Collectively, the metabolic capabilities of Chloroflexota, spanning aerobic and anaerobic conditions, thermophilic adaptability, anoxygenic photosynthesis, and utilization of toxic compounds as electron acceptors, underscore the phylum's resilience and ecological significance. These diverse metabolic strategies, driven by the interplay between temperature, oxygen availability, and energy metabolism, exemplify the complex adaptations that enabled Chloroflexota to colonize a wide range of ecological niches. In demonstrating the metabolic richness of the Chloroflexota phylum, specific members exemplify the diverse capabilities of these microorganisms: Chloroflexus aurantiacus showcases adaptability through its thermophilic and phototrophic growth, whereas members of the Anaerolineae class are known for their role in the degradation of complex organic compounds, contributing significantly to the carbon cycle in anaerobic environments, highlighting the phylum's potential for biotechnological exploitation in varying environmental conditions. In this context, the metabolic diversity of Chloroflexota must be considered a promising asset for a large range of applications. Currently, this bacterial phylum is organized into eight classes possessing different metabolic strategies to survive and thrive in a wide variety of extreme environments. This review correlates the ecological role of Chloroflexota in such environments with the potential application of their metabolisms in biotechnological approaches.

Nitrogen-rich carbon composite fabricated from waste shrimp shells for highly efficient oxo-vanadate adsorption-coupled reduction

Protein, calcium carbonate, and chitin are abundant in shrimp shells. In this study, chemical treatment followed by hydrothermal carbonization was used to synthesize the nitrogen-rich hydrochar (HSHC) from shrimp shells. The untreated hydrochar exhibited a higher amount of calcium (25.37%) and less amount of nitrogen (2.68%) with alkaline pH (9.1). Interestingly chemical pre-treatment on shrimp shells boosted the nitrogen content to 6.81% and eliminated the calcium while controlling the pH to 6.4, which was beneficial for oxo-vanadate removal. The HSHC achieved vanadium(V) adsorption capacity of 21.20 mg/g at an optimal solution pH of 3.0, whereas the pristine hydrochar performed poorly (0.66 mg/g). The abundance of oxygen and nitrogen-based functional groups that developed through the chemical treatment resulted in improved adsorption coupled reduction performance of HSHC. This study proposed an inexpensive and environmentally friendly method for converting waste shrimp shells into value-added adsorbent.

Copper recovery from printed circuit boards leaching solution with bioelectricity generation using microbial fuel cell

Recovery of valuable metals via leaching printed circuit boards (PCBs) has gained moment recently. This work studied the Microbial fuel cell (MFC) performances for recovery of Cu from a Cu²⁺ solution by examining key operating parameters. A dual-chamber MFC with 6 cm × 6 cm × 7 cm dimensions was constructed. Both anode and cathode electrodes were made of a carbon cloth sheet. The anodic and cathodic chambers were separated by a Nafion membrane. The highest Cu recovery efficiency was 99.7% after 240 h batch mode operation, yielding 102 mW/m² MFC power density output using 1 g/L Cu²⁺ solution as the catholyte (initial pH 3) and an anolyte containing 1 g/L sodium acetate inoculated with a sludge from a wastewater treatment plant's anaerobic pond, with 2 cm distance between the electrodes made of polyacrylonitrile polymer. The highest open circuit voltage, current density (based on cross-section cathode area) and power density with an external load of 1 kΩ was 555 mV, 347 mA/m² and 193 mW/m², respectively. Additionally, recovery of Cu in the leachate of PCBs using sulfuric acid leaching after 48 h was performed and the highest Cu recovery was 50% in 48 h.

Study on the coordination conduct and kinetic insights within the oxo-vanadate and organic reductive nitrogen and sulfur functionalities during the reduction coupled adsorption processes: Implications in practical applications

Vanadium(V) is arising wastewater contaminant recently. Although bio-reduction of vanadium(V) is effective, the knowledge of electron transfer pathways and coordination nature by cellular organic functionalities is seriously lacking. Herein, the coordination conduct and kinetic modes for the reduction of V(V) by organic nitrogen and sulfur functionalities in working pHs are comprehensively investigated for the first time. The kinetics follow 3 steps; (1) diffusion of V(V) species, (2) reduction of V(V) to V(IV), and (3) adsorption of existing V species. The diffusion of V(V) is controlled by the protonated =NH₂⁺, -SH₂⁺, -CSH⁺ functional groups and oxo-vanadate speciation. The reduction of V(V) to V(IV) was efficient by -SH than =NH, -NH- , because of the higher oxidation potential of sulfur and which acted as the sole electron donor in the process. The coordination of V(V)/V(IV) species interacted with oxygen, nitrogen and sulfur atoms via parallel orientation and leads to multi-docking or single-ionic interactions, revealing the previously unrecognized track. Hence, the system tested in four types of wastewaters with different pHs and resulted the comprehensive practical applicability of the system. This study proposes a novel tactic to design an efficient V(V) wastewater treatment system by considering its water parameters.

Risk assessment and microbial community structure in agricultural soils contaminated by vanadium from stone coal mining

High health risks of vanadium (V) released by the mining of vanadium titanomagnetite (VTM) have been widely recognized, but little is known about the risks and microbial community responses of V pollution as a consequence of the stone coal mining (SCM), another important resource for V mining. In this study, the topsoils and the profile soils were collected from the agricultural soils around a typical SCM in Hunan Province, China, with the investigation of ecological, health risks and microbial community structures. The results showed that ∼97.6% of sampling sites had levels of total V exceeding the Chinese National standard (i.e., 130 mg/kg), and up to 41.1% of V speciation in the topsoils was pentavalent vanadium (V(V)). Meanwhile, the proportions of HQ > 1 and 0.6-1 in the topsoils were ∼8.3% and ∼31.0% respectively, indicating that V might pose a non-carcinogenic risk to children. In addition, the microbial community varied between the topsoils and the profile soils. Both sulfur-oxidizing bacteria (e.g. Thiobacillus, MND1, Ignavibacterium) and sulfate-reducing bacteria (e.g. Desulfatiglans, GOUTB8, GOUTA6) might have been involved in V(V) reductive detoxification. This study helps better understand the pollution and associated risks of V in the soils of SCM and provides a potential strategy for bioremediation of the V-contaminated environment.

Bioelectrochemical systems-based metal recovery: Resource, conservation and recycling of metallic industrial effluents

Metals represent a large proportion of industrial effluents, which due to their high hazardous nature and toxicity are responsible to create environmental pollution that can pose significant threat to the global flora and fauna. Strict ecological rules compromise sustainable recovery of metals from industrial effluents by replacing unsustainable and energy-consuming physical and chemical techniques. Innovative technologies based on the bioelectrochemical systems (BES) are a rapidly developing research field with proven encouraging outcomes for many industrial commodities, considering the worthy options for recovering metals from industrial effluents. BES technology platform has redox capabilities with small energy-intensive processes. The positive stigma of BES in metals recovery is addressed in this review by demonstrating the significance of BES over the current physical and chemical techniques. The mechanisms of action of BES towards metal recovery have been postulated with the schematic representation. Operational limitations in BES-based metal recovery such as biocathode and metal toxicity are deeply discussed based on the available literature results. Eventually, a progressive inspection towards a BES-based metal recovery platform with possibilities of integration with other modern technologies is foreseen to meet the real-time challenges of viable industrial commercialization.

Dynamics of vertical vanadium migration in soil and interactions with indigenous microorganisms adjacent to tailing reservoir

Severe vanadium pollution in deep soil through surface infiltration during mining activities has been particularly concerned, but little is known about vanadium migration dynamics in vertical soil profile. Indigenous microorganisms widely exist in soil, however, their functions and suffered impacts during vertical vanadium migration have rarely been investigated. In this study, 100 cm height columns were constructed with undisturbed soil around vanadium tailing reservoir were constructed to describe vertical vanadium transport process and corresponding interactions between vanadium and indigenous microorganisms. 91 d continuous leaching with pentavalent vanadium [V(V)] showed that V(V) gradually downward migrated. Soil microorganisms slowed down vertical V(V) migration rate by transferring V(V) to insoluble tetravalent vanadium. Enriched Gemmatimonadaceae and Actinobacteria were identified to contribute to microbial V(V) transformation. Co-existing nitrate weakened the soil's ability to intercept V(V) via electron competition. Microbial communities were reshaped by vanadium during leaching, while enzyme activities increased slightly due to vanadium stimulation. This work advances the understanding of vertical vanadium migration characteristics in soil, which is essential to risk management and effective remediation of vanadium-polluted sites.

Field study on the characteristics of scales in damaged multi-material water supply pipelines: Insights into heavy metal and biological stability

Microbial corrosion and heavy metal accumulation in metal water supply pipelines aggravate scale formation and may result in pipeline leakage or bursting events. To better understand the corrosion and corrosion products in the damaged pipes, deposits excavated from three damaged pipes after 22-26 year service periods were analyzed. Using a combination of advanced micro-mineral techniques and 16S rRNA high-throughput sequencing, the micromorphology, chemical composition, and bacterial community were investigated systematically. Unlined pipe wall scales ruptured while lined pipes leaked due to joint scales. Dendrogram correlation results demonstrated that V/As, Al/Pb, and Cr/Mn clusters exhibited co-adsorption and co-precipitation characteristics. FTIR and XRD analysis detected the presence of γ-FeOOH, α-FeOOH in loose scales, and Fe₃O₄ in rigid scales. Scales were colonized by various corrosion bacteria, with sulfate reducing bacteria and ammonia producing bacteria being dominant in the scales of anticorrosive and non-corrosive pipe, respectively. Tl, Ca, Al, and Pb exhibited an extremely positive correlation with Rhodocyclaceae, Ferritrophicum, Thermodesulfovibrionia, and Clostridiaceae. Al and V presented a potential Hazard Quotient risk to consumers, while Cd was potentially bioavailable in all inner scales. Overall, this study provides valuable information for the effective management and avoidance of corrosion-induced pipeline damage and heavy metal release.

Microbial selenate detoxification linked to elemental sulfur oxidation: Independent and synergic pathways

Elevated selenium levels in the environment, with soluble selenate [Se(VI)] as the common chemical species, pose a severe threat to human health. Anaerobic Se(VI) bioreduction is a promising approach for selenium detoxification, and various organic/inorganic electron donors have proved effective in supporting this bioprocess. Nevertheless, autotrophic Se(VI) bioreduction driven by solid inorganic electron donors is still not fully understood. This work is the first to employ elemental sulfur [S(0)] as electron donor to support Se(VI) bioreduction. A batch trial with mixed culture demonstrated the feasibility of this bioprocess, with Se(VI) removal efficiency of 92.4 ± 0.7% at an initial Se(VI) concentration of 10 mg/L within 36 h. Continuous column tests showed that increased initial concentration, flow rate, and introduction of NO₃^--N depressed Se(VI) removal. Se(VI) was mainly bioreduced to solid elemental Se with trace selenite in the effluent, while S(0) was oxidized to SO₄^2-. Enrichment of Thiobacillus, Desulfurivibrio, and Sulfuricurvum combined with upregulation of genes serA, tatC, and soxB indicated Se(VI) bioreduction was coupled to S(0) oxidation. Thiobacillus performed S(0) oxidation and Se(VI) reduction independently. Intermediate metabolites as volatile fatty acids, hydrogen and methane from S(0) oxidation were utilized by heterotrophic Se(VI) reducers for Se(VI) detoxification, indicative of microbial synergy.

Biologically removing vanadium(V) from groundwater by agricultural biomass

Vanadium (V) in groundwater can pose a serious threat on both environment and health. Agricultural biomass contains solid carbon source (SCS) and could be attractive for biologically removing V(V). For this purpose, cypress sawdust, corn cob and wheat straw were selected as SCSs to remove vanadate (NaVO₃). The experiments demonstrated a high efficiency of V(V) up to 98.6%, and the anaerobically biological reduction of V(V) to V(IV) by wheat straw was identified to be the best SCS by the spectrum analysis of XRD and FTIR. Along with increasing the fragment size of wheat straw, the V(V)-removal efficiency decreased, and the fragment size down to 1-3 mm was confirmed to have a significant bio-removal performance on V(V). Based on the analysis of 16s rRNA sequencing, the microbial abundance and diversity increased in the suspension liquid in the end, indicating that the microbial community could tolerate and/or detoxify V(V), besides degrading lignocellulosic materials.

Selective Adsorption of Amino Acids in Crystals of Monohydrocalcite Induced by the Facultative Anaerobic Enterobacter ludwigii SYB1

The morphology, crystal structure, and elemental composition of biominerals are commonly different from chemically synthesized minerals, but the reasons for these are not fully understood. A facultative anaerobic bacterium, Enterobacter ludwigii SYB1, is used in experiments to document the hydrochemistry, mineral crystallization, and cell surface characteristics of biomineralization. It was found that carbonate anhydrase and ammonia production were major factors influencing the alkalinity and saturation of the closed biosystem. X-ray diffraction (XRD) spectra showed that calcite, monohydrocalcite (MHC), and dypingite formed in samples with bacterial cells. It was also found that the (222) plane of MHC was the preferred orientation compared to standard data. Scanning transmission electron microscopy (STEM) analysis of cell slices provides direct evidence of concentrated calcium and magnesium ions on the surface of extracellular polymeric substances (EPS). In addition, high-resolution transmission electron microscopy (HRTEM) showed that crystallized nanoparticles were formed within the EPS. Thus, the mechanism of the biomineralization induced by E. ludwigii SYB1 can be divided into three stages: (i) the production of carbonate anhydrase and ammonia increases the alkalinity and saturation state of the milieu, (ii) free calcium and magnesium ions are adsorbed and chelated onto EPS, and (iii) nanominerals crystallize and grow within the EPS. Seventeen kinds of amino acids were identified within both biotic MHC and the EPS of SYB1, while the percentages of glutamic and aspartic acid in MHC increased significantly (p < 0.05). Furthermore, the adsorption energy was calculated for various amino acids on seven diffracted crystal faces, with preferential adsorption demonstrated on (111) and (222) faces. At the same time, the lowest adsorption energy was always that of glutamic and aspartic acid for the same crystal plane. These results suggest that aspartic and glutamic acid always mix preferentially in the crystal lattice of MHC and that differential adsorption of amino acids on crystal planes can lead to their preferred orientation. Moreover, the mixing of amino acids in the mineral structure may also have a certain influence on the mineral lattice dislocations, thus enhancing the thermodynamic characteristics.

Vanadium in soil-plant system: Source, fate, toxicity, and bioremediation

Vanadium(V) is an important component of industrial activities, while it may pose toxic hazards to plants, animals, and humans at high levels. Owing to its various uses in numerous industrial processes, high amount of V is released into the soil environment. Previous literature has focused on the biogeochemistry and ecotoxicity of V in soil-plant system. Consequently, this overview presents its source, fate, phyto-uptake, phyto-toxicity, detoxification, and bioremediation based on available data, especially published from 2015 to 2020. Vanadium occurs as various chemical forms (primarily as V(V) and V(IV)) in the soil environment, and its biogeochemical behaviour is easily influenced by soil conditions including redox potential, soil pH, organic matter, and microorganisms. Vanadium mainly accumulates in plant roots with very limited translocation to shoots. However, plants such as dog's tail grass and green bean are reported to accumulate high levels of V in aboveground tissues. An insight into the processes and mechanisms that allow plants to absorb and translocate V in soil-plant system is also stressed in this overview. In plants, low levels of V have beneficial effects on plant growth and development. Nevertheless, excessive V provokes numerous deleterious effects including reducing seed germination, inhibiting root and shoot growth, depressing photosynthesis, interfering with nutrients uptake, inducing overgeneration of ROS, and leading to lipid peroxidation. Mechanisms related to detoxification strategies like sequestration in root system, compartmentation in vacuoles and cell wall, and antioxidant defence systems to endure V-induced toxicity in plants are discussed as well. The detailed knowledge of bioremediation involved in the cleanup of V-contaminated soils would immensely help understand and improve the remediation process. Furthermore, this overview outlines several research gaps requiring further investigation in order to advance our understanding of the biogeochemical roles of V in soil-plant systems.

Using multiple carbon brush cathode in a novel tubular photosynthetic microbial fuel cell for enhancing bioenergy generation and advanced wastewater treatment

A novel tubular-type photosynthetic microbial fuel cell (PMFC) with algal growth and multiple electrodes in the cathode chamber was operated at various hydraulic retention times (HRTs). When the HRT in the cathode was fixed to 24 h, cell voltage gradually increased as the HRT in the anode was decreased from 24 h to 6 h, and at 6 h, 315 mV of electricity was generated and the dissolved oxygen concentration was 10.31 ± 2.60 mg/L. However, HRT changes in the cathode did not affect cell voltage generation much, although a sharp decrease in cell voltage was observed at 2-h HRT. With wastewater passing through the chambers in series (19.3-h total HRT), the PMFC was able to successfully generate cell voltage and remove nutrients. The maximum COD and phosphorus removal percentages were obtained for an initial COD of 300 mg/L, while the maximum nitrogen removal was obtained for an initial COD of 400 mg/L.

Metal removal and recovery using bioelectrochemical technology: The major determinants and opportunities for synchronic wastewater treatment and energy production

Microbial fuel cell (MFC) technology has emerged as a new and attractive bioelectrochemical approach in the last one and a half decade that offers an alternative to conventional treatment methods to remove and recover heavy metals and organics from wastewaters with simultaneous energy production. This technique has advantage over the conventional wastewater treatment techniques, which are energy intensive, sludge producing and with little effectivity at high concentrations. Significant work has been done in the recent years on MFC principle, electrode configuration, biofilm composition, application of MFC in wastewater treatment, metal removal or recovery and energy production. Basically, metal in the cathode chamber acts as acceptor of the electrons released from the oxidation of organic matter in the anode chamber by electrogenic microbes. Literature shows that efficacy of MFCs in removal and recovery of metals and power production is significantly influenced by redox potential of the metal, initial concentration, mix metal systems, carbon source in substrate, pH, biocathode, biofilm composition, gaseous environment in cathode, electrode modification and external resistance, which have been critically reviewed for the first time in the present paper to understand the role of the determinant factors that may be explored for improvement of the MFC performance. The paper provides further insights into the techno-economic aspects of MFC technology and suggests research needs for enhanced performance and reduced costs to increase its feasibility for application at commercial level.

Soil vanadium(V)-reducing related bacteria drive community response to vanadium pollution from a smelting plant over multiple gradients

The mining and smelting of navajoite has resulted in a serious vanadium pollution in regional geological environments and significant influence on soil microorganisms. However, the core microbiome responsible for adjusting community response to vanadium pollution and the driving pattern have been kept unclear. In this study, a suite of surface and profile soil samples over multiple gradients were collected in four directions and distances of 10-2000 m from a vanadium smelting plant in Panzhihua, China. The indigenous microbial communities and vanadium(V)-reducing related bacteria (VRB) were profiled by 16S rRNA gene high-throughput sequencing technique. Five VRB were detected in the original collected soil samples including Bacillus, Geobacter, Clostridium, Pseudomonas and Comamonadaceae based on high-throughput sequencing data analysis, and their abundances were significantly related with the content of vanadium. Low vanadium concentration promoted the growth of VRB, while high vanadium concentration would inhibit VRB multiplication. The Gaussian equation could be used to quantitatively describe the nonlinear relationship between VRB and vanadium. Network analysis demonstrated that the microbial communities were significantly influenced by VRB assemblage, and 1.32-52.77% of microbes in the community showed a close association with VRB. A laboratory incubation experiment also confirmed the core role of VRB to drive community response to vanadium pressure.

Enhancement of gasworks groundwater remediation by coupling a bio-electrochemical and activated carbon system

Here, we show the electrical response, bacterial community, and remediation of hydrocarbon-contaminated groundwater from a gasworks site using a graphite-chambered bio-electrochemical system (BES) that utilizes granular activated carbon (GAC) as both sorption agent and high surface area anode. Our innovative concept is the design of a graphite electrode chamber system rather than a classic non-conductive BES chamber coupled with GAC as part of the BES. The GAC BES is a good candidate as a sustainable remediation technology that provides improved degradation over GAC, and near real-time observation of associated electrical output. The BES chambers were effectively colonized by the bacterial communities from the contaminated groundwater. Principal coordinate analysis (PCoA) of UniFrac Observed Taxonomic Units shows distinct grouping of microbial types that are associated with the presence of GAC, and grouping of microbial types associated with electroactivity. Bacterial community analysis showed that β-proteobacteria (particularly the PAH-degrading Pseudomonadaceae) dominate all the samples. Rhodocyclaceae- and Comamonadaceae-related OTU were observed to increase in BES cells. The GAC BES (99% removal) outperformed the control graphite GAC chamber, as well as a graphite BES and a control chamber both filled with glass beads.

Opportunities for groundwater microbial electro-remediation

Groundwater pollution is a serious worldwide concern. Aromatic compounds, chlorinated hydrocarbons, metals and nutrients among others can be widely found in different aquifers all over the world. However, there is a lack of sustainable technologies able to treat these kinds of compounds. Microbial electro‐remediation, by the means of microbial electrochemical technologies (MET), can become a promising alternative in the near future. MET can be applied for groundwater treatment in situ or ex situ, as well as for monitoring the chemical state or the microbiological activity. This document reviews the current knowledge achieved on microbial electro‐remediation of groundwater and its applications.

An Overview of Electron Acceptors in Microbial Fuel Cells

Microbial fuel cells (MFC) have recently received increasing attention due to their promising potential in sustainable wastewater treatment and contaminant removal. In general, contaminants can be removed either as an electron donor via microbial catalyzed oxidization at the anode or removed at the cathode as electron acceptors through reduction. Some contaminants can also function as electron mediators at the anode or cathode. While previous studies have done a thorough assessment of electron donors, cathodic electron acceptors and mediators have not been as well described. Oxygen is widely used as an electron acceptor due to its high oxidation potential and ready availability. Recent studies, however, have begun to assess the use of different electron acceptors because of the (1) diversity of redox potential, (2) needs of alternative and more efficient cathode reaction, and (3) expanding of MFC based technologies in different areas. The aim of this review was to evaluate the performance and applicability of various electron acceptors and mediators used in MFCs. This review also evaluated the corresponding performance, advantages and disadvantages, and future potential applications of select electron acceptors (e.g., nitrate, iron, copper, perchlorate) and mediators.

Microbial fuel cells as pollutant treatment units: Research updates

Microbial fuel cells (MFC) are a device that can convert chemical energy in influent substances to electricity via biological pathways. Based on the consent that MFC technology should be applied as a waste/wastewater treatment unit rather than a renewable energy source, this mini-review discussed recent R&D efforts on MFC technologies for pollutant treatments and highlighted the challenges and research and development needs. Owing to the low power density levels achievable by larger-scale MFC, the MFC should be used as a device other than energy source such as being a pollutant treatment unit.

Spontaneous arsenic (III) oxidation with bioelectricity generation in single-chamber microbial fuel cells

Arsenic is one of the most toxic elements commonly found in groundwater. With initial concentration of 200μgL(-1), spontaneous As(III) oxidation is realized completely during 7 days operation in single-chamber microbial fuel cells (MFCs) in the present study, with the maximum power density of 752.6±17mWm(-2). The product is less toxic and mobile As(V), which can be removed from aqueous solution more easily. High-throughput 16S rRNA gene pyrosequencing analysis indicates the existence of arsenic-resistant bacteria as Actinobacteria, Comamonas, Pseudomonas and arsenic-oxidizing bacteria as Enterobacter, with electrochemically active bacteria as Lactococcus, Enterobacter. They interact together and are responsible for As(III) oxidation and bioelectricity generation in MFCs. This study offers a potential attractive method for remediation of arsenic-polluted groundwater.

Effects of various organic carbon sources on simultaneous V(V) reduction and bioelectricity generation in single chamber microbial fuel cells

Four ordinary carbon sources affecting V(V) reduction and bioelectricity generation in single chamber microbial fuel cells (MFCs) were investigated. Acetate supported highest maximum power density of 589.1mW/m(2), with highest V(V) removal efficiency of 77.6% during 12h operation, compared with glucose, citrate and soluble starch. Exorbitant initial V(V) concentration led to lower V(V) removal efficiencies and power outputs. Extra addition of organics had little effect on the improvement of MFCs performance. V(V) reduction and bioelectricity generation were enhanced and then suppressed by the increase of conductivity. The larger the external resistance, the higher the V(V) removal efficiencies and voltage outputs. High-throughput 16S rRNA gene pyrosequencing analysis implied the accumulation of Enterobacter which had the capabilities of V(V) reduction, electrochemical activity and fermentation, accompanied with other functional species as Pseudomonas, Spirochaeta, Sedimentibacter and Dysgonomonas. This study steps forward to remediate V(V) contaminated environment based on MFC technology.

Enhanced bioelectricity generation of double-chamber air-cathode catalyst free microbial fuel cells with the addition of non-consumptive vanadium(v)

Improvement of microbial fuel cells (MFCs) via bioelectricity recovery is urgently needed in micro-energy devices nowadays.

Behavior of dissolved organic carbon sources on the microbial reduction and precipitation of vanadium(v) in groundwater

The performance of anaerobic microbial vanadium(v) reduction using five ordinary dissolved organic carbon sources was evaluated.

Electrochemical decolorization of methyl orange powered by bioelectricity from single-chamber microbial fuel cells

Methyl orange (MO), a typical azo dye, is a well-known recalcitrant pollutant in dye wastewater. An aeration electrochemical system with single-chamber microbial fuel cell (MFC) as renewable power sources is proposed for MO decolorization. The enhanced color removal efficiency up to 90.4% within 360 min is observed with voltage across the aeration electrolytic reactor fixed at 700 mV. The results from gas chromatography-mass spectrometry (GC-MS) analysis indicate the destruction of MO, with generation of low molecular weight compounds such as benzene derivatives. Comparison experiments imply the indirect electrochemical oxidation of MO by generated H2O2 is mainly responsible for MO decolorization in present study. This work offers a cost-effective electrochemical method for enhancing electrochemical degradation of dyes with bioelectricity generated from MFCs.

Bioleaching of an oil-fired residual: process optimization and nanostructure NaV6O15 synthesis from the bioleachate

The main objective of this work was to optimize metals recovery from a residual oil-fired ash produced in a thermal power plant using Acidithiobacillus ferrooxidans.