Browsing by Author "Yuan, Heyang"

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    Bioelectrochemical production of hydrogen in an innovative pressure-retarded osmosis/microbial electrolysis cell system: experiments and modeling
    Yuan, Heyang; Lu, Yaobin; Abu-Reesh, Ibrahim M.; He, Zhen (Biomed Central, 2015-08-14)
    Background While microbial electrolysis cells (MECs) can simultaneously produce bioelectrochemical hydrogen and treat wastewater, they consume considerable energy to overcome the unfavorable thermodynamics, which is not sustainable and economically feasible in practical applications. This study presents a proof-of-concept system in which hydrogen can be produced in an MEC powered by theoretically predicated energy from pressure-retarded osmosis (PRO). The system consists of a PRO unit that extracts high-quality water and generates electricity from water osmosis, and an MEC for organic removal and hydrogen production. The feasibility of the system was demonstrated using simulated PRO performance (in terms of energy production and effluent quality) and experimental MEC results (e.g., hydrogen production and organic removal). Results The PRO and MEC models were proven to be valid. The model predicted that the PRO unit could produce 485 mL of clean water and 579 J of energy with 600 mL of draw solution (0.8 M of NaCl). The amount of the predicated energy was applied to the MEC by a power supply, which drove the MEC to remove 93.7 % of the organic compounds and produce 32.8 mL of H2 experimentally. Increasing the PRO influent volume and draw concentration could produce more energy for the MEC operation, and correspondingly increase the MEC hydraulic retention time (HRT) and total hydrogen production. The models predicted that at an external voltage of 0.9 V, the MEC energy consumption reached the maximum PRO energy production. With a higher external voltage, the MEC energy consumption would exceed the PRO energy production, leading to negative effects on both organic removal and hydrogen production. Conclusions The PRO-MEC system holds great promise in addressing water-energy nexus through organic removal, hydrogen production, and water recovery: (1) the PRO unit can reduce the volume of wastewater and extract clean water; (2) the PRO effluents can be further treated by the MEC; and (3) the osmotic energy harvested from the PRO unit can be applied to the MEC for sustainable bioelectrochemical hydrogen production.
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    Bioelectrochemical Systems: Microbiology, Catalysts, Processes and Applications
    Yuan, Heyang (Virginia Tech, 2017-11-01)
    The treatment of water and wastewater is energy intensive, and there is an urgent need to develop new approaches to address the water-energy challenges. Bioelectrochemical systems (BES) are energy-efficient technologies that can treat wastewater and simultaneously achieve multiple functions such as energy generation, hydrogen production and/or desalination. The objectives of this dissertation are to understand the fundamental microbiology of BES, develop cost-effective cathode catalysts, optimize the process engineering and identify the application niches. It has been shown in Chapter 2 that electrochemically active bacteria can take advantage of shuttle-mediated EET and create optimal anode salinities for their dominance. A novel statistical model has been developed based on the taxonomic data to understand and predict functional dynamics and current production. In Chapter 3, 4 and 5, three cathode catalyst (i.e., N- and S- co-doped porous carbon nanosheets, N-doped bamboo-like CNTs and MoS2 coated on CNTs) have been synthesized and showed effective catalysis of oxygen reduction reaction or hydrogen evolution reaction in BES. Chapter 6, 7 and 8 have demonstrated how BES can be combined with forward osmosis to enhance desalination or achieve self-powered hydrogen production. Mathematical models have been developed to predict the performance of the integrated systems. In Chapter 9, BES have been used as a research platform to understand the fate and removal of antibiotic resistant genes under anaerobic conditions. The studies in this dissertation have collectively demonstrated that BES may hold great promise for energy-efficient water and wastewater treatment.
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    Effects of electron acceptors on removal of antibiotic resistant Escherichia coli, resistance genes and class 1 integrons under anaerobic conditions
    Yuan, Heyang; Miller, Jennifer H.; Abu-Reesh, Ibrahim M.; Pruden, Amy; He, Zhen (Elsevier, 2016-11-01)
    Anaerobic biotechnologies can effectively remove antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs), but there is a need to better understand the mechanisms. Here we employ bioelectrochemical systems (BES) as a platform to investigate the fate of a native tetracycline and sulfonamide-resistant Escherichia coli strain and its ARGs. The E. coli strain carrying intI1, sulI and tet(E) was isolated from domestic wastewater and dosed into a tubular BES. The BES was first operated as a microbial fuel cell (MFC), with aeration in the cathode, which resulted in enhanced removal of E. coli and ARGs by ~ 2 log (i.e., order of magnitude) when switched from high current to open circuit operation mode. The BES was then operated as a microbial electrolysis cell (MEC) to exclude the effects of oxygen diffusion, and the removal of E. coli and ARGs during the open circuit configuration was again 1–2 log higher than that at high current mode. Significant correlations of E. coli vs. current (R2 = 0.73) and ARGs vs. E. coli (R2 ranged from 0.54 to 0.87), and the fact that the BES substrate contained no electron acceptors, implied that the persistence of the E. coli and its ARGs was determined by the availability of indigenous electron acceptors in the BES, i.e., the anode electrode or the electron shuttles generated by the exoelectrogens. Subsequent experiments with pure-culture tetracycline and sulfonamide-resistant E. coli being incubated in a two-chamber MEC and serum bottles demonstrated that the E. coli could survive by respiring anode electrode and/or electron shuttles released by exoelectrogens, and ARGs persisted with their host E. coli.
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    Energy Consumption by Recirculation: A Missing Parameter When Evaluating Forward Osmosis
    Zou, Shiqiang; Yuan, Heyang; Childress, Amy; He, Zhen (American Chemical Society, 2016-07-05)
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    Graphene-modified Electrodes for Enhancing the Performance of Microbial Fuel Cells
    Yuan, Heyang; He, Zhen (The Royal Society of Chemistry, 2014-11-03)
    Graphene is an emerging material with superior physical and chemical properties, which can benefit the development of microbial fuel cells (MFC) in several aspects. Graphene-based anodes can enhance MFC performance with increased electron transfer efficiency, higher specific surface area and more active microbe-electrode-electrolyte interaction. For cathodic processes, oxygen reduction reaction is effectively catalyzed by graphene-based materials because of a favorable pathway and an increase in active sites and conductivity. Despite challenges, such as complexity in synthesis and property degeneration, graphene-based electrodes will be promising for developing MFCs and other bioelectrochemical systems to achieve sustainable water/wastewater treatment and bioenergy production.
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    Oxygen reduction reaction catalysts used in microbial fuel cells for energy-efficient wastewater treatment: a review
    Yuan, Heyang; Hou, Yang; Abu-Reesh, Ibrahim M.; Chen, Junhong; He, Zhen (Royal Society of Chemistry, 2016-09-01)
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    When Bioelectrochemical Systems Meet Forward Osmosis: Accomplishing Wastewater Treatment and Reuse through Synergy
    Lu, Yaobin; Qin, Mohan; Yuan, Heyang; Abu-Reesh, Ibrahim M.; He, Zhen (MDPI, 2014-12-23)
    Bioelectrochemical systems (BES) and forward osmosis (FO) are two emerging technologies with great potential for energy-efficient water/wastewater treatment. BES takes advantage of microbial interaction with a solid electron acceptor/donor to accomplish bioenergy recovery from organic compounds, and FO can extract high-quality water driven by an osmotic pressure. The strong synergy between those two technologies may complement each other and collaboratively address water-energy nexus. FO can assist BES with achieving water recovery (for future reuse), enhancing electricity generation, and supplying energy for accomplishing the cathode reactions; while BES may help FO with degrading organic contaminants, providing sustainable draw solute, and stabilizing water flux. This work has reviewed the recent development that focuses on the synergy between BES and FO, analyzed the advantages of each combination, and provided perspectives for future research. The findings encourage further investigation and development for efficient coordination between BES and FO towards an integrated system for wastewater treatment and reuse.