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Gajda I.,Bristol BioEnergy Center | Greenman J.,Bristol BioEnergy Center | Melhuish C.,Bristol BioEnergy Center | Santoro C.,University of Connecticut | And 4 more authors.
Water Research | Year: 2015

In Microbial Fuel Cells (MFCs), the recovery of water can be achieved with the help of both active (electro-osmosis), and passive (osmosis) transport pathways of electrolyte through the semi-permeable selective separator. The electrical current-dependent transport, results in cations and electro-osmotically dragged water molecules reaching the cathode. The present study reports on the production of catholyte on the surface of the cathode, which was achieved as a direct result of electricity generation using MFCs fed with wastewater, and employing Pt-free carbon based cathode electrodes. The highest pH levels (>13) of produced liquid were achieved by the MFCs with the activated carbon cathodes producing the highest power (309 μW). Caustic catholyte formation is presented in the context of beneficial cathode flooding and transport mechanisms, in an attempt to understand the effects of active and passive diffusion. Active transport was dominant under closed circuit conditions and showed a linear correlation with power performance, whereas osmotic (passive) transport was governing the passive flux of liquid in open circuit conditions. Caustic catholyte was mineralised to a mixture of carbonate and bicarbonate salts (trona) thus demonstrating an active carbon capture mechanism as a result of the MFC energy-generating performance. Carbon capture would be valuable for establishing a carbon negative economy and environmental sustainability of the wastewater treatment process. © 2015 The Authors.


Gajda I.,Bristol BioEnergy Center | Greenman J.,Bristol BioEnergy Center | Melhuish C.,Bristol BioEnergy Center | Santoro C.,University of New Mexico | And 3 more authors.
Water Research | Year: 2015

In Microbial Fuel Cells (MFCs), the recovery of water can be achieved with the help of both active (electro-osmosis), and passive (osmosis) transport pathways of electrolyte through the semi-permeable selective separator. The electrical current-dependent transport, results in cations and electro-osmotically dragged water molecules reaching the cathode. The present study reports on the production of catholyte on the surface of the cathode, which was achieved as a direct result of electricity generation using MFCs fed with wastewater, and employing Pt-free carbon based cathode electrodes. The highest pH levels (>13) of produced liquid were achieved by the MFCs with the activated carbon cathodes producing the highest power (309μW). Caustic catholyte formation is presented in the context of beneficial cathode flooding and transport mechanisms, in an attempt to understand the effects of active and passive diffusion. Active transport was dominant under closed circuit conditions and showed a linear correlation with power performance, whereas osmotic (passive) transport was governing the passive flux of liquid in open circuit conditions. Caustic catholyte was mineralised to a mixture of carbonate and bicarbonate salts (trona) thus demonstrating an active carbon capture mechanism as a result of the MFC energy-generating performance. Carbon capture would be valuable for establishing a carbon negative economy and environmental sustainability of the wastewater treatment process. © 2015.


Santoro C.,University of New Mexico | Artyushkova K.,University of New Mexico | Gajda I.,Bristol BioEnergy Center | Babanova S.,University of New Mexico | And 7 more authors.
International Journal of Hydrogen Energy | Year: 2015

This study showed the electrochemical performance of different cathode electrodes tested on a ceramic separator functioning as a cation exchange membrane. Particularly, three different carbonaceous-based materials (carbon cloth (CC), carbon mesh (CM) and carbon veil (CV)) have been used as an electrode and as the current collector. When used as an electrode, CC outperformed the others. The carbonaceous materials have been modified using conductive paint (PA) and micro porous layer (MPL). With these modifications, the current output was two-three times higher. Generally, the current produced was slightly higher with MPL treatment compared to PA except in the case of CV-MPL that had lower output probably due to the negative effect of the heat treatment on the mechanical strength of the CV. In the case of PA, the current collectors do not seem to affect the output. The same consideration can also be done for the MPL except for the CV. The surface morphology seems to explain the results. Linear correlation was found between current produced and nanoscale roughness and skewness. The results indicated that those morphological parameters increased the contact between the cathode and the ceramic surface, thus enhancing the current generated. The further addition of the inorganic non-platinum group catalyst (Fe-AAPyr) on the surface significantly enhanced the performances. Following MPL modification and MPL-Fe-AAPyr addition, CM was the most cost effective support. CV was the most cost effective support with PA modification. © 2015 Hydrogen Energy Publications, LLC.


Houghton J.,University of New Mexico | Santoro C.,University of New Mexico | Soavi F.,University of Bologna | Serov A.,University of New Mexico | And 3 more authors.
Bioresource Technology | Year: 2016

Supercapacitive microbial fuel cells with various anode and cathode dimensions were investigated in order to determine the effect on cell capacitance and delivered power quality. The cathode size was shown to be the limiting component of the system in contrast to anode size. By doubling the cathode area, the peak power output was improved by roughly 120% for a 10 ms pulse discharge and internal resistance of the cell was decreased by ∼47%. A model was constructed in order to predict the performance of a hypothetical cylindrical MFC design with larger relative cathode size. It was found that a small device based on conventional materials with a volume of approximately 21 cm3 would be capable of delivering a peak power output of approximately 25 mW at 70 mA, corresponding to ∼1300 W m−3. © 2016 The Author(s)


Salar-Garcia M.J.,Technical University of Cartagena | Gajda I.,Bristol BioEnergy Center | Ortiz-Martinez V.M.,Technical University of Cartagena | Greenman J.,Bristol BioEnergy Center | And 3 more authors.
Bioresource Technology | Year: 2016

In this work, the by-product generated during the operation of cylindrical MFCs, made out of terracotta material, is investigated as a feasible means of degrading live microalgae for the first time. In addition to the low cost materials of this design, the reuse of the solution produced in the cathode renders the technology truly green and capable of generating bioenergy. In this study, the effect of a light/dark cycle or dark conditions only on the digestion of live microalgae with the catholyte is investigated. The results show that a combination of light/dark improves degradation and allows algae to be used as substrate in the anode. The addition of 12.5. mL of a 1:1 mix of catholyte and microalgae (pre-digested over 5. days under light/dark) to the anode, increases the power generation from 7. μW to 44. μW once all the organic matter in the anode had been depleted. © 2016 Elsevier Ltd.

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