Electro-osmotic-based catholyte production by Microbial Fuel Cells for carbon capture

Abstract

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.

Microbial fuel cells: From fundamentals to applications. A review

“…Carbonaceous materials used as cathode catalysts are generally based on graphene [352], [353], [354], [355] (that is probably the most expensive among all the carbonaceous materials), activated carbon [356], [357], [358], [359], [360], [361], [362], [363], carbon nanotubes [364], [365], carbon nanofibers [366], [367], [368], [369], simple or modified carbon black [233], [370], [371]. It was shown that high surface area conductive carbonaceous materials and nanometric pores enhance the ORR in neutral media [320], [331].…”

Novel Analytical Microbial Fuel Cell Design for Rapid in Situ Optimisation of Dilution Rate and Substrate Supply Rate, by Flow, Volume Control and Anode Placement

“…For instance, the same working principles applied to the MFC technology can be used, with the supply of external power, for producing useful products such as hydrogen [1,2], acetate [3,4], methane [5,6] as well as desalinate water [7,8]. Resource recovery and bio-sensing [9][10][11][12][13] are also highly active fields in the MFC research. Along with practical development of the technology, microorganisms involved in electricity generation have drawn a great deal of attention too.…”

Urine in Bioelectrochemical Systems: An Overall Review

“…In MFCs, cation species move through the membrane and accumulate in the aqueous cathodic chamber resulting in increased solution conductivity and pH . In air breathing cathodes, the electroosmotic drag was first observed in MFCs by Kim et al ., as the net water loss through the membrane that varied according to external resistance, that later led to the demonstration of the catholyte being accumulated as a result of the electrical current in wastewater operated MFCs . The composition of the catholyte primarily depends on the type of anolyte (feedstock) .…”

“…The ORR determines the physico-chemical properties of the catholyte by forming OH À as a product of the peroxide pathway [81] leading to local alkalisation of the cathode where the increase in current flow will lead to higher pH. [82][83] It was shown recently that the shift between the acidic ORR pathway and alkaline ORR pathway occurs around pH 11. [84][85] When protons or cations move through the membrane, water molecules accompany them or are actually "dragged".…”

“…[89] In air breathing cathodes, the electroosmotic drag was first observed in MFCs by Kim et al, as the net water loss through the membrane that varied according to external resistance, [90] that later led to the demonstration of the catholyte being accumulated as a result of the electrical current in wastewater operated MFCs. [82][83][84][85][86][87][88][89][90][91] The composition of the catholyte primarily depends on the type of anolyte (feedstock). [92][93][94] Therefore, in urine operated MFCs, this opens new opportunities for nutrient recovery and recycling of elements suitable for fertilisers or irrigation.…”