Regeneration of the power performance of cathodes affected by biofouling

Grzegorz Pasternak,John Greenman,Ioannis Ieropoulos

doi:10.1016/j.apenergy.2016.04.009

Abstract

Air cathode microbial fuel cells (MFCs) were used in a cascade-system, to treat neat human urine as the fuel. Their long-term operation caused biodeterioration and biofouling of the cathodes. The cathodes were made from two graphite-painted layers, separated by a current collector. The initial performance of the MFCs was reaching average values of 105.5±32.2μW and current of 1164.5±120.2μA. After 3months of operation the power performance decreased to 9.8±3.5μW, whilst current decreased to 461.2±137.5μA. Polarisation studies revealed significant transport losses accompanied by a biofilm formation on the cathodes. The alkaline lysis procedure was established to remove the biomass and chemical compounds adsorbed on the cathode’s surface. As a result, the current increased from 378.6±108.3μA to 503.8±95.6μA. The additional step of replacing the outer layer of the cathode resulted in a further increase of current to 698.1±130μA. Similarly, the power performance of the MFCs was recovered to the original level reaching 105.3±16.3μW, which corresponds to 100% recovery. Monitoring bacterial cell number on the cathode’s surface showed that biofilm formed during operation was successfully removed and composed mainly of dead bacterial cells after treatment. To the best of the authors’ knowledge, this is the first time that the performance of deteriorating cathodes, has been successfully recovered for MFCs in-situ. Through this easy, fast and inexpensive procedure, designing multilayer cathodes may help enhance the range of operating conditions, if a biofilm forms on their surface.

Highlights

Microbial Fuel Cell (MFC) is a bioelectrochemical reactor in which electroactive bacteria convert the energy stored in various chemical substrates, into electricity [1]
An interesting example of a hybrid technique using MFCs was described by Chen et al who reported an electrodialysis system, consisting of an MFC used for alkali production and demonstrated its use for biogas upgrading [9]
The power performance of the air–cathode MFCs decreased after three months of operation by one order of magnitude in comparison to their initial performance

Summary

Introduction

Microbial Fuel Cell (MFC) is a bioelectrochemical reactor in which electroactive bacteria convert the energy stored in various chemical substrates, into electricity [1]. It was shown that urine can be successfully treated in MFCs [5], and in some other examples, H2 production has been reported [6]. Successful transformation of urea into electrical energy was only demonstrated in conventional fuel cells, including solid oxide fuel cells [8]. An interesting example of a hybrid technique using MFCs was described by Chen et al who reported an electrodialysis system, consisting of an MFC used for alkali production and demonstrated its use for biogas upgrading [9]. Bioelectrochemical systems (BESs) can be employed to techniques for sustainable synthesis of chemicals in a process known as microbial electrosynthesis [10], as well as for the recovery of valuable metals by reduction on the anode surface as demonstrated by Wang et al [11]. The cathodic reactions may lead to the removal of toxic hexavalent chromium as reported by Xafenias et al [12]

Methods

Results

Conclusion