A new method for urine electrofiltration and long term power enhancement using surface modified anodes with activated carbon in ceramic microbial fuel cells

Iwona Gajda,Jiseon You,Carlo Santoro,John Greenman,Ioannis A Ieropoulos

doi:10.1016/j.electacta.2020.136388

Iwona Gajda, Jiseon You + Show 3 more

Open Access

https://doi.org/10.1016/j.electacta.2020.136388

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Abstract

This work is presenting for the first time the use of inexpensive and efficient anode material for boosting power production, as well as improving electrofiltration of human urine in tubular microbial fuel cells (MFCs). The MFCs were constructed using unglazed ceramic clay functioning as the membrane and chassis. The study is looking into effective anodic surface modification by applying activated carbon micro-nanostructure onto carbon fibres that allows electrode packing without excessive enlargement of the electrode. The surface treatment of the carbon veil matrix resulted in 3.7 mW (52.9 W m−3 and 1626 mW m−2) of power generated and almost a 10-fold increase in the anodic current due to the doping as well as long-term stability in one year of continuous operation. The higher power output resulted in the synthesis of clear catholyte, thereby i) avoiding cathode fouling and contributing to the active splitting of both pH and ions and ii) transforming urine into a purified catholyte - 30% salt reduction - by electroosmotic drag, whilst generating - rather than consuming – electricity, and in a way demonstrating electrofiltration. For the purpose of future technology implementation , the importance of simultaneous increase in power generation, long-term stability over 1 year and efficient urine cleaning by using low-cost materials, is very promising and helps the technology enter the wider market.

Highlights

Microbial Fuel Cells (MFCs) are transforming chemical energy locked in organic waste materials into electrical energy using natural bacterial metabolism [1]
It shows smooth long fibres forming a network with large void spaces between them where each fibre has cylinder-like shape (Fig. 2A and B)
It can be seen that the activated carbon clusters form a micro and nanoporous structure enhancing the surface roughness (Fig. 2E and F) that is visibly different from the smooth and uniform surface of an unmodified carbon veil (CV) fibre (Fig. 2C)

Summary

Introduction

Microbial Fuel Cells (MFCs) are transforming chemical energy locked in organic waste materials into electrical energy using natural bacterial metabolism [1]. One of the substrates that has recently received significant attention is neat human urine, which has been reported as an ideal feedstock for energy generation from individual as well as collective MFC systems [6]. Anodes with micro and nanoscale structures have been developed over the last decade, modified with carbon nanotubes [25], carbon black particles [26] and graphene [27,28], which promote electricity generation in MFCs thanks to increased specific surface area, improved conductivity and enhanced biofilm formation. Nanoscale would facilitate electron transfer by providing multiplexed and highly conductive pathways, whilst the microscale would support the microbial attachment Such a strategy is an important factor in building efficient systems, in order to implement the technology into larger scale, cost and fabrication simplicity should be considered. Cost effective carbon veil has been shown to be efficient in lab-scale systems [13] and validated in larger-scale applications [11]

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