Effect of pore size on the current produced by 3-dimensional porous microbial anodes: A critical review

Abstract

Microbial anodes are the cornerstone of most electro-microbial processes. Designing 3-dimensional porous electrodes to increase the surface area of the electroactive biofilm they support is a key challenge in order to boost their performance. In this context, the critical review presented here aims to assess whether an optimal range of pore size may exist for the design of microbial anodes. Pore sizes of a few micrometres can enable microbial cells to penetrate but in conditions that do not favour efficient development of electroactive biofilms. Pores of a few tens of micrometres are subject to clogging. Sizes of a few hundreds of micrometres allow penetration of the biofilm inside the structure, but its development is limited by internal acidification. Consequently, pore sizes of a millimetre or so appear to be the most suitable. In addition, a simple theoretical approach is described to establish basis for porous microbial anode design.

Redox Potential Heterogeneity in Fixed‐Bed Electrodes Leads to Microbial Stratification and Inhomogeneous Performance

“…Therefore, the formed biomass at the granules started to hinder mass transfer processes (i. e., supply of acetate to EAM and removal of counter ions from biofilm towards liquid) at key positions within the 3D network, i. e., between the granules or in granule pores. Thus, mass transfer became rate limiting leading to a decline of the overall performance [46,47] . Furthermore, the current decrease could be related to a minuscule movement of the bed (e. g., due to collapsing of voids within the bed caused by sampling of granules) leading to the loss of electrical contact between granules and CC indicating a poor polarization behavior of granular electrode beds (see below).…”

Allochthonous and Autochthonous Halothermotolerant Bioanodes From Hypersaline Sediment and Textile Wastewater: A Promising Microbial Electrochemical Process for Energy Recovery Coupled With Real Textile Wastewater Treatment

“…Colonization of the carbon felt electrodes was evaluated at the end of the experiments, mainly on the outer surface of the felts but also within the porosity of the felt. Indeed, previous work has shown the difficulty of electroactive biofilms to colonize the internal surfaces of felt electrode structures (Chong et al, 2019), especially when real effluents either viscous, highly charged with suspended solids, or very highly loaded with COD are used (Blanchet et al, 2016). Carbon felt WEs possibly covered with HSCE and/or TDWW microorganisms were removed from the reactors and imaged by epifluorescence microscopy (Figure 3).…”

Benchmarking of Industrial Synthetic Graphite Grades, Carbon Felt, and Carbon Cloth as Cost-Efficient Bioanode Materials for Domestic Wastewater Fed Microbial Electrolysis Cells

“…Graphite, in addition to offering many proven advantages as an anode material in MEC (conductive, chemically stable, biocompatible...), has a relatively low price (Wei et al, 2011;Zhou et al, 2011) and a mechanical resistance over time that has already proven to be successful in many industrial fields other than MECs (metallurgical industry, electrical and electronic industries, aerospace...). In addition, graphite can be machined and assembled to create three-dimensional geometries of customized electrodes, with a controlled pore size (Chong et al, 2019), which could offer compact electrodes with maximized oxidation kinetics in domestic wastewater in the near future.…”