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In this study, CO 2 conversion to acetate and CH 4 was achieved in a flow-through laboratory-scale microbial electrosynthesis (MES) cell composed of a 3D conductive polylactic acid (cPLA) lattice cathode with electrodeposited metal electrocatalyst coatings. The MES cell with a bare cPLA cathode showed the poorest performance with the lowest H 2 and CH 4 production rates and low Coulombic efficiency. This was ascribed to a poor electrocatalytic activity of cPLA towards H 2 production and high electrode resistivity. When the cPLA electrode was modified with metal coatings, the CH 4 , acetate and H 2 production rate increased significantly, with the following trend: cPLA < Ni < NiFe < NiFeMn. The better performance of the metal-coated cPLA in terms of CH 4 production was attributed to the lower electrical resistance, enhanced H 2 production and enhanced electron transfer between the cathode and the biofilm. At the cell potential of 2.8 V, the best-performing NiFeMn cPLA cathode showed stable production of CH 4 (50 ± 6 mL d−1), acetate (185 ± 27 mg d−1), and H 2 (545 ± 175 mL d−1) at close to 100% Coulombic efficiency. [Display omitted] • Conductive polylactate (cPLA) lattice cathode developed for microbial electrosynthesis. • CH 4 , acetate, and H 2 continuously produced in a microbial electrosynthesis (MES) cell. • Electrodeposition of Ni, Fe, and Mn increased cPLA performance by up to 80%. • NiFeMn cPLA showed best performance with nearly 100% Coulombic efficiency. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three cathode materials were compared for CH 4 and acetate bioelectrosynthesis. • Carbon felt cathode showed the highest CH 4 production per cathode volume. • Conductive polymer cathode promoted acetate and ethanol production. • Cathode material selection affects biofilm activity and bioelectrosynthesis pathways. This study compares carbon felt (CF), granular activated carbon (GAC), and a conductive acrylonitrile butadiene styrene (cABS) polymer cathodes for CH 4 and acetate production in a microbial electrosynthesis (MES) cell. At an applied voltage of 2.8 V and continuous CO 2 flow, the CF biocathode MES cell showed the highest CH 4 production rate of 1420 ± 225 mL V c -1 d-1 (V c = cathode volume), also producing acetate at a rate of 710 ± 110 mg V c -1 d-1. The volumetric rates of acetate and CH 4 production decreased when using the GAC cathode (720 ± 94 mL V c -1 d-1 and 236 ± 65 mg V c -1 d-1, respectively). When the cABS cathode was used, the CH 4 production declined to 250 ± 35 mL V c -1 d-1, while the acetate production increased to 1105 ± 130 mg V c -1 d-1. The biocatalytic activity of cABS increased after in-situ electrodeposition of Ni and Fe, resulting in a current increase from 205 mA to 380 mA accompanied by increasing acetate and ethanol production (1405 mg V c -1 d-1 and 240 mg V c -1 d-1, respectively), while the CH 4 production decreased. The cABS cathode showed the highest specific (per surface area) activity for acetate and CH 4 production. [ABSTRACT FROM AUTHOR]

This study demonstrated the removal of selenite and selenate in flow-through permeable bioelectrochemical barriers (microbial electrolysis cells, MECs). The bioelectrochemical barriers consisted of cathode and anode electrode compartments filled with granular carbon or metallurgical coke. A voltage of 1.4 V was applied to the electrodes to enable the bioelectrochemical removal of selenium species. For comparison, a similarly designed permeable anaerobic biobarrier filled with granular carbon was operated without voltage. All biobarrier setups were fed with water containing up to 5,000 µg L−1 of either selenite or selenate and 70 mg L−1 of acetate as a source of organic carbon. Significant removal of selenite and selenate was observed in MEC experimental setups, reaching 99.5–99.8% over the course of the experiment, while in the anaerobic biobarrier the removal efficiency did not exceed 88%. By simultaneously operating several setups and changing operating parameters (selenium species, influent Se and acetate concentrations, etc.) we demonstrated enhanced removal of Se species under bioelectrochemical conditions. ga1 • Selenate and selenite removal in a flow-through bioelectrochemical barrier was demonstrated. • Anaerobic treatment resulted in 85% Se removal efficiency. • A 1.4 V applied voltage coupled with acetate addition enhanced selenate and selenite removal. • Up to 99.5% selenate and selenite removal achieved in the bioelectrochemical system. [ABSTRACT FROM AUTHOR]