Abstract
The aim of the study was to assess the effect of anode materials, namely a carbon nanotube (CNT)-buckypaper and a commercial carbon paper (CP) on the performance of a two-chamber microbial electrolysis cell (MEC), in terms of hydrogen production and main electrochemical characteristics. The experiments were performed using both acetate-based synthetic wastewater and real wastewater, specifically the effluent of a dark fermentative hydrogenogenic reactor (fermentation effluent), using cheese whey (CW) as substrate. The results showed that CP led to higher hydrogen production efficiency and current density compared to the CNT-buckypaper anode, which was attributed to the better colonization of the CP electrode with electroactive microorganisms, due to the negative effects of CNT-based materials on the bacteria metabolism. By using the fermentation effluent as substrate, a two-stage process is developed, where dark fermentation (DF) of CW for hydrogen production occurs in the first step, while the DF effluent is used as substrate in the MEC, in the second step, to further increase hydrogen production. By coupling DF-MEC, a dual environmental benefit is provided, combining sustainable bioenergy generation together with wastewater treatment, a fact that is also reinforced by the toxicity data of the current study.
Highlights
The microbial electrolysis cell (MEC) is a new bio-electrochemical reactor that takes advantage of the metabolism/respiration of a specific group of microorganisms, called exoelectrogens, towards hydrogen production [1,2]
Cyclic voltammograms (CVs) and electrochemical impedance spectroscopy (EIS) measurements, with the results presented in the form of Nyquist and Bode plots, were conducted in order to study the electrochemical characteristics of the anode electrodes
Ated with the graphite tangential E2g Raman allowed mode, where the two atoms in the band at 1365 cm−1 and the tangential G band at 1578 cm−1. The latter is associated with the graphene unit cell vibrate tangentially one against the other; neighboring atoms are movgraphite tangential E2g Raman allowed mode, where the two atoms in the graphene unit ingcell in opposite directions along the surface of the neighboring tube as in 2Datoms graphite
Summary
The microbial electrolysis cell (MEC) is a new bio-electrochemical reactor that takes advantage of the metabolism/respiration of a specific group of microorganisms, called exoelectrogens, towards hydrogen production [1,2]. Exoelectrogens, forming an electro-active biofilm, oxidize the organic substrates and use the electrode as a direct electron acceptor. The cathode limitations are significant [8,9,10], the anode characteristics contribute significantly to the overall MEC performance [11]. Along this line, research efforts have been done for improving the electro-catalytic properties of the anode materials, so as to overcome the anode limitations and realize the practical application of MECs
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