The Effect of Anode Material on the Performance of a Hydrogen Producing Microbial Electrolysis Cell, Operating with Synthetic and Real Wastewaters

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.

Tofu Wastewater (TWW) Treatment and Hydrogen (H2) Production by Using A Microbial Electrolysis Cell (MEC) System

“…According to some references, the presence of impurities on the electrode surface inhibits the bio-electrochemical reaction due to the current flow being slow (Apostolopoulos et al, 2021;Satar et al, 2020b;Carmona-Martínez et al, 2015). Consequently, the MEC performance gradually dropped after three months of the system operation (Carmona-Martínez et al, 2015).…”

“…Theoretically, the performance of MEC depends on some parameters such as anode and cathode performance, type and characteristics of substrates, and amount of additional energy input into the system (Apostolopoulos et al, 2021). The substrate with a high simple organic acid, rich nutrient, and neutral pH are very appropriate for generating H 2 .…”

A study of electron source preference and its impact on hydrogen production in microbial electrolysis cells fed with synthetic fermentation effluent

“…These values are comparable to those reported in previous studies using two-chamber MECs. Cario et al [ 39 ] reported a maximum current density of approximately 5 A/m 2 in acetate-fed AEM-MECs equipped with carbon felt anodes and Pt/C-treated stainless steel mesh cathodes at an applied voltage of 0.8 V. Apostolopoulos et al [ 40 ] observed a peak current density of approximately 3.8 A/m 2 in PEM-MECs installed with carbon paper anodes and Pt-coated carbon cloth cathodes, using a mixture of volatile fatty acids (C 2 –C 6 ) as the substrate at an applied voltage of 0.9 V.…”

Electrochemical Characteristics of Microbial Fuel Cells Operating with Various Food Industry Wastewaters

“…Four identical H-type MFC devices [37] were used, working with four different substrates. A PEM (Nafion 117, Sigma-Aldrich, St. Louis, MO, USA) was placed in the connection point between the two chambers to allow for the proton transfer from the anode to the cathode.…”

“…During both phases, the cathode compartments were filled with a nutrient medium consisting of a buffer solution (3.45 g L −1 Na 2 HPO 4 •2H 2 O, 3.67 g L −1 NaH 2 PO 4 •2H 2 O) and KCl (0.16 g L −1 ). During the acclimation phase, the anode compartments were filled with the above nutrient medium, acetate (chemical oxygen demand (COD): 0.8 g L −1 ) alkalinity (5 g L −1 NaHCO 3 ) and a solution of trace elements [37]. Inoculation was performed with the addition of methanogenic sludge (10% v/v) obtained from an anaerobic digester with the following characteristics: pH: 7.2 ± 0.1, total COD (tCOD): 24.72 ± 1.12 g L −1 , dissolved COD (dCOD): 0.51 ± 0.21 g L −1 , total suspended solids (TSS): 30.44 ± 1.71 g L −1 , volatile suspended solids (VSS): 15.25 ± 1.53 g L −1 .…”