Feasibility of quaternary ammonium and 1,4-diazabicyclo[2.2.2]octane-functionalized anion-exchange membranes for biohydrogen production in microbial electrolysis cells

Hydrophilic porous materials provide efficient gas-liquid separation to advance hydrogen production in microbial electrolysis cells

Preventing methane evolution is a key issue to guarantee stable hydrogen production in microbial electrolysis cell (MEC). In this study, low-cost hydrophilic porous materials, such as non-woven cloth (NWC) and polyvinylidenedifluoride (PVDF), were investigated as alternatives to proton exchange membrane (PEM) in MEC. The MEC with a NWC (NWC-MEC) improved the current density and hydrogen production rate (HPR) of 262.5±10 A m^-3 and 2.5±0.2 m³ m^-3 d^-1, respectively, due to its lower pH gradient (0.37) and ion transport resistance (0.9±0.1 mΩ m²). Hydrogen production in NWC-MEC (from 2.5 to 2.1 m³ m^-3 d^-1) and PVDF-MEC (from 2.2 to 2.0 m³ m^-3 d^-1) showed more stable performance compared to PEM-MECs (from 2.2 to 1.6 m³ m^-3 d^-1) during 30 days of operation. Moreover, results of anodic microbial community analysis indicate that the growth of methanogens of NWC-MEC and PVDF-MEC was effectively inhibited in 30 days.

Efficiency, operational stability and biofouling of novel sulfomethylated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene cation exchange membrane in microbial fuel cells

In this work, a novel cation exchange membrane, PSEBS SU22 was deployed in microbial fuel cells (MFCs) to examine system efficacy in line with membrane characteristics and inoculum source. It turned out that compared to a reference membrane (Nafion), employing PSEBS SU22 resulted in higher current density and electricity generation kinetics, while the electron recoveries were similar (19-28%). These outcomes indicated more beneficial ion transfer features and lower mass transfer-related losses in the PSEBS SU22-MFCs, supported by membrane water uptake, ion exchange capacity, ionic conductivity and permselectivity. By re-activating the membranes after (bio)foulant removal, PSEBS SU22 regained nearly its initial conductivity, highlighting a salient functional stability. Although the particular inoculum showed a clear effect on the microbial composition of the membrane biofouling layers, the dominance of aerobic species was revealed in all cases. Considering all the findings, the PSEBS SU22 seems to be promising for application in MFCs.

Evaluation and ranking of polymeric ion exchange membranes used in microbial electrolysis cells for biohydrogen production

This work characterizes and comparatively assess two cation exchange membranes (PSEBS SU22 and CF22 R14) and one bipolar membrane (FBM) in microbial electrolysis cells (MEC), fed either by acetate or the mixture of volatile fatty acids as substrates. The PSEBS SU22 is a new, patent-pending material, while the CF22 R14 and FBM are developmental and commercialized products. Based on the various MEC performance measures, membranes were ranked by the EXPROM-2 method to reveal which of the polymeric membranes could be more beneficial from a complex, H₂ production efficiency viewpoint. It turned out that the substrate-type influenced the application potential of the membranes. Still, in total, the PSEBS SU22 was found competitive with the other alternative materials. The evaluation of MEC was also supported by analyzing anodic biofilms following electroactive bacteria's development over time.

Hydrogen production in two-chamber MEC using a low-cost and biodegradable poly(vinyl) alcohol/chitosan membrane

Hydrogen production was evaluated in two-chamber microbial electrolysis cells (MEC), where the chambers of the cell were separated using a new economical and environmentally friendly membrane made of poly (vinyl) alcohol/chitosan (PVA/CS). The MEC performance was compared to that of Nafion. The obtained results indicated that the MEC performance for hydrogen production did not show significant differences between the PVA/CS and Nafion membranes. MEC with PVA/CS showed the hydrogen production rate and hydrogen yield of 1277 ± 46 mL H₂L_cat^-1d^-1 and 974 ± 116 mL H₂ g_acetate^-1, respectively. The PVA/CS membrane allowed acetate removal that was 7% higher than that of Nafion due to the lower pH gradient and a lower voltage drop that increased the ion transfer across the membrane.