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 H2Lcat-1d-1 and 974 ± 116 mL H2 gacetate-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.

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

In this work, two commercialized anion-exchange membranes (AEMs), AMI-7001 and AF49R27, were applied in microbial electrolysis cells (MECs) and compared with a novel AEM (PSEBS CM DBC, functionalized with 1,4-diazabicyclo[2.2.2]octane) to produce biohydrogen. The evaluation regarding the effect of using different AEMs was carried out using simple (acetate) and complex (mixture of acetate, butyrate and propionate to mimic dark fermentation effluent) substrates. The MECs equipped with various AEMs were assessed based on their electrochemical efficiencies, H2 generation capacities and the composition of anodic biofilm communities. pH imbalances, ionic losses and cathodic overpotentials were taken into consideration together with changes to substantial AEM properties (particularly ion-exchange capacity, ionic conductivity, area- and specific resistances) before and after AEMs were applied in the process to describe their potential impact on the behavior of MECs. It was concluded that the MECs which employed the PSEBS CM DBC membrane provided the highest H2 yield and lowest internal losses compared to the two other separators. Therefore, it has the potential to improve MECs.

Effect of volatile fatty acids mixtures on the simultaneous photofermentative production of hydrogen and polyhydroxybutyrate.

Purple non-sulfur bacteria generate hydrogen and polyhydroxybutyrate (PHB) as a mechanism for disposing of reducing equivalents generated during substrate consumption. However, both pathways compete for the reducing equivalents released from bacteria growing under certain substrates, thus the formation of hydrogen or PHB is detrimental to the formation of each other. The effect of mixtures of acetic, propionic and butyric acids on the formation of H2 and PHB was evaluated using Box-Behnken design. A bacterial community mainly constituted by Rhodopseudomonas palustris was used as inoculum. It was observed that the three volatile fatty acids had a significant effect on the specific PHB production. However, only the propionic acid had a significant effect on the specific H2 production activity and the highest value was observed when acetate was the main component in the mixture. The maximum values for the specific PHB and hydrogen production rates were 16.4 mg-PHB/g-TSS/day and 391 mL-H2/g-TSS/day, respectively.