The different behaviour of Thermotoga neapolitana in the anodic and cathodic compartment of a bioelectrochemical system

Thermotoga neapolitana is a hyperthermophilic bacterium that can metabolize glucose and several organic wastes in hydrogen and lactate at a temperature of 80°C. Their high performance in producing hydrogen at so high a temperature as 80°C suggests a potential energy application of them where hydrogen is an important element of the process. In this view, experimentation of a T.neapolitana strain is carried out in double-chamber electrochemical systems. The aim is to explore the interaction of these bacteria with the anode and the cathode, stressing their capability to survive in presence of a polarized electrode which can drastically change the pH of the media. A culture enriched of 5 g/L of glucose, under CO2 pressure (80 °C) was used to fill both the anodic and cathodic compartments of the electrochemical system, applying a voltage of 1.5 V between the anode and the cathode. The test lasted ten days. Results clearly indicate that bacteria colonize both electrodes, but the glucose metabolism is completely inhibited in the anodic compartments. On the contrary, metabolism is stimulated in the cathodic compartment. Bacteria are alive on the electrodes in the pH interval of 3 - 9.

Photo-Tunable Azobenzene-Anthraquinone Schiff Base Copper Complexes as Mediators for Laccase in Biofuel Cell Cathode

Induced chirality (achiral target in chiral matrix such as proteins) sometimes play a useful role in evaluating supramolecular systems involving biomolecules. Enzymatic fuel cells, which generate electricity via enzymatic redox reactions at electrodes hold a significant potential for sustainable power. Bacterial laccase, a multi-copper oxidase, was used in the cathodic compartment of the enzymatic biofuel cells because of its low redox potential. Three new salen Cu(II) complexes were designed and investigated as mediators. The Schiff base ligands consisted of both a redox-active (anthraquinone) and a photochromic (azobenzene) moiety. The interaction between laccase and a mediator was examined with induced circular dichroism (CD) and the docking tool to observe in which of the laccase domains the mediators bind as well as study the photo-induced tuning of both the cis-trans photoisomerization and orientation by the Weigert effect. Both the electrochemical and photochromic properties are also discussed and compared using density functional theory (DFT), time-dependent (TD)-DFT, and docking simulations.

Direct Energy Production From Hydrogen Sulfide in Black Sea Water - Electrochemical Study

A sulfide driven fuel cell is proposed to clean the Black Sea with the simultaneous A sulfide driven fuel cell is proposed to clean the Black Sea with the simultaneous production of energy. The process is hopeful even at low sulfide concentrations, i.e.10 to 25 mg/l being close to the ones in the Black Sea water. The main problem for the practical application of this type of fuel cell are the low current and power densities. The measurement of the generated electric current compared to the sulfide depletion show that the most probable anode reaction is oxidation of sulfide to sulfate. It is evident that parasite competitive reactions oxidation of sulfide occurs in the anode compartment of the fuel cell. The pH measurements shows that the transfer of hydroxylic anions from the cathodic compartment to the anodic one across the separating membrane is not fast enough to compensate its drop in the anode compartment.

Treatment of methyl orange dye wastewater by cooperative electrochemical oxidation in anodic–cathodic compartment

Electrochemical oxidation of methyl orange wastewater was studied using Ti/IrO2/RuO2 anode and a self-made Pd/C O2-fed cathode in the divided cell with a terylene diaphragm. The result indicated that the appropriate rate of feeding air improved the methyl orange removal efficiency. The discoloration efficiency of methyl orange in the divided cell increased with increasing current density. The initial pH value had some effect on the discoloration of methyl orange, which became not obvious when the pH ranged from 2 to 10. However, the average removal efficiency of methyl orange wastewater in terms of total organic carbon (TOC) can reach 89.3%. The methyl orange structure had changed in the electrolytic process, and the characteristic absorption peak of methyl orange was about 470 nm. With the extension of electrolysis time, the concentration of methyl orange gradually reduced; wastewater discoloration rate increased gradually. The degradation of methyl orange was assumed to be cooperative oxidation by direct or indirect electrochemical oxidation at the anode and H2O2, ·OH, O2−· produced by oxygen reduction at the cathode in the divided cell. Therefore, the cooperative electrochemical oxidation of methyl orange wastewater in the anodic–cathodic compartment had better degradation effects.

Degradation of 2-Chlorophenol Using a Pd/MWNTs Gas Diffusion Electrode in the Divided Cell

In a diaphragm electrolyze system with a Ti/RuO2/IrO2 anode and the Pd/MWNTs gas diffusion cathode, the degradation of 2-chlorophenol was fully studied by the electrochemical reduction and the simultaneous oxidation of the cathode and anode. The results indicated that the Cl- removal reached 90.5% after 80 min electrolysis with H2 feeding. After 120 min electrolysis, the removal of 2-chlorophenol in the anodic and cathode compartments were 88.8% and 98.5%, respectively. Additionally, the TOC removal reached 75% and 85.6% in the anodic and cathodic compartment respectively after 140 min. By the UV scanner analysis of the electrolyte, the 4-chlorophenol and benzoquinone were oxidized by the oxides formed on the cathode, while the benzoquinone was found accumulated in the anodic compartment. Based on the analysis of electrolysis intermediates using high performance liquid chromatography (HPLC) and ion chromatography (IC), the electrolysis degradation of 2-chlorophenol was proposed containing the intermediates, such as phenol, hydroquinone, benzoquinone, maleic acid, fumaric acid, succinic acid, malonic acid, oxalic acid, acetic acid and formic acid.

Investigation of Ni and Cd electrokinetic removal from a sediment

In this paper we examine the efficacy of the enhanced electrokinetic remediation of a sediment from the Tamis River contaminated with Ni and Cd. The moving anode technique and an increased cathodic compartment length were simultaneously used to enhance the technique. The removal efficacy increase appeared after the enhanced treatment for Ni (23%) and Cd (73%). The increased cathodic compartment length successfully prevented OH- ions migration in the sediment. Finally, sediment classification according to different risk assessment methodologies indicates that further remediation is required even after the enhanced treatment. Here we indicate that enhanced electroremediation resulted in the removal of efficacy increase but it is highly influenced by sediment characteristics.

Degradation of 4-Chlorophenol Using a Pd/MWNTs Gas Diffusion Electrode

In a diaphragm electrolyze system with a Ti/RuO2/IrO2 anode and the Pd/MWNTs gas diffusion cathode, the degradation of 4-chlorophenol was fully studied by the electrochemical reduction and the simultaneous oxidation of the cathode and anode. The results indicated that the optimization electrolyte concentration is 0.08 mol/L. The Cl- removal reached 94.8% after 80 min electrolysis with H2 feeding. After 120 min electrolysis, the removal of 4-chlorophenol in the anodic and cathode compartments were 98.5% and 90.6%, respectively. Additionally, the TOC removal reached 65% and 70% in the anodic and cathodic compartment respectively after 140 min. By the UV scanner analysis of the electrolyte, the 4-chlorophenol and benzoquinone were oxidized by the oxides formed on the cathode, while the benzoquinone was found accumulated in the anodic compartment.

Preferential Use of an Anode as an Electron Acceptor by an Acidophilic Bacterium in the Presence of Oxygen

ABSTRACT Several anaerobic metal-reducing bacteria have been shown to be able to donate electrons directly to an electrode. This property is of great interest for microbial fuel cell development. To date, microbial fuel cell design requires avoiding O2 diffusion from the cathodic compartment to the sensitive anodic compartment. Here, we show that Acidiphilium sp. strain 3.2 Sup 5 cells that were isolated from an extreme acidic environment are able to colonize graphite felt electrodes. These bacterial electrodes were able to produce high-density electrocatalytic currents, up to 3 A/m2 at a poised potential of +0.15 V (compared to the value for the reference standard calomel electrode) in the absence of redox mediators, by oxidizing glucose even at saturating air concentrations and very low pHs.

Dependency of Advanced Oxidation Performance on the Contaminated Water Feed Mode for Ozonation Combined with Electrolysis Using a Two-compartment Electrolytic Flow Cell

The effect of the contaminated water feed mode on advanced oxidation performance, for a combined system, using ozonation with electrolysis (ozone-electrolysis) in a two-compartment electrolytic flow cell, was discussed for ozone injection to the cathodic compartment of the cell. When ozone-electrolysis was applied, removal of the chemical oxygen demand (COD) proceeded in the cathodic compartment. The overall COD removal rate increased with the increase in current density for direct feed of contaminated water to the anodic compartment (DFA mode). However, the overall COD removal rate decreased at high current density for direct feed to the cathodic compartment (DFC mode), although the overall performance for the DFC mode was better than the DFA mode. The difference in the dependency of the performance on current density was determined to be due to the difference in the advanced oxidation mechanisms for each mode.