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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.

This work investigates Reduced Titanium Oxide (RTO) in comparison with Carbon Cloth (CC) and commercial Boron Doped Diamond (BDD) as anodes in hyperthermophilic bioelectrochemical systems operating at 80°C by Thermotoga neapolitana. Two samples of RTO were synthesized by plasma electrolytic oxidation (PEO) of titanium plates and subsequent electrochemical reduction. Electrochemical performance of CC, BDD, and RTO are tested by performing cyclic voltammetry in the anodic region (0-1V, 50 mV/s), in abiotic and biotic conditions. The surface of colonized materials is observed by SEM microscopy. Results show that bacteria fast settle on all tested material, significantly affecting their electrochemical conductivity. The integration of voltammetric cycles reveals that biofilm generates capacitive effects on the anodic surfaces, particularly evident in RTO, less in CC and absent in BDD. Charge densities provided by capacitive response of RTO and CC are of the order of 5.58 and 0.77 mC/cm2, respectively.

Recently, among AOPs, photoelectrocatalysis (PEC) on TiO2 is gaining interest. In this study, five different real waters sampled in four different points of the integrated urban water management (IUWM) system were tested with PEC and UV alone, for comparison. This work aims to verify the effect of the PEC suggesting the optimal position in IUWM system where the PEC should be located to obtain the best performance. In groundwaters (GWs), PEC effectively removed atrazine-based compounds (> 99%), trichloroethylene, and perchloroethylene (96%), after 15 min of reaction time. However, given the low concentrations of emerging compounds, the synergistic effect of UV radiation with the catalyst and with the polarization of the mesh was not visible, with very few differences compared with the results obtained with UV alone. Pharmaceutical industrial wastewater (IWW) showed a significant increase in biodegradability after 2 h, both if subjected to PEC or UV (200%), despite the absence of COD removal. The PEC applied on IWW from a sewage sludge treatment plant allowed to effectively remove the COD (39.6%) and increase the biodegradability (300%). Good results in terms of COD removal (33.9%) and biodegradability increase (+900%) were also achieved testing PEC on wastewater treatment plant effluent. Except for GWs, PEC allowed significant EEO savings respect to UV alone (76.2–99.1%). [ABSTRACT FROM AUTHOR]

The fast, single‐step and easily scalable production by plasma electrolytic oxidation (PEO) of large area TiO2 electrodes with excellent photoactivity in water splitting under simulated solar light is systematically investigated here. In particular, the effects that the cell voltage (100–180 V) and the processing time (0.5–15 min) have on the electrode properties are studied. The PEO‐produced oxide layers are porous, the predominant crystalline structure shifting from anatase, to an anatase‐rutile mixture, and finally to rutile by rising the cell voltage. The electrodes show a double‐layered structure, with a more compact layer at the interface with the titanium substrate and a thick porous layer on the external surface. The photocurrent density versus wavelength reflects the phase composition, with a maximum incident photon‐to‐current efficiency of 90% at 320 nm. The highest H2 production rate is attained with the mixed anatase‐rutile electrode prepared by 300 s‐long PEO at 150 V. [ABSTRACT FROM AUTHOR]