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The flow-by electrochemical reactor is generally used in batch mode with extended process time in order to achieve high efficiency in the removal of organic contaminant from aqueous solution. Moreover, the batch mode system is inappropriate for the treatment of wastewater in high volume or as a continuous stream. This paper presents a new operational mode for the electrochemical reactor in which the electrolyte passes over the electrodes just once at a reduced flow rate and with high hydraulic retention time. The concentration of hydrogen peroxide generated in the reactor running in the single-pass flow mode attained 10.2 mg L −1 cm −2 in acid medium, a value similar to that obtained previously with the same type of reactor operating in batch mode. In the single-pass mode, the electrochemical reactor showed high rates of removal of the antibiotic levofloxacin (initial 50 mg L −1 ) and organic load (initial 130 mg L −1 ) up to 99 and 86%, respectively, when operated under electro- or photo-Fenton degradation conditions (acid medium with Fe 2+ ions; absence or presence of UV irradiation). Degradation of levofloxacin generated high levels of nitrate (up to 4.5 mg L −1 ) and various by-products that could be identified by liquid chromatography-mass spectrometry. [ABSTRACT FROM AUTHOR]

In this paper, an analysis of experimental results on the behavior under impulse currents of various grounding electrodes: rod and horizontal electrodes, a ground grid, and tower footings, is presented. The parameters used for analyzing transient performance are reviewed, and the differences are highlighted based on test data. The analysis is extended to the following: 1) to quantify the effect of impulse shape; 2) to quantify the effect of current magnitude; 3) to compare low-frequency and impulse performances; 4) to compare impulse and high-frequency performances; and 5) to examine the effects of the test setup on measured results, e.g., in the case of field tests, the effect of current return leads, and proximity and extent of return electrodes. A generalized impulse index is introduced to help elucidate the differences between different parameters used for the analysis of transient test results on ground electrodes. It is found that the analysis of test data based on different parameters may lead to different assessments of impulse performance. The results also show that the impulse parameters used for the analysis of test data can be influenced by several factors such as electrode length, impulse current rise time, and experimental setup. In addition, variable-frequency test results are analyzed by introducing a “harmonic coefficient” which quantifies the deviations of the harmonic impedance from the low-frequency resistance over different frequency ranges covering the entire lightning frequency spectrum. Significant variations of the harmonic coefficient with frequency were observed, highlighting the importance of taking the frequency dependence of soil properties when modeling the impulse and high-frequency behavior of grounding systems. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the electrochemical degradation of dipyrone in a single compartment electrochemical cell equipped with a gas diffusion electrode (GDE) modified with cobalt (II) phthalocyanine. Degradations were performed under conditions of anodic oxidation (GDE pressurized with N2) and under conditions promoting the electrogeneration of H2O2 (GDE pressurized with O2) both in the absence and presence of 1 mmol FeS04.7H20 (electro-Fenton conditions). The efficiency of the electro-Fenton process was satisfactory at all studied potentials, and achieved a maximum reduction of 67% in electrolyte absorbance at 262 nm after 90 min electrolysis at -0.7 V (vs. Ag/AgCl). The reduction in dipyrone concentration attained 95% after 90 min of reaction with electrogenerated H2O2 in the absence or presence of Fe2+ ions at all potentials except -0 .5 V (vs. Ag/AgCl). The removal of total organic carbon (TOC) was most efficient under electro-Fenton conditions with a decrease of 54.4% in organic load attained at -0.9 V (vs. Ag/AgCl) and energy consumption (EC) of 270 kWh per kg of TOC removed. [ABSTRACT FROM AUTHOR]

Abstract: Methane fed TiO2/RuO2/PTFE gas diffusion electrodes (GDEs) have been used for the electrosynthesis of methanol in 0.1molL−1 of Na2SO4 supporting electrolyte. By-products such as formaldehyde and formic acid are usually also formed during electrolyses, with the latter formed at a similar rate as that of methanol. In this study, V2O5 was added to the composition of the GDE to improve its selectivity for methanol. TiO2/RuO2/V2O5 powder hot-pressed with PTFE resulted in a GDE suitable for oxidative electrosynthesis with simultaneous oxygen evolution. By feeding the TiO2/RuO2/V2O5/PTFE GDE with methane, it was possible to enhance its selectivity for methanol at low values of current density. Furthermore, the formation of formic acid and formaldehyde was suppressed, allowing for higher current efficiencies. The addition of 5.6% of V2O5 increased the electrode''s current efficiency to 57% at 2.0V, which is 2-fold higher than the efficiency achieved in the absence of vanadium oxide. [Copyright &y& Elsevier]

A new electrode for the photoelectrochemical removal of 17β-estradiol from water using ruthenium oxide nanoparticles supported on reduced graphene oxide is proposed in this study. The morphology, microstructure and the electrochemical performance of the material were characterized using HRTEM, XRD and Raman spectroscopy. The characterization showed the formation of reduced graphene oxide from a micro-wave assisted hydrothermal method with a particle size of 5.0 nm + 2.4 nm. The electrochemical measurements point to a high performance of the electrode in the presence of a white light source. The hormone removal efficiency in water containing 50 μmol L −1 of 17β-estradiol was evaluated using chronoamperometry at +1.0 V and the process was monitored using liquid chromatography. The reaction is pseudo first order with the removal of 92.2% of 17β-estradiol after 60 min of photoelectrocatalytic treatment. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen peroxide (H2O2) is a commonly used oxidant with a wide variety of applications in, for example, organic synthesis and wastewater treatment. This paper describes the development of catalysts for the electrogeneration of H2O2 in acidic medium using gas diffusion electrodes (GDE). Initial experiments were performed using rotating ring-disk electrodes modified with microporous layers of Printex 6L carbon containing various amounts of cobalt (II) phthalocyanine (CoPc) in order to evaluate catalytic activities. The results showed that the current efficiency for the formation of H2O2 increased from 69.7% for Printex 6L carbon without catalyst to 81.5% when using Printex 6L carbon with CoPc, and this was accompanied by a decrease in the number of electrons involved in the oxygen reduction reaction from 2.6 to 2.3. Based on these findings, modified GDEs were constructed containing 3.0, 5.0 and 10.0% of CoPc on Printex 6L carbon. The concentration of H2O2 that formed after 90min electrolysis with the GDE modified with Printex 6L carbon alone was 176mgL−1, while the GDE with 5.0% CoPc on carbon produced 331mgL−1 of H2O2, i.e. an increase in yield of 89.1% relative to Printex 6L carbon. Additionally, using GDE s modified with CoPc on carbon, the potential at which H2O2 formation attained its maximum value shifted to less negative values in comparison with electrodes without catalyst. It is concluded that CoPc is an appropriate catalyst for efficient electrogeneration of H2O2. [Copyright &y& Elsevier]