International audienceStudies on the degradation and mineralization of tetracycline by means of the electro-Fenton process are lacking in the available literature. Its relevance as a pre-treatment prior to a biological process for the removal of tetracycline was therefore examined

This study aims to investigate the effectiveness of the electro-Fenton process on the removal of a second generation of fluoroquinolone, enoxacin. The electrochemical reactor involved a carbon-felt cathode and a platinum anode. The influence of some experimental parameters, namely the initial enoxacin concentration, the applied current intensity and the Fe(II) amount, was examined. The degradation of the target molecule was accompanied by an increase of the biodegradability, assessed from the BOD5 on COD ratio, which increased from 0 before treatment until 0.5 after 180 min of electrolysis at 50 mg L(-1) initial enoxacin concentration, 0.2 mmol L(-1) Fe(II) concentration and 300 mA applied current intensity. TOC and COD time-courses were also evaluated during electrolysis and reached maximum residual yields of 54% and 43% after 120 min of treatment, respectively. Moreover, a simultaneous generation of inorganic ions (fluorides, ammonium and nitrates) were observed and 3 short chain carboxylic acids (formic, acetic and oxalic acids) were identified and monitored during 180 min of electrolysis. By-products were identified according to UPLC-MS/MS results and a degradation pathway was proposed.

Dielectric barrier discharge DBD-plasma based technologies have been widely investigated for the abatement of air pollutants. More recently, photocatalysis (TiO 2 /UVlamp) has also showed promising results for air pollution abatement. In this work, these two methods were used separately and combined (TiO 2 /UV-lamp/DBD-plasma) in order to enhance the performance of the process for air pollutants degradation/mineralization. Ammonia (NH 3) and butyraldehyde (C 4 H 8 O) have been firstly treated alone and then an equimolar mixture (NH 3 /C 4 H 8 O) was monitored in a continuous reactor. Effect of operational parameters such as pollutants inlet concentration, flowrate, humidity and specific energy of plasma were thoroughly determined. Results showed that coupling both methods in the same reactor improves removal efficiency for single pollutant or a mixture of two pollutants. This processes combination showed a synergy between DBDplasma and photocatalytic oxidation. Moreover, pollutant mineralization and potential 2 intermediate byproducts have been characterized and discussed. Coupling both processes contributes to enhanced mineralization in comparison with DBD-plasma alone regarding the CO 2 selectivity. As for selectivity of byproducts: (i) Relative Humidity (RH), (ii) mixture effect and (iii) (TiO 2 /UV-lamp/DBD-plasma) combined processes inhibit ozone production during the pollutants removal/oxidation.

Fe-ABs were fabricated by simple gelation procedure at 25 °C. The incorporation of iron on beads was confirmed by EDS results. The Fe-ABs catalyst present good stability and can be used for at least four times without obvious decrease in activity. Mineralization pathways of indole was proposed. In this work the characterization and the performance of iron immobilized in alginate beads (Fe-ABs) as catalyst for heterogeneous electro-Fenton (EF) treatment of a malodorous compound, indole, was investigated. Experimental results demonstrated that indole was effectively removed through the electro-Fenton process; while in the considered experimental conditions, the performances of EF were only slightly improved by the addition of UVA radiation. The most efficient operating conditions were achieved at pH 3.0 in the presence of 200 mg.L-1 Fe-ABs catalyst (corresponding to an average iron concentration of 64 mg L-1) with a current density of 0.53 mA cm-2. Under these conditions, 60 min were sufficient to completely degrade 20 mg L −1 of indole, whose removal was found to obey the pseudo-first order model. In terms of organic carbon removal, about 90% mineralization yield was reached in the optimal conditions for 7 h heterogeneous electro-Fenton treatment time. UPLC-MS/MS analysis was applied to identify and follow the evolution of indole oxidation products. Five stable organics intermediates were observed and four of them were identified as dioxindole, isatin, oxindole and anthranilic acid. A reaction sequence was therefore proposed for indole degradation according to the detected products. Subsequent attack of these intermediates by •OH radicals led to the formation of short chain acids such as succinic, acetic, oxamic and oxalic identified by ion-exclusion chromatography.

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International audienceIn the present work the abatement of butyraldehyde (BUTY), dimethyl disulfide (DMDS) and their mixtures in gas phase was studied in continuous reactor at three different configurations: photocatalysis (TiO2 + UV), dielectric barrier discharge (DBD) plasma and their association in the same system (DBD+ TiO2 + UV). The effect of some operating parameters such as inlet concentration of pollutant and flowrate on planar reactor performance in term of (i) BUTY removal (ii) selectivity of CO and CO2, selectivity of byproducts has been also investigated. Moreover, ozone formation has been studied to evaluate the performance of the combined process. A synergetic effect was observed by combining (DBD) plasma and photocatalysis on BUTY removal but has not been present when it was in air mixture with dimethyl disulfide (DMDS) due to the poisoning of the catalyst. Additionally, degradation was observed as a consequence of by-products accumulation on the surface of the catalyst. Moreover, the regeneration/recovery of the initial photocatalytic activity was explored in details. A significant regeneration has been occurred by combining photocatalysis and nonthermal plasma. This trend of nonthermal plasma on catalytic surface can explain the synergetic effect during the pollutant degradation time. Moreover, the catalyst was concomitant with the time required for the hydrophobic to hydrophilic transition on the catalyst surface as followed by contact angle measurement (CA). Redox catalysis was detected by X-ray Photoelectron Spectroscopy (XPS) showing Ti4+/Ti3+ switching during the degradation, poisoning and regeneration times

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Highlights  Highest hydrogen peroxide concentration and MTZ mineralization obtained for 0.07 mA.cm-2  The evolution • OH concentration was not in accordance with that of MTZ mineralization  Dissolved oxygen can become a limiting reagent for • OH quantification with DMSO  DMSO can be oxidized and reduced at the electrodes surface distorting • OH quantification  DMSO efficient as • OH probe until 0. 07 mA.cm-2 in this study, not efficient for electrooxidation