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A coupled process was studied for the removal of a chlorinated pesticide: 2,4-Dichlorophenoxyacetic acid (2,4-D). A home-made electrochemical flow cell was used for the pre-treatment and a biological treatment was then carried out using activated sludge supplied by a local wastewater treatment plant. 2,4-D was used as a target compound for the study. Several parameters were monitored during the biological treatment, like Dissolved Organic Carbon (DOC), the target compound and the major by-product. Pretreatment led to a quick decrease of DOC during the biological process, since a 66% mineralization yield was measured after the second day, and 79% after the seventh day of culture. After two days of treatment, HPLC results revealed a total degradation of Chlorohydroquinone, the major by-product. The electrochemical pretreatment shortened the length of the biological treatment, since DOC measurements showed that in the case of non-pretreated 2,4-D, no mineralization was observed before day 7. These promising results should be subsequently confirmed on commercial 2,4-D-containing solutions and then on real effluents.

International audienceThe main objective of this study was to examine the effect of an electro-Fenton pretreatment on the biodegradability of sulfamethazine-polluted solutions. The aim of the pretreatment was only to degrade this molecule in order to increase the biodegradability of the effluent and therefore allow a subsequent biological treatment. Preliminary tests showed the absence of biodegradability of the target compound. The degradation of sulfamethazine by electro-Fenton process was then examined using a carbon felt cathode and a platinum anode in an electrochemical reactor containing 1 L of solution. The influence of some experimental parameters such as initial concentration, temperature and current intensity on the degradation by electro-Fenton step has been investigated. In addition, the biodegradability of the solution after electrochemical pretreatment was examined and showed a Biological Oxygen Demand (BOD5) on Chemical Oxygen Demand (COD) ratio above the limit of biodegradability, namely 0.4, for several experimental conditions. The feasibility of coupling an electro-Fenton pretreatment with a biological degradation of by-products in order to mineralize polluted solutions of sulfamethazine was confirmed

International audienceThe aim of this work was to set up a novel electrochemical system allowing an efficient transformation of concentrated nitrate solutions to ammonium and which can be subsequently implemented on a large scale application. First, this paper describes the preparation of a porous copper modified electrode by successive electrodeposition of nickel then copper on a graphite felt of large specific surface area. Homogeneous Cu coating of all fibers in the 3D porous structure was successfully obtained using low concentrations of copper salts and high applied current intensities. The porous copper electrode was then used in a flow electrochemical process to achieve a selective and quantitative transformation of concentrated nitrate into ammonium. Different electrolytic solutions, slightly acid (acetate buffer) or neutral (phosphate buffer), and flow rates were investigated. The nitrate solution was quantitatively reduced into NH4+ with high selectivity in only one pass through the electrode. When the applied current was similar to the theoretical one, the maximum selectivity (96%) and the best current efficiency (72%) for NH4+ formation were reached at pH 7.2 with a flow rate of 2 mL min−1. The obtained ammonium solution can be subsequently used either as a potential nitrogen source during microbial culture or simply as a fertilizer

International audienceNew 3D electrodes are prepared and tested in reductive herbicide dechlorination as the first step of an environmental remediation process. Commercial nickel foams are modified through the spontaneous deposition of silver nanoparticles. Some of the solutions of Ag+ ions employed in the galvanic displacement reactions contain complexing agents, such as thiosulfate or thiocyanate, and a capping agent, polyvinylpyrrolidone (PVP), which influences the morphology and growth kinetics of the silver deposits. Modified foams are used as cathodes for the reductive dechlorination of Alachlor(TM), a common chloroacetanilide herbicide, in a series of tests that confirm the catalytic activity of silver. Electrodes prepared in a thiosulfate solution containing PVP allow extensive reduction of Alachlor(TM) to give deschloroalachlor as the only dechlorinated product

The electrochemical oxidation of phenol on Pb/PbO2 electrode was carried out in order to develop a predictive model. A central composite design (CCD) was employed for the screening of significant operating parameters and to identify their most relevant interactions. The model equation obtained led to a classification of these parameters based on their level of significance, namely the current density, the temperature, the initial phenol concentration, and the agitation speed. In addition, three relevant interactions were found, current density—temperature, initial phenol concentration—current density and initial phenol concentration—temperature. After performing a screening of the various factors, response surface analysis led to the following optimal conditions for the yield of phenol degradation: 189 ≤ [pOH]0 ≤ 200 mg L−1, 19.66 ≤ i ≤ 25 mA cm−2, 600 rpm, and 60°C for the initial phenol concentration, the current density, the agitation speed, and the temperature , respectively. Under these conditions, the obtained phenol degradation yield was 71% and the chemical oxygen demand (COD) was reduced more than 45%. © 2011 American Institute of Chemical Engineers Environ Prog, 2011

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