Recyclage du Cryptand (222)

International audienc

Ultramicroelectrode study without deliberately added electrolyte: Application to the analysis of liquid-liquid extraction processes in dichloromethane

International audienceA platinum ultramicroelectrode was used for the in situ study of partition reactions of Bu4NI and Et4NPic between phosphate buffer, pH 7.5, and dichloromethane, without adding supporting electrolyte. Extraction and dissociation constants are determined by voltammetry in the organic phase and compared with those determined by UV-visible spectrophotometry. The results show the significance of the migration effect in the determination of the extracted species by electrochemistry

Proton reduction at a platinum ultramicroelectrode : the effect of supporting electrolyte on the limiting current

International audienc

Reduction of acids at a platinum ultramicroelectrode: application to “in situ” acid number control of fluid lubricants (phosphate esters)

International audienceThe strength of acids, their charge and possibly their behaviour as polyacids can be deduced by comparing their limiting currents at a platinum ultramicroelectrode in the absence and presence of an excess of supporting electrolyte. Acid-base reactions in tributyl phosphate can be followed without deliberately added supporting electrolyte even if their dielectric constant is low. The acidity of phosphate esters resulting from their hydrolysis can be monitored by amperometry at a platinum ultramicroelectrode

Treatment of highly concentrated tannery wastewater using electrocoagulation: Influence of the quality of aluminium used for the electrode

International audienceThis paper deals with the ability of electrocoagulation (EC) to remove simultaneously COD and chromium from a real chrome tanning wastewater in a batch stirred electro-coagulation cell provided with two aluminium-based electrodes (aluminium/copper/magnesium alloy and pure aluminium). Effects of operating time, current density and initial concentration of Cr(III) and COD have been investigated. The concentrations of pollutants have been successfully reduced to environmentally acceptable levels even if the concentrated effluent requires a long time of treatment of around 6 h with a 400 A/m2 current density. The aluminium alloy was found to be more efficient than pure aluminium for removal of COD and chromium. Dilution of the waste has been tested for treatment: high abatement levels could be obtained with shorter time of treatment and lower current densities. Energy consumption of the electrocoagulation process was also discussed. The dilution by half of the concentrated waste leads to a higher abatement performance of both COD and chromium with the best energy efficiency

Electrochemical analysis of a microbial electrochemical snorkel in laboratory and constructed wetlands

International audienceMicrobial electrochemical snorkel (MES) is a short-circuited microbial fuel cell applicable to water treatment that does not produce energy but requires lower cost for its implementation. Few reports have already described its water treatment capabilities but no deeper electrochemical analysis were yet performed. We tested various materials (iron, stainless steel and porous graphite) and configurations of snorkel in order to better understand the rules that will control in a wetland the mixed potential of this self-powered system. We designed a model snorkel that was studied in laboratory and on the field. We confirmed the development of MES by identifying anodic and cathodic parts, by measuring the current between them and by analyzing microbial ecology in laboratory and field experiments. An important application is denitrification of surface water. Here we discuss the influence of nitrate on its electrochemical response and denitrification performances. Introducing nitrate caused the increase of the mixed potential of MES and of current at a potential value relatively more positive than for nitrate-reducing biocathodes described in the literature. The major criteria for promoting application of MES in artificial wetland dedicated to mitigation of non-point source nitrate pollution from agricultural water are considered