•COD and Cr(III) species can be simultaneously removed by electrocoagulation.•Cu-containing Al alloy is more efficient than pure Al as electrodes.•Dilution of too concentrated tannery wastewater is ...required for efficient treatment.
This 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 6h with a 400A/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.
The scanning reference electrode technique and voltammetric measurements allow visualising the corrosion currents on the pyrite surface in aerated solutions or in the presence of Fe(III). When thymol ...is present, the oxidation phenomenon is limited. The passivation of the mineral occurs after the previous oxidation of thymol on the pyrite surface.
Voltammetry with single particles of Ag
2Se, Ag
2Te and Ag
2S of a size ranging from 10 to 100 μm and put on an electrolyte soaked separator, has been performed and compared with previous ...measurements at carbon paste electrodes in concentrated sulphuric acid and NaClO
4 medium. The results confirm those obtained with traditional electrodes and point out the disturbing role of the binder. Moreover, the fact that chalcogenide particles behave as ultramicroelectrodes, except that cyclic voltammograms display peaks at extremely low scan rates, has allowed studies in the absence of deliberately added supporting electrolyte.
Micellar-based separation processes have been shown in the past few years to be especially attractive for the removal of metal ions from dilute aqueous solutions, when micellar extraction is combined ...with ultrafiltration. In the present paper we consider two ways of removing copper ions from micellar processes: the first is based on ion-exchange (anionic SDS micelles), the second on metal ion complexation by a micelle-solubilized extractant (CTAB/butanol/water/Kelex 100 microemulsions). The influence of the relative concentrations of the species involved and of the pH on the yield of extraction is investigated, and in the first case the results are compared with a theoretical prediction. In a second part we compare for the first time the electrochemical behavior of copper ions whether they are simply bound to the micelle surface or more deeply imbedded in the core of a microemulsion as a hydrophobic complex. The electroreduction of the copper ions is easily obtained when the metal ions are simply bound to the micellar surface, offering a way of recycling the micellar phase after the metal ions have been removed. The situation is more complicated when the copper ions form stable complexes solubilized in microemulsions, since the electroreduction is possible only once the complex has been destroyed in acidic media.
A wood‐free resin pencil comprised of a lead made of graphite particles dispersed in a polymeric matrix is proposed as a convenient low‐cost electrode for the ‘Voltammetry of Microparticles’ ...technique instead of paraffin impregnated graphite rods. The pencil electrode was successfully applied for the characterization of insulating (Prussian blue, zeolites) and conductive (silver selenide, pyrite) microparticles in various media. The voltammetric responses were comparable to, sometimes even better than, those obtained with applying other electrochemical techniques.
Pyrite and/or galena particles previously conditioned with U(VI) at pH 6 have been characterized by micro-Raman spectrometry, voltammetry, scanning electron microscopy and high resolution X-ray ...photoelectron spectroscopy. U
is first formed on the sulphide surfaces
a redox process, then, if an excess of U(VI) remains in solution it is sorbed as UO
and shoepite. Galvanic phenomena occur when the minerals are in mixture in a medium containing U(VI): galena particles are oxidized whereas U(VI) is reduced at the pyrite particle surface. The maximum amounts of fixed uranium are 0.4 mmol/g for pyrite and 0.1 mmol/g for galena and the 50:50 pyrite:galena mixture.
A platinum ultramicroelectrode was used for the in situ study of partition reactions of Bu
4NI and Et
4NPic 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.
Ultramicroelectrodes have been used to follow continuously the hydrolysis of triarylphosphate esters, these compounds being envisaged as lubricants of the primary pump motor in nuclear plants. The ...amperometric ultramicroelectrochemical device gives the expected results in industrial site testing.
Complex-impedance variations of the ion-exchange resin DOWEX 50X8 with the type of counterion allow one to follow the Cu
2+/H
+ and Ca
2+/Na
+ exchange reactions without chemical analysis of ...solutions. Frequency and ionic strength effects are specified. This method is effective for following the Na
+/K
+ separation by displacement of Ca
2+ ions.
