Electrochemical removal of cadmium using a batch undivided reactor with a rotating cylinder electrode

The performance of an undivided electrochemical batch reactor with a rotating cylinder electrode under potentiostatic control is examined for the removal of cadmium from a sodium sulfate solution containing 500ppm Cd(II) at pH ≅ 7. The effect of hydrogen evolution as a side cathodic reaction on the figures of merit of the reactor is analysed. The best results were obtained for a cathode potential of -0.9 V against the saturated calomel electrode. With an angular velocity of 1500rpm the space time yield and the normalized space velocity were 0.66 mol m-3s-1 and 3.9 h-1 respectively, while the fractional conversion was 67.3% with a current efficiency of 66.7%. The surface morphology of the deposits as a function of the applied potential is also reported. © 2001 Society of Chemical Industry.Fil: Grau, Javier Mario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; ArgentinaFil: Bisang, Jose Maria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentin

Coupling K convection-diffusion and Laplace equations in an open-source CFD model for tertiary current distribution calculations

A mathematical model to calculate tertiary current distributions in electrochemical reactors is presented taking into account the potential and concentration fields together with the hydrodynamics under laminar or turbulent conditions. Multiple reactions with different kinetic controls are considered at both electrodes. The computational algorithm solving the model was implemented in OpenFOAM. It allows the calculations for a given local potential at the working electrode, potentiostatic control, or for a fixed cell potential difference and also for a current flowing through the cell, galvanostatic operation. The model was validated by using the reduction of ferricyanide and the oxidation of ferrocyanide from dilute solutions as main test reactions and hydrogen and oxygen evolution as secondary ones, in a modified hydrocyclone. A close agreement between experimental and predicted current distributions was obtained. The hydrocyclone presents a promising electrochemical performance being the mass-transfer conditions in its cylindrical part better than in the conical region. The computational tool developed in this paper can be employed to optimize both cells stack design and system operation conditions. Likewise, the algorithm can also be used to check, when limiting current studies are needed, whether the desired reaction is under mass-transfer or charge-transfer control for a given geometric configuration.Fil: Colli, Alejandro Nicolás. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Bisang, Jose Maria. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin

Removal of cadmium and production of cadmium powder using a continuous undivided electrochemical reactor with a rotating cylinder electrode

The behaviour of a continuous undivided electrochemical reactor with a rotating cylinder electrode under potentiostatic control is examined for the abatement of cadmium from synthetic sodium sulfate solutions with Cd(II) concentrations lower than 500 mgdm-3 at a reactor inlet pH ≅ 7. The process was designed to convert the metal ions in solution to metal powder, which settles to the conical of the reactor and may be removed at intervals as a sludge by opening a drop valve. The effect of applied potential, inlet cadmium concentration, rotation speed and hydrogen evolution as side cathodic reaction on the 'figures of merit' of the reactor are analysed. The best results were obtained for cathode potentials in the range from -0.9V to -1.0V against the saturated calomel electrode. Therefore, when the rotation speed was 1000rpm the space time yield and the normalized space velocity were 0.64 × 10-2 mol m-3s-1 and 0.89h-1 respectively, while the fractional conversion per pass was 35% with a current efficiency higher than 74%. The surface morphology of the deposits as a function of the process variables is also reported. © 2002 Society of Chemical Industry.Fil: Grau, Javier Mario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; ArgentinaFil: Bisang, Jose Maria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentin

Evaluation of a decaying swirling flow electrochemical reactor for the manufacture of colloidal sulphur by reduction of sulphur dioxide

The behaviour of an electrochemical reactor with decaying swirling flow is analysed for the production of colloidal sulphur using sulphur dioxide from synthetic effluents as raw material. The experiments were done under potentiostatic control with single- and two-phase flow. The best results were obtained at a cathodic potential of −0.7 V, against a saturated calomel electrode. Thus, in a single-phase experiment at a volumetric flow rate of 8 dm3 min−1 and 1 g dm−3 SO2 in 0.5 mol dm−3 H2SO4 as a supporting electrolyte, the current efficiency was 64% with a specific energy consumption of 22.7 kW h kg−1 and a space time yield of 5.6 kg m−3 h−1, achieving a total removal of sulphur dioxide after 15 min of operation. For sulphur dioxide concentrations lower than 2.5 g dm−3 the cathode surface remained free of a sulphur layer due to the impingement action of the swirling flow. Similar results were obtained under a two-phase flow of 5% SO2 in nitrogen. In this case, the sulphur particles presented mainly spheroidal shape with an average size of 2.8 μm being of high purity. The comparison with other types of electrochemical reactors concludes that the equipment with swirling flow represents the best option.Fil: Contigiani, Camila Cecilia. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Fornés, J. P.. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; ArgentinaFil: González Pérez, Omar. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; ArgentinaFil: Bisang, Jose Maria. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin

Electrochemical treatment of waste solutions containing ferrous sulfate by anodic oxidation using an undivided reactor

This paper describes an analysis of the performance of an electrochemical undivided reactor for the recycling of waste solutions containing ferrous sulfate. The effect of oxygen evolution as side anodic reaction on the figures of merit of the reactor is studied. The results suggest that the anode potential must represent a compromise between the increase in space time yield and the increase in the specific energy consumption. Experimental data are correlated with a mathematical treatment based on the stirred tank model.Fil: Bisang, Jose Maria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentin

Producción electroquímica de polvos metálicos

El trabajo revisa la producción de polvos metálicos por vía electroquímica. Se discuten los parámetros que condicionan sus características y propiedades. Se comentan los procesos convencionales de producción y se enfatiza sobre la posibilidad de generarlos a partir del tratamiento electroquímico de productos contaminados o de efluentes.Fil: Bisang, Jose Maria. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentin

The effect of a perpendicular and cumulative inlet flow on the mass-transfer distribution in parallel-plate electrochemical reactors

A perpendicular inlet flow of electrolyte is analysed as a means of improving mass-transfer in a parallel-plate electrochemical reactor. Experimental local Sherwood numbers along the electrode length are reported for different values of the hydraulic diameter and Reynolds number, using the reduction of ferricyanide as a test reaction. The Reynolds numbers, evaluated with the inlet velocity in the reactor, range from 0.7 to 30 with interelectrode gaps varying between 3.2 to 9.8 mm. The perpendicular and cumulative flow makes uniform the mass-transfer distribution at the reactor inlet under laminar flow conditions. The experimental data are compared with theoretical calculations obtained by computational fluid dynamics and also with an analytical simplified model. The mean relative deviation between the experimental and theoretical results was lower than 5% and a close agreement was observed between both theoretical treatments.Fil: Colli, Alejandro Nicolás. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada E Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bisang, Jose Maria. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada E Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Study of the influence of boundary conditions, non ideal stimulus and dynamics of sensors on the evaluation of residence time distributions

The study of the residence time distribution is usually made in order to diagnose the hydrodynamic behaviour of the equipment. This paper reports on the residence time distribution according to six combinations of the open and closed boundary conditions, which are compared in order to determine an appropriate equation tofit experimental data from the stimulus-response method. The residence timedistribution under laminar flow is analysed and the mathematical modelling of the pure convection regime, zone of axial dispersion and intermediate case is discussed. The disturbances in the residence time distribution produced by a non-ideal impulse and also by the dynamic behaviour of the sensor are quantified and the errors in its evaluation are given.Fil: Colli, Alejandro Nicolás. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Bisang, Jose Maria. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin

Generalized study of the temporal behaviour in recirculating electrochemical reactor systems

This paper outlines and compares mathematical models to predict the temporal variation of concentration and current in an electrochemical reactor coupled with a reservoir operating with continuous recirculation of the electrolyte. The reservoir is considered as a well mixed tank while the dispersion model is used for the reactor. The performances according to the idealized models to represent a reactor, stirred tank and plug flow, are also deduced as limiting cases. Applied studies carried out in rotating cylinder electrodes using the removal of copper from dilute solutions as test reaction are reported. The experimental data are correlated with the theoretical model, numerically solved, using a dimensionless number β, proportional to the kinetic constant, as fitting parameter. The results in accordance with this rigorous model are compared with those of the conventional equations based on the stirred tank model and the error in the evaluation of the kinetic constant can be as high as 26%. From an engineering point of view, a generalized plot to estimate the error is reported, which requires as inputs the experimental slope of the temporal variation of concentration in the reservoir, the Peclet number and the ratio between the reservoir and reactor space times.Fil: Colli, Alejandro Nicolás. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Bisang, Jose Maria. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin

Electrochemical removal of cadmium from dilute aqueous solutions using a rotating cylinder electrode of wedge wire screens

Rates of mass transfer at rotating cylinder electrodes of wedge wire screens were studied by measuring the limiting current for the cathodic reduction of ferricyanide as test reaction. The experimental data are well correlated by an empirical expression between the Sherwood number and the Reynolds number, both in terms of the internal slot opening as characteristic length, and including two additional dimensionless parameters in order to characterize the geometry of the screens. The performance of an undivided electrochemical batch reactor with a rotating cylinder cathode of wedge wire screens was tested analyzing the cadmium removal from dilute solutions. The effect of cathodic applied potential and size of the screen is studied. Taking into account the residual cadmium concentration the best results were obtained for a cathode potential of -1.1 V vs. SCE at 700 rpm, where the cadmium concentration decreased from 54 to 0.9 mg l-1 after 30 min of electrolysis with a specific energy consumption of 10.7 kWhkg-1 and a normalized space velocity of 3.54 h-1.Fil: Grau, Javier Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Bisang, Jose Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin