Search results for "limiting current"
showing 8 items of 8 documents
Oxidation of organics in water in microfluidic electrochemical reactors: Theoretical model and experiments
2011
The electrochemical oxidation of organics in water performed in micro reactors on boron doped diamond (BDD) anode was investigated both theoretically and experimentally in order to find the influence of various operative parameters on the conversion and the current efficiency CE of the process. The electrochemical oxidation of formic acid (FA) was selected as a model case. High conversions for a single passage of the electrolytic solution inside the cell were obtained by operating with proper residence times and low distances between cathode and anode. The effect of initial concentration, flow rate and current density was investigated in detail. Theoretical predictions were in very good agr…
Electrodialysis with asymmetrically profiled membranes: Influence of profiles geometry on desalination performance and limiting current phenomena
2021
Abstract Electrodialysis (ED) has recently gained much attention in the wide field of desalination and water treatment. However, energy consumption and capital costs may impair the process competitiveness. In this regard, limiting current density (LCD) and current efficiency (η) are key performance parameters for optimized ED systems. In this work, an experimental campaign was carried out characterizing the performance of ED stacks when adopting asymmetrically profiled membranes. Current–voltage curves were recorded under different operating conditions mimicking the operation of brackish water or seawater desalination units. Results showed that there was a preferable direction of the electr…
A Simple Model for Ac Impedance Spectra in Bipolar Membranes
1996
A new model accounting for the ac impedance spectra of synthetic ion-exchange bipolar membranes is presented. The theoretical approach is based on the Nernst−Planck and Poisson equations and applies some of the concepts used in the semiconductor pn junctions to the case of a bipolar membrane. The results presented are the current−voltage curves and the impedance spectra at electric currents above the limiting current. It is shown that the model is able to identify the main contributions to the bipolar membrane impedance and gives valuable information about the bipolar junction structure and its influence on the characteristic parameters involved in the field-enhanced water dissociation phen…
DC polarographic reduction of chloroguanide hydrochloride.
1984
Chloroguanide hydrochloride, an antimalarial drug, shows one well-defined DC polarographic wave in Britton-Robinson buffered media. In the pH range 3–9 the observed reduction wave is related to the reduction of the two azomethine centers on the monoprotonated biguanide group (BH+). The effects of pH and other experimental variables on the limiting current and half-wave potentials as well as the reduction mechanism are discussed.
Experiments and modelling for determining the Limiting Current Density in Electrodialysis units
2018
In the present work, in order to explore such issues on the LCD identification, we performed in-situ measurements with ED units, assessing the influence of operating conditions and validating a purposely implemented process simulator, which was then used for further investigation
Effect of membrane profiles on the limiting current density in electrodialysis
2019
In the present work, we experimenrtally investigated the effect of different membrane profiles on the LCD, testing also different operating conditions.
Limiting current phenomena in electro-membrane processes: local occurrence or stack-dependent one?
2021
Background Electro-membrane processes are gaining great interest in the field of desalination and brine valorisation. However, limiting current phenomena can be a bottleneck for their techno-economic performances. In the present work, the in-out distribution of current density is measured to elucidate the achievement of limiting conditions in real stacks. Materials and Methods A 10-cell pairs Electrodialysis stack (10×40 cm2 active area), equipped with four-segmented electrodes, was tested. NaCl solutions at an inlet concentration ranging from 0.5 to 60 g/l were fed at velocities of either 2 or 4 cm/s in parallel flow. Current density-voltage curves were built by applying equal increasing s…
Determination of limiting current density and current efficiency in electrodialysis units
2018
Abstract A crucial parameter for the design and operation of electrodialysis (ED) units is the limiting current density (LCD). This is often identified with the diffusion-limited current density, which corresponds to the complete solute depletion in the layer adjacent to the membrane. Current-voltage curves obtained from measurements with electrodes in contact with the solution (i.e. without membranes) are consistent with this interpretation and exhibit a horizontal plateau identifying LCD. However, real ED systems show more complex behaviours, with a reduced-slope tract instead of a plateau and a third region in which the current increases more markedly (overlimiting current). The phenomen…