6533b7d8fe1ef96bd126b744
RESEARCH PRODUCT
Determination of limiting current density and current efficiency in electrodialysis units
Michele TedescoAlessandro TamburiniAndrea CipollinaLuigi GurreriMichele CiofaloMariagiorgia La CervaGiorgio Micalesubject
Work (thermodynamics)Settore ING-IND/26 - Teoria Dello Sviluppo Dei Processi ChimiciMaterials scienceGeneral Chemical Engineering02 engineering and technologyPlateau (mathematics)Electrodialysi020401 chemical engineeringGeneral Materials ScienceChemical Engineering (all)0204 chemical engineeringDiffusion (business)Concentration polarizationSettore ING-IND/19 - Impianti NucleariConcentration polarizationIon exchange membraneWater Science and TechnologyMechanical EngineeringChemistry (all)Limiting currentGeneral ChemistryMechanicsElectrodialysis021001 nanoscience & nanotechnologyLimiting current densityCurrent efficiencyMaterials Science (all)Current (fluid)0210 nano-technologyCurrent densitydescription
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 phenomena involved in the limiting region are not yet totally characterized and the determination of LCD in ED units is still ambiguous. In the present work, we explore the issues related to the identification of LCD, by measurements on ED units, assessing the influence of operating conditions and validating a simplified process simulator. A new method to determine LCD, based on the current efficiency, is proposed and compared with other methods presented in the literature. A second limiting quantity is also identified, i.e. the critical current density, below which diffusion phenomena prevail on migration and a method for its assessment is proposed.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2018-11-01 | Desalination |